Occurrence and distribution of organochlorine pesticides (HCH and DDT) in sediments collected from East China Sea

Sediments used in this study were collected from different depths of eight sites in East China Sea in November 2002. The levels and distribution patterns of the selected organochlorine pesticides (OCPs = p,p′-DDT, o,p′-DDT, p,p′-DDE, p,p′-DDD, α-, β-, γ- and δ-HCH) in samples were investigated by the technique of sonication extraction followed by the analysis of gas chromatography (GC) coupled with a micro-electron capture detector (μECD). The concentrations of ΣHCH and ΣDDT in the surface sediments were in the range of < 0.05-1.45 ng/g (mean 0.76 ng/g), < 0.06-6.04 ng/g (mean 3.05 ng/g) based on dry weight (dw), respectively. In the vertical distributions, the ΣHCH and ΣDDT were in the range of < 0.05-2.52 ng/g, < 0.06-10.94 ng/g dw, respectively. Residues of OCPs varied significantly with different sampling sites. ΣDDT in the surface sediments was correlated well with total organic carbon (TOC) content (r2 = 0.71), while ΣHCH showed no obvious correlation. The distribution showed that the sediments from the vicinity estuary or near shore had higher TOC contents, and higher OCPs concentrations. The contamination record indicated an extensive use of OCPs in the catchments from Yangtze River in the past might greatly affect the OCP residues.