ATRAZINE AND OTHER S-TRIAZINE HERBICIDES IN LAKES AND IN RAIN IN SWITZERLAND

All of the 18 Swiss lakes analyzed contained detectable quantities of some s-triazine herbicides. Atrazine was the major herbicide present, accompanied by smaller amounts of simazine, terbuthylazine, and occasionally (methyl-thio)-s-triazines. The concentration of atrazine was lowest (1 ng/L or less) in mountain lakes (altitude >800 msl) and highest (up to 460 ng/L) in lakes situated in areas with intensive use of atrazine. Seasonal trends were observed, with a concentration increase in the epilimnia around June, apparently resulting from previous spring applications of the herbicides. Vertical concentration profiles of the herbicides in Lake Zurich were consistent with stratification of the lake during the warmer season and mixing in the colder one. The data suggest atrazine to be rather stable and its removal from the lakes is mainly by export via outflowing waters and less by degradation. Atrazine and other s-triazines were also detected in rainwater during the warmer season. Volatilization and wind erosion of soil particles from areas treated with these herbicides are likely the cause for the presence of these compounds in rain and aerial transport and subsequent deposition the reasons that we find these compounds in mountain lakes. However, major input of these herbicides in most other lakes stems from agricultural practices and nonagricultural uses along roads and railroads. © 1990, American Chemical Society. All rights reserved.