Chemical Characteristics Of Groundwater And Source Analysis Of Sulfate In Piedmont Inclined Basin

Affected by the landform,the groundwater in Jiyuan basin is enriched,the water yield of a single well is large,and it is easy to exploit.It has become the main water supply source for industry,agriculture and domestic water.In recent years,the concentration of SO₄^2-in groundwater has increased year by year,threatening the safety of regional water use.However,the source of sulfate(SO₄^2-)is not clear,so it is particularly important to analyze the hydrochemical characteristics and sulfate source for the development,utilization and protection of groundwater.Therefore,the samples of surface water and groundwater in the study area were collected,and the characteristics of chemical components,hydrogen,oxygen,and sulfur stable isotopes were analyzed by using mathematical statistics,ion proportion analysis and Bayesian stable isotope mixing model.The sources of chemical components,hydrochemical evolution law and sulfate sources of surface water and groundwater were discussed.The results show that:The ions in surface water and groundwater in the study area are mainly Ca²⁺、Mg²⁺、HCO₃^-and SO₄^2-,The hydrogen and oxygen isotope values of surface water and groundwater are similar and increase along the runoff direction.The water body in the area is mainly supplied by atmospheric precipitation,with strong water circulation,close hydraulic connection and long water rock interaction time.And the hydrochemical type is mainly Ca·Mg-HCO₃·SO₄,followed by Ca·Mg-HCO₃.The weathering of carbonate rock is the main controlling factor of water chemical composition,and the dissolution of dolomite,calcite and salt rock is the main source of ions.Among them,sulfuric acid and carbonic acid participate in the chemical weathering of carbonate rocks,and the proportion of sulfuric acid is less.Different types of water bodies are mainly supplied by modern atmospheric precipitation,with close hydraulic connection,strong water circulation and long water rock interaction time.Affected by the dilution of precipitation and surface water,the content of SO₄^2-decreases andδ³⁴S increases along the runoff path.Sulfuric acid is involved in rock weathering and affects SO₄^2-content,which has nothing to do with gypsum.Sulfate in surface water in the East and South mainly comes from atmospheric precipitation,chemical fertilizer,sewage and soil,24.5%、23.4%、28.7%and 23.4%respectively,and groundwater mainly comes from sewage,about 32%;Sulfate in surface water in the west mainly comes from atmospheric precipitation and sewage,28.8%and 28.5%respectively;sulfate in pore groundwater mainly comes from sewage,about 40.7%;Sulfate in surface water in the North mainly comes from atmospheric precipitation and sewage,28.8%and 28.5%respectively.Sulfate in pore water mainly comes from sulfide oxidation and sewage in coal measures,30.5%and 24.6%respectively.Sulfate in karst water mainly comes from sulfide oxidation and atmospheric precipitation in coal measures,25.5%and 21.8%respectively.Karst water near"skylight"is mainly affected by atmospheric precipitation and sewage.The research results provide a basis for the development and protection of water resources.There are 31 figures,5 tables and 93 references.