Groundwater Contamination
Groundwater is an important source of drinking water for more than half of the nation's population and nearly all its rural population. In recent years, widespread reports of bacteria, nitrate, synthetic organic chemicals and other pollutants in groundwater have increased public concern about the quality of groundwater. What do we know - and what don't we know - about groundwater quality? What causes groundwater contamination, and to what extent are the nation's groundwater supplies at risk?
How Much Do We Depend on Groundwater?
According to 1985 U.S. figures, groundwater provides an estimated: * 22 percent of all freshwater withdrawals * 53 percent of drinking water for the total population and 97 percent of drinking water for …show more content…
In general, shallow, permeable water table aquifers are the most susceptible to contamination, but susceptibility of all aquifers to contamination is determined largely by such site-specific characteristics as: * distance from the contamination source to the aquifer and residence time of the water in the unsaturated zone; * presence of clay and organic matter in the unsaturated zone materials; * potential of a particular contaminant to biodegrade and decompose; * amount of precipitation, which affects recharge and the rate at whieh contaminants move downward; * evapotranspiration, which in recharge areas may decrease the amount of water that moves downward to the aquifer.
What Causes Groundwater Contamination
Natural …show more content…
In 1987, about 330 million acres were used for growing crops in the United States, of which 45 million acres were irrigated.
Fertilizers
During the 1960s and 1970s, nitrogen, phosphorus and potassium fertilizer use steadily increased to a peak of 23 million tons in 1981. By 1987, however, fertilizer use had declined to 19.2 million tons, reflecting the large number of acres withdrawn from production as part of the Conservation Reserve Program and other government programs.
If nitrogen supply exceeds nitrogen uptake by crops, excess nitrogen ean be leached to groundwater. In such areas, local nitrate-nitrogen concentrations may exceed the federal drinking water standard of 10 mg/L
Pesticides
Pesticides have been used since the 1940s to combat a variety of agricultural pests. Between 1964 and 1982, the amount of active ingredients applied to croplands increased 170 pereent. Herbicide usage peaked in 1982, and since then has declined from about 500 million pounds of active ingredients per year to about 430 million pounds in
How Much Do We Depend on Groundwater?
According to 1985 U.S. figures, groundwater provides an estimated: * 22 percent of all freshwater withdrawals * 53 percent of drinking water for the total population and 97 percent of drinking water for …show more content…
In general, shallow, permeable water table aquifers are the most susceptible to contamination, but susceptibility of all aquifers to contamination is determined largely by such site-specific characteristics as: * distance from the contamination source to the aquifer and residence time of the water in the unsaturated zone; * presence of clay and organic matter in the unsaturated zone materials; * potential of a particular contaminant to biodegrade and decompose; * amount of precipitation, which affects recharge and the rate at whieh contaminants move downward; * evapotranspiration, which in recharge areas may decrease the amount of water that moves downward to the aquifer.
What Causes Groundwater Contamination
Natural …show more content…
In 1987, about 330 million acres were used for growing crops in the United States, of which 45 million acres were irrigated.
Fertilizers
During the 1960s and 1970s, nitrogen, phosphorus and potassium fertilizer use steadily increased to a peak of 23 million tons in 1981. By 1987, however, fertilizer use had declined to 19.2 million tons, reflecting the large number of acres withdrawn from production as part of the Conservation Reserve Program and other government programs.
If nitrogen supply exceeds nitrogen uptake by crops, excess nitrogen ean be leached to groundwater. In such areas, local nitrate-nitrogen concentrations may exceed the federal drinking water standard of 10 mg/L
Pesticides
Pesticides have been used since the 1940s to combat a variety of agricultural pests. Between 1964 and 1982, the amount of active ingredients applied to croplands increased 170 pereent. Herbicide usage peaked in 1982, and since then has declined from about 500 million pounds of active ingredients per year to about 430 million pounds in