Review on the determination methods for early warning grade and threshold of groundwater pollution risk

It is very important to determine the reasonable threshold of groundwater pollution risk early warning for the establishment of a groundwater pollution early warning system. At present, however, the threshold of groundwater pollution risk early warning in our country is in the exploration stage, and has not formed a perfect theoretical method system. Based on the relevant research results at home and abroad, this paper systematically combs the research methods of groundwater pollution risk early warning, summarizes the research progress of groundwater pollution risk early warning levels and threshold delimitation methods. The methods of threshold delimitation mainly include the established criteria method, threshold setting method, comprehensive evaluation method and other methods. This paper compares the applicable conditions of various threshold delimitation methods. The established criteria method is applicable to the macro region on a large scale. The threshold setting method has strong pertinence and accuracy in the research region with perfect basic data. The comprehensive evaluation method can deal with multiple variable factors, make quantitative evaluation on qualitative factors, and is applicable to the research region with more variables and qualitative factors. The conclusions provide a theoretical basis for the early warning classification of groundwater pollution risk and the selection of threshold delimitation methods in different study areas. Finally, this paper points out that the following two works should be further strengthened in improving the theoretical methods of groundwater pollution risk early warning system in China: (1) Strengthen the cross penetration of multi-disciplinary research results, with the help of multi-method interactive application. (2) Strengthen the hydrogeological investigation and monitoring related to groundwater pollution, and continuously improve the level of groundwater pollution investigation and research. (3) In order to obtain the scientific early warning results, the influencing factors of groundwater pollution, such as geology, pollution sources, groundwater value and dynamics, are analyzed comprehensively.