Risk assessment of heavy metal pollution in degraded alpine meadow in Maqu County
To analyze the risk assessment of heavy metal pollution in maqu alpine meadow,we collected the surface soil samples(0-20 cm)of degraded alpine meadow in maqu county to determining the contents of eight heavy metals in soil,including Cr,Ni,Cu,Zn,As,Cd,Hg and Pb.Single factor pollution index,Nemerow pollution index and geoaccumulation index were used to evaluate the pollution degree of heavy metals and analyze the potential ecological risk.We used correlation analysis,principal component analysis and cluster analysis to characterize the homologous heavy metals.The results showed that:(1)There was greater mass fraction of As and Cd than the background value in soil,while there was lower mass fraction of Ni than the background value in soil.The ranking of variation coefficient was Cr>Hg>Cd>Cu>As>Ni>Zn>Pb.(2)The single factor pollution index of Cd was slight pollution,the ground accumulation index reflects that As was between unpolluted and slight pollution.Each heavy metal element was no potential ecological risk.Based on the national standard and soil background value,Nemerow composite pollution index showed that maqu was not contaminated by heavy metals.(3)Principal component analysis and correlation analysis showed that Ni,Cu,Zn,As,Cd,Pb in Maqu soil had the same or similar sources.The Ni and Pb had the highest priority order,while Cr and Hg contents showed a weak correlation.
Alpine meadowHeavy metal pollutionPollution indexPotential ecological riskPrincipal component analysis