Organochlorine pesticide residues in Songkla Lake

The water quality of Songkla Lake for organochlorine (OC) pesticide contamination was studied from chosen sampling sites (stations) using the lakes geographic data and pollution sources. The water samples were collected monthly from 13 stations in Songkla Lake during September 1991–November 1992. The OC pesticide residues found were Heptachlor, Heptachlor Epoxide, DDD, DDE, DDT and Aldrin in the range 0–0.5690 ppm. This study showed that DDT and its metabolite products (DDD and DDE) dominated OC pesticide residues in the lake. The concentration of OC residues also depended on the season, i.e. at some sampling stations the concentration of OC residues in the dry season (July–September) were higher than in the wet season (October–January).