Environmental risk assessment of heavy metal and PAH contamination at Kalasin e-waste dumpsite and screening of native hyperaccumulators

Abstract

Electronic waste (e-waste) has become a global concern due to its environmental health risks. The Kalasin e-waste dumpsite is the largest illegal e-waste landfill in Kalasin province, Thailand. This study presents a multi-year assessment (2018–2020) of heavy metals (Ni, Pb, Cu, Zn, and Cd) in soils from e-waste recycling sites, all exceeding UNEP and WHO/FAO permissible limits at multiple locations. Temporal trend analysis demonstrated increasing median concentrations for most metals over the three years, except for Zn. The contamination factor (CF), geoaccumulation index (I<inf>geo</inf>), and pollution load index (PLI) indicated that the soil was heavy to extremely contaminated with heavy metals. Furthermore, the site was highly contaminated with polycyclic aromatic hydrocarbons ranging from 822.03–1267.00 ng g⁻¹ from 2018 to 2020, dominated by high-molecular-weight PAHs (4–5 rings). The diagnostic ratio indicated the pyrogenic sources linked to combustion processes, and the ILCR level indicated that the soil poses a significant cancer risk to the population. Concurrent phytoremediation assessments identified several native plant species with bioaccumulation factor (BCF) and translocation factor (TF) values greater than 1 for Pb, Zn, and Cd, suggesting strong hyperaccumulation potential. Ricinus communis has been identified as the most potent hyperaccumulator of Pb. These findings report the persistent co-contamination of soil with heavy metals and PAHs and the potential use of native, economically valuable plants in sustainable remediation strategies.