[Potential Ecological Risk Assessment and Source Analysis of Heavy Metals in Soil-crop System in Xiong'an New District].

In order to evaluate the potential ecological risk of heavy metals in the soil-crop system in the Xiong'an New District, the heavy metal contents and forms in wheat seed and root soil samples are analyzed, and the comprehensive pollution index (IPI), potential ecological risk index (RI), bio-enrichment coefficient (BFC), risk assessment code (RAC), principal component analysis, and correlation analysis are used to assess the potential ecological risk of heavy metals and analyze their sources. The results indicate that the average content of Cd, Cu, Pb, and Zn in the root soil is significantly higher than the soil background value in Hebei province. The IPI ranges from 0.2 to 5.18, 94.83% of the soil samples are in the safe and pollution-free grade, and the potential ecological risks of heavy metal are slight and moderate, accounting for 64.66% and 30.17%, respectively. Cd has the greatest potential ecological harm, followed by Hg, Cr, Ni, and Zn. All the heavy metal elements besides Cd in the root soil are dominated by the residual form, which accounts for 60%, and the bioactive form (ion-exchange and water-soluble state) of Cd accounts for 33.43%, indicating relatively high bio-availability. The risk assessment code can be ranked as Cd > Ni > Hg > As > Cu > Cr > Zn > Pb, and the risk of Cd is moderate, while other elements are of low or no risk. The leading potential source of heavy metals is human activity combined with the geological background. The migration and enrichment capability of the wheat seeds is in order from strong to weak of Zn > Cu > Cd > Hg > As > Ni > Pb > Cr, and the biological effective components of As, Cd, Pb, and Zn plays an substantial role in promoting the absorption of heavy metals. The content of heavy metals in the wheat seeds has a negative correlation with the soil pH, and the physical and chemical indices, such as OM and CEC, has bi-directional influence on the biological effective state of the heavy metals.