Composition and distribution of organochlorine pesticide residues in surface sediments from Gediz and Bakircay Rivers (Eastern Aegean)

The contamination of organochlorine pesticides (OCPs) in sediments from Gediz and Bakirgay Rivers were investigated to evaluate the pollution potentials and distribution of OCPs in Western Turkey. In the selected rivers, the rapidly developing industrial and agricultural activities, municipal development and use of chemicals caused serious environmental problems. Surface sediments were sampled in January (rainy season) and July 2004 (dry season) at sampling stations from Gediz and Bakirgay Rivers. The concentrations of OCPs, by high resolution gas chromatography-electron capture detector, were detected in the sediment samples from the rivers that flow into the Aegean Sea. The concentration of organochlorine pesticides in surficial sediments from Gediz River were 0.88-47.4 ng g(-1)dw for Sigma DDTs (4.4'-DDT+ 4,4'-DDE+ 4,4'-DDD); 0.04-2.0 for Sigma. HCHs (alpha-, beta-, gamma-, delta-HCH) and 0.34-7.5 ng g(-1)dw for Sigma cyclodienes. Results showed that the concentrations of pesticides in sediments were in the range of 3.2-45.9 ng g(-1)dw for Sigma DDT; 0.43-2.0 ng g(-1)dw for Sigma HCH and 0.78-8.6 ng g(-1)dw for Sigma cyclodienes in Bakircay River. Among the OCPs, 4,4'-DDE was the most dominant compound in the Gediz and Bakirgay River sediments during rainy and dry seasons. In this study, the ratios of DDD+DDE/Sigma DDT and DDD/DDE were used to indicate the most probable source of contamination. The result of these ratios showed that most of the OCP contamination comes from the weathered agricultural areas. The ratios of DDD/DDE for the sediment samples were smaller than unity. This means that DDE was the most frequent OCP in the river sediments.