Nitrate nitrogen concentrations in ground water in a 900-square-mile agricultural area in the Pasco Basin, which includes eastern Benton and western Franklin Counties, ranged from less than 0.1 to 100 milligrams per liter. Nitrate nitrogen concentrations in water from 31 percent of wells sampled in Franklin County and 10 percent in Benton County, exceeded 10 milligrams per liter. Nitrogen fertilizers are a major source of nitrate in ground water in the study area. Septic systems contribute some nitrate to ground water near the town of Finley in Benton County, but they are not the primary source. Naturally occurring nitrate may be a source of nitrate in ground water in parts of Benton County. Surface water used for irrigation does not contribute to elevated nitrate concentrations in ground water. Instead, canal seepage, which constitutes about 50 percent of the ground-water recharge in the study area, dilutes nitrate already present in ground water. Although fluoride concentrations in ground water ranged from less than 0.1 to 4.7 milligrams per liter; concentrations of fluoride in water from only two of 143 wells equalled or exceeded 2.0 milligrams per liter, the secondary maximum contaminant level for drinking water. One or more pesticide compounds were detected in 10 of 29 ground-water samples. Pesticides found included atrazine, dicamba, metribuzin, picloram, and 2,4,5-T; also present were aldicarb sulfone and aldicarb sulfoxide, which are degradation products of aldicarb. Concentrations of pesticides detected were below health advisory levels issued by the U.S. Environmental Protection Agency.
Additional Publication Details
USGS Numbered Series
Distribution and sources of nitrate, and presence of fluoride and pesticides, in parts of the Pasco Basin, Washington, 1986-88
Water-Resources Investigations Report
U.S. Geological Survey ;
Earth Science Information Center [distributor],