Analysis And Research On Internal Pollution Characteristics Of Urban River

Urban rivers provide functions such as providing water,convenient transportation,flood control and drainage,and urban landscapes.However,urban rivers have the characteristics of receiving many pollutants,poor self-purification ability,and easy eutrophication.In view of this,this paper takes the dynasty river,one of the six main rivers in the downtown area of Chengdu as an example,using organic matter pollution assessment method,correlation analysis,ground accumulation index method and ecological risk assessment method to analyze the nutrient content and heavy metal content of sediments.The pollution level of the sediments of the Dianhe River was comprehensively analyzed in three aspects: pollution level and risk assessment.The release of total phosphorus,total nitrogen and organic matter in sediments under different temperatures,pH and disturbances were analyzed by internal endogenous pollution release experiments in Chengdu.The main findings are as follows:(1)The contents of nutrients and heavy metals in the river were significantly changed,reflecting the trend of increasing the content from upstream to downstream.The Cd element is the main factor causing excessive heavy metal pollutants in rivers.Through correlation analysis,it is further clarified that the organic matter content is easy to cause heavy metal enrichment in the sediment.(2)The potential risk of composite pollution of rivers is similar to that of heavy metals.The results are found at 4 sampling points: the risk degree of 4# sampling point(South River entrance)> the risk degree of 3# sampling point(downstream of branch inlet)> the risk degree of 2# sampling point(Downstream of the city park)> the risk degree of 1# sampling point(start of artificial river).(3)According to the indoor simulation experiment,the effects of temperature,pH and release of TN,TP and COD under different disturbance conditions should be analyzed.It is found that:(1)The nutrient release rate under high temperature conditions is higher than the low temperature condition,and after the nutrient concentration reaches a peak,it gradually decreases to equilibrium.(2)Temperature has a polarized effect on COD,which easily inhibits the release of organic matter in sediments.(3)The increase in pH causes the concentration of nutrients in the overlying water to show a trend of decreasing first and then increasing.(4)With the increase of the disturbance frequency,the release rates of TP,TN and COD gradually increase,and tend to balance after reaching the peak.