Effects of Acidic Deposition on Aquatic Resources in the Southern Appalachians with a Special Focus on Class I Wilderness Areas Prepared for the Southern Appalachian Mountains Initiative ( SAMI)

August 20, 1996 Alan T. Herlihy and Philip R. Kaufmann Department of Fisheries and Wildlife Oregon State University, c/ o U. S. EPA NHEERL 200 SW 35th St. Corvallis, OR 97333 John L. Stoddard, Dynamac Corp. c/ o U. S. EPA NHEERL 200 SW 35th St. Corvallis, OR 97333 Keith N. Eshleman Appalachian Environmental Laboratory CEES, University of Maryland System Frostburg, MD 21532 Arthur J. Bulger, Department of Environmental Sciences University of Virginia Charlottesville, VA 22903 iii EXECUTIVE SUMMARY The Southern Appalachian Mountains Initiative ( SAMI) was established to address concerns about the adverse effects of air pollution on environmental resources in the Southern Appalachians. Acidic deposition and its effects on surface waters is a major air pollution issue in this area. This report has two main objectives:

1. Summarize the existing state of knowledge about the effects of acidic deposition on surface water resources in the Southern Appalachians.

2. Evaluate and make recommendations on the use of available methodologies for predicting future changes in the aquatic effects of acidic deposition in the Southern Appalachians.

The major findings of this report are as follows.

Factors Controlling the Response of Surface Waters to Acidic Deposition The two major processes influencing the response of surface waters in the Southern Appalachians to acidic deposition are sulfate/ nitrate retention and base cation mobilization. The amount of watershed sulfate/ nitrate retention controls how much of the incoming anions from deposition reach the lake/ stream. The degree of base cation mobilization controls the cation composition entering surface waters. If the entering anions are all balanced by base cations, there is little effect on the acid base status of the water and consequently little effect on aquatic biota. However, if the anions are balanced by significant concentrations of acid cations ( H+, Al), surface water acidity increases and there can be significant adverse effects on many aquatic species. Base cation mobilization is controlled primarily by the composition of the watershed bedrock and soils and is reflected in surface water acid neutralizing capacity ( ANC).

Current Status of Aquatic Resources Lakes in the Southern Appalachians are mostly reservoirs and are not very numerous ( estimated total of 71 lakes > 4 ha in the southern Blue Ridge). The Eastern Lake Survey found no acidic lakes; 5% of the lakes had ANC

50 µ eq/ L and would be considered sensitive to acidic deposition.

Acidic and very low ANC streams are located in small (< 20 km2), upland, forested catchments in areas of base poor bedrock. The National Stream Survey estimated ( in 1986) that of the 62,200 km of streams on 1: 250,000 scale maps in the acid sensitive part of the SAMI region, 815 km ( 1%) were acidic and 4,410 km ( 7%) had ANC

50  eq/ L. In these acidic Southern Appalachian streams, sulfate and nitrate from atmospheric deposition are the dominant source of acid anions, and the low pH ( median = 4.7) and high levels of inorganic monomeric aluminum ( median = 364  g/ L) are causing damage to aquatic biota. Watersheds in the SAMI region are currently retaining significant proportions of the incoming sulfur and nitrogen from acidic deposition.

The SAMI Class I wilderness areas are much more sensitive to acidic deposition than the region as a whole. Based on geology, physiography, and stream chemistry, the 10 Class I areas in the SAMI region can be aggregated into four groups for assessing the aquatic effects of acidic deposition:

1. West Virginia Plateau: Dolly Sods and Otter Creek wilderness areas 2. Northern Blue Ridge: James River Face wilderness area and Shenandoah National Park iv 3. Southern Blue Ridge: Great Smoky Mountains National Park, Joyce Kilmer/ Slickrock, Linville Gorge, Shining Rock, and Cohutta wilderness areas 4. Alabama Plateau: Sipsey wilderness area In terms of adverse aquatic effects of acidic deposition, the four Class I groups can be ranked: West Virginia Plateau >> Northern Blue Ridge > Southern Blue Ridge > Alabama Plateau.

Streams in the West Virginia Plateau Class I areas had the highest percentage of acidic stream length ( 53% in Otter Creek, 82% in Dolly Sods), the highest sulfate and inorganic aluminum concentrations, and the lowest pH of any of the Class I areas. Organic acids play a significant role in a portion ( 13%) of the stream length in Otter Creek, but the rest of the stream length in both areas was dominated by acid anions from deposition. Streams in both Otter Creek and Dolly Sods are heavily impacted by acidic deposition. The Alabama Plateau Class I area ( Sipsey) is of least concern for acidic deposition impacts because sulfate appears to be at steady state with deposition and this area has higher streamwater ANC concentrations.

The Plateau areas retain less sulfate than do the Blue Ridge areas, so any delayed effect of acidic deposition will be more pronounced in the Blue Ridge. Watershed soils in all the Blue Ridge wilderness areas retain most of the sulfate entering from deposition. In these areas, low ANC streams are common and some acidic streams are found in areas of resistant bedrock and/ or higher elevations. Streams in the northern Blue Ridge areas have higher sulfate concentrations than streams in the southern Blue Ridge areas and appear to be more influenced by acidic deposition.

The southern Blue Ridge areas stand out from the other Class I areas in terms of having the highest streamwater nitrate concentrations ( lowest nitrogen retention). It appears that nitrate is breaking through these watersheds and is entering streams in concentrations that approach and sometimes exceed sulfate concentrations.

Few detailed studies of episodic acidification have been conducted in forested watersheds in the Southern Appalachian Mountains. However, results from several field studies suggest that streams in the region with antecedent baseflow ANC values below about 25  eq/ L ( 2,280 km or 4% of the 1: 250,000 scale stream network) may experience substantial depressions in pH (> 0.5 units) and increases in inorganic aluminum concentrations (> 50  g/ L) during major rainstorm and snowmelt periods.

Chemical properties of surface waters that are most important in influencing biological responses to acidic deposition are pH, aluminum, and calcium concentrations.

Many aquatic species cannot survive, reproduce, or compete in acidic waters. Thus, with increasing acidity, the " acid sensitive" species are lost and species richness ( the number of species living in a given lake or stream) declines. These changes in aquatic community structure occur at chronic pH levels < 6.0B6.5. Ecosystem level processes, such as decomposition, nutrient cycling, and productivity, are fairly robust and are affected only at relatively high levels of acidity ( e. g., chronic pH < 5.0B5.5).

Biological damage is occurring in this region due to the high levels of inorganic aluminum and low pH in acidic streams. Direct quantification of the extent of biological effects, however, is not possible from existing data.

Current Trends in Acidification Impacts There are few long term monitoring sites in the SAMI region from which to draw conclusions about trends. In the control water v sheds at Coweeta ( North Carolina Blue Ridge) and White Oak Run in Shenandoah National Park, sulfate concentrations in streamwater have been increasing over the last 10 20 years. The sulfate increases at these sites are consistent with a gradual saturation of soils in the region with sulfate from deposition, and have been predicted by acidification models.

It is likely that many parts of the SAMI region have undergone increases in stream nitrate over the past several decades. At Fernow Experimental Forest in the West Virginia Appalachian Plateau, streamwater nitrate concentrations have increased from near zero to 50B60  eq/ L at baseflow from 1970 to the present. In the Great Smoky Mountains National Park, streamwater nitrate shows strong correlations with elevation and forest age, with the highest concentrations occurring at high elevations ( where deposition is highest) and in areas of old growth forest, where biological demand for nitrogen is lowest.

More recently, chemical trends in Shenandoah National Park have been altered as a result of forest defoliation by gypsy moth larvae. Defoliation has resulted in large increases in streamwater nitrate, decreases in sulfate, and little change in ANC or pH at baseflow.

Data do not exist to determine trends in the episodic acidification of surface waters related to atmospheric deposition in the Southern Appalachian Mountains. However, episodic mobilization of nitrate resulting from recent forest defoliation by the gypsy moth caterpillar has been shown to exacerbate episodic changes in ANC, pH, and aluminum in streams in the region.

There are virtually no data from which to draw quantitative conclusions about recent trends in biological condition due to acidification Methodologies for Predicting Impacts of Acidic Deposition on Aquatic Resources The two dynamic watershed models that would be most useful for a SAMI assessment are ILWAS and MAGIC. Both these models attempt to describe the major processes controlling surface water response to acidic deposition and require information on deposition, watershed attributes, soils, hydrologic flow, and water chemistry. ILWAS models more processes with more compartments than MAGIC and thus requires more data input and has a greater computational complexity. Both models were extensively tested in the National Acid Precipitation Assessment Program ( NAPAP) and there was no evidence that either model was more accurate than the other. Most of the NAPAP modeling effort focused on sulfur dynamics. A number of models that examine nitrogen dynamics have been developed in the past few years ( MAGICWAND MERLIN, PnET CN).

Several models are available for predicting future episodic effects on surface waters in the region; these models were all developed by linking a long term acidification model ( e. g., MAGIC) with a hydrological mixing model ( e. g., a two component mixing model). Although major uncertainties are associated with applying any of these models, the models are expected to predict the occurrence of biologically significant episodic effects prior to the onset of chronic acidification effects.

Modeling of biotic effects of acidic deposition has focused mainly on fish. Fish effects models are either empirical, toxicity based, or a combination of the two. The model used in the NAPAP assessment was based on calculating an Acid Stress Index ( ASI) derived from surface water pH, ANC, and inorganic aluminum. The ASI values were related to field observations of fish distributions to set critical ASI values for effects on sensitive, intermediate, and tolerant fish species. vi Results from NAPAP Assessments The Direct/ Delayed Response Project and the NAPAP Integrated Assessment projected future acidification based on the MAGIC model at a subset of the National Stream Survey sites in the mid Appalachians ( Pennsylvania, Maryland, Virginia, West Virginia) and the southern Blue Ridge.

NAPAP future projections ( 50 year) in the mid Appalachians show that at 1985 rates of deposition, the number of acidic streams is projected to triple, while the number with ANC

50  eq/ L would increase by a factor of 1.6. At sulfur deposition 20% and 30% greater than 1985 levels, the number of acidic streams is projected to increase by factors of 5.4 and 6.2, respectively. A 20% to 30% reduction in sulfur deposition would be necessary to prevent further acidification.

NAPAP future projections ( 50 year) in the southern Blue Ridge show that 1985 deposition rates are projected to increase the percentage of acidic streams from 0 to 10%; the number of streams with ANC

50  eq/ L is projected to increase by a factor of 1.6. At sulfur deposition 20% and 30% greater than 1985 levels, the number of acidic streams is projected to increase to 10% of the modeled population; the number of streams with ANC

50  eq/ L would increase by a factor of 2.2. A 30% to 50% reduction in sulfur deposition would be necessary to prevent further acidification

Recommendations for SAMI Assessment We recommend that MAGIC be used to model surface water acid base chemistry and that the PnET CN model be used to input time to nitrogen saturation into MAGIC. We also recommend that the regression approach of Eshleman be applied to MAGIC projections to predict episodic changes in stream chemistry. For modeling effects on fish, we recommend the acid stress index ( ASI) approach. We have outlined four possible levels of effort for the SAMI assessment:

1. Level 1: Qualitative summary of existing modeling information 2. Level 2: Re run MAGIC model at existing regional network sites with new SAMI deposition scenarios.

3. Level 3: Collect new field data and run the MAGIC model for three acidic/ low ANC sites in each of the Class I wilderness area groups ( e. g., West Virginia Plateau). Also collect the information needed to run the PnET CN nitrogen model and the episodic acidification model. Do for one, two, three, or all groups as resources allow.

4. Level 4: Do Level 3 analyses for the regional network of sites in the SAMI region.

Fish Effects: Fish effects can be added through the ASI approach in levels 2B4. However, field information on the relationship between fish distributions and ASI values needs to be collected and evaluated to set critical ASI levels.

Uncertainties in the absolute magnitudes and timing of aquatic effects projections are high, but we have confidence in the projected direction of change and in the relative amounts of change. Thus, we are fairly comfortable with running the models and making conclusions about the relative differences in aquatic effects among different deposition scenarios. However, we are uncomfortable with using the absolute results ( e. g., acidic stream length or stream length that has lost fish due to acidic deposition) of these models because of their high uncertainty. We are very uncomfortable with taking these absolute results, linking them together with absolute results from other effects models ( e. g., vii visibility, ozone), running them all through a socio economic valuation model, and using some kind of overall " cost" estimate as the decision making tool for evaluating different emissions scenarios. viii ix TABLE OF CONTENTS Section Page Executive Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii List of Illustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiii Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xiv Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv 1. INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2 The SAMI Region . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. FACTORS CONTROLLING AQUATIC RESPONSE TO ACIDIC DEPOSITION . . . . . . 4 2.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 Acidic Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2.1 Current Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2.2 Historical Evidence for Acidification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.3 Hydrologic Flow Path . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4 Anion Mobility/ Retention . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4.1 Sulfur . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4.2 Nitrogen . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.5 In lake and In stream Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2.6 Other Acidity Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 3. CURRENT STATUS OF AQUATIC RESOURCES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1 Surface Water Acid Base Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.1 Regional Status . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 <IP_ADDRESS> Lakes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 <IP_ADDRESS> Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1.2 Relationship of Stream ANC to Geology . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.1.3 Detailed Analysis of Class I Areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 <IP_ADDRESS> West Virginia Appalachian Plateau . . . . . . . . . . . . . . . . . . . . . . . . . 20 <IP_ADDRESS> Northern Blue Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 <IP_ADDRESS> Southern Blue Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 <IP_ADDRESS> Alabama Appalachian Plateau . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.1.4 Class I Area Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 3.2 Episodic Chemical Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2.1 Synopsis of Synthesis Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 3.2.2 Current Episodic Impacts in the Southern Appalachians . . . . . . . . . . . . . . . . . 35 <IP_ADDRESS> Local Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 <IP_ADDRESS> Regional Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 3.3 Biological Effects of Acidic Deposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 x 3.3.1 Synopsis of Synthesis Documents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 <IP_ADDRESS> Chemical Factors Influencing Biota . . . . . . . . . . . . . . . . . . . . . . . . . 38 <IP_ADDRESS> Effects on Species Richness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 <IP_ADDRESS> Effects on Ecosystem Level Processes . . . . . . . . . . . . . . . . . . . . . . . 39 <IP_ADDRESS> Recovery of Biological Communities . . . . . . . . . . . . . . . . . . . . . . . . 39 <IP_ADDRESS> Developing Regional Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 <IP_ADDRESS> Documentation of Effects on Fish . . . . . . . . . . . . . . . . . . . . . . . . . . 40 3.3.2 Current Biological Impacts in the Southern Appalachians . . . . . . . . . . . . . . . . 40 <IP_ADDRESS> Mid Appalachians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 <IP_ADDRESS> Interior Southeast Streams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 4. RECENT TRENDS IN ACIDIFICATION IN THE SOUTHERN APPALACHIANS . . . . 44 4.1 Trends in Surface Water Chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.2 Trends in Episodic Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 4.3 Trends in Biological Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 5. METHODOLOGIES FOR PREDICTING FUTURE EFFECTS OF ACIDIC DEPOSITION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.1 Surface Water ChemistryModels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.1.1 Steady state Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 5.1.2 Dynamic Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 <IP_ADDRESS> ILWAS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 <IP_ADDRESS> MAGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 5.1.3 Nitrogen Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 <IP_ADDRESS> Model of Acidification of Groundwater in Catchments B With Aggregated Nitrogen Dynamics ( MAGICBWAND) . . . . . . . . . . . . . 49 <IP_ADDRESS> Model of Ecosystem Retention and Loss of Inorganic Nitrogen ( MERLIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 <IP_ADDRESS> Net Photosynthesis and Evapo Transpiration ( PnET) B Carbon and Nitrogen ( CN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 5.2 Episodic Chemical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 5.3 Modeling the Effects of Acidic Deposition on Fish Communities . . . . . . . . . . . . . . . . 50 5.3.1 Empirical Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50 5.3.2 Toxicity Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51 5.3.3 Combined Toxicity Field Models C the Acid Stress Index . . . . . . . . . . . . . . . 51 <IP_ADDRESS> Acid Stress Index Model Structure . . . . . . . . . . . . . . . . . . . . . . . . . . 52 <IP_ADDRESS> Acid Stress Index Model Evaluation . . . . . . . . . . . . . . . . . . . . . . . . . 53 6. PREDICTIVE STUDIES OF ACIDIC DEPOSITION EFFECTS IN THE SOUTHERN APPALACHIANS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.1 NAPAP Modeling Efforts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 6.1.1 Model Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 <IP_ADDRESS> Sensitivity to Acidification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 xi <IP_ADDRESS> Projections for Current and Increased Deposition . . . . . . . . . . . . . . 56 <IP_ADDRESS> Reduced Deposition Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 <IP_ADDRESS> Chemical Conditions for Fish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58 <IP_ADDRESS> Uncertainties in Model Projections . . . . . . . . . . . . . . . . . . . . . . . . . 58 6.2 Nitrogen Bounding Study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 7. RECOMMENDATIONS FOR SAMI ASSESSMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 7.1 Model Recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 7.2 Levels of Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60 7.2.1 Level 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 7.2.2 Level 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 7.2.3 Level 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61 7.2.4 Level 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 7.2.5 Fish Assessment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 7.3 Limitations and Relationship to a SAMI Integrated Assessment . . . . . . . . . . . . . . . . . 62 7.4 Data Availability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 8. LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 9. ANNOTATED BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70 APPENDIX A B Stream Networks in the SAMI Class I Wilderness Areas . . . . . . . . . . . . . . . . 83 xii LIST OF ILLUSTRATIONS Figure Page Figure 1 Map of the Southern Appalachian study area showing the location of the Class I wilderness areas . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Figure 2 Conceptual diagram of ( a) major processes and ( b) hydrologic flowpaths that control surface water acid base chemistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Figure 3 Annual 1995 volume weighted pH in wet deposition in the United States measured at the field laboratories in the National Acid Deposition Program/ National Trends Network sites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Figure 4 Map of the acid sensitive part of the Southern Appalachians sampled in the National Stream Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Figure 5 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Dolly Sods wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Figure 6 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Otter Creek wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Figure 7 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the James River Face wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . 24 Figure 8 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Joyce Kilmer/ Slickrock wilderness area . . . . . . . . . . . . . . . . . . . . 27 Figure 9 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Shining Rock wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 Figure 10 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Cohutta wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Figure 11 Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Sipsey wilderness area . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Figure 12 Future projections of stream ANC and pH after 50 years for 6 sulfate deposition scenarios for ( a) Mid Atlantic Highlands and ( b) Southern Blue Ridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57 xiii LIST OF TABLES Table Page Table 1 Estimates of Regional Acid base Status for Streams and Lakes in the Southern Appalachians from National Surface Water Survey Data . . . . . . . . . . . . 13 Table 2 Median Values for Major Ion Chemistry in Streams in Class I Wilderness Areas and in the entire Southern Appalachians . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Table 3 Surface Area and Stream Length at 1: 100,000 and 1: 24,000 Map Scales for Streams in the Southern Appalachians and in Class I Wilderness Areas . . . . . . 16 Table 4 Observed and Estimated Steady state Sulfur and Nitrogen Concentrations for Streams in Class I Wilderness Areas of the Southern Appalachians . . . . . . . . . 18 Table 5 Length of Stream ( km) in Various ANC Classes in Class I Wilderness Areas in the Southern Appalachians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Table 6 Summary of Acidic and Acid sensitive Stream percentages in Class I Wilderness Areas and Other Aggregate Physiographic Regions of the Southern Appalachians . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Table 7 General Summary of Biological Changes Anticipated with Surface Water Acidification, Expressed as a Change in pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 xiv ACKNOWLEDGEMENTS This study was funded by the Southern Appalachian Mountains Initiative ( SAMI). We'd like to thank Rebecca Kemp, then Coordinator of SAMI's Technical Oversight Committee, and Leslie Cox, SAMI Coordinator, for smoothly handling all administrative aspects of the project with SAMI. We'd also like to thank Rick Webb, the SAMI work assignment manager, for guidance and reviews of early drafts of the report. The report also benefitted from review comments from a number of SAMI members. Data for the Class I wilderness areas was kindly provided by Rick Webb and Frank Deviney from University of Virginia ( Otter Creek, Dolly Sods, and James River Face), Terry Flum from University of Tennessee ( Smokies), and Richard Burns, Bill Jackson, and David Wergowske of the U. S. Forest Service ( Shining Rock, Slickrock, Sipsey and Cohutta). Gary Lear from NADP provided the national 1995 deposition pH map. Finally, we'd like to acknowledge Charley Barrett for digitizing the Class I stream networks, GIS work, and map production, and Susan Christie for technical editing and producing the final report. xv GLOSSARY ANC Acid Neutralizing Capacity ASI Acid Stress Index DDRP Direct/ Delayed Response Project DOC Dissolved Organic Carbon ELS Eastern Lake Survey EPA Environmental Protection Agency ETD Enhanced Trickle Down FISH Fish in Sensitive Habitats ( Shenandoah National Park Project)

GSMNP Great Smoky Mountains National Park IA Integrated Assessment ( 1990 NAPAP report)

ILWAS Integrated Lake Watershed Acidification Study LAF Lake Acidification and Fisheries model MAGIC Model of Acidification of Groundwater in Catchments MAGIC WAND MAGIC  With Aggregated Nitrogen Dynamics model MERLIN Model of Ecosystem Retention and Loss of Inorganic Nitrogen MIDAPP Mid Appalachians ( as region modeled in DDRP)

N Nitrogen NADP/ NTN National Atmospheric Deposition Program/ National Trends Network NAPAP National Acid Precipitation Assessment Program NBS Nitrogen Bounding Study NHEERL National Health and Environmental Effects Research Laboratory NSS National Stream Survey NSWS National Surface Water Survey PnET CN Net Photosynthesis and Evapo Transpiration ( PnET)  Carbon and Nitrogen ( CN) model S Sulfur SAMI Southern Appalachian Mountains Initiative SBRP Southern Blue Ridge Province ( as region modeled in DDRP and IA)

SOS/ T State of Science/ Technology ( 1990 NAPAP reports)

USGS United States Geological Survey VTSSS Virginia Trout Stream Sensitivity Study xvi 1 1. INTRODUCTION The Southern Appalachian Mountains Initiative ( SAMI) was established to address concerns about the adverse effects of air pollution on environmental resources in the Southern Appalachians. Acidic deposition and its effects on surface waters is a major issue associated with air pollution in this area. For this study, we define the Southern Appalachians as the Blue Ridge, Ridge and Valley, and Appalachian Plateau provinces ( as defined by Fenneman, 1938) in the states of Alabama, Georgia, Kentucky, North Carolina, South Carolina, Tennessee, Virginia, and West Virginia ( Figure 1). This report has two main objectives:

1. Summarize the existing state of knowledge about the effects of acidic deposition on surface water resources in the Southern Appalachians. 2. Evaluate and make recommendations on the use of available methodologies for predicting future changes in the aquatic effects of acidic deposition in the Southern Appalachians under alternate deposition scenarios.

In this report, we examine the SAMI region as a whole, but the primary focus is on the 10 Class I wilderness areas located in the Southern Appalachians ( Figure 1).

A comprehensive study of the effects of acidic deposition in the United States was completed under the National Acid Precipitation Assessment Program ( NAPAP) in 1990. This study was documented in the 27 volumes of NAPAP's State of Science/ Technology ( SOS/ T) report. The following six reports pertain to our objectives:

SOS/ T # 9 Current Status of Surface Water Acid Base Chemistry L. Baker et al., 1990 SOS/ T # 10 Watershed & Lake Processes Affecting Surface Water... Turner et al., 1990 SOS/ T # 11 Historical Changes in Surface Water Acid Base Chem... Sullivan, 1990 SOS/ T # 12 Episodic Acidification of Surface Water ... Wigington et al., 1990 SOS/ T # 13 Biological Effects of Changes in Surface Water ... J. Baker et al., 1990 SOS/ T # 14 Methods for Projecting Future Changes in Surface ... Thornton et al., 1990 These SOS/ T reports contain detailed reference lists that document the work done before 1990. In general, we cite the appropriate SOS/ T report for our summaries and conclusions rather than all the pertinent pre 1990 literature. To bridge the gap between 1990 and 1995, we have compiled an annotated bibliography of pertinent literature published after 1990. The annotated bibliography focuses on surface waters in the SAMI region but it also includes some citations relating to acidic deposition effects in general.

The first part of this report summarizes our current understanding of acidic deposition effects, broken down into sections on important processes ( Section 2), current status of aquatic resources ( Section 3), and current trends in acidification ( Section 4). Each section addresses surface water chemistry, episodic effects, and biological effects. A 2 Figure 1. Map of the Southern Appalachian study area showing the location of the Class I wilderness areas. 3 review of assessment methodologies appears in Section 5, followed by results from other predictive assessments in Section 6. Section 7 provides recommendations for the SAMI assessment. The report concludes with an annotated bibliography of post 1990 literature in Section 9.

1.1 Terminology The terminology used to describe acidbase status can get rather confusing. In order to avoid problems, we follow the conventions developed during NAPAP. In brief, it is important to understand the following distinctions:

Acidity is the amount of acid in a sample, usually measured on the pH scale (  log[ H+]).

Acid Neutralizing Capacity ( ANC) is a measure of the ability of a water sample to neutralize acid inputs ( determined by acid titration). ANC is used as the main indicator of the sensitivity of a surface water to acid inputs.

Acidic refers to a water sample that has lost all ANC. By definition, we consider waters with ANC

0 to be acidic ( not pH < 7). Most waters with ANC

0 have pH < 5.3.

Acidification refers to declines in ANC or pH over time. Acidified waters had higher ANC or pH in the past. A lake or stream may have acidified but not be acidic ( e. g., ANC decline from 80 to 40  eq/ L).

1.2 The SAMI Region The SAMI region consists of three, somewhat linear, southwest to northeast trending physiographic provinces. From east to west, they are the Blue Ridge Mountains, Valley and Ridge, and Appalachian Plateau ( Figure 1). Streams are the dominant aquatic resource in this region.

In Virginia, the Blue Ridge Mountains make up a narrow complex ridge lying between the Piedmont and the Great Valley of the Valley and Ridge Province ( Figure 1). In the southern Blue Ridge, the range broadens into a range of uniformly dissected mountains with elevations ranging from 500 m to 2000 m above sea level. The highest mountains in the eastern United States are found in the southern Blue Ridge. Bedrock typically is composed of Cambrian and Precambrian metamorphosed sedimentary and complex gneissic and plutonic rocks.

The Valley and Ridge Province ( Figure 1) is composed of a series of folded Paleozoic sedimentary rock layers, resulting in a sequence of valleys separated by narrow, parallel, linear ridges. The ridges typically are composed of more resistant sandstones, whereas limestone and shale formations are common in the valley bottoms. The proportion of ridge area to valley area is quite variable throughout the province. The streams often show a trellis drainage pattern due to the valley and ridge structure.

In West Virginia, the Appalachian Plateau Province ( Figure 1) is separated from the Valley and Ridge Province to the east by a steep outfacing escarpment ( e. g., Allegheny Front). The southern part of the Appalachian Plateau is often referred to as the Cumberland Plateau. The rocks in the Appalachian Plateau Province are younger than those in the other provinces, and clastic conglomerates, sandstones and shales predominate. The mountains of the Appalachian Plateau are the result of severe plateau dissection. 4 2. FACTORS CONTROLLING AQUATIC RESPONSE TO ACIDIC DEPOSITION 2.1 Overview Watershed soils/ geology and hydrology are the major factors controlling streamwater ANC response to acidic deposition. In fact, on a regional scale, there is no relationship between deposition and surface water ANC ( L. Baker et al., 1990). Two watersheds a mile apart can have vastly different responses to acidic deposition; one can be acidic, while the other is so well buffered that deposition poses no problem. Quantifying the effects on any one stream will tell very little about the effects across the region. Thus, a study of the effects of acidic deposition should be related to the population of streams in the study region.

The NAPAP SOS/ T Processes Report summarizes the major processes influencing the response of surface water acid base chemistry to acidic deposition. Figure 2 presents a summary figure from that report ( Turner et al., 1990). For the SAMI region, the two most important processes are base cation neutralization reactions ( cation exchange, geologic weathering) and anion retention/ mobility ( Elwood, 1991). The synthesis statement of Turner et al. ( 1990) provides a summary of the effects of acidic deposition on surface waters:

" The magnitude of change in water chemistry parameters in response to acidic deposition and changes in watershed drainage chemistry may range from an equivalent increase in base cation concentrations to a reduction of 50 or more  eq/ L ANC, to a shift from a low ANC or acidic, organic dominated system, or to a sulfate dominated system with little change in ANC or pH. The first response is probably most common. In the latter two cases, the net effect of atmospheric deposition of S on lake and stream chemistry is a shift toward systems that are dominated by mineral acidity and that have higher concentrations of inorganic aluminum which is toxic to aquatic organisms."

In the SAMI region, the major control that determines the ability of a watershed to buffer its surface waters against the influence of acidic deposition is its base cation mobilization ability. Watersheds that have soils with high base saturation/ cation exchange capacity and/ or highly weatherable geologic material have streams and lakes virtually unaffected by acidic deposition. The abundance of available base cations in these systems balances the added sulfate/ nitrate from deposition, preventing any depression of ANC or pH. Systems that can't balance the added sulfate/ nitrate from deposition with base cations have decreased ANC/ pH and/ or increased inorganic aluminum. In the SAMI region, the most important factors controlling the supply of base cations are the watershed soil and the bedrock type.

2.2 Acidic Deposition 2.2.1 Current Pattern Relative to " pristine" deposition, acidic deposition contains elevated concentrations of sulfate, nitrate, acidity, base cations, and ammonia. There are two types of deposition: wet ( e. g., rain, snow, sleet, hail) and dry ( e. g., aerosols, gases, particulates). The amount and content of wet deposition are much better known than the amount and content of dry deposition. Deposition throughout the SAMI area would be considered acidic ( Figure 3). In the Southern Appalachians, the amount of 5 Figure 2. Conceptual diagram of ( a) major processes and ( b) hydrologic flowpaths that control surface water acid base chemistry. Taken from Figure 10 41 in Turner et al., 1990. 6 7 acidic deposition decreases from north to south. For example, if we use the volume weighted 1995 wet deposition pH as an indicator of acidic deposition, the deposition in northern West Virginia ( pH= 4.3) has twice the acidity ( pH is log scale) of that in northern Alabama ( pH= 4.6). Similar patterns occur in the deposition of sulfate and nitrate, as well ( NADP/ NTN, 1996).

On a national scale, there is a close relationship between sulfate deposition and sulfate concentration in lakes and streams ( L. Baker et al., 1990). The same general pattern is evident, although less clear, for the relationship between nitrate/ ammonia deposition and nitrate concentration in streams of the eastern United States ( Kaufmann et al., 1991). Lakes and streams in the SAMI region are an exception to the national deposition/ surface water sulfate relationship. Sulfate concentrations in these southeastern lakes and streams are much lower than would be expected, given their sulfate deposition levels, due to substantial retention of sulfate by adsorption in the soils of their watershed.

2.2.2 Historical Evidence for Acidification It would be very valuable if the current status of acid sensitive streams in the region covered by SAMI could be placed in a historical contextCthat is, if we could know the acid base status of streams in the region in pre industrial times. No historical data are available for streams in this region, however, and the kinds of retrospective techniques ( e. g., paleolimnology) that yield historical records in other regions ( Sullivan et al., 1992) are not applicable to streams. Historical data from the Catskill Mountains, a northern extension of the same physiographic province that makes up much of the SAMI region, suggest that large changes in streamwater chemistry have occurred ( Stoddard, 1991). While small streams in the Catskills show signs of acidification over the past 50 years, many large streams have actually increased in ANC and base cation concentrations, presumably due to watershed disturbances.

In the absence of historical information on stream chemistry and biology for the SAMI region, we are forced to use a historical context based on deposition and estimated deposition. Husar et al. ( 1991) report that the northern and southern parts of the SAMI region probably have experienced differences in historical sulfur deposition. In West Virginia and Virginia, S deposition rates rose from a background near 4 kg/ ha/ yr in the late 1800s to a peak near 30 kg/ ha/ yr around 1970. Since that time, S deposition rates have declined, although they still remain high, relative to background rates ( ca. 25 kg/ ha/ yr).

In the southern Blue Ridge, S deposition rates were not significantly different from background rates prior to the 1950s. Husar et al. ( 1991) also report similar information for Florida, and it seems likely that the region from the southern Blue Ridge southward has undergone the same history. Beginning in the 1960s, S deposition increased significantly in this region, to near 20 kg/ ha/ yr, and there was no evidence of a decline in deposition through 1984, the last year of data reported by Husar et al. ( 1991).

Similar historical estimates for nitrogen deposition are not available, because of the difficulty of translating nitrogen emissions rates into reliable estimates of deposition ( Husar, 1986). Husar et al. ( 1991) do document the changes in N emissions that have occurred in the area upwind of the southeastern United States. Nitrogen emissions began rising ca. 1900, with a significant part of the increase occurring after 1940. Current rates of emission ( ca. 7 million tons of NO 2 per year) in the Southeast are almost twice those in the northeastern United States.

2.3 Hydrologic Flow Path 8 Watersheds in which the greatest proportion of the flow is through shallow, more acidic soils have surface waters with lower ANC than watersheds in which a large proportion of the flow is through deeper, more weatherable materials. The longer the flowpath the more intimate the contact with weathering soil and rock and the longer the time available to acquire solutes through biogeochemical reactions ( Turner et al., 1990).

2.4 Anion Mobility/ Retention Watershed soils typically contain acid cations ( H+, Aln+) in abundance. The mobile anion hypothesis explains how acid anions ( bicarbonate, sulfate, nitrate, organics) are needed to transport acid cations from soils into lakes and streams. Thus, cation leaching in soils is controlled by the availability of mobile anions. In systems affected by acidic deposition, elevated levels of SO 4 2

and NO 3

leach either equivalent amounts of base cations ( medium to high base saturation soils) or acid cations ( low base saturation soils). Thus, the mobility of the SO 4 2

and NO 3

through the watersheds is an important factor controlling the response of surface waters to acidic deposition ( Turner et al., 1990). If all the SO 4 2

and NO 3

derived from deposition were retained within the watershed, there would be little surface water response to acidic deposition.

2.4.1 Sulfur Of the two major anions in deposition, SO 4 2

received a major share of the attention during the NAPAP process. In many parts of the United States, there is little retention of SO 4 2

within the watershed. Observed lake/ stream SO 4 2

concentrations are roughly the same as calculated surface water SO 4 2

concentrations assuming evapoconcentration of SO 4 2

in deposition. These surface waters are considered to be in " steady state" with SO 4 2

in deposition. A notable exception to this pattern is represented by the lakes and streams in the southeastern United States, where most of the incoming SO 4 2

is retained in the watershed and does not reach the lake or stream ( L. Baker et al., 1990). The H+ and Aln+ in soils thus does not reach the lake or stream either.

Soils adsorb SO 4 2

according to a concentration dependent function. They continue to adsorb SO 4 2

until the concentration of adsorbed SO 4 2

reaches equilibrium with SO 4 2

in the soil solution. Different soils have different equilibrium points and SO 4 2

adsorption capacities. The adsorption capacity is thought to be directly related to the amount of Fe/ Al oxide in soil and inversely related to soil pH and organic matter content. The higher the SO 4 2

adsorption capacity, the longer it will take for atmospherically derived SO 4 2

to break through the watershed and enter surface water. In the Southern Appalachians, much of the SO 4 2

is still being adsorbed in the watershed and the response to atmospheric deposition is considered to be " delayed." Watersheds currently in SO 4 2

steady state either never had much SO 4 2

adsorption capacity or the SO 4 2

adsorption sites have been filled by a longer history of deposition, such that their response to SO 4 2

deposition is considered " direct." A big remaining question is the reversibility of SO 4 2

adsorption. It is not well known what happens when SO 4 2

deposition declines. It is likely that SO 4 2

adsorption will show some degree of irreversibility; SO 4 2

desorption will not follow the same path as adsorption ( Turner et al., 1990).

2.4.2 Nitrogen In the past several years, our scientific understanding of the impacts of long term N deposition to forested watersheds has undergone significant improvement. Although S deposition has been the focus of most research on acid deposition effects in the past decades, we now recognize that N deposition is also a 9 threat to the integrity of aquatic and terrestrial systems, especially in areas that historically have received elevated levels of N deposition ( Aber et al., 1989; Driscoll and Schaefer, 1989; Murdoch and Stoddard, 1992). The danger is that relatively undisturbed watersheds aside from elevated deposition, may through time become N saturated. Nitrogen saturation has been variously defined, but central to all definitions is the concept that the supply of nitrogenous compounds from the atmosphere exceeds the demand for these compounds on the part of watershed plants and microbes ( Skeffington and Wilson, 1988; Aber et al., 1989). Under conditions of N saturation, forested watersheds that previously retained nearly all N inputs, due to a high demand for N by plants and microbes, begin to undergo higher loss rates of N. These losses may be in the form of leaching to surface waters or to the atmosphere through denitrification.

The key processes of the N cycle that affect acidification of soils and surface waters are assimilation, mineralization, nitrification, and denitrification. Nitrogen assimilation is the uptake and metabolic use of N by plants and soil microbes. Because N is the most commonly limiting nutrient in forest ecosystems in North America ( Cole and Rapp, 1981; Vitousek and Howarth, 1991), assimilation plays a key role in the development of N saturation. The form of N used by terrestrial ecosystems strongly affects the acidifying potential of N deposition. Ammonium uptake is an acidifying process ( i. e., uptake of NH 4 +

releases one mole of H+ per mole of N assimilated), whereas biological uptake of NO 3

is an alkalinizing process ( i. e., uptake of NO 3

consumes one mole of H+ per mole of N assimilated).

Mineralization is the bacterial decomposition of organic matter, releasing NH 4 + that can subsequently be nitrified to NO 3

. Mineralization is an important process in watersheds as it recycles N that would otherwise be tied up in soil organic matter following the death of plants, or as leaf litter. Nitrification is the oxidation of NH 4 + to NO 3

; it is mediated by bacteria and fungi in both the terrestrial and aquatic parts of watersheds. It is an important process in controlling the form of N released to surface waters by watersheds, as well as in controlling the acid base status of surface waters. Nitrification is a strongly acidifying process, producing two moles of H+ for each mole of nitrogen ( NH 4 +) nitrified. Because nitrification in forest soils transforms NH 4 +

into NO 3

, the acidifying potential of deposition ( attributable to N) is often defined as the sum of NH 4 + and NO 3

, assuming that all N will leave the watershed as NO 3

( Hauhs et al., 1989).

Denitrification is the biological reduction of NO 3

to produce gaseous forms of reduced nitrogen ( N 2 , NO, or N 2 O). Denitrification is an anaerobic process ( i. e., it occurs only in environments where oxygen is absent), whose end product is lost to the atmosphere. It is always an alkalinizing process, consuming one mole of H+ for every mole of N denitrified. In terrestrial ecosystems, denitrification occurs in boggy, poorly drained soils, or in anaerobic microsites. It has traditionally been considered a relatively unimportant process outside of wetlands ( Post et al., 1985), although it may be locally important after such events as spring snowmelt and heavy rain storms, when soil oxygen tension is reduced ( Melillo et al., 1983; Groffman et al., 1993). On a watershed scale, denitrification is not likely to be an important sink for N ( Bowden, 1986; Bowden and Bormann, 1986), because it is limited by the availability of anaerobic sites ( Klemedtsson and Svensson, 1988).

A number of factors may predispose watersheds to become N saturated, including elevated N deposition, stand age, and high soil N pools ( Stoddard, 1994). High rates of N deposition play a clear role, as the ability of 10 forest biomass to accumulate N must be finite. At very high, long term rates of N deposition, the ability of forests and soils to accumulate N is exceeded, and the only remaining pathway for loss of N ( other than runoff) is denitrification High rates of N deposition may favor increased rates of denitrification, but many watersheds lack the conditions necessary for substantial denitrification ( e. g., low oxygen tension, high soil moisture, and temperature).

Another important factor in N loss from watersheds is the age of the forest stands. A loss in the ability to retain N is a natural outcome of forest maturation, as both older trees and those that occur later in a successional sequence grow more slowly and therefore exhibit lower N demand ( Vitousek and Reiners, 1975). Uptake rates of N into vegetation are generally maximal around the time of canopy closure for conifers, and somewhat later ( and at higher rates) in deciduous forests, due to the annual replacement of canopy foliage in these ecosystems ( Turner et al., 1990). Finally, soil N status may also affect N loss rates; where large soil N pools exist, they imply that soil microbial processes that are ordinarily limited by the availability of N are instead limited by some other factor ( e. g., availability of labile organic carbon, or another inorganic nutrient), and contribute to the likelihood that watersheds will leach NO 3

( Johnson, 1992; Joslin et al., 1992). To be N saturated, both the vegetational and soil microbial N demands of a watershed must be fulfilled; the existence of large soil N pools suggests that the second of these requirements may be easily met.

2.5 In lake and In stream Processes A number of processes operating within lakes and streams can modify their acid base chemistry, including SO 4 2

/ NO 3

retention mechanisms and base cation production. These processes are most important, however, in waters with long residence times ( Turner et al., 1990). Thus, they would be expected to be of minor importance in streams and reservoirs in the SAMI region.

2.6 Other Acidity Sources In addition to acidic deposition, the two other major sources of acid anions for lakes and streams are natural organic acids and oxidation of watershed sulfur compounds. Lakes and streams naturally acidic due to organic acids are found in areas where bedrock and soils are resistant to weathering and where there is a large buildup of organic matter. These naturally acidic waters are typically colored from high dissolved organic carbon ( DOC) concentrations and are often found in places of low relief terrain and poor drainage ( Turner et al., 1990). Lakes and streams may also be acidic due to oxidation of naturally occurring sulfur compounds within their watersheds. This process is similar to acidic deposition in that a sulfuric acid solution is carried into the receiving water, but the sulfur source is internal to the watershed rather than deposited on it. The source of the sulfur is usually bedrock that contains sulfide ( e. g., Anakeesta Formation in the Great Smoky Mountains or pyrite ( FeS 2) associated with coal seams in the Appalachian Plateau). Significant SO 4 2

mobilization from internal sources, however, usually requires some kind of watershed disturbance ( mining or road cut) to expose bedrock materials to water/ air. 11 3. CURRENT STATUS OF AQUATIC RESOURCES 3.1 Surface Water Acid Base Chemistry 3.1.1. Regional Status As part of NAPAP, EPA conducted a National Surface Water Survey ( NSWS) of lakes and streams in acid sensitive areas of the United States. In the SAMI area, lakes were sampled in the Southern Blue Ridge subregion during the Eastern Lake Survey ( ELS). The National Stream Survey ( NSS) sampled streams throughout the SAMI region, except for the western parts of the Appalachian Plateau ( Figure 4). The western part of the plateau was not sampled in the NSS because existing data at the time indicated that it had high ANC (> 400  eq/ L).

The results of the NSWS reflect chronic, not worst case episodic, acid base conditions ( see Section 3.2). Due to the probability basis of the sample, and its regional extent, the NSWS is the best picture we have about the regional status and extent of chronic acid base chemistry ( L. Baker et al., 1990). For this report, we have used two ANC criteria to define acid base status: acidic ( ANC

0) and low ANC (

50  eq/ L). In the SAMI region, acidic streams are those most affected by acidic deposition; they typically have pH in the 4' s and low 5' s and they have elevated levels of inorganic monomeric aluminum that is toxic to fish. Surface waters with ANC between 0 and 50  eq/ L are not chronically acidic, but many of them become acidic during storm events or snowmelt ( episodes). During these episodes, they experience the low pH and elevated aluminum levels of chronically acidic systems ( see section 3.2). Acidic deposition does not usually cause substantial environmental impacts in surface waters with ANC > 50  eq/ L.

<IP_ADDRESS> Lakes. In the Southern Blue Ridge subregion, the ELS sampled lakes in both the Piedmont and Blue Ridge physiographic provinces between southern Virginia and northern Georgia ( L. Baker et al., 1990). The following analysis ( Table 1) reflects only those lakes in the Blue Ridge part of the SAMI region. The ELS lake population was determined by listing all lakes ( with surface area > 4 ha) in the study region present on 1: 250,000 scale USGS topographic maps. The ELS sampled 45 lakes in the Blue Ridge during fall 1984, after overturn; 90% of the estimated total population of 71 lakes were reservoirs. It was estimated that 5% of the lakes ( 3 lakes) had ANC

50  eq/ L. No sample lakes were acidic and 1% had pH < 6. The lakes had very low SO 4 2

, NO 3

, and DOC concentrations ( Table 2). Given that most of these lakes are reservoirs, it appears that they have large enough drainage areas to buffer inputs from acidic deposition. For SAMI, lakes can thus be considered of minor interest with respect to acidic deposition impacts due to:

$ The low percentage of sensitive systems $ The low lake density in the study area ( for comparison there are > 2000 lakes in the Adirondack Mountains of New York)

$ Lack of a significant lake resource in the Class I areas Lakes are not discussed further in any of the remaining sections of this report.

<IP_ADDRESS> Streams. The NSS sampled the stream network in the SAMI area present on 1: 250,000 scale USGS topographic maps ( those with watershed areas < 155 km2). The NSS used a randomized, systematic approach to selecting stream segment sample sites. Chemistry was sampled at both the upstream and the downstream ends of each segment ( Kaufmann et al., 1991). In the SAMI study 12 Figure 4. Map of the acid sensitive part of the Southern Appalachians sampled in the National Stream Survey. Areas outside the NSS study boundary were expected to have ANC > 400

eq/ L. 13 Table 1. Estimates of Regional Acid base Status for Streams and Lakes in the Southern Appalachians from National Surface Water Survey Data. For streams, the sampling unit was stream segments. Streams were sampled at both the upstream and downstream ends of each segment. The sampling unit for lakes was individual lakes.

Region Percent ANC

0  eq/ L Upper C Lower End Percent ANC

50  eq/ L Upper C Lower End Estimated Population Total Upper C Lower End Blue Ridge Streams 0% C 0% 12% C 2% 4,850 C 4,350 Valley and Ridge Streams Ridges Valleys 10% C 0%

0% C 0% 25% C 2%

0% C 0% 3,160 C 2,720 2,990 C 4,350 Appalachian Plateau Streams 5% C 2% 31% C 24% 8,940 C 8,780 All Streams 4% C 1% 20% C 11% 19,900 C 20,200 Southern Blue Ridge Lakes 0% 5% 71 region, 306 segment ends were sampled, statistically representing 19,900 upstream segment ends and 20,200 downstream ends ( or 62,000 km of stream). Streams were sampled in the spring during 1985 and 1986. There was a strong upstream/ downstream gradient in the NSS data; ANC increased in the downstream direction due to increasing mobilization of base cations. For example, 12% of the stream segments in the Blue Ridge had low ANC (

50  eq/ L) at the upstream ends versus only 2% at the downstream ends ( Table 1). Overall, 4% of the stream segments were acidic at the upstream ends in the SAMI part of the NSS study area ( 1% at the downstream end).

Of the three physiographic provinces, the Appalachian Plateau had the highest proportion of acidic ( 5%) and low ANC ( 31%) streams. Streams acidic because of acid mine drainage were screened out of the NSS population and are not included in any of the estimates presented here ( Herlihy et al., 1990). In the Valley and Ridge province, the effects of acidic deposition are restricted to the ridges. Low ANC streams are very rare or absent ( none were observed in the NSS sample) in the valleys, due to the easily weatherable bedrock ( e. g., limestone). Streams on the ridges are more sensitive to acidification due to the resistance to weathering of the bedrock geology. Thus ridges have less ability to neutralize acidic deposition. At the upstream ends, 10% of the ridge streams were acidic and 25% had low ANC ( Table 1). The ANC increases rapidly as streams flow down off the ridges. At the downstream ends, none of the sample segments were acidic and only 2% had low ANC.

There is also a gradient in the percentage of acidic and low ANC streams from the northern to the southern parts of the SAMI region. Acidic and low ANC stream segments are more common in Virginia/ West Virginia 14 ( 26%) than in the six southern SAMI states ( 8%). This is probably due to a combination of higher S and N deposition and lower SO 4 2

retention in the more northern watersheds.

The NSS data from the SAMI region indicated that acidic streams and streams with very low ANC were almost all located in small (< 20 km2), upland, forested catchments in areas of base poor, weathering resistant, bedrock ( Herlihy et al., 1993). By interpolating between segment ends, NSS estimates for the whole SAMI region show that of the 62,200 km of stream length on 1: 250,000 scale maps, 815 km ( 1%) were acidic and 4,410 km ( 7%) had ANC

50  eq/ L. Sulfate and NO 3

from atmospheric deposition are the dominant sources of acid anions in these acidic NSS Southern Appalachian streams. As a group, they had low pH ( median = 4.7) and high levels of inorganic monomeric aluminum ( median = 364  g/ L) that can cause damage to aquatic biota ( Table 2).

The NSS data also reflect distinct patterns of SO 4 2

retention among the three physiographic provinces. Streamwater SO 4 2

concentrations in the Appalachian Plateau were near steady state with respect to SO 4 2

deposition whereas Blue Ridge streams were retaining large amounts (> 50%) of incoming SO 4 2

deposition. Valley and Ridge streams showed intermediate levels of SO 4 2

retention ( Herlihy et al., 1993).

3.1.2 Relationship of Stream ANC to Geology Several investigators have described the association between bedrock geology and the ANC of streams in the northern Blue Ridge ( Lynch and Dise, 1985; Bricker and Rice, 1989). Lynch and Dise ( 1985) described a strong correlation ( r2 = 0.95) between bedrock distribution and streamwater ANC in Shenandoah National Park; percentile distributions of streamwater ANC are distinctly different for the park's five major bedrock types. In theory, the distribution of bedrock types within the region should provide a basis for predicting the ANC of unsampled streams in the region, as well as for explaining the ANC of sampled streams. In practice, however the success of this approach on regional scales is limited by the generality of much of the geologic information available for the Southern Appalachians. Herlihy et al. ( 1993) had little success in relating geological information at the 1: 250,000 map scale to stream ANC in data from the 1987 synoptic component of the Virginia Trout Stream Sensitivity Study ( VTSSS). This map scale was too coarse to adequately characterize small streams. Thus, a geological approach to predicting ANC works well in areas for which geologic maps are available at high levels of detail. Just recently, a detailed geologic lithofacies map for the Southern Appalachians has been developed to provide regional scale information on stream ANC ( Peper et al., 1995). It may prove to be a useful tool for regionalizing acidic deposition impacts, but the predictive power of this new map against observed stream ANC needs to be tested.

3.1.3 Detailed Analysis of Class I Areas A major focus of the SAMI effort is to evaluate air pollution effects on the Class I wilderness areas in the Southern Appalachians. Stream networks from both 1: 100,000 scale and 1: 24,000 scale USGS topographic maps were digitized for each of the eight smaller Class I areas ( see Appendix A). Stream networks for the two largest Class I areas ( two national parks) and the region were taken from the digitized version of the 1: 100,000 scale blue line network ( from EPA River Reach File B Version 3).

In the entire SAMI study region ( Figure 1), there are just under 200,000 km of streams at the 1: 100,000 scale ( Table 3). Roughly 60% of this length is in the acid sensitive part 15 Table 2. Median Values ( with First and Third Quartiles in Parentheses) for Major Ion Chemistry in Streams in Class I Wilderness Areas and in the Entire Southern Appalachians. Year( s) of data collection and number of observations ( n) are given below the wilderness area name; data sources are discussed in text.

Wilderness Area ANC (  eq/ L) pH Sulfate (  eq/ L) Nitrate (  eq/ L) Chloride (  eq/ L) DOC ( mg/ L)

Dolly Sods 1994 ( n= 34)  18 (  53   3) 4.7 ( 4.3 5.1) 105 ( 91 115) 4 ( 2 6) 11 ( 9 12) 2.2 ( 1.7 3.1)

Otter Creek 1994 ( n= 63)  28 (  82  11) 4.6 ( 4.1 6.0) 129 ( 111 153) 6 ( 1 14) 9 ( 8 10) 2.0 ( 0.9 3.1)

Shenandoah NP 1981 1982 ( n= 47) 82 ( 21 120) 6.7 ( 6.0 6.9) 85 ( 66 103) 7 ( 3 23) 28 ( 25 32)

James River Face 1991 1994 ( n= 8) 25 ( 22 44) 6.3 ( 6.1 6.5) 68 ( 54 74) 0 ( 0 0) 19 ( 18 20)

Great Smoky Mt. NP 1994 1995 ( n= 337) 44 ( 24 64) 6.4 ( 6.2 6.6) 31 ( 18 46) 15 ( 6 29) 14 ( 12 16)

Joyce Kilmer/ Slickrock 1992 1994 ( n= 9) 70 ( 53 80)   7 ( 6 11)

Shining Rock 1992 1995 ( n= 9) 70 ( 65 80) 6.8 ( 6.7 7.0)  7 ( 6 7)

Cohutta 1992 1994 ( n= 16) 41 ( 26 56) 6.5 ( 6.2 6.6) 35 ( 25 53) 14 ( 9 21) 24 ( 21 28) 1.8 ( 1.4 2.5)

Sipsey 1991 1993 ( n= 30) 245 ( 120 699) 7.3 ( 6.8 7.6) 94 ( 83 106) 2 ( 1 3) 33 ( 32 34) 2.2 ( 1.6 2.7)

SAMI Region Streams a 1986 NSS ( N= 19,940) 172 ( 65 491) 7.1 ( 6.5 7.5) 135 ( 62 229) 16 ( 4 34) 36 ( 18 68) 1.0 ( 0.7 1.7)

Acidic SAMI Streams a 1986 NSS ( N= 730)  24 (  35   24) 4.7 ( 4.5 4.7) 142 ( 117 229) 0.3 ( 0.2 3.5) 16 ( 12 25) 1.4 ( 1.0 1.7)

S. Blue Ridge Lakes a 1984 ELS ( N= 71) 152 ( 87 246) 6.8 ( 6.7 7.0) 29 ( 23 36) 1 ( 0 6) 25 ( 18 42) 1.0 ( 1.2 1.5)

a Regional estimate for SAMI region streams is calculated using National Stream Survey ( NSS) data ( Figure 4) for the upstream segment end population ( extrapolated from 154 sample streams). The Southern Blue Ridge lake estimate is extrapolated from 45 lakes sampled in the Eastern Lake Survey ( L. Baker et al., 1990).

 Not measured, no data found. 16 Table 3. Surface Area and Stream Length at 1: 100,000 and 1: 24,000 Map Scales for Streams in the Southern Appalachians and in Class I Wilderness Areas.

Region Land Area ( km2) 1: 100,000 Scale Stream Length ( km) 1: 24,000 Scale Stream Length ( km)

SAMI REGION Blue Ridge 44,950 40,200

Valley and Ridge 78,980 60,600

Appalachian Plateaus 117,100 97,800

Total SAMI region 240,700 198,600

Acid sensitive part ( NSS boundary) 142,700 117,800

CLASS I AREAS Dolly Sods 43 25 29 Otter Creek 81 57 85 Shenandoah National Park 788 259

James River Face 35 30 44 Great Smoky Mountain National Park 2,300 2,035

Joyce Kilmer/ Slickrock 69 73 159 Linville Gorge 44 21 38 Shining Rock 75 44 102 Cohutta 121 140 208 Sipsey 52 70 108 CLASS I TOTAL 3,608 2,754

 = not determined. 17 of the Southern Appalachians as defined by the NSS study boundary ( Table 3; Figure 4). At the same map scale, there are 2,754 km of streams in the 10 Class I areas ( 1.4% of the total in the SAMI region); 74% of the total Class I stream length is in the Great Smoky Mountains National Park and 9% is in Shenandoah National Park. The eight smaller Class I areas have a total length of 466 km at the 1: 100,000 map scale and 773 km at the 1: 24,000 map scale ( Table 3). Based on geology, physiography, and stream chemistry, the 10 Class I areas in the SAMI region can be aggregated into four groups for assessing the aquatic effects of acidic deposition:

1. West Virginia Plateau: Dolly Sods and Otter Creek wilderness areas 2. Northern Blue Ridge: James River Face wilderness area and Shenandoah National Park 3. Southern Blue Ridge: Great Smoky Mountains National Park and Joyce Kilmer/ Slickrock, Linville Gorge, Shining Rock, and Cohutta wilderness areas 4. Alabama Plateau: Sipsey wilderness area For each of these wilderness areas, we gathered as much information on stream chemistry as possible. Summary statistics of available chemical data can be found in Table 2. We also estimated SO 4 2

and NO 3

steadystate concentrations for each Class I area by identifying the 3 B 5 NSS sample streams closest to each area. As part of the Direct/ Delayed Response Project ( DDRP; Church et al., 1989; 1992), the steady state concentrations of SO 4 2

and NO 3

in streamwater for each NSS site were estimated by interpolating available precipitation, runoff, and S and N deposition isopleths. Sulfate steady state estimates incorporated estimates of dry deposition The N steady state estimates were based on wet deposition only and are almost certainly underestimated ( Table 4). We calculated percent S and N retention for each Class I area using the observed median streamwater concentration for each area and the median of the 3 B 5 steady state estimates from the closest NSS sites. Although these are rather rough estimates, they give a reasonably good picture of the differences in retention capabilities of the Class I areas and the potential for delayed response to acidic deposition.

Available stream chemistry data were also overlain on the digitized 1: 100,000 scale stream network maps. The entire 100,000 scale map stream length was then ordered into the following classes, similar to the ones developed by Herlihy et al. ( 1991) for NSS data:

1. ANC

0 2. 0 < ANC

50  eq/ L 3. ANC > 50  eq/ L 4. Organic dominated ( DOC > 5 mg/ L)

5. No data Stream length between two sample points with the same class was assumed to reflect that class. If the class changed between sample points, the stream length was split in half to reflect each of the sample points. Stream length between a sample point and a confluence or upstream termination was assumed to have the class of the sample point. The stream length in each of the five classes was then calculated from the digitized stream map ( Table 5). A DOC level of 5 mg/ L was used to distinguish streams whose acid anion source is primarily organic, rather than inorganic anions from deposition. None of the available data from the Class I areas had streamwater SO 4 2

concentrations indicative of a predominantly watershed source ( e. g., acid mine drainage). Thus, we did not include a 18 Table 4. Observed and Estimated Steady state Sulfur and Nitrogen Concentrations for Streams in Class I Wilderness Areas of the Southern Appalachians. Observed data are the median concentrations from Table 2. Steady state values are based on precipitation, runoff, and deposition isopleth maps that were interpolated for each NSS site by the DDRP. Value in the table is the median of the 3   5 NSS sample streams closest to each wilderness area. Percent retention is calculated as ( steady state

observed)/ steadystate

100.

Wilderness Area Observed Sulfate (

eq/ L) Steady state Sulfate (

eq/ L) Percent Sulfur Retention Observed NO3+ NH4 (

eq/ L) Steady state NO3+ NH4 (

eq/ L) Percent Nitrogen Retention Dolly Sods 105 177 41% 4 61 93%

Otter Creek 129 177 27% 6 61 90%

Shenandoah NP 85 196 57% 7 93 93%

James River Face 68 213 68% 0 99 100%

Great Smoky Mt. NP 31 104 70% 15 43 65%

Joyce Kilmer/ Slickrock  112  7 46 85%

Shining Rock  86  7 41 83%

Cohutta 35 103 66% 14 40 65%

Sipsey 94 95 1% 2 60 97%

 Not measured, no data found. 19 Table 5. Length of Stream ( km) in Various ANC Classes in Class I Wilderness Areas in the Southern Appalachians. This analysis is based on the 1: 100,000 scale mapped stream length. Year( s) of data collection and number of unique stream sample points ( n) are given below the wilderness area name; data sources are discussed in the text. The percentages below the lengths are based on percent of the total stream length with measured stream chemistry data.

Wilderness Area ANC  0 (

eq/ L) ANC 0 50 (

eq/ L) ANC > 50 (

eq/ L) Organic Dominated No Data Dolly Sods 1994 ( n= 28) 20.6 ( 82%) 4.6 ( 18%) 0 0 0 Otter Creek 1994 ( n= 45) 28.5 ( 53% ) 8.9 ( 17%) 9.4 ( 18%) 6.7 ( 13% ) 3.9 Shenandoah NP 1981 1982 ( n= 47)

( 6%)

( 19%)

( 75%)

James River Face 1991 1994 ( n= 8) 0 20.5 ( 92%) 1.7 ( 8%) 0 7.6 Great Smoky Mt. NP 1994 1995 ( n= 337) 32 ( 4%) 336 ( 46%) 368 ( 50%) 0 1,300 Joyce Kilmer/ Slickrock 1992 1994 ( n= 9) 0 8 ( 36%) 14 ( 64%) 0 51 Shining Rock 1992 1995 ( n= 9) 0 0 10 ( 100%) 0 34 Cohutta 1992 1994 ( n= 15) 0 102 ( 96%) 4.8 ( 4%) 0 33.2 Sipsey 1991 1993 ( n= 10) 0 13.6 ( 37%) 23.3 ( 63%) 0 33.1  = Length estimates not made; percentage estimates based on sample percentages. 20 watershed SO 4 2

source class in this classification system. There were a few sites in the Great Smoky Mountains National Park, however that had SO 4 2

concentrations somewhat higher than typical, indicative of a watershed SO 4 2

contribution from the weathering of bedrock containing sulfide ( Anakeesta formation see section <IP_ADDRESS>).

<IP_ADDRESS>. West Virginia Appalachian Plateau. The Dolly Sods and Otter Creek Class I wilderness areas are located about 25 km apart in the Appalachian Plateau of northeastern West Virginia ( Figure 1). Both areas are drained by a third order ( 1: 100,000 scale) stream. The Dolly Sods wilderness ( 43 km2) is drained by Red Creek but the headwaters of the stream lie outside the wilderness area. The area is mainly a plateau top dissected by Red Creek and its tributaries. Elevations in the Dolly Sods range from 2600 to 3900 ft. The Otter Creek wilderness ( 81 km2) contains almost the entire Otter Creek watershed. Elevations range from 1800 to 3900 ft. Both areas have similar bedrock geology ( West Virginia, 1968), underlain by numerous formations including the Pottsville, Allegheny, Conemaugh, and Mauch Chunk. These formations are dominated by sandstone and shale and are all associated with coal deposits. The geology maps also indicate the presence of Greenbrier limestone in the downstream ends of each of the major creeks. In addition to the streams in the area, there are 7.5 ha of small ponds in the Dolly Sods wilderness. Both wilderness areas also contain vernal pools and a number of bogs and wetlands that serve as habitat for amphibians in the area.

An extensive synoptic survey of chemistry data for the Dolly Sods and Otter Creek wilderness areas was undertaken by the U. S. Forest Service in May, 1994. The survey sampled a total of 78 sites in Otter Creek and 43 sites in Dolly Sods ( Webb, 1995). Figures 5 and 6 show the ANC of the sample sites on the 100,000 scale stream network. The Dolly Sods area is strongly affected by acidic deposition All the streams in the Dolly Sods had ANC

50  eq/ L and 82% of the stream length was acidic ( Table 5). The interquartile range in pH was 4.3 to 5.1. None of the streams had high DOC ( max = 4.7, median = 2.2 mg/ L), so organic acids are unlikely to be an important source of acidity. Some of the vernal pools sampled in Dolly Sods, however, did have high DOC ( max = 10 mg/ L). Sulfate concentrations ( median = 105  eq/ L, Table 2) were lower than steady state estimates ( 177  eq/ L), indicating about 40% retention within the watershed ( Table 4). There was no evidence of any watershed sources of SO 4 2

( maximum stream SO 4 2

= 143  eq/ L). Concentrations of the other acid anions were very low ( Table 2).

In the Otter Creek wilderness, the majority of the stream length was acidic ( 53%), 17% had ANC between 0 and 50  eq/ L, and 18% had ANC > 50  eq/ L ( Table 5; Figure 6). Another 13% of the stream length was heavily influenced by organic anions ( DOC between 5 and 8.5 mg/ L). This stream length is probably influenced more by organic acids than acidic deposition. For the wilderness area as a whole, the interquartile range in pH was 4.1 B 6.0. Interpretation of this information is complicated by the fact that a limestone doser is operated on the main stem of Otter Creek to ameliorate the acidic conditions ( see Figure 6 for location). The resulting chemical change from the doser is quite apparent in Figure 6. The main stem of Otter Creek had high ANC for ~ 4 km and low ANC for ~ 3 km downstream of the doser before becoming acidic again. This section of the creek would probably be acidic in the absence of the limestone additions. The only naturally high ANC stream section is a tributary in the northwest corner of the wilderness area ( Figure 6). Although SO 4 2

concentrations were higher in 21 Figure 5. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Dolly Sods wilderness area. The dots indicate sample sites. 22 Figure 6. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Otter Creek wilderness area. The dots indicate sample sites. 23 Otter Creek than in Dolly Sods ( median of 129 vs. 105

eq/ L), there still do not appear to be any significant watershed sources of SO 4 2

. The maximum SO 4 2

concentration in any stream in Otter Creek was 224

eq/ L, only 26% higher than the expected steady state value of 177

eq/ L for this wilderness area ( Table 5).

In summary, both the Otter Creek and the Dolly Sods wilderness areas in the West Virginia Plateau lie on base poor, resistant bedrock and have very high percentages ( 70%, 100%, respectively) of acidic and low ANC streams. In the vast majority of the systems, the acid anions in the streamwater are dominated by anions from deposition. Among acidic streams in these two areas, inorganic monomeric aluminum concentrations ( interquartile range = 52 B 112

g/ L for Dolly Sods, 140 B 348

g/ L for Otter Creek) were above threshold levels for adverse biological impacts ( see Section 3.3).

It is virtually impossible to quantify the degree of acidification in these systems. Anecdotal reports indicate that these systems were " always acidic" or are " naturally acidic." It is hard to assess what that means quantitatively ( pH < 7?, turns litmus paper red?). It is very difficult to compare ANC and pH measurements of 50 years ago to current measurements. Also, these systems were probably receiving acidic deposition 50 years ago. A likely scenario is that in pre industrial times, these streams had very low ionic strength, almost distilled water supersaturated with CO 2 ( ANC levels of 0 B 20

eq/ L, pH in the low 5s, and little aluminum). If so, then the degree of acidification over the last 150 years would be about 0.5 B 1 pH unit, 20 B 40

eq/ L of ANC, and 50 B 250

g/ L of inorganic aluminum. This would be consistent with the historic pH and ANC changes reported from paleolimnological analysis of sediment cores in many deposition dominated acidic lakes in the Adirondack Mountains of New York ( Sullivan, 1990, Sullivan et al., 1992).

<IP_ADDRESS> Northern Blue Ridge. Shenandoah National Park and the James River Face wilderness area are both located in the Blue Ridge Mountains in the northern and middle parts of Virginia, respectively ( Figure 1). Shenandoah National Park is a thin linear band straddling a 110 km segment of the Blue Ridge ( 788 km2) over an elevation range of 600 B 4050 ft above sea level. Logging, farming and mining occurred in various parts of the park before its establishment in 1935. There are five major bedrock formations in the park: the Old Rag ( a coarsely crystalline granite), Pedlar ( feldspathic granodiorite), Catoctin ( a metamorphosed basalt), Hampton ( phyllite, shale, sandstone, and quartzite), and the Antietam ( sandstone and quatzite) ( Lynch and Dise, 1985). As discussed in Section 3.1.2, there is a strong relationship between geology and ANC in the park. The Hampton and Antietam formations in the southwestern part of the park are most resistant to weathering and have the streams with the lowest ANC. The streams in the park are virtually all first and second order ( 1: 100,000 scale), draining east and west off the crest of the Blue Ridge. The James River Face wilderness area ( 35 km2) is located on the southern bank of the James River, where it cuts through the Blue Ridge Mountains. Elevation ranges from 650 to 2950 ft above sea level. The streams are almost all first order and drain outwards from the high elevation area in the middle of the wilderness area ( Figure 7). The geologic formations in the James River Face are from the Chilhowee Group ( sandstone and quartzite and are similar to the Hampton and Antietam formations found in the southwestern part of Shenandoah National Park. There is also a minor amount of the Pedlar Formation in the James River Face ( Virginia, 1963). 24 Figure 7. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the James River Face wilderness area. The dots indicate sample sites. 25 The most comprehensive survey of streams in Shenandoah National Park was conducted by Lynch and Dise ( 1985) in 1981 and 1982. Sample sites were not selected with a statistical design and we did not attempt to make estimates of the lengths in various chemical classes. Based on flow weighted annual average data from 47 of these sites, covering 70% of the park area, Cosby et al. ( 1991) reported that 6% of the sample sites were acidic and 25% had ANC  50

eq/ L ( Table 5). Over 300 streams were sampled in the mountains of western Virginia as part of the VTSSS ( Cosby et al., 1991). Eight of these sites were within or on streams draining from the James River Face wilderness area ( Figure 7). According to chemistry data from the VTSSS collected at these sites between 1991 and 1994, virtually all ( 92%) the stream length had ANC between 0 and 50

eq/ L ( Table 5). Anion chemistry in the Shenandoah is similar to that of the James River Face; median SO 4 2

values were 85 and 68

eq/ L, and median NO 3

values were 7 and 0

eq/ L, respectively ( Table 2). ANC and pH are lower in the James River Face due to the concentration of more resistant bedrock in that wilderness area compared to Shenandoah Park. Both areas retain most of the incoming SO 4 2

( 57 B 68%) and almost all the incoming N ( Table 4).

<IP_ADDRESS>. Southern Blue Ridge. Most of the land area and stream length in the SAMIregion Class I wilderness areas are in the Great Smoky Mountains National Park ( GSMNP; Table 3). The GSMNP ( 2,300 km2) is located on the Tennessee/ North Carolina border in an area of uplifted sedimentary rock. Elevations in the park range from 900 to 6640 ft. Bedrock is primarily sandstone with some limestone ( Elwood et al., 1991). Many investigators have noted that one of the formations ( Anakeesta) contains pyrite that can be oxidized to sulfuric acid when exposed to air and water during watershed disturbances ( landslides road cuts). The state geologic map also notes the presence of sulfidic bedrock in other formations within the park ( e. g., Copperhill, Boyd Gap; North Carolina, 1985).

Based on a number of biogeochemical studies, the following conclusions can be made about streams in GSMNP ( Silsbee and Larson, 1982; Elwood et al., 1991; Cook et al., 1994; Flum and Nodvin, 1995).

$ As in Shenandoah National Park, bedrock geology is a good predictor of general streamwater ANC status.

$ Low ANC (  50

eq/ L) streams are common in the park.

$ Acidic streams exist in the park, primarily at higher elevations.

$ ANC tends to be lower and NO 3

tends to be higher at higher elevations.

$ Nitrate and SO 4 2

concentrations are comparable in many streams; in higher elevation catchments, NO 3

concentrations are often greater than SO 4 2

concentrations. Streams in watersheds with a history of logging have lower NO 3

than streams in unlogged watersheds. Thus, N/ forest dynamics play a major role in controlling stream anion chemistry in GSMNP.

$ Most of the incoming SO 4 2

and N is retained within the watershed in the majority of the studied streams.

$ Streams that were acidic and had SO 4 2

concentrations > ~ 65

eq/ L probably are influenced by sulfide mineral weathering and are in watersheds containing the Anakeesta Formation.

$ Higher ANC systems (> 100

eq/ L) probably are influenced by limestone weathering and are concentrated in the far western end of the park.

On the 1: 100,000 scale maps, there are 2,035 km of streams. Elwood et al. ( 1991) 26 report a length of 1,173 km of streams in the GSMNP capable of supporting trout and/ or small mouth bass. Flum and Nodvin ( 1995) have conducted a large survey of streamwater chemistry in GSMNP. Using their data, we calculated average spring chemistry for their sample sites by averaging all March, April, and May chemistry data they collected in 1994 and 1995. These streams ( 337 sites) had very low ionic strength, and had median SO 4 2

and NO 3

concentrations of 31

eq/ L and 15

eq/ L, respectively ( Table 2). These medians signify a 70% retention of deposition SO 4 2

and 65% retention of deposition NO 3

( Table 4). These 337 sites represent 736 km of the 2,035 km of streams on the 100,000 scale maps in GSMNP. Of this assessed length, 4% ( 32 km) was acidic and 46% ( 336 km) had ANC between 0 and 50

eq/ L ( Table 5).

The expected steady state SO 4 2

concentration in GSMNP is 104

eq/ L. Typically, SO 4 2

concentrations are much lower than steady state but streams with higher SO 4 2

do exist in GSMNP, probably due to bedrock sulfide weathering. In the Flum and Nodvin ( 1995) data, 9 of the 337 sites had SO 4 2

> 100

eq/ L ( maximum= 248

eq/ L), corresponding to about 8 km of stream length ( 1% of total assessed length). Of the 23 stream sites that were acidic, 11 had SO 4 2

> 65

eq/ L and 1 had SO 4 2

> 100

eq/ L.

The Joyce Kilmer/ Slickrock wilderness area ( 69 km2) contains the headwaters of Slickrock and Little Santeetlah Creeks and is adjacent to the southwest boundary of the GSMNP. As such, it has geology and topography similar to those of the GSMNP and the conclusions listed above for GSMNP are probably applicable to the Slickrock wilderness area. Elevations in the Slickrock wilderness area range from 2000 to 5300 ft and the bedrock geology is composed primarily of the Copperhill ( metagraywacke, slate, schist) and Boyd Gap Formations ( slate, metasiltstone, and metagraywacke). Both formations have notations on the geologic maps indicating that they contain sulfidic bedrock ( North Carolina, 1985). We were able to obtain chemistry data for 9 stream sites in the Slickrock wilderness area from Bill Jackson and Richard Burns with the U. S. Forest Service in Asheville, North Carolina ( Figure 8; unpublished data). These 9 sites represent about 22 km of the 73 km of streams on the 100,000 scale map of the area; about one third of the assessed stream length had ANC between 0 and 50

eq/ L and the rest had ANC > 50

eq/ L ( Table 5).

The Linville Gorge wilderness area covers a stretch of the Linville River roughly 20 km long as it flows through Linville Gorge. Other than the Linville River, there are virtually no aquatic resources in this wilderness area ( see Appendix A). It is highly unlikely that the Linville River is acid sensitive. In any event, water quality is not an air quality related value for the Linville Gorge wilderness area ( Bill Jackson, pers. comm.). Thus, we will not assess its acid base status any further.

The Shining Rock wilderness area ( 75 km2) drains parts of the headwaters of the East Fork of the Pigeon River in North Carolina, just north of the South Carolina border. Elevations in this area range from 3300 to 6000 feet. The bedrock geology is primarily from the Tallulah Falls Formation, a locally sulfidic muscovite biotite gneiss ( North Carolina 1985). We were able to obtain chemistry data for 9 stream sites in the Shining Rock wilderness area from Bill Jackson and Richard Burns with the U. S. Forest Service in Asheville, North Carolina ( Figure 9; unpublished data). All 9 sites had ANC between 50 and 100

eq/ L. These 9 sites represented about 10 km of the 44 km of streams on the 100,000 scale map of the area ( Table 5). 27 Figure 8. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Joyce Kilmer/ Slickrock wilderness area. The dots indicate sample sites. 28 Figure 9. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Shining Rock wilderness area. The dots indicate sample sites. 29 The Cohutta wilderness area ( 121 km2) drains the headwaters of the Conasauga and Jacks rivers in northern Georgia. Elevation ranges from 1000 to 3900 feet and the bedrock is composed primarily of mica and graphite schists, gneiss, and amphibolite ( Georgia, 1976). David Wergowske ( pers. comm.), from the U. S. Forest Service Chattahoochee Oconee National Forest provided streamwater chemical data from 15 sites in the Cohutta. Data were collected during 1992 1994 and represent about threefourths of the 145 km of streams represented on the 1: 100,000 scale maps of the wilderness area ( Figure 10). Virtually all ( 96%) of the sampled stream length had ANC  50

eq/ L but was not acidic ( Table 5). Streamwater chemistry in Cohutta was very similar to that observed in the GSMNP. Streams have very low DOC ( median= 1.8 mg/ L) and high NO 3

concentrations ( median= 14

eq/ L) relative to the rest of the SAMI region. Roughly twothirds of the incoming SO 4 2

and NO 3

is retained within the watershed ( Table 4). Thus, watersheds in Cohutta are " leaking" nitrogen.

<IP_ADDRESS> Alabama Appalachian Plateau. The Sipsey wilderness area ( 52 km2) in northern Alabama is located in the Cumberland Plateau ( southern part of the Appalachian Plateau). The area is drained by Sipsey Fork, formed by the confluence of Thompson and Hubbard creeks. The headwaters of this basin lie outside the wilderness area boundary. Elevation ranges from 500 to 1000 ft. A study of the stream chemistry in the Sipsey wilderness area was undertaken by Dr. G. Milton Ward of the University of Alabama during 1991B1993. He described the results in a series of reports to the U. S. Forest Service ( Ward, 1991, 1992, 1993). Parts of this wilderness area ( around mainstem Sipsey Fork) are underlain by the Bangor limestone formation and the streams draining this formation have such high ANC levels that they are not likely ever to be affected by acidic deposition ( Table 2, Figure 11). Other parts of this wilderness area are drained by bedrock of the Pottsville ( pebbly quartzose sandstone) and Parkwood ( shale, sandstone) formations ( Osborne et al., 1989). These streams have lower ANC and may be sensitive to acidic deposition. Just over half ( 52%) of the 100,000 scale map stream length in the area was sampled for stream chemistry ( Table 2). Sampling was concentrated on the mainstem Sipsey Fork and major tributaries. Within the half of the network that was sampled, 63% ( including Sipsey Fork) had very high ANC ( 200B800

eq/ L) and the other 37% ( 14 km) had ANC levels of 40B50

eq/ L ( Figure 11). In terms of anion chemistry, Sipsey is the only Class I area that appears to be at steady state with respect to SO 4 2

deposition ( i. e., little to no watershed SO 4 2

retention). Thus, a delayed response to S deposition is unlikely in this area. Nitrate, on the other hand, is largely retained in the watershed ( Table 4).

3.1.4 Class I Area Summary Upon comparing results, it is clear that the smaller Class I areas are much more sensitive to acidic deposition ( higher percentages of low ANC streams) than their specific regions as a whole ( Table 6). In terms of adverse aquatic effects of acidic deposition, the four Class I groups can be ranked: West Virginia Plateau >> Northern Blue Ridge > Southern Blue Ridge > Alabama Plateau.

Streams in the West Virginia Plateau Class I areas had the highest percentage of acidic stream length ( 53% in Otter Creek, 82% in Dolly Sods), the highest SO 4 2

and inorganic aluminum concentrations, and the lowest pH of any of the Class I areas. They are currently heavily impacted by acidic deposition. The Sipsey wilderness area is of least concern for acidic deposition impacts because 30 Figure 10. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Cohutta wilderness area. The dots indicate sample sites. 31 Figure 11. Stream ANC classification for the 1: 100,000 scale USGS map stream network in the Sipsey wilderness area. The dots indicate sample sites. 32 Table 6. Summary of Acidic and Acid sensitive Stream Percentages in Class I Wilderness Areas and Other Aggregate Physiographic Regions of the Southern Appalachians. Data for the Class I wilderness area is from Table 5 and is based on the 1: 100,000 scale stream network. % total length assessed refers to the percentage of the length of streams in the region with which there were available data to infer ANC status.

REGION % Assessed Length with ANC

0 (  eq/ L) % Assessed Length with ANC

50 (  eq/ L) Total Length ( km) % Total Length Assessed ( had Data)

WEST VIRGINIA PLATEAU Dolly Sods Wilderness Area 92 100 25 100%

Otter Creek Wilderness Area 53 70 57 93%

Entire Province  NSS ( n= 37) 5 17 14,100 100%

NORTHERN BLUE RIDGE Shenandoah National Park 6** 25** n= 47** **

James River Face Wilderness Area 0 92 30 75%

Entire Province  NSS ( n= 13) 0 4 8,700 100%

Virginia Blue Ridge  VTSSS 6** 42** n= 147** **

SOUTHERN BLUE RIDGE Great Smoky Mt. National Park 4 50 2,035 36%

Slickrock Wilderness Area 0 36 73 30%

Shining Rock Wilderness Area 0 0 44 23%

Cohutta Wilderness Area 0 96 140 77%

Entire Province  NSS ( n= 55) 0 7 10,800 100%

Entire Province  WINGER 2** 4** n= 62** **

ALABAMA PLATEAU Sipsey Wilderness Area 0 37 70 53%

** Estimate reflects percentage of sample size, not length. Representativeness of the sample to the population is unknown and may not accurately reflect the entire population. The sample size used in the estimate is shown in the Total Length column.

VTSSS  Estimates are based on the Virginia Trout Stream Sensitivity Study data ( Webb et al., 1989a).

NSS  Estimates based on weighted extrapolation from probability sample data from the National Stream Survey ( Kaufmann et al., 1988); stream network from 1: 250,000 scale maps.

WINGER  Estimates are based on study by Winger et al., 1987. 33 SO 4 2

appears to be at steady state and it has higher streamwater ANC concentrations. The Plateau areas retain less SO 4 2

than do the Blue Ridge areas so any delayed effect of acidic deposition will be more pronounced in the Blue Ridge. Watersheds in both of the Blue Ridge areas retain the majority of the entering SO 4 2

from deposition. Low ANC streams are common and some acidic streams are found in areas of resistant bedrock and/ or higher elevations. The northern Blue Ridge areas have higher sulfate concentrations than the southern Blue Ridge areas and seem to be more influenced by acidic deposition. The southern Blue Ridge areas stand out from the other Class I areas in terms of having the highest NO 3

concentrations ( lowest N retention It appears that NO 3

is breaking through these watersheds and is entering streams in concentrations that approach and sometimes exceed SO 4 2

concentrations.

3.2 Episodic Chemical Conditions Most of the research on ( and modeling of) acidification of surface waters has dealt with the problem of chronic acidification over relatively long time scales ( years to centuries) and most regional assessments of surface water acid base status have focused on average annual conditions or on so called " index" periods. However, transient changes in acid base status associated with hydrological events ( i. e., those occurring during snowmelt and rainfall periods) represent a potentially important acidification processC known as episodic acidificationCin regions that receive acidic deposition, including the entire SAMI region. In this section of the report, we briefly summarize the synthesis documents pertaining to the problem of episodic acidification of surface waters, namely NAPAP State of Science and Technology Report 12, entitled Episodic Acidification of Surface Waters Due to Acid Deposition ( Wigington et al., 1990), and the NAPAP 1990 Integrated Assessment Report ( NAPAP, 1991). This summary focuses on the factors most likely to control episodic acidification of surface waters and on the techniques that can be used to quantify current regional and localscale episodic acidification impacts. In the second part of the section, we focus our discussion specifically on surface waters of the Southern Appalachians, including those in the Class I wilderness areas.

3.2.1 Synopsis of Synthesis Documents Episodic acidification is defined as the process by which lakes and streams experience short term decreases in ANC, generally during hydrological events and over time scales varying from several hours to several weeks. ANC depressions are usually accompanied by changes in concentration of one or more of the following: hydrogen ion, base cations, dissolved organic carbon, sulfate, nitrate, and various forms of dissolved aluminum. In highly acid sensitive lakes and streams ( chronically low levels of ANC), episodic ANC depressions are usually accompanied by increases in hydrogen ion concentrations ( i. e., decreases in pH) and increases in dissolved aluminum concentrations. These transient increases in hydrogen ion and aluminum concentrations can cause significant nonlethal stress or increased mortality of some species and life stages of fish and other aquatic organisms ( Wigington et al., 1990).

In a thorough review and synthesis of results published from studies of episodic acidification conducted in the United States, Canada, and Europe, Wigington et al. ( 1990) were able to draw four important conclusions:

1. Episodic acidification is a ubiquitous process in streams and drainage lakes and is not necessarily symptomatic of anthropogenically produced chronic acidification ( i. e., episodic acidification occurs both in waters that are chronically acidic and in those that are not). However, episodic and chronic acidification are clearly 34 related, as the magnitude of ANC depressions is usually larger in intermediate to high ANC systems than in low ANC or acidic systems, and the lowest minimum ANC and pH levels occur during episodes in surface waters with low preepisode ANC levels. These observations at least qualitatively support the explanation that ANC dilution is an important component of episodic acidification.

2. The characteristics of episodes are determined largely by changes in hydrological flowpaths during rainfall and snowmelt events. During baseflow periods, streamflow is derived largely from drainage of relatively alkaline groundwater, whereas during stormflow periods, both pre event and event water can be routed through either acidic upper soil layers ( as subsurface stormflow) or across the soil surface as overland flow ( as saturation overland flow). In drainage lakes in cold temperate regions where surface ice forms, inverse thermal stratification accentuates the episodic acidification response by restricting the hydrological mixing of snowmelt and ambient lake water under ice cover.

3. Episodic acidification can be attributed to several different anthropogenic and natural processes, including direct inputs of mineral acids ( sulfuric and nitric) from the atmosphere during events, antecedent deposition of mineral acids to watershed soils ( chronic or antecedent " conditioning hydrological dilution, nitrification, organic acid production, and deposition of neutral sea salts. Any one or several of these mechanisms may be operative in a particular watershed. In many watersheds of the northeastern and mid Atlantic regions of the United States, atmospheric deposition appears to be operating in conjunction with several natural processes to generate episodes with lower minimum ANC and pH and higher dissolved aluminum levels. Most likely atmospheric deposition is affecting episodic acidification in these ( and perhaps other) regions by providing direct inputs to surface waters, by conditioning watersheds during antecedent periods, and by reducing chronic ANC levels. Thus, relatively small ANC depressions are capable of creating acidic, high Al conditions in streams and lakes.

4. Modeling of episodic acidification has been only moderately successful, due primarily to a lack of understanding of hydrological pathways and biogeochemical reactions. Several fairly simple empirical models have been successfully linked to surface water survey databases to provide crude estimates of regional episodic acidification impacts on streams in the eastern United States and on lakes in the Adirondack Mountains of New York.

While these conclusions were based on a relatively large number of field studies, the authors also concluded that a clear scientific consensus regarding the primary causes of episodic acidification had not yet emerged. In addition, the report concluded that there was little knowledge of the regional extent or environmental significance of episodic acidification in any of the regions where field studies had been conducted and that statistically rigorous population estimates of current or future episodic acidification impacts could not be made with data that were available at the time.

Finally, the possible biological significance of episodic acidification had not been properly addressed at the time the synthesis document was written ( Wigington et al., 1990). To address these assessment issues, Wigington et 35 al. ( 1990) identified several critical knowledge gaps:

1. Additional field data collected with high temporal resolution in various geographic regions of the United States ( in particular the southeastern, upper midwestern, and western regions) that could be used for calibrating simple models of episodic acidification for estimating current regional impacts.

2. Long term episodic data for describing the behavior of systems over longer time periods.

3. New techniques for quantifying watershedscale hydrological flowpaths.

4. Better understanding of biogeochemical processes involving nitrogen, sulfur, and natural organic acids.

The 1990 NAPAP assessment of current and future acidification impacts of acidic deposition recognized that assessments based solely on chemical conditions during index periods ( i. e., periods approximating average annual or seasonal conditions) did not account for the worst case chemical conditions that usually occur during extreme hydrological events. However, due to the rather large uncertainties associated with incorporating episodic acidification into the regional assessment framework, model based projections of watershed responses to emissions reduction scenarios were not formulated to account for changes in episodic acidification over long time periods.

3.2.2 Current Episodic Acidification Impacts in the Southern Appalachians As summarized by Wigington et al. ( 1990), field studies of current episodic acidification impacts have been conducted on at least two continents ( North America and Europe), including many physiographic regions of the United States and much of Canada. As previously observed, episodic acidification has been found to be virtually ubiquitous; therefore, episodes must be accounted for in any overall scheme to assess the current acidbase status of surface waters, either at local or regional scales. For several regions of the eastern United States, models have been employed to predict current episodic acidification impacts. Most of these modeling studies have unfortunately been based on extremely limited data sets. The following paragraphs summarize our current understanding of episodic acidification in the Southern Appalachians at the two scales of interestClocal and regional.

<IP_ADDRESS> Local Scale. Wigington et al. ( 1990) specifically identified the southeastern United States as a region for which no complete data sets on episodic acidification were available and for which incomplete data were available for fewer than 10 streams in the entire region. Declines in pH and ANC were noted in all studies, but only one study reported minimum episodic pH values below 5.0 ( Raven Fork, North Carolina). Since 1990, however, data from several intensive studies of episodic acidification in the Southern Appalachians have been reported ( Miller Marshall, 1993; Hyer et al., 1995; Eshleman et al., 1995; Nodvin et al., 1995), from which local episodic impacts can be quantified. These studies suggest that streams with antecedent baseflow ANC values less than about 25

eq/ L may experience substantial depressions in pH ( as much as one unit) and increases in dissolved Al concentrations ( perhaps as much as 100

g/ L). Streams with higher antecedent baseflow ANC values probably experience much smaller changes in pH and Al concentrations.

Another interesting aspect of this problem, addressed by Eshleman et al. ( 1995), was the effect of insect defoliations on the episodic mobilization of nitric acid and the associated acidification response. At White Oak Run in 36 Shenandoah National Park, a statistical analysis of 13 years of data suggested that mean episodic depressions of ANC have increased by about a factor of 2 since the first outbreak of forest defoliation by the gypsy moth caterpillar during the summer of 1990; the mean episodic change in NO 3

concentration also has increased by about 12

eq/ L, while the mean episodic dilution of C B has decreased from  8.5

eq/ L to  1.7

eq/ L during the same period. Episodic changes in SO 4 2

have remained the same, however.

<IP_ADDRESS> Regional Scale. Eshleman ( 1988) estimated regional scale episodic acidification impacts in the Southern Appalachians using an empirical two component mixing model with minimal calibration. Eshleman ( 1988) estimated that 5B7% of the population of Southern Appalachian stream reaches sampled during the National Stream Survey may become acidic ( ANC < 0) during extreme hydrological conditions, compared to 0B3% during typical spring baseflow conditions. Recently, Hyer et al. ( 1995) presented results from an intensive study of episodic acidification of three streams in Shenandoah National Park ( Virginia) that support the use of the two component mixing model of ANC and provide data for model parameterization. No comparison of the model parameters has been conducted, although the data are available to do so. Additional field data are needed, however to determine the robustness of the model ( and of the existing parameters) for quantifying regional impacts in other regions of the Southern Appalachians ( including Class I areas). 3.3 Biological Effects of Acidic Deposition 3.3.1 Synopsis of Synthesis Documents The NAPAP SOS/ T report on biological effects ( J. Baker et al., 1990) states that there is no doubt that acidification, at pH levels as high as 6.0B6.5, results in changes in biological communities. All major groups of aquatic organisms have been affected, but individual species differ greatly in acid tolerance. Two readily observable consequences are ( 1) shifts in species composition and ( 2) reduction in the total number of species in a body of water. Ecological processes are more robust than some acid sensitive species. A general summary of the biological changes associated with declining pH is shown in Table 7.

It is more difficult to state precisely the magnitude of community effects on a regional scale. The report provides guidelines and methods for estimating the magnitude of effects, given regional differences in data availability. The use of suggested models provides three significant advances: ( 1) improved definition of chemical ranges critical for specific biological responses, ( 2) quantification of the interactions among pH, aluminum, and calcium ( the most important parameters for understanding biological responses in this context) at realistic, regional levels, and ( 3) estimates of the current and projected numbers of lakes and streams unsuitable for fish due to acidification. However, given the complexity of natural systems, it would be misleading to consider model outputs as absolute; although sources of uncertainties in models have been identified, their influence on model outputs can be only partly quantified.

The discussions of biological effects cover all components of aquatic communities ( algae, 37 Table 7. General Summary of Biological Changes Anticipated with Surface Water Acidification, Expressed as a Change in pH. Taken from Table 13 37 in the NAPAP SOS/ T report ( J. Baker et al., 1990).

pH Decrease General Biological Effects 6.5 to 6.0 Small decrease in species richness of phytoplankton, zooplankton, and benthic invertebrate communities resulting from the loss of a few highly acid sensitive species, but no measurable change in total community abundance or production Some adverse effects ( decreased reproductive success) may occur for highly acid sensitive species ( e. g., fathead minnow, striped bass)

6.0 to 5.5 Loss of sensitive species of minnows and dace, such as blacknose dace and fathead minnow; in some waters decreased reproductive success of lake trout and walleye, which are important sport fish species in some areas Visual accumulations of filamentous green algae in the littoral zone of many lakes, and in some streams Distinct decrease in the species richness and change in species composition of the phytoplankton, zooplankton, and benthic invertebrate communities, although little if any change in total community biomass or production Loss of a number of common invertebrate species from the zooplankton and benthic communities, including zooplankton species such as Diaptomus silicis, Mysis relicta, Epsichura lacustris; many species of snails, clams, mayflies, and amphipods, and some crayfish 5.5 to 5.0 Loss of several important sport fish species, including lake trout, walleye, rainbow trout, and smallmouth bass; as well as additional non game species such as creek chub Further increase in the extent and abundance of filamentous green algae in lake littoral areas and streams Continued shift in the species composition and decline in species richness of the phytoplankton, periphyton, zooplankton, and benthic invertebrate communities; decrease in the total abundance and biomass of benthic invertebrates and zooplankton may occur in some waters Loss of several additional invertebrate species common in oligotrophic waters, including Daphnia galeata mendotae, Diaphanosoma leuchtenbergianum, Asplanchna priodonta; all snails, most species of clams, and many species of mayflies, stoneflies, and other benthic invertebrates Inhibition of nitrification 38 5.0 to 4.5 Loss of most fish species, including most important sport fish species such as brook trout and Atlantic salmon; few fish species able to survive and reproduce below pH 4.5 ( e. g., central mudminnow, yellow perch, and in some waters largemouth bass)

Measurable decline in the whole system rates of decomposition of some forms of organic matter, potentially resulting in decreased rates of nutrient cycling Substantial decrease in the number of species of zooplankton and benthic invertebrates and further decline in the species richness of the phytoplankton and periphyton communities; measurable decrease in the total community biomass of zooplankton and benthic invertebrates in most waters.

Loss of zooplankton species such as Tropocyclops prasinus mexicanus, Leptodora kindtii, and Conochilis unicornis; and benthic invertebrate species, including all clams and many insects and crustaceans Reproductive failure of some acid sensitive species of amphibians such as spotted salamanders, Jefferson salamanders, and the leopard frog zooplankton, benthic invertebrates, fish, amphibians and waterfowl) and major ecological processes. However, quantitative methods and models, plus regional discussions, cover only fish responses. The reasons for this limitation include data availability ( historical and experimental), as well as the ability to make direct linkages between water chemistry and toxic mechanisms in fish.

The major conclusions of this SOS/ T report are shown in italics ( J. Baker et al., 1990) and discussed in the following subsections.

<IP_ADDRESS> Chemical Factors Influencing Biota. The most important chemical properties of surface waters influencing biological responses to acid base chemistry are pH, aluminum, and calcium.

Surface water pH is probably the most important of the three; decreases in pH ( particularly at levels below 6.0B6.5) have been shown to produce negative effects on many aquatic animals. Species ( and life history stages within species) differ greatly in tolerance to acid conditions; in brook trout, for example, adults do not typically disappear from streams until baseflow pH falls below 5.5, but sublethal effects on the growth of young fish are detectable when pH drops below 6.5. Increased H+ concentration ( decreased pH) has been shown to be directly toxic itself, but perhaps more importantly in nature, increased acidity mobilizes aluminum, which is toxic under acidic conditions, even though it is harmless under acid neutral conditions. Animals typically tolerate lower pH values in the absence of aluminum. Aluminum is the most abundant metal in the Earth's crust, and is virtually ubiquitous in terrestrial environments. The aqueous chemistry of aluminum is complex, and it can exist in multiple chemical forms differing in toxicity in solution; inorganic monomeric aluminum is thought to be the most toxic form. Organically bound aluminum is relatively nontoxic, so waters with high organic content usually contain little toxic aluminum. Concentrations of inorganic monomeric aluminum above 30B50

g/ L cause adverse effects in the most sensitive organisms; concentrations over 100

g/ L affect many organisms.

Many aquatic animals are more sensitive to acid conditions when calcium concentrations are low. Calcium ameliorates the negative effects of acid conditions by directly supporting the physiological processes and structures damaged by H+ and aluminum in fish. Small changes in calcium concentration can produce substantial changes in response; most of the benefits of increased calcium concentration are evident at concentrations of 39 150

eq/ L, and further increases produce smaller improvements.

<IP_ADDRESS> Effects on Species Richness. A number of the species that commonly occur in surface waters susceptible to acidic deposition cannot survive, reproduce, or compete in acidic waters. Thus, with increasing acidity, the " acid sensitive" species are lost and species richness ( the number of species living in a given lake or stream) declines. These changes in aquatic community structure occur at chronic pH levels < 6.0 B 6.5.

Acid sensitive species occur in all groups of aquatic organisms. The drop in species richness is most dramatic between pH 5 and 6. For example, many species of minnows, zooplankton, mollusks, and mayflies are adversely affected at chronic pH levels between 5.5 and 6. Long term declines in pH from 5.5 to 5.0 result in the loss of several important sport fish species, including lake trout, rainbow trout, walleye, and smallmouth bass. Brook trout generally cannot survive or reproduce successfully at pH levels below 4.8B5.2. Few fish are found at pH levels below 4.5. Both chronic and acute ( episodic) acidification contribute to species loss; episodic acidification is more pronounced in streams than in lakes.

<IP_ADDRESS> Effects on Ecosystem Level Processes. Ecosystem level processes, such as decomposition, nutrient cycling, and productivity are fairly robust and are affected only at relatively high levels of acidity ( e. g., chronic pH < 5.0 B 5.5).

Among nonvertebrate organisms, acidsensitive species lost in the early stages of acidification are " replaced" to some degree by acid tolerant organisms; as a result, the net change in total community productivity is relatively small; however, less information is available for system level processes than for community structure, so subtle effects on system processes may not yet have been detected.

<IP_ADDRESS> Recovery of Biological Communities Relatively few studies have been conducted on the recovery of biological communities following reductions of acid inputs. Nevertheless, it is predicted that, with decreasing acidity, acid sensitive species would reappear and species richness would increase.

Much of the information on recovery is derived from liming experiments, involving the addition, in most cases, of calcium carbonate. With few exceptions, this treatment results in improved water quality, to levels that would support more acid sensitive species. Problems in interpreting these results remain. Although liming adds calcium, decreases in acid precipitation may reduce surface water calcium. Preliminary results from Norway suggest that fish community declines have continued in the last 10B15 years in regions where acid deposition has decreased. In these low calcium waters ( 50B100

g/ L), small decreases in calcium have apparently offset the benefits of lower acid and aluminum concentrations. In contrast, preliminary results from Ontario indicate improved biological status following reductions in atmospheric loading; calcium levels there tend to be higher than in Norway. Rates of recovery are poorly known in general, but algae appear to recover more rapidly than other groups of organisms. Additional research on recovery ( and management steps to accelerate it) is much needed.

<IP_ADDRESS> Developing Regional Models. Laboratory toxicity experiments and field surveys provide an adequate basis for quantifying the relationship, on a regional scale, between changes in pH, aluminum, and calcium and acidity induced stress on fish populations. Thus, toxicity based models, field based models, and models that combine 40 laboratory and field data can be used to evaluate the biological significance of projected changes in acid base chemistry, given alternate deposition and emission scenarios.

Regional assessments of the effects of surface water acidification on fish require two components: the expected distribution of fish in the area in the absence of acidification effects ( baseline status) and the ways to predict changes in the fish community as a function of water chemistry changes ( prediction The NAPAP Integrated Assessment developed two procedures for determining baseline status: ( 1) habitat evaluations based on fish habitat requirements known from the literature and ( 2) field based empirical models that rely on statistical associations between fish status and measured habitat characteristics Three procedures have been developed for prediction. The first, using toxicity models, predicts conditional mortality rates, or an acidic stress index ( ASI), based on water chemistry and fish mortality in laboratory bioassays. The second procedure uses fieldbased empirical models, relating fish status to water chemistry. In the third procedure, models combining toxicity and field survey data were developed. Two types of models are available, Bayesian models and the Lake Acidification and Fisheries framework.

Development of baseline status is often more difficult and less precise than prediction. The approaches for the NAPAP Integrated Assessment vary among regions, due to fish data availability. Methods for conducting regional assessments of potential effects on fish in Mid Appalachian streams include habitat evaluation for baseline status, and both toxicity models and field based models for prediction of acidification effects.

<IP_ADDRESS> Documentation of Effects on Fish. The loss of fish populations and/ or absence of fish species as a result of acid base chemistry has been documented for some lakes and streams in several regions of the United States. Applications of fish response models suggest that the percentage of NSWS waters with acid base chemistry unsuitable for acidsensitive fish species ranges from < 5% in the Upper Midwest to nearly 60% for upper stream reaches in the Mid Atlantic Coastal Plain. An estimated 23% of the Adirondack lakes and 18% of the Mid Appalachian streams classified as potential brook trout habitat currently have acid base chemistry unsuitable for brook trout survival.

Good quality survey data on the regional status of fish communities in the United States are limited; other natural and human factors also affect fish distributions. As a result, effects caused by acidification can be difficult to document. Nevertheless, intensive studies at a small number of sites in Mid Appalachian streams have documented toxic conditions during episodes, fishkills, and loss of fish populations as a result of increasing stream acidity. An estimated 18% of potential brook trout streams in the Mid Appalachians are too acid for brook trout survival; in about 30% of the streams, ASIs indicate that conditions are too acid for more acid sensitive species that might be expected there.

In the southern Blue Ridge, few systems currently have baseflow pH levels detrimental to fish. However, these streams have low buffering capacity, and are vulnerable during increases in acidity, especially episodically.

Acidification of mountain streams in the SAMI region apparently has consequences outside the SAMI region. Declines in anadromous fish stocks may be explained partly by acidification. Nearly 60% of upper reaches of streams entering the Mid Atlantic Coastal Plain are unsuitable for acid sensitive species. Anadromous fishes ( those that are spawned in freshwater, spend various amounts of time there, migrate to seawater where they attain sexual maturity, and then return to freshwater 41 to spawn) have been shown to be among the most acid sensitive fish in their freshwater phase. These species include Atlantic salmon, striped bass, and blueback herring; all show acid induced stress at pH levels of 6.0B6.5. The contribution of acidification to losses of these species is difficult to evaluate because other factors such as overfishing and habitat loss also affect them.

3.3.2 Current Biological Impacts in the Southern Appalachians The NAPAP synthesis documents ( J. Baker et al., 1990) did not use regional boundaries perfectly coincident with the SAMI region. However, two of the regions overlap with the SAMI study area and the conclusions of the NAPAP study are applicable to surface waters in the SAMI region. The NAPAP mid Appalachians region covers the SAMI study area in Virginia and West Virginia, plus most of Pennsylvania, western Maryland, and the Catskill Mountains of New York. The NAPAP Interior Southeast region consists of parts of the Piedmont and the SAMI study region ( Figure 1) south of the Virginia/ North Carolina, and Kentucky/ Tennessee state lines.

<IP_ADDRESS> Mid Appalachians. In the mountains of western Virginia, the high elevation, low ANC headwater streams in the area have fish assemblages dominated by eastern brook trout, the only salmonid native to the region ( Cosby et al., 1991). Stocking with brown and rainbow trout is partly responsible for displacing brook trout from low elevation reaches, but it has not displaced brook trout from habitats at higher elevations. The reaches farthest upstream contain brook trout or no fish at all. Farther downstream, mottled sculpins and blacknose dace co occur with brook trout.

The extent of aquatic biological responses to acidic deposition has not been studied region wide in the Mid Appalachians. A study in western Maryland measured aluminum, calcium, pH, and fish abundance in 79 trout streams ( Morgan et al., 1990). The mean pH of streams with fish was 7.1, compared with 5.4 for fishless streams; no brook trout were found in streams with baseflow pH < 5.5. In situ bioassays on brook trout and other fish species in the Mid Appalachians have demonstrated adverse affects, including altered spawning behavior, reduced egg viability, decreased hatching rate, reduced survival, and reduced growth.

The current status and trends regarding region wide acidification effects in the mid Appalachians is difficult to assess because of the absence of large scale fish surveys. In the SAMI region, losses of fish species associated with increasing stream acidity have been reported in Virginia ( Little Stony Creek and St. Mary's River; Webb et al., 1989a, b) and in West Virginia ( Cranberry River drainage; Zurbuch et al., 1986). In Pennsylvania, a study of 61 streams in the Laurel Hills region showed that 16% of the sites were fishless. Fishless streams had significantly lower pH values than streams with fish and they did not have acid mine drainage impacts. All the fishless streams were in largely undisturbed forests with base poor bedrock types ( Sharpe et al., 1987). Also in Pennsylvania, fish kills due to pH depressions during rainfall events have been confirmed in some Appalachian Plateau streams Wigington et al., 1993).

A three year project on the effects of acidbase chemistry on fish communities in mountain streams in Virginia was started in Shenandoah National Park in 1992 ( Bulger et al., 1995). Both chronic and episodic acidification are occurring in these streams. Biological differences in low ANC versus high ANC streams include fish species richness, population density, condition factor, age, size, and bioassay survival. In particular, both episodic and chronic mortality occurred in young brook trout exposed in low ANC streams, but not in high ANC streams 42 ( MacAvoy and Bulger, 1995), and blacknose dace in low ANC streams were in poor condition relative to dace in high ANC streams ( Dennis and Bulger, 1995; Dennis et al., 1995). In the same study, blacknose dace and brook trout from a low ANC stream were able to detect and avoid acid pulses simulating an acid episode in the laboratory; they could also find neutral pH refugia ( Newman and Dolloff, 1995). Predictive models relating fish status to future water chemistry are to be produced.