Agricultural chemicals and groundwater quality

CHEMICALS of concern in ground-water quality degradation by agriculture are nitrate and pesticides, including insecticides, herbicides, fungicides, nematicides, and rodenticides. Although salt and trace-element contamination of groundwater is a direct result of agricultural activities, it is not due to anthropogenic chemicals. The focus here is on nitrate and pesticides. Health effects Nitrate is the final form of fertilizer nitrogen in soil. Very mobile in the underground environment, nitrate moves readily with deep percolation through the vadose zone to underlying groundwater. Thus, fertilizer nitrogen not used by crops and not denitrified or volatilized eventually reaches underlying groundwater. Nitrate-nitrogen concentrations in vadose-zone water below agricultural fields typically are in the range of 5 to 100 parts per million ( 7, 21, 39 ), with frequent detections of concentrations of 20 to 40 parts per million. The maximum limit for drinking water is 10 parts per million nitrate-nitrogen. Too much nitrate in drinking water can cause methemoglobinemia, or blue-baby disease, in infants (7). It may also increase cancer in the population as a whole (29) through reduction to nitrite in the oral cavity or stomach and reaction with amines to form nitrosamines. These chemicals, along with aflatoxin B1, are …