Nitrogen Deposition Can Harm Forests and Coastal Ecosystems Sensitive Forests ° High nitrogen deposition can cause " nitrogen saturation," which occurs when too much nitrogen enters sensitive forest soils and begins to leach out, stripping soil nutrients and affecting water quality.

° Sensitive forests showing signs of nitrogen saturation are found in the eastern and western U. S. and include the Great Smoky Mountains,

Adironack/ Catskill Mountains, the Colorado Front Range and southern California. Wet Nitrate Deposition ( Kg/ ha)

1 > 24 Annual Wet Nitrate Deposition to Sensitive Resources Nitrogen Saturated Forest Coastal Estuary Area Deposition measured by CASTNET and NADP, 1997 1999 ° Nitrogen deposition occurs when nitrogen in deposited to the Earth's surface.

° Power plant NOx emissions are a significant source of the nitrogen that reaches our coastal ecosystems and sensitive forests. When nitrogen levels in these ecosystems are too high, problems develop.

° Coastal ecosystems: 10 to 40 percent of the nitrogen reaching many East and Gulf coast estuaries comes from the air.

° Too much nitrogen in these waters leads to a condition known as " eutrophication."

° Two thirds of U. S. estuaries ( more than 80 estuaries) show symptoms of moderate to high eutrophication.

° Eutrophication can result in:

° Fish and shellfish " kills" due to low levels of dissolved oxygen ° Algal blooms, including toxic red and brown tides;

° Loss of important habitat, such as seagrass beds and coral reefs;

° Changes in marine biodiversity and species distribution; and ° Economic and social impacts resulting from a loss of fisheries and tourism The Proposed Interstate Air Quality Rule Will Reduce Nitrogen Deposition in the Eastern U. S.

Projected Improvements in 2010 and 2015 resulting from the Interstate Air Quality Rule * Base case assumes implementation of existing Clean Air Act programs and the proposed nonroad diesel rule.

Projected nitrogen deposition changes in 2010, compared to the base case* Projected nitrogen deposition changes in 2015,

compared to the base case*

Legend 100th Parallel Percent Reduction 0 to 5 6  10 11  15 16  20 21  25 26  32 Estimates for 2015 show additional and larger reductions across a broader region in the East.

By 2010, nitrogen deposition would be lower   up to 15 percent in many areas of the eastern U. S. Acid Rain Damages Lakes, Streams,

Forests and Buildings ° Acid deposition occurs when emissions of SO 2 and NOx react in the atmosphere to create acidic gases and particles that reach the ground in wet and dry forms.

° The greatest sulfur and nitrogen deposition occurs in areas of the Midwest and northeastern United States which are downwind of the highest SO 2 and NOx emission areas.

° Impacts occur both in the East and mountainous areas of the West.

° Effects of acid deposition include:

  Acidification of lakes and streams, making them unable to support fish and other aquatic life;

  Damage to forests through acidification of soil, depletion of soil nutrients, and direct injury to sensitive tree leaves and needles;

  Harm to buildings, statues and monuments. ° Despite substantial emissions reductions over the last 20 years, significant amounts of sulfur and nitrogen still deposit to acid sensitive lakes and streams, leading to high levels of acidity.

° Southeastern streams will continue to grow more acidic without significant further reductions in sulfate and nitrogen deposition.

° Many scientists believe that significant further reductions in SO 2 and NOx emissions are necessary to fully protect acidsensitive ecosystems. Wet Sulfate Deposition ( Kg/ ha)

1 35 Acid sensitive surface waters Source: CASTNet/ NADP; National Surface Water Survey Projected changes in sulfur deposition,

compared to the base case in 2010 IAQR Sulfur Deposition Improvements in 2010 and 2015 Projected changes in sulfur deposition,

compared to the base case in 2015 Legend 100th Parallel Percent Reduction 0  5 6  10 11  15 16  20 21  25 26  30 31  35 36  40 41  45 46  50 51  55 56  61 * Base case assumes implementation of existing Clean Air Act programs and the proposed nonroad diesel rule. portions of Pennsylvania, Virginia, Maryland and West Virginia will see reductions of up to 45 percent. Estimates for 2015 show additional reductions, especially in the Southeast.

By 2010, the proposed Interstate Air Quality Rule would reduce sulfur deposition beyond reductions expected without implementation of this rule. The majority of the East will see sulfur deposition reductions of up to 20 percent in 2010, while some