Pollution Risk Assessments of Heavy Metals in Soils Around a Municipal Solid Waste Incinerator

To assess the environmental risk of heavy metals caused by a municipal solid waste incinerator (MSWI) in the Pearl River Delta, the topsoil in the vicinity was sampled for determination of heavy metal contents (As, Hg, Pb, Cu, Zn and Cd) during 2016~2019. Furthermore, single pollution index (P_i), ecological risk index (RI), and EPA risk assessment guidance for superfund (USEPA model) were employed to comprehensively assess the potential ecological risk and underlying health risk. The average contents of six heavy metals in topsoil were below the risk screening values for contamination of agricultural land in national standard (GB15618-2018), while those of Hg, Pb, Cd and Cu were 7.00, 0.91, 0.15 and 1.40-fold above the corresponding background values. P_i of As, Hg and Zn were 0.012~0.838, indicating low-contamination (P_i < 1), while P_i of Pb, Cd and Cu were 0.083~1.608, which indicated that some samples were moderately contaminated (1≤P_i < 3). In particular, the samples showed that moderate contamination by Pb accounted for the highest ratio (account for 50%). RI ranging from 8.687 to 49.983 indicated low ecological risk, with Hg and Pb contributing the most to the mean value of RI (35.9% and 26.2% respectively). The hazard indexes (HI, 0.092~0.731) and carcinogenic risk (CR, 3.72×10^-7~1.56×10^-5) below safety threshold value revealed limited health risk. However, 95th percentile value of HI for children was 0.717, close to the risk safety value 1, and Pb contamination accounted for 92.2%, 69.0% and 73.4% of HI to males, females and children. In conclusion, Hg and Pb contamination should be more strictly monitored to further minimize the underlying environmental risk.