The understanding of F⁻ concentration in groundwater in humid areas is limited although there are lots of research on high-fluoride groundwater in arid areas. In this paper, with controlling factors of F⁻ concentrations in humid areas as the focus, 130 groundwater samples, obtained from four subsystems in Northwest Xingguo County, Jiangxi Province, China, were investigated to demonstrate the controlling factors of F⁻ concentrations in humid areas. According to analytical results, the following hydrogeochemical characteristics of the fluorine in humid mountainous areas were determined: (1) F⁻ concentration is positively correlated with total dissolved solids (TDS), Ca²⁺, , and pH; (2) the groundwater features a high flow rate and low TDS; (3) the equilibrium constant of CaF₂ is less than its solubility product constant, and the fluorine-bearing minerals in rocks are in a dissolved state; and (4) the dissolved fluoride-bearing minerals constitute the main sources of F⁻ in the groundwater. Fluorine mainly comes from groundwater fluorine-bearing minerals in metamorphic rocks. Moreover, the low F⁻ concentration in the groundwater mainly results from the fast flow rate of groundwater. Fluoride in groundwater has great potential hazards in humid areas.

Drawing upon an understanding of the distribution characteristics of groundwater in the Taoshan rock mass within the Yushan Uplift region of southern Jiangxi, this study utilizes mathematical statistics, ion ratio coefficients, factor analysis, and mineral dissolution equilibrium methods to characterize in detail the hydrochemical features of groundwater in humid mountainous areas. Furthermore, the study delves into the lithological source control and the primary natural mechanisms that underlie these characteristics. The results indicate that the average pH of groundwater in the study area is 7.13, classifying it as weakly alkaline. The dominant cations are Ca²⁺ and Na⁺, accounting for 61% and 26% of the total cations, respectively, while the dominant anion is HCO₃⁻, constituting 91% of the total anions. The total dissolved solids (TDS) range from 37.93 mg/L to 228.16 mg/L, indicating low mineralization. The groundwater types are primarily HCO₃-Ca·Na and secondarily HCO₃-Ca. The groundwater type is mainly controlled by rock weathering, with the primary ion sources influenced by the weathering and dissolution of silicate rocks, supplemented by contributions from carbonate rock dissolution. Ion ratio analysis further confirms that the major ions in groundwater predominantly originate from the weathering of silicate minerals, with minimal influence from human activities. Na⁺, K⁺, and H₂SiO₃ are primarily derived from the weathering and dissolution of silicate rocks, while the weathering and dissolution of carbonate rocks (e.g., calcite) significantly contribute to Ca²⁺ and Mg²⁺. TDS shows significant positive correlations with Mg²⁺, SO₄²⁻, HCO₃⁻, Na⁺, and Ca²⁺, with the most pronounced correlations observed between TDS and Ca²⁺ and HCO₃⁻, exhibiting a correlation coefficient of 0.89. Factor analysis reveals that the first principal component has relatively high loadings for TDS, Ca²⁺, HCO₃⁻, Mg²⁺, and SO₄²⁻. Additionally, among 45 natural spring water samples, 36 exhibit metasilicic acid (H₂SiO₃) concentrations exceeding 30 mg/L, meeting the standards for metasilicic acid mineral water and demonstrating significant potential for development and utilization.

This study systematically unravels the hydrochemical evolution mechanisms and driving forces in multi-aquifer systems of Qingdao, a coastal economic hub. Integrated hydrochemical analysis of porous, fissured, and karst water, combined with PHREEQC modeling and Positive Matrix Factorization (PMF), deciphers water–rock interactions and anthropogenic perturbations. Groundwater exhibits weak alkalinity (pH 7.2–8.4), with porous aquifers showing markedly higher TDS (161.1–8203.5 mg/L) than fissured (147.7–1224.8 mg/L) and karst systems (361.1–4551.5 mg/L). Spatial heterogeneity reveals progressive hydrochemical transitions (HCO₃-Ca → SO₄-Ca·Mg → Cl-Na) in porous aquifers across the Dagu River Basin. While carbonate (calcite) and silicate weathering govern natural hydrochemistry, evaporite dissolution and seawater intrusion drive severe groundwater salinization in the western Pingdu City and the Dagu River Estuary (localized TDS up to 8203.5 mg/L). PMF source apportionment identifies acid deposition-enhanced dissolution of carbonate/silicate minerals, with nitrate contamination predominantly sourced from agricultural runoff and domestic sewage. Landfill leachate exerts pronounced impacts in Laixi and adjacent regions. This study offering actionable strategies for salinity mitigation and contaminant source regulation, thereby providing a scientific framework for sustainable groundwater management in rapidly urbanizing coastal zones.

This study aims to reveal the extent of the impact of mining activities on groundwater in a specific mining area in Hunan Province, assess the current quality of groundwater in the study area, investigate the correlations among heavy metal elements, and understand the migration and enrichment processes of different elements in groundwater. The findings will provide scientific data support for the establishment of groundwater monitoring systems by local governments and environmental protection departments. This paper presents the monitoring work conducted on the current status of heavy metal ions in groundwater within a mining area. Sampling and analysis were performed to measure pH, total dissolved solids (TDS), manganese (Mn), arsenic (As), cobalt (Co), molybdenum (Mo), barium (Ba), antimony (Sb), and selenium (Se) in both groundwater and surface water surrounding the study area. An improved hierarchical ladder evaluation method was used to comprehensively assess the degree of heavy metal pollution in the groundwater of the mining area. Additionally, statistical analysis was conducted to examine the correlations between heavy metal evaluation factors and TDS. The results show that the TDS values at various water quality monitoring points range from 187.34 to 1359.67, with a median of 400 and an average of 460.83. Additionally, the analysis of heavy metal pollution characteristics indicates that the water bodies in the mining area are severely impacted by mining activities, falling into the category of severe pollution. Among the heavy metals, As and Sb are the most serious pollutants, while the other heavy metal evaluation factors are less affected by mining activities. Correlation analysis further reveals that the correlation coefficients between Mo and Se and between Se and TDS are 0.772 and 0.778, respectively, indicating strong correlations. The correlation coefficients between As and Sb, Ba and Sb, and Mo and TDS are 0.455, 0.55, and 0.499, respectively, indicating moderate correlations. Other factor pairs exhibit weak correlations or even negative correlations.

Groundwater chemical composition often exhibits complex characteristics under the combined influence of anthropogenic activities and natural geological conditions. Accurately distinguishing between human-derived and naturally occurring constituents is crucial for formulating effective pollution control strategies and ensuring sustainable groundwater resource management. However, conventional hydrogeochemical analytical methods often face challenges in quantitatively differentiating these overlapping influences. In this study, 66 groundwater samples were collected from the midstream section of the Dawen River Basin, an area subject to significant anthropogenic pressure. An integrated approach combining hydrogeochemical analysis, Self-Organizing Map (SOM) clustering, and Positive Matrix Factorization (PMF) receptor modeling was employed to identify sources of chemical constituents and quantify the proportional contributions of various factors. The results indicate that: (1) The predominant groundwater types in the study area were Cl·SO₄·Ca. (2) SOM clustering classified the groundwater samples into five distinct groups, each reflecting a dominant influence: (i) natural geological processes—samples distributed within the central geological mining area; (ii) agricultural activities—samples located in intensively cultivated zones along both banks of the Dawen River; (iii) hydrogeochemical evolution—samples concentrated in areas with impermeable surfaces on the eastern and western sides of the study region; (iv) mining operations—samples predominantly found in industrial zones at the periphery; (v) domestic wastewater discharge—samples scattered relatively uniformly throughout the area. (3) PMF results demonstrated that natural geological conditions constituted the largest contribution (29.0%), followed by agricultural activities (26.8%), consistent with the region’s extensive farming practices. Additional contributions arose from water–rock interactions (23.9%), mining operations (13.6%), and domestic wastewater (6.7%). This study establishes a methodological framework for quantitatively assessing natural and anthropogenic impacts on groundwater quality, thereby providing a scientific basis for the development of protection measures and sustainable management strategies for regional groundwater resources.

Ecological security evaluation serves as the cornerstone for ecological management decision-making and spatial optimization. This study focuses on the Dongping Lake Basin. Based on the Pressure–State–Response (PSR) model framework, it integrates ecological risk, ecosystem health, and ecosystem service indicators. Utilizing methods including Local Indicators of Spatial Association (LISA), Transition Matrix, and GeoDetector, it analyzes the spatio-temporal evolution characteristics and driving mechanisms of watershed ecological security from 2000 to 2020. The findings reveal that the Watershed Ecological Security Index (WESI) exhibited a trend of “fluctuating upward followed by periodic decline”. In 2000, the status was “relatively unsafe”. It peaked in 2015 (index 0.332, moderately safe) and experienced a slight decline by 2020. Spatially, a significantly clustered pattern of “higher in the north and lower in the south, higher in the east and lower in the west” was observed. In 2020, “High-High” clusters of ecological security aligned closely with Shandong Province’s ecological conservation red line, concentrating in core protected areas such as the foothills of the Taihang Mountains and Dongping Lake Wetland. Level transitions were characterized by “predominant continuous improvement in low levels alongside localized reverse fluctuations in middle and high levels,” with the “relatively unsafe” and “moderately safe” levels experiencing the largest transfer areas. Geographical detector analysis indicates that the Human Interference Index (HI), Ecosystem Service Value (ESV), and Annual Afforestation Area (AAA) were key drivers of watershed ecological security change, influenced by dynamic interactive effects among multiple factors. This study advances watershed-scale ecological security assessment methodologies. The revealed spatio-temporal patterns and driving mechanisms provide valuable insights for protecting the ecological barrier in the lower Yellow River and informing ecological security strategies within the Dongping Lake Watershed.