Research On Pollution Characteristics And Quality Evaluation Of Water Body In The Mining Area At The Upper Stream Of Cihu River

Cihu River is located in Ma’anshan City,Anhui Province.The upper reaches of this river basin is a typical mining area.Because the pollution of the mining area watershed has a certain degree of particularity,and different existing evaluation methods have different focuses,it is of great significance to comprehensively evaluate the water quality of the watershed based on the characteristics of the pollutants in the watershed.Improving the traditional evaluation method can make it better play the role of water quality evaluation according to the characteristics of the small watershed in the mining area.Through this research,it provides theoretical basis and data support for the comprehensive treatment and watershed management of the Cihu River Basin.The study took the mining area of the upper reaches of the Cihu River as the research object,and carried out pollution source surveys.On this basis,the pollution characteristics of the watershed were analyzed,the main pollution factors were obtained,the spatial distribution of pollutants were studied,and the single factor index method,Nemeiro water quality index method,fuzzy comprehensive method and grey correlation method are used for water quality evaluation,and the traditional fuzzy comprehensive method is improved,the evaluation results are compared and analyzed,and the water quality evaluation results are obtained.The main research results obtained in this study are as follows:（1）The upper reaches of the Cihu River showed acidic water quality as a whole.The acidic wastewater in the tributaries II and IV of the Yanghe River was seriously polluted,with p H 4.54 and 3.71 respectively.According to the weighting calculation of pollutant concentration exceeding the standard,BOD₅ and ammonia nitrogen are the main pollution factors in the upper reaches of the Cihu River;the Yanghe River Basin is seriously polluted by BOD₅,COD,and ammonia nitrogen,and the Yanghe Tributary II has heavy metal Cu pollution.（2）In terms of the spatial distribution of pollutant concentrations,the concentrations of p H,COD,BOD₅,ammonia nitrogen,Cd,and Fe are mainly distributed in Yanghe tributary IV,and As and Cd are mainly distributed in Yanghe tributary III.The distribution of p H,ammonia nitrogen,Cd,and Fe in the Yanghe River Basin is the highest,BOD₅,Cr⁶⁺,and As have the highest concentration distribution in the Xiushan Lake Basin,and COD concentration is the highest in the main river basin.Overall,the concentration distribution has the spatial distribution law of upstream>downstream,tributary>main stream（3）There is homology between BOD₅ and COD indicators in the study area,and its pollutants mainly come from industrial wastewater and domestic sewage in the mining area;hexavalent chromium,cadmium and copper have certain homology,mainly from industrial wastewater from copper-zinc metal mining and beneficiation enterprises Pollution.（4）Considering four water quality evaluation methods comprehensively,the evaluation results of single factor index method and Nemeiro index method are relatively pessimistic.The compliance rates are 14.3%and 43.3%respectively,and the influence of indicator weight is not taken into consideration.The main reason is the main pollution in the basin.The concentration of BOD₅and NH₃-N is very high;the fuzzy comprehensive method and the gray correlation method weaken the influence of this indicator.Combining the advantages of the weighting method for exceeding the concentration,the weight distribution of each indicator is more reasonable,and all indicators are in line with Grade V water quality.Standards;the improved fuzzy comprehensive method makes further continuous judgments of water quality grades on points with large differences in water quality judgments,which is more in line with the actual water quality situation.（5）In terms of water quality evaluation,the water quality grade of Yanghe River Basin is 4.313,Xiushan Lake is 3.698,and the main river reaches 4.066;the water quality grade of Yanghe Tributary I is 3.968,Yanghe Tributary II is 4.172;Yanghe Tributary III is 4.148;Ⅳis 4.494;Yanghe Mainstream I is 4.382;Yanghe Mainstream II is 4.722.There are four tributaries from north to south in the Yanghe River Basin,namely tributariesⅠ～Ⅳ.Pollution degree:Yanghe River Basin>Main River Basin>Xiushan Lake Basin;tributaryⅣ>tributaryⅡ>tributaryⅢ>tributaryⅠ.（6）The water quality indicators of the upper mining area of the Cihu River can meet the needs of ecological functions,but the Yanghe tributariesⅡandⅣneed targeted pollution control.