Study On Surface Water Quality Characteristics And Water Quality Evaluation Of Typical Watershed In Wanjiang Economic Belt

The Wanjiang Economic Belt is a key development area for implementing the strategy of the rise of the central region.Understanding the water quality of the river basin from the macro level is not only the demand for regional economic development,but also an important basis for water environment management.Because the characteristic pollutants in different watersheds have certain differences,and the existing different evaluation methods have different emphases,it is necessary to establish a scientific comprehensive evaluation model of water quality in a specific river basin based on the identification of characteristic pollutants in the river basin.On the other hand,due to the large differences in monitoring section settings,water body functions and land use types within the basin,if a water quality assessment method that takes water availability and comprehensively considers the above factors can be proposed,it can directly serve the water resources management of the basin.Therefore,it is of great significance for regional water environment management to develop the comprehensive water quality assessment methods river basins.Firstly,this study takes the secondary rivers in the Wanjiang Economic Belt as the research object,conducts river water quality survey,and focuses on the investigation of pollution status such as heavy metals and organic pollution.Based on the research results,the water quality evaluation indicators are selected based on the research results in the area;The Qingyi River Basin and Chaohu Lake Basin with different degrees of urbanization and economic development were selected as typical research areas,and the evaluation model of water quality index method of Minjiang River was constructed,and compared with the evaluation results of Nemero water quality index method and water quality labeling index method.Finally,on the basis of the constructed model,with the aim of water availability,considering the difference between the water body function compliance rate of the monitoring section and the land use type in the buffer zone,it is proposed to comprehensively reflect the water quality availability of the whole basin.A composite index of risk of change.The main research results obtained in this study are as follows:(1)The typical heavy metal,TOC,TN,TP,DO and pH characteristics of 106 monitoring sections in the basin were identified.The pollution risk of heavy metals Hg,Cr,Cd,Pb,Zn,Cu and As in the waters of the Wanjiang Economic Belt is small.The heavy metal content of most monitoring sections is much lower than the standard limit of Class ⅡI water bodies,and the Zn content is relatively high.The average TOC concentrations was 5.45 mg/L,which was at a medium level;the average concentrations of TN and TP were 1.99 mg/L and 0.07 mg/L,respectively.The nitrogen phase was more serious than the phosphorus pollution;except for the individual monitoring sections,the pH was Both are 6~9;the average DO concentration is 9.28mg/L,which meets the requirements of Class Ⅱ water quality.(2)To identify the pH,DO,TP,NH3-N and CODMn characteristics of the water bodies in the Chao Lake Basin and the Qingyi River Basin in the typical basin.The concentrations of CODMn,TOC and NH3-N in the Chao Lake Basin were significantly higher than those in the Qingyi River basin,and there was no significant difference in TP concentration.The water body function compliance rate of the Chao Lake Basin monitoring section is higher than that of the Qingyi River.The water quality of the Qingyi River Basin section has a large difference with the water body function compliance rate.(3)Based on the results of watershed water quality survey and the current monitoring indicators of the national control(provincial control)section,pH,DO,TP,NH3-N and CODMn were included in the water quality evaluation index of this study.Based on the Environmental Quality Standards for Surface Water(GB 3838-2002),the concentration grading limits of the evaluation indicators are combined with the results of the pH survey of this study.The function-fitting method is used to construct each sub-index model,and the harmonic mean is used to construct the Wanjiang Water Quality Index(WJWQI).The WJWQI is sensitive to pH and DO changes.The model not only highlights the pollution characteristics of different monitoring sections,but also considers the comparability of different section evaluation results.(4)The WJWQI,Nemero Water Quality Index(NWQI)and Water Quality Identification Index(WQⅡ)have all shown that the pollution situation in Chao Lake Basin is more serious than that in the Qingyi River Basin.Compared with the NWQI and the WQⅡ,WJWQI is superior in the sensitivity of each index change,the comparability of the evaluation results,identification of the inferior V water body evaluation and the ease of operation,and it has a certain practicality.(5)Comprehensive consideration of the water function target and the weight of the land type of the watershed monitoring section The WJWQI comprehensively visualizes the water quality target management achievement status and the potential trend of water quality change in the basin;the WJWQI calculation obtained by the arithmetic average method is more important than The comprehensive evaluation of the water quality category of the river basin is consistent with the evaluation results of the comprehensive water quality index based on the section type ratio method and the water quality labeling index method,but it is more detailed in the water quality change of the basin.The combined use of WJWQI and WJWQI can provide managers with an intuitive and effective management basis.