Pollution level and risk assessment of heavy metals in a metal smelting area of Xiong'an New District

In order to support the scientific management of land resource in Xiong'an New District and improve the assessment system of soil pollution in China, a metal smelting area in the District was selected to conduct geological survey. Total 541 surface soil samples collected from the smelting area were analysed for the concentrations of eight heavy metal elements of Cd, Hg, Pb, As, Cu, Zn, Cr, Ni and pH values. The principal component analysis method was used to study the combination and distribution characteristics of the heavy metals. The methods of the single pollution index, Nemerow synthesis pollution index, geological accumulation index and potential ecological hazard index and health risk assessment model were adopted to evaluate the degree and risk of heavy metals pollution in soil. The results show that the excessive concentrations of Cu, Zn, Cd, Pb in soil of the area are mainly influenced by smelting activity, the high value anomalies of As and Pb are principally caused by irrigation of the polluted groundwater from Tanghe River. The order of over-standard rate of the single pollution indices of the elements is Cd>As> Cu>Zn>Pb>Hg>Cr=Ni. The assessment results by the Nemerow synthetic pollution index method show that fifty-four percent of the samples reaches the pollution standard. The order of over-standard rate of the geological accumulation indices is Cd>Cu>Pb>As>Zn>Hg>Ni>Cr, of which the extremely heavy pollution ratios for the elements of Cu, Cd, Zn, Pb and As are 13.5%, 10.2%, 9.1%, 10.9% and 17.2%, respectively. Cd and Hg are the major ecological risk elements. The ratio of moderate-considerable potential ecological risk of Cd is 65.2%, and that of Hg is 71.3%. As, Cr and Pb are of major non-carcinogenic factors. There are 95.2% of the samples (As, Cr, Pb) with non-carcinogenic risk index over 1, and 29 samples with carcinogenic index of As over 10^-4 to children, indicating that heavy metals in the soil of study area have a relatively high health risk to children.