Quantitative assessment of groundwater pollution risk in reclaimed water irrigation areas of northern China.

The application of reclaimed water for agricultural irrigation can effectively reduce the use of freshwater resources including groundwater, addressing the increasingly severe challenge of water shortage. However, reclaimed water irrigation will cause potential pollution risks to groundwater, which needs to be further studied to ensure the safety of reclaimed water irrigation. An integrated quantitative assessment system including the modified DRASTIC model was developed to evaluate the pollution risks caused by reclaimed water irrigation and scientific strategies were offered for the development of reclaimed water irrigation in water shortage areas to avoid groundwater pollution. The groundwater intrinsic vulnerability index, the hazards of the characteristic pollutants, and the groundwater values were quantified to obtain the pollution risks distribution map. In the Beijing plain of north China, the low groundwater pollution risk areas were located in the midstream of Chaobai river baisin, Beiyun river basin, and Yongding river basin, accounting for 48.3% of the total study area. These areas in low pollution risk can be considered as safety areas for reclaimed water irrigation. The moderate groundwater pollution risk areas accounting for 46.9% of the total study area were suggested to apply water-saving irrigation measures for preventing groundwater pollution. The reclaimed water irrigation should be prohibited in the high groundwater pollution risk areas, which accounted for 4.8% of the total study area. This study highlights the reasonable strategy for the development of reclaimed water irrigation in water shortage areas and lay a foundation for finding alternative water sources for agricultural irrigation.