Fate of airborne pesticides: photochemical transformation of lindane and chlorothalonil

In summer 1993 air samples were collected at Paine, Germany to determine the concentrations of lindane (gamma-hexachlorocyclohexane), alpha-hexachlorocyclohexane, chlorothalonil (2,4,5,6-tetrachloro-1,3-dicyanobenzene), and of possible transformation products. In all samples gamma-pentachlorocyclohexene and dechloro-chlorothalonil were detected. The good correlation between the concentrations of chlorothalonil and dechloro-chlorothalonil provides evidence for the photochemical transformation of chlorothalonil in the atmosphere. Additionally, laboratory measurements were carried out to estimate the photochemical lifetime of chlorothalonil.