M7 AM Metals in the Environment: Chemistry and Fate Issues
Monday, 14 November 2005: 8:00 AM - 11:40 AM in 327-329

(SCH-1117-771592) Metal speciation and mobility in mine waste piles and surface waters in a mine-impacted area.

Schaider, L.¹, Senn, D.¹, Brabander, D.², Holton, M.¹, Shine, J.¹, ¹ Harvard School of Public Health, Boston, MA, USA² Wellesley College, Wellesley, MA, USA

ABSTRACT- The Tar Creek Superfund Site in northeastern Oklahoma is heavily impacted by decades of lead and zinc mining in the Tri-State Mining area. A notable feature of this area is the presence of mine waste piles that contain elevated concentrations of Zn, Pb and Cd. Runoff from these piles, together with acid mine drainage originating from abandoned mine shafts, contribute to metal loading into Tar Creek. As part of a larger project to identify routes of exposure to children and health impacts of exposure to metals in mining materials, we characterized variations in metal concentration and speciation as a function of particle size using XRF, XRD and sequential extraction techniques. Total concentrations of Zn, Pb and Cd were found to increase with decreasing particle size (up to 10% Zn and 2% Pb by mass and 200 ppm Cd in the <37 m size fraction). The speciation of the metals also changed as a function of particle size. While the parent ore material contained metals in sulfide forms (galena and sphalerite), particles in the smallest size fraction contained metals in secondary mineral phases. We also explored the sources and mobility of Zn, Pb, Cd, Cu, Mn and Ni within Tar Creek, which drains part of the Superfund site. Using sulfate as a conservative tracer and PCA analysis, we estimated relative contributions of waste pile runoff, groundwater seepage and acid mine drainage to metal loading into the creek. Once in the creek, metal mobility was related to affinity for ferric hydroxides, which are abundant in the creek. An improved understanding of the speciation of metals in exposure media and variations in concentration and bioavailability as a function of distance from their sources will lead to a more complete assessment of the health impacts of mining activities on human and ecological health.

Key words: metal speciation, mine waste piles