Occurrence And Risk Of Persistent Toxic Substances In Wetland Soils From The Modern Yellow River Delta

Persistent toxic substances (PTS) such as Organochlorine pesticides (OCPs), polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs), which are environmental persistence, bioaccumulative and toxic, have earned widespread concern. Although OCPs and PCBs have been banned in domestic and abroad, plenty of studies have shown that these contaminants exist in various environmental media, animals, plants and human bodies. To understand the occurrence and concentration levels of theses contaminants, analysis the environmental sources and assess the environmental risk of these target contaminants, will be helpful to provide basic data for the ecological risk assessment and environmental management.In this study,22 wetland soil samples were collected from modern course (Me), middle area (Ma) and old course (Oc) in the modern Yellow River Delta (mYRD). The Ultrasonic extraction, gas chromatography (GC) or gas chromatography-mass spectrometry (GC-MS) were applied to analysis the concentrations of OCPs, PCBs and PAHs. According to the properties and the historical application of these target contaminants, the distribution characteristics of these compounds were studied. Furthermore, source analysis was used to reveal the source of these contaminants. Finally, risk assessment of the target compounds was evaluated.The analysis data have shown that the 19 organochlorine pesticides OCPs were detected in all samples, and heptachlor, chlordane, HCHs and DDTs were the main contributors. The concentrations of∑OCPs in Me, Ma and Oc were 15.86,11.11,15.08 ng g-1 dw. The distribution trend of HCHs was Mc>Oc>Ma, DDTs was Oc>Mc>Ma, and heptachlor and y-chlordane are Mc>Ma>Oc. The average concentrations of∑PCBs and EPAHs in Me, Ma and Oc were 45.0,35.7,29.5 ng g-1 dw and 148.7,133.2,192.1 ng g-1 dw. The level of the OCPs in the modern Yellow River Delta wetland soils compared to that of other countries or regions was relatively moderate, however, the level of PCBs was slightly higher than that in other countries or regions, and the pollution level of PAHs was relatively lower.The source analysis has indicated that the HCHs in the modern Yellow River Delta wetland soils are probably derived from the long-range transport and atmospheric residue, and it has exposure risk to the wildlife lived in this area, also has contribution to the inputs of the OCPs into Bohai sea. The environmental risks and sources of chlorine and chlordane are worthy of further concern. The PAHs are mainly originated form combustion of coal, wood, and other fule. In general, the eco-environment risks of the PAHs are acceptable, but the BbF, BkF, Ind and BghiP may have some ecological risks.