Pesticide residue levels in soils and crops from 37 states, 1972--National Soils Monitoring Program (IV).

Residue data from the 1972 (FY--73) National Soils Monitoring Program are summarized. Composite samples of agricultural soil and mature crops were collected from 1,483 of the 1,533 selected 4-hectare sites in 37 states. Analyses were performed for organochlorine and organophosphorus compounds, trifluralin and polychlorinated biphenyls (PCBs); analysis for atrazine was performed only when pesticide application data indicated current-year use. Organochlorine pesticides were detected in 45 percent of the soil samples. The most frequently detected compound was dieldrin, found in 27 percent of all soil samples. Other compounds detected, in order of frequency, included DDT, aldrin, chlordane, and heptachlor epoxide, found, respectively, in 21, 9, 8, and 7 percent of all soil samples. Crop samples were collected from 727 sites. All were analyzed for organochlorines; analyses were performed for organophosphates and atrazine only when pesticide application data indicated current-year use. For all crops, 40 percent of the samples contained detectable levels of organochlorines and 10 percent contained detectable levels of organophosphates. Atrazine was not detected.