Studies On The Evolution Characteristics And The Controlling Factors Of Hydrochemical Components In Pingdingshan Mining Area

Pingdingshan mining area is a typical karst type coal field in North China.There are sandstone aquifer of Permian system,limestone aquifer of Taiyuan Formation and limestone aquifer of Cambrian System in the roof and floor of the coal seam.Under the mining conditions,the confined water of the strata is easy to fill the mine,so the hydrogeological conditions of the mine are complex and the water disasters are frequent.To find out the hydrochemical composition,characteristic evolution and control factors of each water filled aquifer is the premise to determine the hydrogeological conditions of the mine and to do well in water control.For this reason,according to the unified standard,13 pairs of mine water samples were collected,the chemical composition of the water was tested,and 375 water quality analysis reports were collected.The hydrochemical characteristics and formation mechanism of each water filled aquifer are analyzed by means of hydrochemical diagram,ion proportion coefficient?principal component analysis and so on.Furthermore,by studying the main component load scores and the spatial distribution characteristics of the main hydrochemical types,the evolution and control factors of the chemical characteristics of each water filled aquifer are revealed.Finally,according to the TDS isolines and the source of hydrochemical components of three limestone aquifers,14 reasonable paths,mineral phases and reaction equations are determined,and the reverse simulation is carried out by using the software PHREEQC.The results show that:(1)The water filled aquifers in the mining area are generally weakly alkaline,with large coefficient of variation of conventional ions,unstable formation of hydrochemical components and various hydrochemical types.Among the main hydrochemical types,the HCO₃·Na type sandstone water mainly comes from the dissolution and filtration of silicate minerals,the emergence of HCO₃·Cl-Na·Ca·Mg type sandstone water is due to the positive alternating adsorption of cations and human pollution,the HCO₃-Ca·Mg?HCO₃·Ca type cambrian limestone water,seventh layers of limestone water and second layers of limestone water are mainly from the carbonate karst filtration,the emergence of HCO₃·SO₄-Ca·Na·Mg type cambrian limestone water and seventh layers of limestone water are due to oxidation of pyrite and negative alternating adsorption of cations,the emergence of HCO₃·SO₄-Na·Ca·Mg type second layers of limestone water are due to the oxidation of pyrite and the mixing of sandstone water.(2)The isolines of S_F1 and S_F2 based on the main component load scores of conventional ions and the spatial distribution characteristics of the dispersion points of the main hydrochemical types show that:The geological structure of Pingdingshan mining area more or less controls the hydrochemical formation of the water filled aquifer,the cambrian limestone water is mainly controlled by the burial depth and major dislocation,the seventh layers of limestone water and second layers of limestone water are mainly controlled by the fault fold and burial depth,and the sandstone water is mainly controlled by the fault.The comparative analysis of the two periods before 2010 and from 2010 to 2018 shows that:The influence of mining disturbance on the change of conventional ion components in the aquifer of cambrian limestone,the second limestone aquifer of Taiyuan Formation and sandstone aquifer is more significant than that in the seventh limestone aquifer of Taiyuan Formation.(3)The reverse simulation results of each limestone water filled aquifer show that:The dissolution of calcite and the sedimentation of gypsum take place in 6 simulation paths of cambrian limestone aquifer;the dissolution of calcite,dolomite and salt rock and the cation alternating adsorption take place in 4 simulation paths of the seventh limestone aquifer of Taiyuan Formation;The dissolution of calcite and the sedimentation of dolomite take place in 4 simulation paths of the second limestone aquifer of Taiyuan Formation;almost all paths all of them have cation alternating adsorption,and pyrite oxidation is reflected in some parts of the simulated paths of limestones aquifers.