Liaohe River Water System Survey Of Polychlorinated Organic Compounds (pcocs) And Risk Evaluation

The contamination of our environment by polychlorinated organic compounds (PCOCs), such as polychlorinated benzenes, organochlorine pesticides, polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxinlfurans (PCDD/Fs), is. well known. Most PCOCs are persistent pollutants. They are resistant to biological or chemical degradation. Therefore, although some organochlorine pesticides such as DDT have been banned from use for many years, they can still be detected in the environment. In addition, these compounds are highly hydrophobic, resulting in accumulation in organisms, or organic phase of soils or sediments. Therefore, it is of crucial importance to know the pollution conditions of PCOCs in the environment. The Liao River situated in northeastern China is the seventh largest river and it plays an important role in the sustainable development of Liaoning Province. With the rapid economy development in the Liao River region, the river has been polluted seriously. The main pollution factors are found to be organic substances, such as COD~~, oils, etc. However, To date, no investigation on pollution of PCOCs in the Liao River has been performed. In order to assess the pollution conditions of PCOCs in the Liao River, a project named nvestigation and Risk Assessment of Polychlorinated Organic Compounds (PCOCs) in Drinking Water Resources of Developing Regions in Eastern China?was performed from November 98 to October 99. This project enables us for the first time to perfonn a pollution investigation of PCOCs in the Liao River on a large scale. A one-year period sampling project consisted of 4 sampling campaigns, December 1998, April 1999, June 1999 and October 1999 respectively, was arranged. Through the laboratory analysis, results on PCOC residues in the Liao River were obtained. It is the purpose of this paper to report on the sampling campaigns, analytical methods, as well as analytical results.Residues of polychlorinated organic compounds (PCOCs) were investigated in the Liao River. GC-ECD was used to analyse the water, particulate and sediment samples obtained in a one-year period sampling campaign. Hexachlorocyclohexanes (HCH) and DDTs (DDT) are main organochlorine pesticides in the Liao River. The HCH levels in water and sediment samples are 6.19-62.69 nglkg and <0.10-4.72 ng/g respectively. The maximum possible levels of DDT in water and sediment samples were 7.04 ng/kg and 3.24 ng/g respectively. In addition, PCOCs such as hexachlorobenzene and pentachloroanisole have also been detected in water samples. Hexachlorobenzene, pentachloroanisole, octachlorostyrene, dieldrin, heptachlor endosulfan and some PCBs were seldom detected in sediment samples. The pollution of PCBs in the Liao River is not significant. Compared with other domestic rivers in Northern China and overseas rivers, the PCOCs level in the Liao River is low. The HCHs and DDTs in the Liao River originate mainly from the use of pesticides in agriculture.