河套灌区杭锦后旗段不同盐渍化地下水水化学特征及作用机制OA

Groundwater resources are crucial for the Hetao Irrigation District.However,unsustainable exploita-tion and utilization have caused significant ecological and environmental problems in the region,including soil sa-linization.To better understand how salinization affects groundwater hydrochemical characteristics and to clarify the underlying mechanisms,this study focused on the Hanggin Rear Banner of the Hetao Irrigation District.A to-tal of 36 groundwater samples were collected along the Yangjia River section,spanning from the piedmont area to the Yellow River.By integrating multivariate statistical analysis,hydrochemical methods,and isotope tech-niques,we analyzed the hydrochemical and stable hydrogen-oxygen isotopic characteristics of groundwater across different salinization levels and explored the evolution mechanisms and the influence of various factors.The results indicate that the groundwater in the study area is generally slightly alkaline.The total concentration of anions and cations increases significantly as salinization progresses from non-saline to mildly saline,and then to moderately and severely saline areas.With increasing salinization,the hydrochemical type of groundwater evolves from SO4·Cl-Na to Cl-Na.Principal component analysis(PCA)further indicates that hydrochemical compositions are primarily controlled by evaporation concentration(67.34%contribution)and the coupled pro-cesses of carbonate leaching and cation exchange in a weakly alkaline environment,influenced by groundwater level fluctuations(11.83%contribution).Evaporite weathering and dissolution play a dominant role.In regions with moderatetosevere saline soils,the combined effect of evaporation concentration with silicate weathering and cation exchange is significantly enhanced.Nitrate point-source anomalies suggest that anthropogenic agricultural activities may be the third major driving force behind groundwater evolution in the study area.These findings illu-minate the hydrogeochemical processes linked to salinization and offer a theoretical foundation for optimizing water resource management and controlling salinization in irrigation areas.