Distribution and evolution characteristics of national groundwater quality from 2013 to 2017

Based on the national groundwater quality monitoring data from 2013 to 2017, the variation characteristics of groundwater monitoring indicators are statistically analyzed, the main groundwater indicators based on the national grade groundwater monitoring wells that affecting groundwater quality are investigated, and the variations of groundwater quality from 2013 to 2017 are discussed. 20 groundwater items are selected according to the Quality Standard for Groundwater (GB/T 14848—93). The results show that total hardness, total iron, manganese, ammonium, nitrate and nitrite are the main contaminants that caused the deterioration of groundwater quality, and their over stand rate all exceeds 10%. The pollution of total hardness mainly in the North China, Northeast China, Southwest China and Northwest China, the variation of total hardness among the provinces in China is quite large. The ammonium contamination varies greatly among the provinces, and the contamination mainly in the provinces of Heilongjiang, Jiangsu, Guangdong and Ningxia. The nitrate contamination is stable at an annual rate, which are mainly in North China, Northeast China and Northwest China. Nitrite nitrogen pollution is more serious in North China, Northeast China and Northwest China, as well as in Shanghai, Jiangsu, Hubei, Guangxi and Guizhou. Iron and manganese contamination is mainly in North China, East China, and Central South China, and the provinces of Heilongjiang, Jilin, Liaoning, Anhui, Hubei, Sichuan and Ningxia, which are particularly serious. Based on data from the national grade groundwater monitoring wells, this paper makes a comprehensive analysis and evaluation of groundwater quality on a national scale, and summarizes the pollution items that need to be noticed in future groundwater monitoring.