Spatial analysis and GIS mapping of regional hydrochemistry, groundwater quality, and probabilistic health risk in western Sichuan Basin, southwestern China

Nitrate contamination in groundwater is widespread, and studying the extent of contamination and its health risk effects on the population is beneficial for groundwater protection. In this study, 130 groundwater samples collected from the western Sichuan Basin were analyzed for hydrochemical spatial distribution, groundwater quality, and probabilistic health risk. Piper diagram showed that the hydrochemical type of groundwater samples was Ca-HCO₃. The hydrochemical components were mainly controlled by carbonate dissolution, silicate weathering and cation exchange based on ion ratios and saturation index. The statistical and spatial analysis showed that the concentration of NO₃⁻ exceeded the permission limit for drinking purpose in the central and eastern parts of the study area. The EWQI results showed that about 90.84% of the water samples were of excellent and good quality for drinking purpose. The HI-total values showed that, about 37.40% of samples yielded health risks above the limit value 1 for children. And the percentages of samples were 22.90% and 29.77% for adult females and adult males, respectively. Spatial analysis indicated the samples unsuitable for drinking were concentrated on the cultivated areas of low-hill landform where nitrogen fertilizers were used. Therefore, more attention of groundwater protection should be paid in the central and eastern cultivated areas of low-hill landform. The achievements would provide a vital reference for groundwater management in Sichuan Basin and other similar areas in the world.