Deciphering the pollution risks, sources and their links of heavy metals in soils

Heavy metals in soils pose serious ecological and health risks. To make efficient strategies for mitigating the underlying hazards, it is critical to reveal the pollution sources and their links with the risks. Researchers have investigated source identification and risk evaluation of heavy metals in soils, yet few have systematically deciphered the source-sink relationship of soil metals and the links between source apportionment and risk assessment. In the study, an integrated technological framework has been proposed to address the gaps, and applied to characterize the pollution risks, sources and their links of soil metals in a typical coal resource city in China. The assessment using geochemical tool and ecological risk index shows the soils in study area are polluted by Cd, Hg, Cr, As and Pb in varied degrees, and particularly, Cd and Hg present significant ecological risk. Two advanced receptor models (multivariate curve resolution-weighted alternating least-squares and multilinear engine 2) are comparatively applied for apportioning the potential sources of soil metals, and the results suggest the two models have identified similar sources (r² > 0.90), including agricultural activities, atmospheric depositions and industrial discharges with contributions of 35.5 %-38.3 %, 30.3 %-35.1 %, and 26.6 %-34.1 %, respectively. Then, apportionment results of the two models are jointly employed for evaluating the source-specific health risks of metals in the environment using a probabilistic risk assessment model. The risk levels within the area are overall acceptable or tolerable, and relatively, the industrial discharges present higher contribution on the non-carcinogenic and carcinogenic risks of soil metals to public. Findings will help the managers to design targeted policies for reducing the risks of soil metals, and the framework proposed provides a useful guideline to better understand the source-risk relationship of soil metals in other environments worldwide.