Info

Source: R.G. Thomas, 1982, Volatilization from water, In Handbook of chemical property estimation methods (New York: McGraw-Hill, Inc.).

Source: R.G. Thomas, 1982, Volatilization from water, In Handbook of chemical property estimation methods (New York: McGraw-Hill, Inc.).

isms and oxygen are abundant, but nitrate can be readily leached from the soil into groundwater where it may present a health hazard; nitrate is highly mobile in groundwater because of its negative charge. Denitrlfication is a process whereby NO3 is reduced to nitrous oxide (N2O) and elemental nitrogen (N2) by facultative anaerobic bacteria (Downing, Painter, and Knowles 1964; Freeze and Cherry 1979; Bemner and Shaw 1958).

Phosphorous (P) is found in organic waste, rock phosphate quarries, fertilizers, and pesticides in concentrations high enough to potentially leach into groundwater. The decomposition of organic waste and dissolution of inorganic fertilizers provide soluble phosphorous, soluble orthophosphate, and a variety of condensed phosphates, tripolyphosphates, adsorbed phosphates, and crystallized phosphates (U.S. EPA 1983). The hydrolysis and mineralization of these products provide soluble phosphate which can be used by plants and microorganisms, adsorbed to soil particles, or leached to groundwater. Although phosphorous is not a harmful constituent in drinking water, its presence in groundwater is environmentally significant if the groundwater discharges to a surface water body where phosphorous can produce algae growth and cause eu-

trophication of the aquatic system (Freeze and Cherry 1979).

Sulfur (S) is found in appreciable amounts in waste streams from kraft mills, sugar refining, petroleum refining, and copper and iron extraction facilities (Overcash and Pal 1979). Aerobic bacteria can oxidize the reduced forms of sulfur to form sulfate which can be highly adsorbed to soil when the cation adsorbed on the clay is aluminum; moderately adsorbed when the cation is calcium; and weakly adsorbed when the cation is potassium (Tisdale and Nelson 1975). Leaching losses of sulfur to ground-water can be large because of the anionic structure of sulfur and the solubility of most of its salt. Leaching is greatest when monovalent cations such as potassium and sodium predominate; moderate when calcium and manganese predominate; and minimal when the soil is acidic and appreciable levels of exchangeable iron and aluminum are present (Tisdale and Nelson 1975).

0 0

Post a comment