Integrating sequential fractionation, plant uptake, and health risk to evaluate agricultural reuse potential of a legacy dumpsite

Municipal solid waste dumpsites are the sources of constant heavy metal contamination and are very challenging for future land use planning. This research combines metal analysis, sequential fractionation, plant metal uptake assessment, and human health risk assessment to determine the agricultural reuse potential of a legacy dumpsite. The soils exhibited elevated metal concentrations, with Cd reaching up to 96 ± 3.46 mg/kg, Cr 14,730 ± 75.06 mg/kg, Ni 5,185 ± 49.0 mg/kg, Pb 787 ± 7.22 mg/kg, and Zn 7,915 ± 28.87 mg/kg, and mostly, these concentrations exceeded the international guideline limit. Sequential extraction indicated that a large portion of the metals was bound up as residual fractions with low mobility, although large proportions of the metals were bound up in fractions associated with Fe-Mn oxides and organic matter, and therefore may be remobilised under environmental alterations. Plant analysis demonstrated that the accumulation of heavy metals comprising Cr, Cu, Fe, Mn, and Zn was concentrated in the shoots, and Ni and Pb were preserved in the roots. Health risk assessment revealed that ingestion was the predominant exposure pathway for adults and children, while the inhalation pathway was the least contributive. Chromium (Cr) posed the greatest health risk, with a maximum Health Index (non-carcinogenic risk) of 8.001 for adults and 53.028 for children, which is above the acceptable threshold of 1 and showed significant non-carcinogenic risk. The Lifetime carcinogenic risk values of Cr were 1.18 × 10−3 for adults and 1.41 × 10−2 for children, and children showed significantly higher carcinogenic risk.