Assessment of the contamination and genotoxicity of soil irrigated with wastewater

Wastewater has been widely used for agricultural irrigation in China and countries in arid and semi-arid areas. Because of poor control of the wastewater quality and long-term application, pollutants accumulation and the relevant ecotoxicological effects may occur, especially for persistent pollutants and permanently bound chemical residues. The pollutants accumulated in soil may transfer through the food chains and cause negative effects on human health. In the present study, a field survey in farmlands that have been irrigated with effluents from a sewage treatment plant and untreated wastewater was carried out. The soil quality was evaluated using a battery of chemical and biological parameters to describe the integrated situations of the polluted sites. Organochlorine pesticides (OCPs) were quantified by GC - ECD and polycyclic aromatic hydrocarbons (PAHs) were analyzed by GC-MS with internal standard. Polyphenol oxidase and catalase activities were examined to investigate the soil functions. Vicia faba micronucleus test was performed to detect the potential genotoxicity of water extracts of the soils. It has been concluded that both PAHs and OCPs have accumulated in the soils irrigated with wastewater. The main origin of PAHs was from the wastewater discharged from a coal plant. The site close to the pollution discharge point was heavily polluted by PAHs. OCPs were mainly residues of historical agriculture application. The MN frequencies and the activity of polyphenol oxidase were positively correlated with PAHs concentrations but have no correlation with OCPs. Therefore, polyphenol oxidase activity and MN frequencies were suggested as the biological indicators of PAHs pollution.