| In recent years,with the improvement of urban living standards and the vigorous development of tourism in Tibet,a large number of urban domestic waste and tourism waste have been produced.At present,landfill is the main treatment method for domestic waste in Tibet.But in the process of landfill,the waste will bring pollution to the surrounding ecological environment and human health.In this study,the heavy metals in the surrounding soil of Luqionggang landfill in Shannan city of Tibet Autonomous Region were taken as the research object.The soil around Luqionggang landfill was sampled and analyzed.The content and distribution of 8 heavy metals,Cu,Pb,Zn,Cr,Ni,Cd,As and Hg,were determined.Then single factor pollution index method,Nemero comprehensive pollution index method and land accumulation index method are used to evaluate the pollution status of landfill.The potential ecological risk index method and health risk index method were used for risk assessment.The main analysis results are as follows.?1?The average p H value of the soil around the landfill is 9.37,which belongs to the strong alkaline range.The average values of Hg and Ni in the soil are higher than the background content,while the average contents of Cu,Pb,Zn,Cr,As and Cd in other heavy metals are not higher than the background content.However,the average content of these 8 heavy metal elements did not exceed the range of the national soil environmental quality standard.?2?The average content of heavy metals Cu,Cr,Cd,Hg and Ni in the west is higher than that in the North,East and South.The average content of As,Zn and Pb in the North,East and South are slightly higher than that in the West.The average content of 8 heavy metals fluctuated with the depth in the vertical direction.?3?According to the background value of soil in Tibet as the reference value.The results of single factor pollution index and Geo-accumulation index showed that Hg was the most affected.The results of Nemerow comprehensive pollution index showed that the whole landfill was moderately polluted and the soil on the west side of the landfill was greatly affected.The evaluation results of potential ecological hazard pollution index show that the potential risk index of single pollutant of heavy metal elements Cu,Pb,Zn,Cr,Ni,As,Cd belongs to the low hazard ecological level,and the potential risk index of single pollutant of heavy metal Hg belongs to the heavy ecological hazard level.On the whole,the total potential risk coefficient is of medium pollution hazard degree.?4?The non carcinogenic risk values of 8 heavy metals Cu,Pb,Zn,Cr,Ni,Cd,As and Hg in the soil around the landfill are all within the acceptable level.The main exposure route of non carcinogenic risk in adults and children is oral route.In the whole life cycle,the carcinogenic risk of oral route is higher than that of respiratory route and skin contact route.However,the carcinogenic risk values of all carcinogenic heavy metals are lower than the upper limit of the maximum acceptable level of USEPA by 1×10-4.?5?Based on the results of evaluation and analysis,some suggestions are put forward for the remediation of pollutants in the soil around the landfill site.The method of determining the weight value by AHP is mainly used to select the method suitable for the soil restoration around the landfill site.Among the selected indicators,technical maturity,monitoring management fee,later management fee,pollutant source,soil chemical properties and other weight values are relatively large,which has a certain impact on the selection of pollutant remediation technology.Finally,it is concluded that biological method is suitable for soil remediation around Shannan landfill. |
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