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.

Elucidating the hydrogeochemical processes and quality assessment of groundwater holds significant importance for its sustainable development. In this paper, 53 groundwater samples were collected from a typical agricultural area in the northeastern Chongqing municipality in SW China. The integration of multivariate statistical analysis, ion ratio analysis, geomodelling analysis, the entropy water quality index, health risks assessment, and sensitivity analysis was carried out to explore the hydrochemical processes and quality assessment of groundwater in this study. The statistical results reveal that the cationic concentrations followed the order of Ca²⁺ > Mg²⁺ > Na⁺ > K⁺, while the anionic components were in the order of HCO₃⁻ > SO₄²⁻ > NO₃⁻ > Cl⁻. Based on the Piper trilinear diagram, the hydrochemical types were shown as Ca-HCO₃ and Ca-Mg-HCO₃ types. Hierarchical cluster analysis indicated that the groundwater samples could be categorized into three groups. The hydrochemical compositions were primarily influenced by water–rock interactions (e.g., carbonate dissolution and silicate weathering). In terms of irrigation suitability, the sodium adsorption ratios (SARs) ranged from 0.05 to 1.82, and the electrical conductivity (EC) varied from 116 to 1094 μs/cm, indicating that most groundwater samples were suitable for irrigation. The entropy-weighted water quality index ranged from 15 to 94, suggesting that the groundwater samples were suitable for drinking purposes. Non-carcinogenic human health risks followed the order of children > adult females > adult males, within the average values of 0.30, 0.21, and 0.18, respectively. Sensitivity analysis showed that the parameters had the weight order of NO₃ > body weight (BW) > ingestion rate (IR) > exposure frequency (EF). Hence, we recommend prioritizing the management of areas with high salinity levels, while avoiding the excessive use of nitrogen fertilizers, raising awareness among local residents about safe groundwater, and providing robust support for the sustainable development of groundwater in typical agricultural areas.

Groundwater nitrate (NO₃⁻) contamination has emerged as a critical global environmental issue, posing serious human health risks. This study systematically investigated the hydrochemical processes, sources of NO₃⁻ pollution, the impact of land use on NO₃⁻ pollution, and drinking water safety in an urban area of southwestern China. Thirty-one groundwater samples were collected and analyzed for major hydrochemical parameters and dual isotopic composition of NO₃⁻ (δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻). The groundwater samples were characterized by neutral to slightly alkaline nature, and were dominated by the Ca-HCO₃ type. Hydrochemical analysis revealed that water–rock interactions, including carbonate dissolution, silicate weathering, and cation exchange, were the primary natural processes controlling hydrochemistry. Additionally, anthropogenic influences have significantly altered NO₃⁻ concentration. A total of 19.35% of the samples exceeded the Chinese guideline limit of 20 mg/L for NO₃⁻. Isotopic evidence suggested that primary sources of NO₃⁻ in groundwater include NH₄⁺-based fertilizer, soil organic nitrogen, sewage, and manure. Spatial distribution maps indicated that the spatial distribution of NO₃⁻ concentration correlated strongly with land use types. Elevated NO₃⁻ levels were observed in areas dominated by agriculture and artificial surfaces, while lower concentrations were associated with grass-covered ridge areas. The unabsorbed NH₄⁺ from nitrogen fertilizer entered groundwater along with precipitation and irrigation water infiltration. The direct discharge of domestic sewage and improper disposal of livestock manure contributed substantially to NO₃⁻ pollution. The nitrogen fixation capacity of the grassland ecosystem led to a relatively low NO₃⁻ concentration in the ridge region. Despite elevated NO₃⁻ and F⁻ concentrations, the entropy weighted water quality index (EWQI) indicated that all groundwater samples were suitable for drinking. This study provides valuable insights into NO₃⁻ source identification and hydrochemical processes across varying land-use types.

Basic education is a foundation-laying project of national quality education. Improving the ecological carrying level of basic education is of great practical significance to the coordinated and sustainable development of regional society and economy. Based on the panel data of Chongqing from 2011 to 2017, combined with the DPSIR theoretical model, a comprehensive evaluation index system was conducted, and the spatial and temporal evolution characteristics of ecological carrying capacity of county education in Chongqing was explored by using statistical analysis and spatial analysis methods. The multiple linear regression model was used to analyze differences in the impact of economic structure adjustment on the ecological carrying capacity of county education. It was found that the level of ecological carrying capacity of county education in Chongqing showed a steady upward trend in terms of time sequence, and all the five subsystems showed the characteristics of steady development, but the influence of each subsystem on the overall carrying capacity was different. From the formation mechanism, Chongqing’s educational ecological carrying capacity is the result of a multi-factor complex system, and there are obvious differences in the influencing factors at different development stages. Therefore, it is necessary to narrow the regional differences of education ecological carrying capacity, promote the coordinated development of education among regions, and take multiple measures to effectively ensure the high quality and sustainable development of county education in Chongqing.