Hydrogeochemical evolution of groundwater in a Quaternary sediment and Cretaceous sandstone unconfined aquifer in Northwestern China

• Published in: Environmental earth sciences Vol. 77; no. 18; pp. 1 - 10
• Main Authors: Yu, Zhi-Qiang, Amano, Hiroki, Nakagawa, Kei, Berndtsson, Ronny
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.09.2018; Springer Nature B.V
• Subjects: Anhydrite; Anions; Aquifers; Biogeosciences; Carbonate rocks; Carbonates; Cations; Cluster analysis; Components; Cretaceous; Dissolution; Dissolved solids; Dissolving; Drinking water; Earth and Environmental Science; Earth and Related Environmental Sciences; Earth Sciences; Environmental Science and Engineering; Evaporation; Evolution; Geochemistry; Geology; Geovetenskap och miljövetenskap; Groundwater; Groundwater chemistry; Groundwater quality; Gypsum; Halite; Halites; Hydrogeochemical characteristics; Hydrogeochemistry; Hydrology/Water Resources; Minerals; Natural Sciences; Naturvetenskap; Oceanografi, hydrologi och vattenresurser; Oceanography, Hydrology, Water Resources; Organic chemistry; Original Article; Principal component analysis; Principal components analysis; Quaternary; Sandstone; Sedimentary rocks; Self organizing maps; Sulfate minerals; Sulfates; Sulphates; Terrestrial Pollution; The Dosit River; Travel; Travel time; Unconfined aquifers; Water analysis; Water quality; Water quality standards; Water resources; Water sampling; The Dosit River; Sulfate minerals; Self-organizing maps; Hydrogeochemical characteristics; Principal component analysis
• ISSN: 1866-6280; 1866-6299
• DOI: 10.1007/s12665-018-7816-5

A better understanding of the hydrogeochemical evolution of groundwater in vulnerable aquifers is important for the protection of water resources. To assess groundwater chemistry, groundwater sampling was performed from different representative aquifers in 2012–2013. A Piper trilinear diagram showed that the groundwater types can be classified into Na–SO 4 and Na–Cl types. Only one groundwater sample was Na–HCO 3 type. The dominant cations for all samples were Na + . However, the dominant anions varied from HCO 3 − to SO 4 2− , and as well Cl − . The mean total dissolved solid (TDS) content of groundwater in the region was 1889 mg/L. Thus, only 20% of groundwater samples meet Chinese drinking water standards (< 1000 mg/L). Principal component analysis (PCA) combined with hierarchical cluster analysis (HCA) and self-organizing maps (SOM) were applied for the classification of the groundwater geochemistry. The three first principal components explained 58, 20, and 16% of the variance, respectively. The first component reflects sulfate minerals (gypsum, anhydrite) and halite dissolution, and/or evaporation in the shallow aquifer. The second and third components are interpreted as carbonate rock dissolution. The reason for two factors is that the different aquifers give rise to different degree of hydrogeochemical evolution (different travel distances and travel times). Identified clusters for evolution characteristic and influencing factors were confirmed by the PCA–HCA methods. Using information from eight ion components and SOM, formation mechanisms and influencing factors for the present groundwater quality were determined.