Trace metal mobility and Cd, Zn, and Pb isotopic signatures in electronic waste processing dusts: A combined BCR sequential extraction procedure and multi-element isotopic study

This study combines Cd, Pb, and Zn isotopes and BCR extraction to evaluate trace metal mobility and environmental risks in dust from e-waste facilities. Eight samples were collected by active aspiration from units processing: photovoltaic panels, liquid crystal display (LCD), cathode ray tube (CRT) monitors, and mixed e-waste. One storage facility (SF) floor dust was swept. Trace element concentrations were determined and maximum concentrations reached 1,095 mg kg⁻¹ Cd, 23,107 mg kg⁻¹ Cu, 25,454 mg kg⁻¹ Pb, 31,082 mg kg⁻¹ Zn, 806 mg kg⁻¹ Sb, and 9,365 mg kg⁻¹ Ba. A modified BCR sequential extraction procedure characterized five fractions: exchangeable (F1), reducible (F2), organic-bound (F3), and two residual (F4, F5). Zinc showed the highest mobility (71-98% in F1 and F2 fractions), while copper showed variable behavior depending on e-waste type. Cadmium and lead mobility strongly depended on e-waste type: 93-95% of Cd and 64-85% of Pb were highly mobile in mixed e-waste dusts, but remained predominantly in residual fractions for CRT, LCD, and SF dusts. Less mobile elements (Ba, Sb, As, Cr) remained in least accessible fractions. Isotopic analysis identified three distinct Pb source clusters. Zinc and cadmium isotopes ranged from light isotope enrichment in early fractions to heavy isotope enrichment in residual phases, reflecting both primary source signatures and extraction-induced fractionation. Mixed e-waste dusts pose the highest environmental concern due to high Zn, Cu, Cd, and Li concentrations and mobility. CRT, SF, and LCD dusts present lower immediate risk due to glass/ceramic matrix incorporation, but long-term monitoring remains essential.