Characterization of Zinc, Lead, and\nCadmium in Mine Waste: \nImplications for Transport, Exposure,\nand Bioavailability

Abstract

We characterized the lability and bioaccessibility of Zn,\nPb, and Cd in size-fractionated mine waste at the Tar Creek\nSuperfund Site (Oklahoma) to assess the potential for\nmetal transport, exposure, and subsequent bioavailability.\nBulk mine waste samples contained elevated Zn (9100\n± 2500 ppm), Pb (650 ± 360 ppm), and Cd (42 ± 10 ppm),\nwhile particles with the greatest potential for wind-borne transport and inhalation (<10 μm) contained\nsubstantially higher concentrations, up to 220 000 ppm Zn,\n16 000 ppm Pb, and 530 ppm Cd in particles <1 μm.\nAlthough the mined ore at Tar Creek primarily consisted\nof refractory metal sulfides with low bioavailability, sequential\nextractions and physiologically based extractions indicate\nthat physical and chemical weathering have shifted\nmetals into relatively labile and bioaccessible mineral\nphases. In <37 μm mine waste particles, 50−65% of Zn,\nPb, and Cd were present in the “exchangeable” and\n“carbonate” sequential extraction fractions, and 60−80%\nof Zn, Pb, and Cd were mobilized in synthetic gastric fluid,\nwhile ZnS and PbS exhibited minimal solubility in these\nsolutions. Our results demonstrate the importance of site-specific characterization of size-fractionated contemporary\nmine waste when assessing the lability and bioavailability\nof metals at mine-waste impacted sites.