Spatial distribution characteristics of volatile halogenated hydrocarbons in unsaturated zone of Xiaodian sewage irrigation area, Taiyuan, China.

Sewage irrigation is one of the best options to reduce the stress on limited fresh water and to meet the nutrient requirement of crops. Environment pollution caused by volatile halogenated hydrocarbons (VHCs) associated with sewage irrigation has received increasing attention due to the toxicological importance in ecosystem. The aim of this study was to discuss the spatial distribution characteristics of VHCs in unsaturated zone under sewage irrigation and their migration in the environment. Soil samples were collected from XiaoDian district of TaiYuan city and measured for the major VHCs including of chloroform (CHCl3), tetrachloromethane (CCl4), trichloroethylene (C(2)HCl(3)), tetrachloroethylene(C(2)Cl(4)), pentachlorobenzene (C(6)HCl(5)), hexachlorobenzene (C(6)Cl(6)). Results showed that VHCs were accumulated in the unsaturated zone with long-term sewage irrigation. The contents of VHCs in the unsaturated zone of the study area were 34, 2, 3, 1.5, 8.3, 4.8 times higher than the background value respectively. Soils with long-term irrigation of sewage showed higher contents of VHCs than that with short-term irrigation of sewage. Not only the irrigation time, soil physical properties (e.g. soil texture) also played an important role on VHCs accumulation in soil.