Composition and distribution of organochlorine pesticide residues in surface sediments from the Wu-Shi River Estuary, Taiwan.

The contamination of organochlorine pesticides (OCPs) in sediments from the Wu-Shi River estuary was investigated to evaluate the pollution potentials and distribution of OCPs in central Taiwan. A total of 19 sediment samples were collected at five sampling stations along the River estuary. The concentrations of OCPs were in the range of 0.99-14.5 ng/g-dry weight (dw) for sigmaHCH (alpha-, beta-, gamma-, delta-HCH), 0.46-13.4 ng/g-dw for sigma cyclodiene and 0.53-11.4 ng/g-dw for sigmaDDT (p,p'-DDD, p,p'-DDE, p,p'-DDT). The mean concentrations of sigmaHCH, sigma cyclodiene and sigmaDDT were 3.79, 4.87 and 2.51 ng/g-dw, respectively. The total concentrations of OCPs correspond to 1.73-71.9 microg/g-OC when normalized to TOC contents. Among the organochlorine pesticides, endosulfan sulfate, beta-HCH, and p,p'-DDD were the most dominant compounds in the sediments with the average concentrations of 1.97, 3.43 and 2.08 ng/g, respectively. Also, different contamination patterns among sampling seasons were observed. The measured concentrations of OCPs collected in spring were higher than those in autumn and winter. A linear relationship between sediment characteristics and OCP residues was also demonstrated. The results obtained in this study show that there still exist a variety of organochlorine pesticide residues in the sediments from the near shore of central Taiwan.