Source Identification,Pollution And Potential Ecological Risk Assessment Of The Potentially Toxic Elements (PTEs) In The Area Of The Golmud City-golmud River-dabuxun Lake

In recent years,with the acceleration of the industrialization and urbanization of the Golmud City and the continuous expansion of resources exploitation in the Qarhan Salt Lake,the environmental and ecological problems caused by human activities have drawn increasing attention.As the hydrological channel between the Golmud City and the Qarhan Salt Lake,the Golmud River,which originated from the Kunlun mountains,provide the Golmud industrial,agricultural and domestic water,and also supply 70%fresh water for the Qarhan Salt Lake.On the other hand,kinds of human activities?e.g.,the industrial production,transportation,residents and agricultural activities?in turn directly affect the Golmud River by inputting Potential Toxic Elements?PTEs?.Therefore,in order to scientifically and objectively evaluate the present situation of the region environment as well as identify PTEs migration enrichment regularity,we selected the Golmud City-Golmud River-Dabuxun Lake as the study area.Then 62 soil samples from the Golmud City,9 sites with surface sediment samples from the Golmud River and a core with 20 sub-samples from the estuary of the Golmud River to the Dabuxun Lake were taken for PTEs concentration,source identification,deposition rate and magnetic charcateristics.The pollution and potential ecological risk were evaluated by enrichment factor?EF?,geoaccumulation index(I_geo),modified pollution degree?m C_d?,pollution load index?PLI?,and potential ecological risk index?RI?.The conclusions are as follows.1)Compared with the average concentrations of background values and the values measured by sampling from the background points,the relative cumulative frequency curve method was found more suitable than the standardized method to be used to calculate the baseline values of environmental geochemistry in the study area.2)Multiple pollution evaluation indexes were used to evaluate the regional pollution,and PLI_zone indicated that the regional pollution level was moderate.The index EF of Golmud indicates strong enrichment of Cr,significant enrichment of Cu,Pb,Sb and Sn,moderate enrichment of As,Cd,In,P and Zn,and slight enrichment of Co,Ni,Tl and V.The I_geo value indicates that Cr is seriously polluted,Sb is heavily polluted,Cu,Pb and Sn are moderately to heavily polluted,As,Cd,In and Zn are moderately polluted,and Co,Ni,P,Tl and V are lightly polluted.The m C_d and PLI indicate low to medium and low to high pollution respectively.In the area of the Golmud River and Dabuxun Lake,the EF indicates slight enrichment of Cd,Ni,P and no to slight enrichment of Pb,Sb in the surface sediments,while all the elements are no to slight enrichment in the core.The I_geo indicates that the pollution degree of Cd,Cr,P is non to mild in the surface sediments,As and Cd is non to mild in the core while other elements indicate no pollution.The m C_d indicates zero to very low pollution level and PLI indicates low to medium pollution levels in both areas.3)The results of potential ecological risk assessment showed that,except for elements As,Co,Ni and V,the overall potential ecological risk value decreased with the Golmud City-Golmud River-Dabuxun Lake.The Golmud River and Dabuxun Lake are both with low potential ecological risks.While in the Golmud City,the As,Cu and Pb presented low to medium potential ecological risks,and Cd and Cr presented low to high potential ecological risks.On the regional scale,RI indicates low to high ecological risk.Most regions have low ecological risk,but there are still three ecological risk concentration areas.High ecological risk area is located in logistics park?area??,medium ecological risk clusters corresponding to the Golmud station area?area??as well as industrial park area?area??.The influence elements for the area?are mainly Cd,Cr,Pb,Cu,especially Cd and Cr while Cd for area?and?.The pollution and ecological risk mainly caused by transportation and industrial production.4)After the Golmud River was dredged,the elements content of the upper,middle and lower reaches of the Golmud River as well as the artificial lakes and streams flowing into Golmud River are compared.Except for element P,the elements concentration,pollution degree and ecological risk in the middle reaches of Golmud River are relatively low,indicating that the dredging effect of the river is great.The agricultural planting area is close to the Golmud River,which indicate the continuous increase of P concentration in this section may relate to agricultural activities such as fertilizer application.The PLI_zone indicated the regional pollution degree is Golmud City>Dabuxun Lake>Golmud river and the concentration of surface samples of sediment column in Dabuxun lake is reduced than from the deep,which also reflects that the dredging of Golmud river is very effective in the river regulation.5)The multivariate statistical analysis results show that in addition to Tl,Co,Ni and V for natural source,other elements in the soils mainly from human activities.The Cd and P in the sediments from the Golmud River and Dabuxun Lake are human source.Compared with the distribution of PTEs in the surface soils from the Qinghai-Tibet Plateau,special attention should paid to the region's high Cd value and the PTEs enrichment brought by transportation.Compared with the estuaries of Qinghai Lake,the Dabuxun Lake also needs to consider primarily the input of Cd.6)The core in the Dabuxun Lake was dated by using ²¹⁰Pb.The CIC model was used to calculate the deposition rate of the Dabuxun Lake within a hundred years,which was 0.041cm/a.7)The magnetic magnitude of the study area is obviously Golmud City>Golmud River>Dabuxun Lake.The magnetic materials in soil and sediments are mainly incomplete antiferromagnetic minerals and the grains of magnetic minerals were mainly pseudodomains in the Golmud City,multi-domain in the surface sediments of the Golmud River and false single-domain to multi-domain in the Dabuxun sediment core.The?and SIRM to a certain extent,can be an indicator of urban soil pollution,while a single indicator cannot be relied on to indicate pollution levels.Due to the dredging of the Golmud River,the enrichment of PTEs from the Golmud City in the area outside the Golmud City is mainly considered.The increase of magnetic parameters?,?_ARM,SIRM and HIRM indicating element concentration is feasible to some extent.The magnetic parameters have no strong indication for the changes of the PTEs elements in the Dabuxun Lake.