Integrating pollution indices and Monte Carlo simulation for a comprehensive risk assessment of potentially toxic elements in soils

Abstract

Potentially toxic elements (PTEs) in soil pose significant ecological and human health risks due to their persistence and bioaccumulative nature. This study investigates PTE contamination in soils collected from ten representative contaminated sites across Japan, including industrial zones, construction sites, and shooting ranges. While previous research has focused on specific PTEs such as arsenic (As) and lead (Pb), comprehensive multi-element risk assessments across diverse contamination scenarios remain limited. To address this, a suite of pollution indices, including the geo-accumulation index (I_geo), Pollution Index (PI), Nemerow Pollution Index (PI_N), Potential Ecological Risk Index (RI), Pollution Load Index (PLI), multi-element contamination index (MEC), and the Mean Effects Range-Median Quotient (MERMQ), was employed to assess contamination levels and ecological risks. Additionally, human health risks were assessed using deterministic models and probabilistic Monte Carlo simulations. Results identified As and Pb as primary contaminants, with leaching tests revealing concentrations significantly exceeding environmental standards in most soils. Elevated I_geo and PI values for cadmium (Cd), chromium (Cr), and nickel (Ni), despite concentrations remaining within regulatory thresholds, suggest localized safety concerns. High MEC values revealed extremely high pollution in industrial and shooting range soils, threatening the local ecosystem. Non-carcinogenic risk assessments indicated Pb and As as major contributors, with hazard index (HI) values > 1 in several samples. Carcinogenic risks associated with Cr and As exceeded acceptable thresholds in most samples, emphasizing the need for protective health measures. The findings provide critical data to support local governments and policymakers in implementing targeted remediation strategies for managing PTE-contaminated areas.