The Assessment Of Environmental Pollution In The Chankou Section Of Guanchuan River In Dingxi City Of Gansu Province

With the rapid social and economic leaps and developments in the Yellow River Basin in recent years,many factors have caused the water pollution in the River Basin has become more serious,such as the establishment of various factories,the growing population,the increasing domestic waste,especially in some township areas,due to backwardness of pollutant treatment technology and incomplete environmental awareness..GuanChuan river is located in the middle part of Dingxi city,Gansu province,in which the water quality is worse?class,the coastal vegetation and the water ecosystem are poor.Chankou town is a traffic arteries in the Guanchuan river basin.Local villagers rely mainly on agricultural production,and the population occupied in agriculture account for more than 90%of the sum total,also,the main crops are such as corn,potato which is as raw material of small enterprises along the river basin construction,in which a large number of untreated sewage direct emissions causes the river polluted.In recent years,with the efforts of the local government,the pollution situation of enterprises has been improved.The water quality of Guanchuan River has an impact on local agricultural production.Through the analysis and comparison of organic and heavy metal elements in the sediments of Guanchuan River basin,this paper tends to understand the effect of pollution control,aiming to analyze the current polluted surroundings and pollution situation of Guanchuan river basin,and to provide some scientific basis for the improvement of water quality and environmental rectification of Guanchuan River basin.By collecting and analyzing the sediments in the branches of Guanchuan River in Dingxi City,we can study the pollution of organic matter and heavy metal content in the sediments and obtain as follows:?1?The n-alkanes in most of the samples take nC₂₉9 and nC₃₁1 as the main peaks,and there were n-alkanes with a certain abundance of short chain and medium carbon number,indicating that the organic matter in the sediments is derived from a large number of terrestrial higher plants,as well as lower aquatic plants such as algae and bacteria,and large plants such as submerged plants and floating plants.The values of Paq and DO prove that aquatic plants such as algae may be very flourishing,which leads to eutrophication of water body and low oxygen content in water,thus forming anaerobic water body,which can cause death of aquatic plants such as algae,overall decline in water quality and turbidity of water body.The Pr/Ph value is 0.6¹.2 with an average of 0.80,indicating that the river sediments in the study area are polluted by petroleum.The sediment contains a certain amount of triterpenes,tetracyterpenes and a large amount of pentacyclic triterpenes?Hopane?,indicating that the source of the parent matter of organic matter is partly from bacteria and algae,and partly from microorganisms.?2?Polycyclic aromatic hydrocarbons?PAHs?such as Phe,Ant,FLT,Pyr,BaA,CHR,IPY,BbF,and BKF exist in sediment samples,and their relative abundance is high,indicating that there is a certain degree of PAHs pollution in river sediments.The analysis shows that the main sources of PAHs are man-made,among which Phe,Ant and Pyr are the main emissions from coal and biomass combustion,and BbF is mainly emitted from incomplete combustion of gasoline and diesel,and enters rivers through dust in the air.?3?The content of seven heavy metal elements?Cr,Mn,Ni,Cu,Zn,Pb,and Cd?in river sediment samples from Guanchuan river in the Chankou section of Dingxi city is measured by X-ray Fluorescence analysis and icp-ms,and the analysis shows that the average content is in order from large to small as Mn>Zn>Cr>Ni>Cu>Pb>Cd.The average content is 5.11,1.73,1.69,1.79,1.51,9.67 and 0.23 times of the background values respectively.The variation coefficient value of heavy metal elements in the Guanchuan River sediments is generally small,with an average value of 0.22,indicating that the distribution among sampling points in the river sediments is more uniform and the regional enrichment is less.The variation coefficient of Ni is0.50,which is relatively large,indicating that the distribution of Ni elements in the sediments of Guanchuan River is not uniform and there is a certain local enrichment.Combined with the location of sampling points,it is speculated that the local enrichment of Ni elements may be related to agricultural factories?such as fertilizer plants?to some extent.Zn,Cd and Pb are positively correlated,and the coefficient of variation is not large,so it can be speculated that these three heavy metal elements may have similar sources.Among them,Pb is seriously polluted,Zn is comparatively serious,but Cd is pollution-free.It may be due to the difference in the pollution content at the source.The geological accumulation index method,pollution load index method and potential ecological risk index method are adopted to evaluate the pollution status.The study finds that the pollution degree of seven heavy metal elements in the river sediment is Pb>Cr>Cu>Mn>Ni>Zn>Cd in descending order,which shows that Pb causes the highest pollution in river sediments in the study area,Cr causes the relative high pollution,Cu,Mn,Ni have some pollution,but the zinc and Cd are basically pollution-free.The overall pollution level of the river is between moderate pollution and strong pollution.The pollution at sample points DXCK2017-3 and DXCK2017-8 is more serious than other sampling points,and the pollution at sample points DXCK2017-12 and DXCK2017-13 is lighter than other sampling points.The main factors of pollution are industrial,agricultural and traffic activities.