Groundwater And Surface Water Environmental Research On Characteristics Of Linhuan Coal Mining Subsidence Area

Coal plays a leading role in the energy consumption structure of China.At present,more than 95%of coal mining methods are underground mining in China.The strong surface disturbance will be caused by the process of coal mining,which leads to surface subsidence and a series of other environmental problems.Surface water accumulation,sloping lands,cracks are three major characteristics in coal mining subsidence.Huaibei mining area is located in the middle reaches of Huaihe,which is a typical national resource depletion-type mining area with high dive levels geological conditions.Surface subsidence will be inevitably caused in coal mining processes,and subsidence area is also expanding with the expansion of mining areas.The formation of subsidence area inevitably leads to the changes of cycle conditions between surface water and groundwater.Therefore,it is of great significance to the sustainable use of local water resources and water environment protection through the researches of hydrogeochemistry and water environment quality evaluation.The present paper used Linhuan coal mining subsidence area as the research object.The research was for surface water and shallow groundwater during the period of wet,normal and dry season.Characters of hydrochemistry and influence factors of different water,stable isotope characteristics of hydrogen and oxygen,characteristics of heavy metal content and water environmental quality evaluation were researched systematically.?1?The hydrochemical characteristics of Linhuan coal mining subsidence area showed as follows:The TDS of surface water was higher than that in groundwater,the average concentration of the period of wet is 1170.6 mg/L,slightly lower than the average concentration of 1301.5 mg/L mg/L in normal season,and also lower than the average concentration of 1562.9 mg/L in wet season;The surface water affected by intense evaporation process mainly belonged to water chemistry type of SO₄^2--Cl^--Na⁺;Groundwater mainly affected by rock weathering was the type of HCO₃^--Ca²⁺-Mg²⁺.The mutual complement of surface water and groundwater supplied weakly,both of them reflected the characteristics of atmospheric precipitation recharges.?2?The study about characteristics of hydrogen and oxygen stable isotope showed that:Surface water and shallow groundwater had the same source characteristics of water.Although both of them were derived from atmospheric precipitation,shallow groundwater was more directly infiltrated by atmospheric precipitation,rather than the recharge of surface water.Compared with the stable isotope in deep groundwater,surface water and shallow groundwater were not mixed with deep groundwater;Through the discussion of the two-end member method,supplies of surface water to the surrounding groundwater was about 500m from the river bank.?3?Through comprehensive water quality index method and Nemero index method,the evaluation results of surface water and shallow groundwater showed that:Surface water was generally up to water quality standard ? according to Chinese Standards GB 3838-2002.CODCr?TN?F^-?Cr in surface water exceeded the standard more seriously;F^-?NH4⁺N?Cr?Ni exceeded the standard of ? Water quality for groundwater more seriously;Compared with the traditional Nemerow index,the improved Nemero index method was more objective because of the consideration of the weighted value in the evaluation process.?4?The results of heavy metals?Cd?Cr?Cu?Ni?Zn?showed that:The Cr had the risk of contamination in both surface water and shallow groundwater.The content of heavy metals in surface water was lower than that in shallow groundwater,which was caused by the recharges of the Huihe river and the atmosphere precipitation.The contact between groundwater and surface water was weak,and the enclosed environment leaded to higher content of heavy metals in groundwater.