| As a typical urban lake in Ningxia,Yuehai Lake is connected to other lakes and wetlands in the basin through an artificial canal—Diannong River,which has changed its independent lake properties and has a long process.The habitats along the way are changeable and human activities are extremely frequent.The processes of pollution(non-point source,point source)and endogenous pollution(transformation and release of sediment pollutants)are multiple intertwined,making the causes of changes affecting the quality of the seawater complex and changeable.In response to the above problems,on the basis of comprehensive consideration of different influencing factors such as lake water depth,reed distribution and the distribution characteristics of water inlets and outlets,this paper discusses the characteristics of the temporal and spatial evolution of the water quality in Ningxia,and uses the fuzzy comprehensive evaluation method and the principal component analysis method.Quantitative evaluation of water quality is used to clarify the characteristics of the evolution of the water quality in Ningxia in the past 10 years,and comprehensive evaluation of its water quality is carried out by region.The main findings are as follows:1)The characteristics of the inter-annual changes in the quality indicators of Yuehai Sea are as follows:During the ten years from 2010 to 2020,the average TN content of Yuehai Sea has shown a gradual downward trend,and the water quality has been upgraded from the Grade Ⅳ water standard ten years ago to the Grade Ⅲ water standard;The content of TP in the sea has fluctuated changes,and there is no obvious downward or upward trend;the content of NH3-N in the sea body has changed relatively smoothly in 11 years,and there is no obvious change;in the 11 years,the CODMn content in the sea body has exceeded Ⅲ for 6 years Water-like standard limit;the average content of BOD5 shows a downward trend as a whole.2)In terms of seasonal evolution characteristics,the degree of water pollution in summer is higher than that in spring and autumn.In general,water quality indicators have the smallest value in May and the largest value in August,while November is in the middle.There are obvious differences in seasonal changes,which are different from different seasons.The pollutant load is related.3)The results of fuzzy comprehensive evaluation showed that the water quality of Yuehai was the worst in May,which was classified as Ⅳ water,while the water quality was relatively good in August and November,which were both classified as Fe water.There were also differences in the water quality of Yuehai in different seasons in 2020.In August and September,the water quality was classified as Ⅲ.In October and November,the water quality category was as a whole Ⅱ type water.Water quality in 2020 is obviously better than that in 2019.4)The principal component analysis shows that the main control indexes of the seawater quality in 2019 are TN,TP,NH3-N,and the water quality indexes that affect the seawater quality in 2020 are TN,TP,NH3-N,DO and suspended matter.5)The IDW inverse distance weight interpolation method of ArcGIS10.7 software was used to interpolate the water quality index data of 14 monitoring samples in 8 months from 2018 to 2020.The water quality status and spatial differentiation characteristics reflected by it were not significant in the regularity of spatial distribution characteristics of single factor and different seasons.The results show that the reasons of influencing the spatial distribution of water quality are complicated,and the water quality in shallow water area,reed area and drainage outlet area is poor. |
PDF Full Text Request