Source characteristics and influencing factors of groundwater hydrochemistry in the karst areas of central Guizhou
Based on the results of regional hydrogeological and environmental geological surveys,this study conducted comprehensive water sampling and testing at 43 groundwater points across the karst areas of central Guizhou during the dry and wet seasons.The study utilized three widely-used geochemical diagrams-Piper trilinear plots,Gibbs diagrams,and ion ratio diagrams(including relationships like HCO3--(Mg2+/Ca2+and[SO42-/HCO3-]-[Ca2++Mg2+]/HCO)to identify the sources and characteristics of hydrochemical indicators of groundwater in the karst areas of central Guizhou.In addition to these geochemical methods,principal component analysis(PCA)was performed separately on the results of water quality tests completed from the dry and wet seasons to further clarify and verify the characteristics of groundwater sources during these two seasons,and to pinpoint specific water quality indicators influenced by various environment and human factors in the karst areas.The research findings reveal that the hydrochemical characteristics and influencing factors of groundwater in the study area are relatively consistent during the dry and wet seasons.Hydrochemical types of groundwater in this area is predominantly characterized by HCO3(SO4)-Ca(Mg).The Gibbs diagrams show that the groundwater chemistry across the study area aligns closely with the rock weathering type,with only minor deviations of a single mine water sample(H6).A comprehensive analysis using Gibbs diagrams confirms that karst groundwater in the study area is primarily of a rock weathering type,with its hydrochemical composition predominantly derived from rock weathering and leaching dissolution processes.Further analysis using the[(Ca+Mg)/HCO3]-[SO4/HCO3]diagrams indicates that the molar ratio of[Ca2++Mg2+]/HCO3-in groundwater during both the wet and dry seasons is largely below 0.5.This finding is particularly concentrated in the areas dominated by carbonate rocks,with some samples showing a trend towards gypsum dissolution.Particularly,certain samples,such as Spring S214 in Yongjing town of Xifeng county,and Spring C8 in Longyanpo village of Jinzhong town,Kaiyang county,are located either to the right or near the gypsum dissolution line.These positions indicate a significant influence of gypsum dissolution on groundwater chemistry,suggesting gypsum dissolution plays a crucial role in shaping the hydrochemical profile in parts of the areas.A comprehensive analysis of ion ratio correlations suggests that the soluble carbonate rocks in the study area are primarily affected by carbonate weathering and erosion processes.However,significant impacts from gypsum dissolution are also observed in some samples.This suggests that while the majority of the groundwater chemistry is shaped by carbonate dissolution,there are distinct pockets where gypsum dissolution contributes markedly to the groundwater composition.During the wet season,groundwater composition is mainly influenced by three principal factors:water-rock interactions(PC1),human activities(PC2),and industrial production(PC3).Together,these factors explain 83.7%of the variance in groundwater chemical composition.In contrast,during the dry season,groundwater is primarily influenced by water-rock interactions(PC1*)and human activities(PC2*),jointly accounting for 85.1%of the chemical composition variance.This seasonal variation highlights the dynamic nature of groundwater chemistry in response to both natural and human factors.Water-rock interactions emerge as the predominant factor influencing the hydrochemical composition of groundwater in the study area.These interactions significantly affect the concentrations of major ions such as potassium,sodium,calcium,magnesium,bicarbonate,total phosphorus,fluoride,and silica.Human activities,particularly agricultural and domestic activities,mainly influence the concentrations of ammonium,chemical oxygen demand(CODMn),and chloride.Additionally,the impact of phosphate mining is evident in its contribution to elevated sulfate ion concentrations,particularly in areas near mining operations.The research findings provide valuable insights into the complex hydrochemical dynamics of karst groundwater in central Guizhou.The consistent hydrochemical characteristics observed during the dry and wet seasons,alongside the predominant influence of rock weathering and dissolution processes,underscore the importance of geological factors in shaping groundwater chemistry in karst areas.However,the notable influence of gypsum dissolution in certain samples also highlights the need to consider localized geological variations when groundwater quality and developing management strategies are assessed.Moreover,the identification of human activities and industrial production as significant secondary influences on groundwater quality points to the need for targeted management interventions.These interventions should aim to mitigate the impacts of human activities on groundwater resources,particularly in the areas where agricultural runoff,domestic wastewater discharge,and industrial effluents contribute to the groundwater contamination.Overall,this study enhances our understanding of the hydrochemical characteristics of karst groundwater in central Guizhou,revealing the sources of groundwater ion components and their influencing factors.The findings have significant implications for the rational development and conservation of groundwater resources in karst areas.Effective management strategies should consider both natural geological processes and human influences identified in this study to ensure the sustainable use and protection of groundwater resources in the karst areas in central Guizhou.By integrating hydrogeological surveys with geochemical and statistical analyses,this study provides a comprehensive framework for understanding groundwater systems in karst environment,offering valuable guidance for future research and water resource management.
the karst areas in central Guizhougroundwaterhydrochemical characteristicsprincipal component analysis
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维普
