Organochlorine pesticide residues in a farming area, Nova Scotia--1972-73.

Soil, silt, and water samples from the Habitant Creek water-shed, Nova Scotia, a tobacco-growing area, have been monitored for organochlorine insecticides. Most samples contain measurable quantities of many persistent pesticides used in farming during the past decade. Sediment levels indicate that residues settle in sluggish parts of the stream. Drainage ditches show highest residual content caused in part by mass transport of soil in runoff. Residue content of water samples is normally one-tenth to one-hundredth that of silt, but is much higher during periods of heavy runoff. Levels vary with the seasons and are highest in the fall, decrease through the spring and summer, and are lowest in the winter. Although samples of well water taken fairly close to the stream showed virtually no residual content, a natural drainage reservior had a pesticide content similar to that in the stream.