Assessment and Causes of Groundwater Organic Pollution in Typical Plain Areas in Xinjiang, China

Abstract

To study the organic pollution situation in groundwater in plain areas in Xinjiang, Shihezi region (SHZ), plain area of Yanqi Basin (YQ) and Ruoqiang-Qiemo area (RQ) were selected as the typical areas. 83 groundwater samples were collected, tested, and analyzed for 39 organic indexes for the first time. Results showed that the local groundwater in SHZ, YQ, and RQ had been slightly affected by organic pollution with the detection rates of 8.7, 33.3, and 33.3 %, respectively. Seven organic pollutants were detected, including chloroform (with the highest detection rate of 21.7 %), 1,2-dichloroethane, 1,2-dichlorobenzene, toluene, benzo(a)pyrene, α-BHC, and γ-BHC. The contents of all the detected organic pollutants were low, which were under the limits of the “Standards for Drinking Water Quality (GB5749-2006)”. Vertical distribution of detection rates was that in SHZ, shallow confined groundwater (12.5 %) > deep confined groundwater (10.0 %) > unconfined groundwater (0.0 %); in YQ, unconfined groundwater (66.7 %) > deep confined groundwater (29.2 %) > shallow confined groundwater (25.0 %); in RQ, shallow confined groundwater (66.7 %) > unconfined groundwater (33.3 %) > deep confined groundwater (16.7 %). The sources and properties of organic pollutants were the main factors that affected groundwater organic pollution in the study areas. The infiltration recharge of surface water mainly affected groundwater organic pollution in SHZ and YQ. Besides, the vadose zone had a certain restriction on the occurrence and migration of groundwater organic pollution components in RQ. Direct discharge of sewage came from human life and production without treatment, and leakage due to crude anti-seepage facilities had led to groundwater organic pollution. The organic wastewater produced in livestock and poultry breeding, chemical fertilizers, and insecticides in agricultural activities were also the main sources of groundwater organic pollution.