Concentrations and Distribution Characteristics of Organochlorine Pesticides and Polychlorinated Biphenyls in Seawaters of the South Sea

In recent years, with the operation of coastal chemical production bases and booming maritime transportation of dangerous chemicals, there are threats to the marine environment. Persistent organic pollutants, such as organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs), have been detected in the offshore marine environment. In order to understand the pollution status of persistent organic pollutants (POPs) in the South China Sea, 15 PCBs and OCPs in seawater from the South China Sea were quantitatively determined by using Gas Chromatography- Electron Capture Detector (GC-ECD). Six kinds of OCPs and six kinds of PCBs were detected in these seawater samples. Using an external standard method for quantitative analysis, the detection limits were 0.24-1.07 ng/L, the linear range of the method was 1.0-250 ng/L. The recoveries for blanks were in the range of 89.1% to 109.7% with the relative standard deviations of 2.3%-8.6% and the recoveries for the samples were in the range of 90.1% to 113.5% with the relative standard deviations of 3.1%-10.4%. The results show that the concentration ranges of OCPs and PCBs were 0-92.30 ng/L and 1.16-76.24 ng/L respectively in the surface seawater, 0-69.85 ng/L and 0-49.63 ng/L in seawater from the depth of 200 m, and 0-56.68 ng/L and 0-26.47 ng/L in seawater from the depth of 500 m. The distribution of the contents of OCPs and PCBs tend to be highest in surface water, and lower in 200 m depth layer, and lowest in 500 m depth layer. The main possible pollutant sources are nearby surface runoff and atmospheric input. The pollutants were absorbed by suspended substances and transported from surface to deep seawater column. The detected OCPs and PCBs levels in the South China Sea are lower than those in other offshore marine environments in China, but higher than those in other countries with published data. The concentrations and distribution characteristics of OCPs and PCBs in the South China Sea, provide basic data for future research.