The amount of oxygen that can be held by the water depends on the water temperature, salinity, and pressure. Gas solubility increases with decreasing temperature.
Gases are usually more soluble at colder temperatures. For example, oxygen is more soluble in cold water than in hot water. The decrease in oxygen solubility with increased temperature [ 1 ] has serious consequences for aquatic life. Power plants that discharge hot water into rivers can kill fish by decreasing the dissolved oxygen concentration The amount of oxygen dissolved in water is expressed as a concentration, in milligrams per liter (mg/l) of water. Dissolved oxygen levels are also often reported in percent saturation. Temperature affects DO concentrations, and calculating the percent saturation will factor out the effect of temperature. The saturation level is the maximum concentration of dissolved oxygen that would be present in water at a specific temperature, in the absence of other factors. Scientists have determined the saturation DO level for various temperatures. Saturation levels also vary with elev 1 Dissolved oxygen levels. 2  The solubility of oxygen decreases as water temperature increases. 3  Chemical processes. 4  Temperature affects the solubility and reaction rates of chemicals. 5  In general, the rate of chemical reactions increases with increasing water temperature. 6  Biological processes. Water Quality Indicators: Temperature and Dissolved Oxygen. Water temperature is one of the most important characteristics of an aquatic system, affecting: 1  Dissolved oxygen levels. 2  The solubility of oxygen decreases as water temperature increases. 3  Chemical processes. 4  Temperature affects the solubility and reaction rates of chemical The amount of oxygen that can be held by the water depends on the water temperature, salinity, and pressure. Gas solubility increases with decreasing temperature (colder water holds more oxygen). Gas solubility increases with decreasing salinity (freshwater holds more oxygen than does saltwater). Both the partial pressure and the degree of saturation of oxygen will change with altitude. Finally, gas solubility decreases as pressure decreases. Thus, the amount of oxygen absorbed in water decreases as altitude increases because of the decrease in relative pressure. The mixing of surface waters by wind and waves increases the rate at which oxygen from the air can be dissolved or absorbed into the water. DO levels are influenced by temperature and salinity. The solubility of oxygen, or its ability to dissolve in water, decreases as the waters temperature and salinity increase. DO levels in an estuary also vary seasonally, with the lowest levels occurring during the late summer months when temperatures are highest. Dissolved Oxygen. temperature | depth | salinity | dissolved oxygen | turbidity | pH | nutrients | chlorophyll. Low levels of dissolved oxygen in the water can cause marine life to become very lethargic. Oxygen in Equilibrium Dissolved Oxygen and Henry's Law Oxygen dissolved in water can come from the atmosphere or as a byproduct of the photosynthesis of aquatic plants.For water in equilibrium with the atmosphere, the concentration is governed by Henry's Law, and K H for O 2 is 769.23.  Two bodies of water that are both 100% air-saturated do not necessarily have the same concentration of dissolved oxygen. The actual amount of dissolved oxygen (in mg/L) will vary depending on temperature, pressure and salinity ¹. First, the solubility of oxygen decreases as temperature increases ¹. Gas saturation decreases by 10% per meter increase in depth due to hydrostatic pressure ¹². This means that if the concentration of dissolved oxygen is at 100% air saturation at the surface, it would only be at 70% air saturation three meters below the surface. Dissolved Oxygen Dissolved oxygen (DO) refers to the volume of oxygen that is contained in water. Oxygen enters the water as rooted aquatic plants and algae undergo photosynthesis, and as oxygen is transferred across the air-water interface. Both the partial pressure and the degree of saturation of oxygen will change with altitude. Finally, gas solubility decreases as pressure decreases. Thus, the amount of oxygen absorbed in water decreases as altitude increases because of the decrease in relative pressure. Water temperature is one of the most important characteristics of an aquatic system, affecting: 1  Dissolved oxygen levels. 2  Chemical processes. 3  Biological processes. 4  Species composition of the aquatic ecosystem. 5  Water density and stratification. 6  Environmental cues for life-history stages. Water Quality Indicators: Temperature and Dissolved Oxygen. Water temperature is one of the most important characteristics of an aquatic system, affecting: 1  Dissolved oxygen levels. 2  The solubility of oxygen decreases as water temperature increases. 3  Chemical processes. 4  Temperature affects the solubility and reaction rates of chemical
http://antoine.frostburg.edu/chem/senese/101/solutions/faq/temperature-gas-solubility.shtml http://bcn.boulder.co.us/basin/data/NEW/info/DO.html http://www.ramp-alberta.org/river/water+sediment+quality/chemical/temperature+and+dissolved+oxygen.aspx http://www.michigan.gov/documents/deq/wb-npdes-DissolvedOxygen_247232_7.pdf http://oceanservice.noaa.gov/education/kits/estuaries/media/supp_estuar10d_disolvedox.html http://butane.chem.uiuc.edu/pshapley/GenChem1/L23/web-L23.pdf http://www.fondriest.com/environmental-measurements/parameters/water-quality/dissolved-oxygen/ http://www.michigan.gov/documents/deq/wb-npdes-DissolvedOxygen_247232_7.pdf http://www.ramp-alberta.org/river/water+sediment+quality/chemical/temperature+and+dissolved+oxygen.aspx
why does dissolved oxygen decrease as temperature increases