Characteristics And Evolution Of Chemical Composition Of Groundwater In Hebi Mining Area

Hebi mining area is a typical North China coal field.Coal mining activities destroyed the natural environment of groundwater and changed the seepage field and chemical field of ground water.The chemical field has changed.However,it is not clear that how the characteristics and laws of the chemical field of groundwater change.Therefore,the main water-filled aquifer in Hebi mining area is taken as the research object,the hydrochemical graphic method,ion combination ratio analysis and principal component analysis?PCA?are used to analyze the chemical characteristics and evolution law of groundwater.In order to quantitatively describe the variation characteristics of Ordovician,reverse hydrogeochemical simulation is carried out by means of PHREEQC software.The results are as follows:The water quality of conglomerate water is of HCO₃-Ca·Mg type and a few of them are HCO₃-Ca type,in which Ca²⁺,Mg²⁺and HCO₃^-are derived from the dissolution of carbonate rocks,and the water quality is easily affected.The hydrochemicaltypesofL₂groundwaterareHCO₃·SO₄-Ca·Mgand SO₄·HCO₃-Ca·Mg.The hydrochemical composition is mainly affected by the dissolution of carbonate and sulfate in limestone and the oxidation of pyrite in coal-bearing strata.And with the development of coal mining activities,the influence of pyrite oxidation on the water quality of L₂ water is obviously enhanced.The hydrochemical types of L₈ water mainly include HCO₃-Ca·Mg,HCO₃·SO₄-Ca·Mg and HCO₃-Na.The main source of Ca²⁺and Mg²⁺are the dissolution of carbonate rock and sulfate rock.Derived from the dissolution of rock salt and the mixing of sandstone water,the source of HCO₃^-is the dissolution of carbonate rock and the mixing of sandstone water.The main hydrochemical type of sandstone water is HCO₃-Na type.The main source of Ca²⁺and Mg²⁺in sandstone water is the dissolution of carbonate rock and sulfate rock.Na⁺is mainly from weathering of silicate minerals and dissolution of rock salt,and the chemical composition of water is mainly controlled by silicate minerals weathering.The water chemistry of Ordovician karst water is mainly of HCO₃-Ca·Mg type,which is controlled by dissolution and cationic alternating adsorption,and the coal mining activity has little effect on the water quality.In the runoff area,the main water-rock action of karst water is the incomplete dissolution of calcite and dolomite,the dissolution and precipitation of gypsum and rock salt,and the weak interaction of cation adsorption.In recent years,the strength of the interaction of water and rock increases with time.In the process of karst water flowing to coal mine area,the flow of groundwater is slow and the function of water and rock is adequate.The main water-rock action is the incomplete dissolution of calcite and dolomite,the dissolution of gypsum and rock salt,and the alternating adsorption of cations.As a result,the contents of Cl^-,SO₄^2-and TDS in karst water in the coal mine area are obviously increased.Because of the coal mining activity,there may be hydraulic relation between karst water and other aquifers in the coal mine field,and the chemical composition of the water is affected by other aquifers.