title: Sources and fates of heavy metals in a mining-impacted stream: temporal variability and the role of iron oxides.
abstract: Heavy metal contamination of surface waters at mining sites often involves complex interactions of multiple sources and varying biogeochemical conditions. We compared surface and subsurface metal loading from mine waste pile runoff and mine drainage discharge and characterized the influence of iron oxides on metal fate along a 0.9-km stretch of Tar Creek (Oklahoma, USA), which drains an abandoned Zn/Pb mining area. The importance of each source varied by metal; mine waste pile runoff contributed 70% of Cd, while mine drainage contributed 90% of Pb, and both sources contributed similarly to Zn loading. Subsurface inputs accounted for 40% of flow and 40-70% of metal loading along this stretch. Streambed iron oxide aggregate material contained highly elevated Zn (up to 27,000 μg g(-1)), Pb (up to 550 μg g(-1)) and Cd (up to 200 μg g(-1)) and was characterized as a heterogeneous mixture of iron oxides, fine-grain mine waste, and organic material. Sequential extractions confirmed preferential sequestration of Pb by iron oxides, as well as substantial concentrations of Zn and Cd in iron oxide fractions, with additional accumulation of Zn, Pb, and Cd during downstream transport. Comparisons with historical data show that while metal concentrations in mine drainage have decreased by more than an order of magnitude in recent decades, the chemical composition of mine waste pile runoff has remained relatively constant, indicating less attenuation and increased relative importance of pile runoff. These results highlight the importance of monitoring temporal changes at contaminated sites associated with evolving speciation and simultaneously addressing surface and subsurface contamination from both mine waste piles and mine drainage.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA. Electronic address: lschaide@hsph.harvard.edu.
authors.forename: Laurel A
authors.initials: LA
authors.lastname: Schaider
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA.
authors.forename: David B
authors.initials: DB
authors.lastname: Senn
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA; Department of Geosciences, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA.
authors.forename: Emily R
authors.initials: ER
authors.lastname: Estes
authors.affiliation: Department of Geosciences, Wellesley College, 106 Central Street, Wellesley, MA 02481, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Brabander
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Landmark Center West, 401 Park Drive, Boston, MA 02215, USA.
authors.forename: James P
authors.initials: JP
authors.lastname: Shine
mesh_terms: D004784:Environmental Monitoring; D005290:Ferric Compounds / Q000737:chemistry*; D019216:Metals, Heavy / Q000032:analysis* / Q000737:chemistry; D008906:Mining; D009825:Oklahoma; D012989:Soil Pollutants / Q000032:analysis* / Q000737:chemistry
chemical_list: D005290:Ferric Compounds; D019216:Metals, Heavy; D012989:Soil Pollutants; C000499:ferric oxide
keywords: Heavy metals; Iron oxides; Metal loading; Mine drainage; Mine waste piles; Sequential extractions