Analysis Of Variation Characteristics And Eutrophication Evaluation Of Water Environmental Factors In Qingshui River

Taking Qingshui River in Zhangjiakou City as the research object,33 sampling points of Qingshui River were sampled during the non-freezing period of two consecutive years from 2017 to 2018.Seven water quality indicators of water environmental factors,namely temperature,pH,dissolved oxygen,COD,total nitrogen,total phosphorus and ammonia nitrogen,were analyzed.Water quality was evaluated by water quality comprehensive index method,and pollution sources of Qingshui River were analyzed by cluster analysis and principal component analysis.Recognition with main factors.The sediment of Qingshui River was cultured statically to explore the regularity of pollutant release from sediment of Qingshui River.The general exponential function formula of logarithmic power function is used to evaluate the eutrophication of Qingshui River.The purpose is to reveal the current situation and environmental problems of Qingshui River in Zhangjiakou City,and to provide a theoretical basis for the management and control of the basin.The conclusions are as follows:(1)The Qingshui River is divided into four regions.The spatial and temporal distribution characteristics of water environmental factors are obvious.On the time scale,the content of dissolved oxygen and COD has little change,and the trend of change is basically the same in spring,summer and autumn.The change of total nitrogen is obvious with the seasons,which basically presents autumn(9.87 mg/L)spring(6.86 mg/L)summer(6.38 mg/L);the content of total phosphorus is also obvious and basic to seasonal change.Spring is higher than summer and autumn.On the spatial scale,the distribution of dissolved oxygen content in different regions is as follows: downtown dam area(12.87 mg/L)source area(9.73 mg/L)transitional area(9.17 mg/L)Chongli area(5.38 mg/L);total nitrogen,total phosphorus and COD are widely distributed in Chongli area,and the annual average content is higher than other areas.(2)To evaluate the water quality of Qingshui River by using the method of comprehensive pollution index.In the source area,total nitrogen is the main pollution factor,and the total nitrogen pollution index is greater than 1.0;in Chongli area,the comprehensive pollution index of each monitoring section presents the rule of(?);in the transition area,the comprehensive pollution index of each monitoring section is greater than 3.0,of which;in the central dam area,the pollution index of total nitrogen is,far more than that in the region.Pollution indices of other monitoring indicators.(3)The release rate and limit of ammonia nitrogen in river sediments increase with the increase of temperature of overlying water and decrease with the increase of dissolved oxygen content in overlying water.The higher the temperature of overlying water is,the lower the dissolved oxygen content is,the faster the release rate of total phosphorus in sediment is,and the larger the release amount is.When the culture temperature is5? or DO 6mg/L,the phenomenon of sediment adsorption occurs.The release of COD is obviously affected by temperature: when the temperature is 15? and DO 3mg/L,the release rate of COD is the fastest,and the release rate of COD in sediment is much higher than that in other states.(4)The eutrophication degree of Qingshui River gradually deepens from the source area to Chongli area,and then gradually decreases and changes significantly.The eutrophication level of each region of Qingshui River is different,and the areas with serious eutrophication are mainly distributed in the downtown dam area.The ratio of nitrogen to phosphorus in Chongli area is closest to the ratio of nitrogen to phosphorus needed for algae explosive growth in water body,which has potential threat of algae explosion.The whole Qingshui River is limited by phosphorus nutrients,so the key to control the eutrophication of Qingshui River is to control the total phosphorus content in the water.