Studies On The Characteristic And The Controlling Factors Of Hydrochemical Evolution In Suxian Mining Area

Suxian mining area in Anhui huaibei coalfield is an important part of concealed coal mines in North China.Abundant coal resources bring remarkable economic benefits to the local.However,the mining activities in recent years have changed the input and output of groundwater system,which contributed to complicated hydrogeological conditions and frequent mine water inrush accidents.In this study,we firstly took a deep investigation on the geological background of Suxian mining area,then collected the conventional ions(K⁺+Na⁺,Ca²⁺,Mg²⁺,Cl^-,SO₄^2-,HCO₃^-,CO₃^2-)of dominant inrush aquifers?the fourth aquifer of unconsolidated formation,the fissured aquifer of coal measure and the karst aquifer of Taiyuan formation?.The ion ratio and the principal component analysis were combined and used to discuss the hydrochemical formation.The factors controlling groundwater chemical were studied by observing the spatial distributions of the principal component loading scores and hydrochemical types.In order to quantitatively analyze the groundwater flow path and hydrochemical evolution of the mining area,the hydro-geochemical model was established based on the appropriate groundwater flow path and mineral phase.The main research results are as follows:?1?The order of the cation in dominant inrush aquifers is Na⁺>Ca²⁺>Mg²⁺.The order of the anion in both the fourth aquifer and the karst aquifer is SO₄^2->HCO₃^->Cl^- while in the fissured aquifer is HCO₃^->SO₄^2->Cl^-.There is larger variation coefficient of Na⁺,SO₄^2-,HCO₃^- in the fourth aquifer,Ca²⁺,Mg²⁺,SO₄^2-,HCO₃^-in the fissured aquifer and Ca²⁺,Mg²⁺,SO₄^2- in the the karst aquifer.The difference of conventional ions in the dominant inrush aquifers comprehensively reflects different hydrochemistry actions and groundwater flow path in the Suxian mining area.?2?The fourth aquifer with a close hydraulic connection is characterized by the pyrite oxidation,the cation exchange and adsorption and the carbonate and sulfate dissolution.The fissured aquifer has a poor condition of groundwater runoff and therefore the interaction of the cation exchange and adsorption or the sulfate reduction become stable.The east-central of karst aquifer with a good hydrodynamic condition is characterized by the pyrite oxidation or the carbonate and sulfate dissolution while the weasten of karst aquifer with a bad hydrodynamic condition study area is characterized by the pyrite oxidation or the carbonate and sulfate dissolution.?3?Both the qualitative analysis of spatial evolution of hydrochemistry by Arc GIS and the quantitative simulation of hydro-geochemistry reveal that the geological background and the mining activity control the groundwater flow,and further effect the hydrochemical formation and hydrochemical type.Obviously,the fourth aquifer is controlled by mining activity,the fissured aquifer is controlled by faults and the karst aquifer is controlled by mining activity,faults and folds.The paper which enriches the research about geochemistry techniques in mining area hopefully provides a theoretical support for the prevention and treatment of mine water hazard and also for the exploitation and utilization of groundwater in the concealed coal mining area in North China.