Pesticide residue levels in soils and crops, 1971--National Soils Monitoring Program (III).

Data from the 1971 National Soils Monitoring Program are summarized. Composite samples of soil and mature crops were scheduled for collection from 1,533 4-hectare sites in 37 states. Analyses were performed on 1,486 soil samples for organochlorines, organophosphates, PCBs, and elemental arsenic; samples were analyzed for atrazine only when pesticide application data indicated current-year use. Organochlorine pesticides were detected in 45 percent of the soil samples in the following order of frequency: dieldrin, sigmaDDT, aldrin, chlordane, and heptachlor epoxide. Most pesticide levels ranged from 0.01 to 0.25 ppm. Crop samples were collected from 729 sites, and all were analyzed for organochlorines. Crop samples were analyzed for organophosphates and atrazine only when pesticide application data indicated current-year use. Organochlorines were detected in 42 percent of the crop samples analyzed, organophosphates in 13 percent, and atrazine in 1 percent.