| In this paper,the coal mining subsidence area in Linhuan,Huaibei is the main research object A total of 21 water samples from river water,subsidence area and some mine drainage were collected.The conventional water chemical indexes were analyzed and tested,and sulfur sulfate and oxygen isotopes were used to trace the source of sulphate in rivers and subsidence areas in the mining area.The results showed:(1)The surface water had high TDS content,the cations were mainly Na+and Ca2+,the anions were mainly HCO3-and SO42-,the chemical type of the Huihe River was mainly Na+-Ca2+-HCO3-type,and the subsided water was mainly Na+-Cl--SO42-type.The results of Gibbs graph analysis showed that the composition of river water ions was mainly controlled by rock weathering,while the subsidence area water was mainly affected by evaporation.The content of SO42-in the river water and subsidence area of the mining area was relatively high,with average values of 412.9 mg/L and 506.1 mg/L.(2)The SO42-content showed a certain change range with time in surface water,and it showed obvious seasonal changes in high,flat and dry water periods:dry season>flat water period>high water period.The spatial distribution characteristics of SO42-content were as follows:water in the subsidence area>the main stream of Huihe River>tributary of Baohe River.(3)The values of 834Sso4 and b18Oso4 in the sulphate of the Huihe River water ranged from +8.7‰?+22.‰ and +7.5‰?+12.8‰,with the average values of+17.4‰ and +10.1‰,respectively.The isotope composition of sulfate in the subsidence area water was relatively stable.The values of 834Sso4 and ?18Oso4 were+20.1‰?+22.1‰ and+10.0‰?+13.3‰,and the average values were+20.9‰ and+11.3‰,respectively.The value of SO42-and ?34Sso4 in the direction of the Huihe River flow showed a trend of decreasing first and then increasing.Before flowing through the mining area,the sulphate in the main stream of the Huihe River was mainly derived from the dissolution of the evaporating salt rock in the stratum of the upstream area and the dissolution of sulphate in the soil.The sulphate in the tributary Baohe River was mainly derived from the combined action of atmospheric precipitation and evaporation of salt and a certain degree of human input(agricultural production,sewage discharge).The two mixed rivers discharged into the subsidence area,which caused serious pollution of the sulfate in the subsidence area and affected the water quality.The better correlation between ?33Sso4 and SO42-in river water,subsidence area water and mine drainage indicated that SO42-in the subsidence zone was mainly affected by double-end source.Besides the influence of Huihe River water,the discharge of local mining wastewater was also the source of sulphate,which reflected the impact of coal mining activities on the water environment.(4)According to the analysis of isotope ?34Sso4 and ?18Oso4 values,the main source of SO42-in the river water of the study area was the dissolution of evaporite,the main source of SO42-in the subsided area was the river water supply,mine drainage and a certain degree of gangue leaching.The main source of high SO42-in the mine drainage was that the mine drainage carrying the dissolved sulfate from the evaporation salt formation involved the oxidation of pyrite in the coal gangue.The results showed that the sulphate contribution proportion of the river water source to the subsidence area water was 34.5%-65.3%;the sulphate contribution proportion of the mine drainage source to subsidence area water was 8.2%?32.6%;The sulphate contribution proportion of gangue leaching end source ranged from 12.2%to 56.8%;Different water sample points were affected by different degrees of mine drainage and Gangue Leachate.The source of both mine drainage and gangue leaching could be defined as the influences of coal mining activities.Therefore,the isotope mixing model could more accurately reflect the degree of influence of coal mining activities on the sulphate in the subsided area water. |
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