This seminar will feature Dr. Eric Betterton and Dr. Raina Maier from the University of Arizona Superfund Research Program and will focus on field trials being performed at mining sites in Arizona. Mine tailings are large piles of crushed rock leftover after the minerals of interest have been processed. They often do not support establishment of a plant cover, are prone to wind and water erosion, and may contribute to the dispersion of associated metal toxicants. Dr. Eric Betterton will discuss size-selective characterization of aerosols collected with samplers called "Multiple Orifice Uniform Deposit Impactors" at two Arizona mining sites, the Asarco plant in Hayden, AZ, and the Iron King Mine and Humboldt Smelter Superfund site in Dewey-Humboldt, AZ. Chemical speciation shows that arsenic and lead occur preferentially in the submicron fraction at both sites; lead isotope analysis shows great promise for source apportionment at both sites; and scanning electron microcopy shows evidence for spherical particle formation by high-temperature processing at Hayden. Data from dust flux towers installed at Iron King, and dust modeling studies will be described. Dr. Raina Maier will discuss phytostabilization, a technology being investigated for remediation of mine tailings sites in arid and semi-arid environments. The goal is to create a vegetative cap using native plants that will 1) prevent wind and water erosion of the tailings, 2) stabilize metal contaminants in the rooting zone, and 3) avoid shoot uptake of metal contaminants. The Iron King Mine and Humboldt Smelter Superfund Site is adjacent to the town of Dewey-Humboldt, Arizona. Soil in residential yards contains elevated levels of arsenic, lead, and zinc associated with tailings particles that have been dispersed as dust, primarily by wind. Working together with the site owner and Region 9 EPA, a phytostabilization trial was initiated on site in May 2010, which was further expanded in 2011, using native plants that were shown to meet successful phytostabilization criteria in preliminary greenhouse trials. The site is being monitored to determine whether greenhouse results can be successfully translated to the field and to examine changes in chemical, physical, and biological properties of the tailings as phytostabilization occurs.
For general information contact Justin Crane
by telephone at 919 794-4702
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