Distribution Characteristics And Risk Assessment Of Heavy Metals In The Huixian Wetland,Guangxi Province

The contents,distribution characteristics and potential ecological risk of heavy metal(Zn,Pb,Ni,Cr,Cu,As,Hg,Cd)were investigated in different land use types in Huixian wetland of Guangxi Province,which was to analysis the relationship between heavy metals and its physical properties in soils,to determine the source of heavy metals through the correlation analysis,Principal Component Analysis(PCA),Cluster analysis and other statistical methods.The methods of Geoaccumulation assessment and potential ecological risk index of Hakanson were applied to evaluate heavy metal pollution in this area,which would provide theoretical basis for the conservation and restoration of Huixian Wetland.The results were listed as follows:1.The physical and chemical properties were a little difference among the surface sediment in the Huixian Wetland.The average pH,total nitrogen content and total phosphorus content in soil was 7.16±0.27,4.90±1.40g/kg and 0.80±0.28g/kg,respectively.2.The content of heavy metals in the surface sediment of Huixian wetland were:Zn>Cr>Pb>Ni>Cu>As>Cd>Hg;The average concentrations of Zn,Cr,Pb,Ni,Cu,As,Cd and Hg in soils were 141.25±126.2mg/kg,110.71±30.84mg/kg,46.99±20.14,39.68±13.93mg/kg,38.76±27.51mg/kg,17.32±6.92mg/kg,0.67±0.39mg/kg,0.18±0.16mg/kg,respectively.The metals of Zn,Pb,Ni,Cr,Cu,Hg and Cd were high accumulation in soils compared to the background concentration of soil elements in the Guangxi Province.The content of heavy metals varied in different land use types.For example,the sediment from river,lake,pond and ditch in the Huixian wetland had relatively high content of heavy metals.The content of Hg in the river exceeded the second grade of standard values of Chinese Environmental Quality Standards for Soils,and the content of Cd in sediments of river and lake had exceed the third grade of standard.3.Most of the heavy metals in the soils of Huixian Wetland were correlated with each other.The metal of Pb showed extremely significant correlation with Cr(P<0.01),but had no significant relationship with other heavy metals.The principal component analysis showed that the first main component including Ni,Cr and As with the corresponding load values of 0.924,0.647 and 0.891 respectively;the second component including Cu and Zn with the corresponding load value of 0.746 and 0.629;and the third component including Hg,Pb and Cd with the corresponding load value of 0.746,0.564,0.642,respectively.4.The geoaccumulation index in the Huixian Wetland indicated that 4.84% of Zn,Cd elements in the samples ranked the third grade,belonging to medium-heavy.The average geoaccumulation index level for Pb in sediment of river,marsh,lake,ditch,paddy field and forest land ranked the second grade,belonging to moderate pollution.The heavy metals Cd and Hg were significantly heavy pollution in the Huixian Wetland.