Groundwater Quality in and Around a Landfill in Northwest China: Characteristic Pollutant Identification, Health Risk Assessment, and Controlling Factor Analysis

Landfilling is the main method used for garbage disposal, but landfill leachate can affect groundwater quality. To study the influence of landfill leachate on groundwater, 6 monitoring wells and 14 domestic wells in and around the Jiangcungou landfill site in northwest China were sampled. Groundwater chemistry characteristics were analyzed, and water quality and health risks were assessed. Saturation index and correlation analysis were used to identify the sources of major ions, and the hydrogeochemical mechanism controlling characteristic contaminants was analyzed. The result of single-factor water quality evaluation showed that 35% of groundwater samples had at least one indicator exceeding the drinking water standards. It was confirmed that the landfill had an impact on groundwater, as the average pollution index of the monitoring wells (0.72) was significantly higher than that of the domestic wells (0.31). The major characteristic pollutants were iron (Fe), manganese (Mn), arsenic (As) and fluoride (F−), and their average pollution indices were 12.91, 1.78, 1.1, and 2.47, respectively. The average non-carcinogenic health risks of F−, NO3− and As were 0.96, 0.58, and 0.42, respectively, while the average carcinogenic risk for arsenic was 1.90E−04. The landfill is in the methane production stage, resulting in a reducing redox environment. Among the four characteristic pollutants, Fe and Mn resulted mainly from the landfill, while As and F− were affected by the landfill as well as slow groundwater flow and other human activities. Necessary measures were also proposed to prevent groundwater pollution in and around the landfill.