Organochlorine and organophosphorous pesticides in the Parana River (Argentina)

Organochlorine and organophosphorous pesticide concentrations have been monitored in the Paraná River, Argentina, at a point 600 km upstream from its mouth, since March 1981. Chromatographic analyses performed up to December 1981 indicate that parathion, lindane and α-BHC (benzene hexachloride) are the most ubiquitous species with mean concentrations of 22, 9, and 9 ng 1 −1, respectively. The dissolved-in-water pesticides do not show a clear association with discharge — only lindane, which is adsorbed on the sediments, exhibits a significant positive correlation with discharge. Other chemical compounds (heptachlor, aldrin, methylparathion) have been occasionally determined in the examined samples. Total discharge-weighted mean concentrations for dissolved (175 ng l −1) and adsorbed (453 ng g −1) compounds allow the calculation of a mass transport rate of 10.85 × 10 7 g y −1. a figure valid for the period of study.