Uncovering rare earth and precious metal in landfill-mined soil-like-fractions: distribution prediction, ecological risk and resource potential.
Journal:
Environmental pollution (Barking, Essex : 1987)
Published Date:
May 5, 2025
Abstract
The introduction of rare earth elements (REEs) and precious metals (PMs) containing wastes in aged landfills leads to a significant pollutant and resource potential. Against this backdrop, the accumulation of REEs and PMs in soil-like-fractions (SLF) remains uncertain. This study pioneers a comprehensive analysis of the REE/PM speciation, ecological risks of REEs and economic potential of PMs in SLF. Concentrations of REEs and PMs varied from 146.14 to 464.28 mg/kg and 4.20-111.86 mg/kg, respectively, with a particular enrichment in the upper SLF. REEs and PMs were immobilized by SLF and stabilized into organic- and mineral-bound fractions. A dataset linking urban development and landfill conditions to REE/PM concentrations was created, and the Support Vector Regression (SVR) model was utilized to achieve high-precision prediction of REEs and PMs content (R > 0.9). The Shapley Additive Explanations (SHAP) algorithm revealed development of electronics industry as the primary driver of REE/PM enrichment, followed by organic matter content in SLF. The potential ecological risk index (PERI) showed limited risks of REEs, but the bioavailable REEs posed long-term accumulation and chronic toxicity in terrestrial organisms, emphasizing the detoxification before SLF reusage. The economic potential of PMs reached 871.82 USD per ton of SLF, higher than primary minerals. These findings provide new insights into valuable resources during landfill mining and suggest potential areas for applying modern techniques, such as machine learning, to landfill management.
