Soil–air exchange of organochlorine pesticides in the Southern United States

Soil samples were collected from 30 farms in Alabama, Louisiana and Texas during 1999–2000 to determine residues of organochlorine pesticides (OCPs). One or more of the DDT compounds (p,p′-DDT, o,p′-DDT, p,p′-DDD, p,p′-DDE, o,p′-DDE) was above the quantitation limit (0.1 ng g −1 dry weight) in every soil, and toxaphene was above the quantitation limit (3 ng g −1) in 26 soils. Chlordanes, dieldrin and hexachlorocyclohexane (HCH) isomers occurred less frequently (quantitation limits 0.1 ng g −1 for dieldrin and 0.05 ng g −1 for chlordanes and HCHs). OCPs were measured in air at 40 cm above the soil at selected farms to investigate soil-air partitioning. Concentrations of OCPs in air were positively and significantly ( P