Study On Environmental Risk Assessment System Of Municipal Solid Waste Landfill In Qinghai-Tibet Plateau

In the Qinghai-Tibet Plateau(QTP),more than 18 million people are living in there and generate about 4 million tons of municipal solid waste(MSW)annually.With the development of economy and traffic conditions,many landfills,as the dominant MSW disposal technology,are widely built and run in the QTP.At present,the secondary pollution of landfills has resulted in potentially environmental risk in the QTP,due to the lack of treatment and disposal facilities and equipment,the non-standard operation and management,and the long operation and stabilization time of the landfill.In view of the cold and dry weather,as well as the low oxygen in the QTP,the ecological environment is fragile and sensitive.The QTP is known as Asia's water tower since it is the source of many major rivers not only in China but also in Southeast Asia.Therefore,combining the characteristics of the QTP and the pollution status of the landfill,it is important to study on the environmental risk assessment system of MSW landfills to protect the ecological environment in QTP.In this study,the environmental risk assessment system of MSW landfills in the QTP was constructed and discussed,according to the whole process of potential risk sources,pollutant migration pathways and potential risk receptors,and the perspective of society,economy and technology for the landfill.The expert questionnaire survey and analytic hierarchy process method were used.The results were as follows:(1)The groundwater near the landfills in the QTP were contaminated by Nitrate(PI = 1.87),fluoride(PI = 1.12),and lead(PI = 1.14).The nearby surface water was mainly polluted by TN(PI = 1.12)and TP(PI = 1.4).The nearby soil was obviously affected by the high background content of Arsenic,and the field accumulation index of Mercury(1<Igeo?3)was high.(2)The environmental risk assessment system(ERSS)for MSW landfills in the QTP was constructed.The environmental risk was divided to five levels,including high(?,7 < P ? 10),relatively high(?,4.5 < P ? 7),medium(?,2 < P ? 4.5),low(IV,1 < P ? 2),relatively low(V,0 < P ? 1)5 grades.Each index was quantified and graded.In the ERSS system,the criterion level 1 includes potential risk sources(The weight is 58.27%),migration of pollutants in the environment(The weight is 29.4%),and potential risk receptors(The weight is 12.33%);in the criterion level 2 of potential risk sources,there are landfill characteristics(The weight is 35.79%),landfill management(The weight is 22.49%);in the criterion level 2 of the migration of pollutants in the environment,there are water-soil migration(The weight is 16.07%),atmospheric migration(The weight is 8.41%)and migration distance(The weight is 4.92%);in the criterion level 2 of the potential risk receptors,there are the ecosystem(The weight is 8.99%)and human society(The weight is 3.34%).There are 16 indicators in the indicator level.(3)The weight of the evaluation index is obviously affected by the professional category of the expert,the geographic location and the experience of the practitioner.Experts in scientific research institutes and universities pay more attention to potential sources of risk,experts in administrative management offices attach more importance to the migration of pollutants in the environment,experts are engaged in solid waste treatment in enterprises pay more attention to potential risk receptors.Experts in Tibet pay more attention to the migration of pollutants in the environment.In terms of the experience,senior experts pay more attention to the potential sources of risk.The index weight of the senior experts is finally determined as the evaluation basis.(4)The environmental risk index was 5.71 which is at a high level in the LS MSW landfill.It is mainly due to a relatively high content of hazardous waste,the poor maintenance of landfill facilities and equipment,and the poor landfill management.(5)Some measures of the landfill environmental risk are suggested,including to strengthen the supervision and the management of landfills,to reduce the content of the kitchen waste and hazardous waste through the MSW classification,to improve the marketization of the MSW management,treatment and disposal;to increase capital investment,to improve the staff's technical skill,and to formulate risk prevention measures,and so on.