A joint method to quantify source contributions of heavy metals to ecological and human health risks in oasis farmland soil

Abstract

Source identification and risk assessment of heavy metals are ongoing hot topics in current research, but few studies have been performed on the linkage mechanism between them. In the past, the amount of heavy metals discharged was the identification criterion for high-risk source but failed to consider different toxicity of heavy metals in the risk level of each pollution source. Therefore, it is impossible to accurately determine high-risk pollution source. For this situation, this study introduced a risk assessment model based on the source apportionment model, which can quantitatively analyze the source-based risk. Meanwhile, pollution assessment indexes and a risk assessment model were applied to evaluate the levels of pollution and risk of heavy metals, showing that lead (Pb) caused relatively serious pollution and arsenic (As) generated the highest ecological risk and noncarcinogenic risk. Positive matrix factorization (PMF) model identified and quantified the sources of heavy metals (coal-related activities source, mixed source of mining and traffic emissions, industrial activity source, agricultural source related to the application of agrochemicals) with the corresponding contributions of 42, 30, 26, and 2%, respectively. Then PMF was combined with potential ecological risk index and human health risk assessment model to quantify the risk from pollution sources, indicating that the coal-related activities source was the largest pollution source (31-36%) that caused human health risks, while the mixed source of mining and transportation emissions posed the greatest threat (29%) to the ecosystem health. Therefore, both sources should be identified as the priority pollution sources.

Source Apportionment and Risk Assessment of Heavy Metals in Agricultural Soils in a Typical Mining and Smelting Industrial Area

“…Although the industrial sources (factor 1) made the largest contribution to the total ecological risk, their contribution to the total TCR values was very low (adult: 2.65%, children: 2.65%). The results were comparable with the previous studies [7,63]. In the study area, the weathering processes of parent materials release substantial As into soil, which has much higher toxicity and carcinogenic effects than other metals [9,12,41].…”

“…Industrial activities (factor 1) posed considerable ecological risks (88.1) due to the high contribution to Cd, whereas the ecological risk caused by mixed sources (factor 5) and natural origins (factors 2-4) were classified as "low" categories (Table S1). It suggested that the industrial activities contributed a remarkable proportion to the entire ecological risk due to high toxicity response coefficients of heavy metals (e.g., Cd and Pb) released from the industrial emission [9,14,63]. Figure S5 shows that the spatial distribution of RI resulting from the industrial source was not uniform.…”

“…Overall, the integration of source apportionment and risk assessment could offer an accurate approach to comprehensively capture source contribution to the ecological and health risks [63,65]. Compared to the traditional risk assessment methods, the sourceoriented risk assessment could deliver insight into the impact of natural and anthropogenic sources on soil ecosystems and human health, which is more conducive to providing reliable tools for pollution management and control [64,66].…”

“…Compared to the traditional risk assessment methods, the sourceoriented risk assessment could deliver insight into the impact of natural and anthropogenic sources on soil ecosystems and human health, which is more conducive to providing reliable tools for pollution management and control [64,66]. The in-depth source-oriented risk assessment remains several issues to be addressed, including the influence of soil parent materials, land use type, and bio-availability [63,66], as well as model uncertainty arising from the unidentified component and proper selection of exposure parameters [13]. Hence, further research is required to take the spatial heterogeneity into account and reduce the uncertainty in source apportionment to conduct the comprehensive evaluation of pollution risk in soil.…”