Abstract
Hydrogeochemical processes and quality assessment for shallow groundwater are pivotal issues to be solved in many regions over the world due to the easy access of shallow groundwater. In this study, eighty-six water samples were collected from shallow aquifers of Chongqing, China, during July–September 2019. Multivariate statistical techniques, major ion ratios, and geochemical modeling were integrated to investigate hydrogeochemical characteristics and controlling factors. Afterwards, groundwater quality in spatial was classified by entropy-weighted water quality index and geographic information system (GIS) spatial analysis. Groundwater samples were alkaline and possessed high total dissolved solids (TDS) values. Two-group samples were distinguished as mix cations-HCO3-SO4 (group 1) and Ca-Mg-SO4 (group 2) facies. Hydrogeochemical compositions of group 1 samples were dominated by silicate dissolution and ion exchange, while sulfate and calcite dissolution were the main factors influencing the hydrogeochemical characteristics of group 2. The overall quality of groundwater samples varied greatly from excellent quality to extremely poor quality. Group 1 samples were found with excellent and good quality and suitable for drinking purposes. Group 2 samples were all unsuitable for direct drinking purposes as the quality varied from medium to extremely poor, but were spatially limited. Groundwaters with relatively poor quality were due to dissolution of sulfate that were locally enriched in the aquifers. The new findings of this study are expected to provide the reference for future management and sustainable exploitation of groundwater in Chongqing.
Highlights
Water is one of the most valuable but vulnerable natural resource in the world
This study is aimed to investigate the hydrogeochemical characteristic of shallow groundwater and corresponding controlling factors using the combination of multivariate statistical approaches, major ion ratios, and geochemical modeling, and classify groundwater quality in spatial by entropy-weighted water quality index and geographic information system (GIS) spatial analysis
To better visualize the vast data set, statistical analysis was conducted in this study
Summary
Water is one of the most valuable but vulnerable natural resource in the world. Of note, limited reserves and irregular distribution of surface water lead to it is not being available in many regions of the world, and groundwater would be the solely alternative for human society. Hydrogeochemical compositions of groundwater are usually influenced by a combination of natural processes and anthropogenic activities. Natural processes consist of dissolution and precipitation of different minerals (e.g., calcite, dolomite, silicate, gypsum, halite, etc.) and corresponding ion exchange [7,8,9]. They are determined by flow path and aquifer affinity of the groundwater system
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