Laserfiche WebLink
<br /> <br />o <br /> <br />Effects of Nitrogen Use on the Quality of <br />Ground Water and Surface Water <br /> <br />Nitrate contamination of ground water and surface <br />water in the United States is widespread because nitrate is <br />very mobile in the environment. Nitrate concentrations are <br />increasing in much of the Nation's water, but they are particu- <br />larly high in ground water in the midcontinent region of the <br />United States. Two principal chemical reactions are important <br />to the fate of nitrogen in water: (1) fertilizer ammonium can be <br />nitrified to form nitrate, which is very mobile as a dissolved <br />constituent in shallow ground water, and (2) nitrate can be <br />denitrified to produce nitrogen gas in the presence of chemi- <br />cally reducing conditions if a source of dissolved organic <br />carbon is available. <br /> <br />Waquoit Bay, Massachusetts <br /> <br /> <br />Morgan Creek, Maryland <br /> <br />High concentrations of nitrate can contribute to exces- <br />sive growth of aquatic plants, depletion of oxygen, fishkills, <br />and general degradation of aquatic habitats. For example, a <br />study of Waquoit Bay in Massachusetts linked the decline in <br />eelgrass beds since 1950 to a progressive increase in nitrate <br />input due to expansion of domestic septic-field developments <br />in the drainage basin (Figure 0-1). Loss of eelgrass is a <br />concern because this aquatic plant stabilizes sediment and <br />provides ideal habitat for juvenile fish and other fauna in <br />coastal bays and estuaries. Larger nitrate concentrations <br />supported algal growth that caused turbidity and shading, <br />which contributed to the decline of eelgrass. <br /> <br />- <br /> <br /> <br />Waquoit Bay, Massachusetts. (Photograph by <br />Ivan Valiela.) <br /> <br />Ffgure 0-1. The areal ex/entof eelgrass <br />in Waquoit Bay, Massachusetts, decreased <br />markedly between 1951 and 1987 because <br />of increased inputs of nitrogen related to <br />domestic septic-field developments. (Modified <br />from Valiela, I., Foreman, K., LaMontagne, M., <br />Hersh. D., Costa, J., Peckol, P., DeMeo- <br />Andeson, B., D'Avanzo, C., Babione, M., <br />Sham, C.H., Brawley, J., and Lajtha, K, <br />1992, Couplings of watersheds and coastal <br />waters-Sources and consequences <br />of nutrient enrichment in Waquoit Bay, <br />Massachusetts: Estuaries. v. 15, no. 4, <br />p. 433-457.) (Reprinted by permission of <br />the Estuarine Research Federation.) <br /> <br /> <br />1951 <br /> <br />1971 <br /> <br />1978 <br /> <br />1987 <br /> <br />62 <br />