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Title:: Spatial Distribution and Risk Assessment of Soil Heavy Metals in Typical Region of Lhasa City

Author(s):: Spatial Distribution and Risk Assessment of Soil Heavy Metals in Typical Region of Lhasa City; (Institute of Agricultural Resources and Environment,Tibet Academy of Agricultural and Animal Husbandry Sciences,Lhasa,Tibet 850000)

Keywords:: Lhasa city; soil heavy metals; ecological risk; potential risk assessment

Abstract:: In order to find out the pollution characteristics of heavy metals in different functional farmland surrounding Lhasa city,and provide evidence for making reasonable repairing strategy for soil heavy metals and adjusting the planting mode of the crops timely.27 soil samples were collected from 3 different functional area of the Lhasa city(the sampling depth was 0-20 cm),and the contents of As,Hg,Cd,Pb,Cr,Cu,Zn were determined,then analyzed the spatial distribution,the pollution level of the main pollution factors in environment were evaluated with single pollution index,then assessed the ecological hazard with potential ecological risk index.Compared with the Tibet soil heavy metals background values,the experiment found that As element was enriched most serious in soil sample,and its pollution share rate reached 62.7%,at the same time,the ratio of soil quality which was below soil environmental quality standard class Ⅱwas 94.4%.The potential ecological risk of heavy metals were in order of As>Cr>Cu>Pb>Ni>Zn,the ecological risk of different functional farmland were farmland of Lhasa suburbs>industry areas>facility horticulture areas,except the farmland soil in Cijiaolin county was at medium risk level,the rest sample at slight risk level.The heavy metals in different functional farmland of Lhasa city was downtrend,parts of contaminated soil was determined by As element,on the whole,the potential ecological risk of heavy metals was slight.