Water Quality Characteristics And Changing Trend Of Coal Mining Subsidence Area With High Underground Water In Huainan

Due to the large amount of coal mining in Huainan and the hydrogeological conditions which has high underground water in this area,large area of sunken water was formed in the process of coal mining.In order to alleviate the contradiction between water resource shortage and water demands in coal mine area,the subsided water in mining subsidence area has been fully utilized,and it is very important to ensure the water quality in subsidence area.Therefore,it is of great significance for the utilization and protection of local water resources to grasp the characteristics of water quality in subsidence areas and study the variation trend of pollutant content.The research was based on surface water in Huainan coal mining subsidence area(including subsided water,river)and shallow groundwater as the research object,to the duty summer two season variation characteristics of time.to study the water chemical characteristics and influence factors of all kinds of water,subsidence nutrient distribution characteristics of nitrogen and phosphorus in water and its influencing factors and distribution characteristics of heavy metals and its influence factors,the index of water quality change trend and the water environment quality assessment.(1)The mean value of TDS in subsided water is 535.13 mg/L in summer and 620.35 mg/L in winter,which is higher than the surrounding natural rivers and shallow groundwater;the hydrochemistry type of subsided water and river water is Na-HCO3·Cl type,the groundwater is represented by Na·Ca-HCO3 type.Combined with Gibbs diagram,endmember analysis and factor analysis,it is found that the chemical characteristics of surface water are affected by evaporation,rock weathering and human activities,and evaporation is the main influencing factor.The main source of subsided water components is the evaporation of salt rock,and the river water is affected by both silicate weathering and evaporite weathering.Groundwater chemical characteristics are mainly affected by rock weathering,and silicate rock weathering is the main source of groundwater components.In recent years,there is no change in the type of water chemistry in the subsidence area of Panyi Mine.The water chemistry type in the subsidence area of Xieqiao Mine has gradually changed from Na· Ca-SO4 type to Na-HCO3 type.The water chemistry type in the subsidence area of Guqiao Mine is gradually changed from Ca·Na-HCO3 type which is close to groundwater to Na-HC03 type.(2)The content of nitrogen and phosphorus in subsidence water is seriously higher than the concentration of eutrophication in water.N:P in both seasons is higher than the optimum growth ratio of algae,and phosphorus is the main controlling factor of eutrophication.TN content in summer is higher than the average in the study area in the winter,the average TP content in winter than the summer.The difference of pollution sources in different seasons is the main reason for the seasonal distribution of nitrogen and phosphorus in the subsidence area.The seasonal variation of agricultural production,fish culture and the seasonal distribution of precipitation is the influencing factor of the seasonal distribution of TN.The seasonal variation of temperature and the growth of animals and plants in water are the influencing factors of TP seasonal distribution.The nitrogen and phosphorus pollution in the subsidence area of Guqiao Mine,Xieqiao Mine,Paner Mine and Liuzhuang Mine is serious.The content of nitrogen and phosphorus in the subsidence area of Dingji Mine,Zhangji Mine and Pansan Mine is relatively low.The TN content in the subsidence areas such as Liuzhuang Mine,Guqiao Mine and Pansan Mine is relatively high.The TP content in the study area is higher in the central and eastern regions,and lower in the west.The surrounding environment of the subsided waters and human activities are the main influencing factors of the spatial distribution of nitrogen and phosphorus in the subsidence area.The contents of TN and TP in the water bodies of the two subsidence areas of Panyi Mine and Xieqiao Mine showed seasonal fluctuations,and the annual average content did not change much.However,the content of TN and TP in the water bodies of Guqiao Mine subsidence area increased continuously in recent years,nitrogen and phosphorus,and the trend of nitrogen and phosphorus pollution has increased.(3)Analysis of heavy metal content shows that average content does not exceed the limit of the Class III water standard in the surface water or groundwater environmental quality standard,the heavy metal content in the surface water is higher than the groundwater in general,and the seasonal distribution is slightly lower than the winter in summer,and the spatial distribution characteristics are different.The seasonal variation of precipitation in Huainan area is the main influencing factor of the heavy metal seasonal distribution in the study area,while the spatial distribution of heavy metals is more complicated,which may be related to the use of pesticides and fertilizers,industrial wastewater discharge,atmospheric deposition of heavy metals in automobile exhaust,fish farming and Coal mining activities and other factors.The content of Ni and Zn may increase to some extent with the continuous leaching of the waste rock mountain and the release of the cultured feed.(4)The evaluation results of surface water comprehensive water quality index indicate that the surface water quality in subsidence area is general,belonging to the category III water standard,and the TN,TP and F-index pollution is more serious;The results of the groundwater osculating value method show that the groundwater quality in the subsidence area is in the range of ??? water.