Master of Science / Department of Chemical Engineering / Larry Erickson / Urban soils contaminated with lead can pose a health risk if vegetables and fruits from the garden are consumed. In general, we don’t think our gardens as dangerous or toxic, but unfortunately some garden soils do contain toxic levels of lead. Chipping paint around older structures will raise the lead level in the soils directly adjacent to the building. Restrictions to lead paint started in the 1950’s. Today lead paint content has been reduced; however paint companies are allowed to mix up to 0.05% lead in paints. Lead use has been reduced significantly, but not entirely eliminated. Soil can be contaminated with lead from other sources such as industrial sites, industrial sludge with heavy metals, auto emissions, old lead plumbing pipes or even old orchard sites in production when lead arsenate was in use. The main concern with lead in firing ranges is the fate and transport of heavy metals from bullets fragments accumulating in soil. Of these metals, lead is the predominant contaminant. Lead is considered the top environmental threat to children’s health. The U.S. military alone has cleaned up more than 700 firing ranges across the country over the past several years. The U.S. Air Force conducted a study at Shaw Air Force base to determine the lead concentrations in ground water and soil collected from the Small Arms Firing Range in 1992. The purpose of this study was to determine the levels of contamination in the soil in order to develop a restoration plan. The goal of the restoration plan was to clean up the land for future use. The Defense Environmental Restoration Program (DERP) conducted a project at Beale Air Force Base to clean up contaminated lead soil and to prevent any future fine and environmental expenses for the base. The main goal was to protect the base population from the lead and other contaminants hazards. In 1992 the Air Force conducted an investigation that included environmental sampling of soil and lead of the Tyndall Elementary School grounds. The Air Force collected lead samples in areas where children play on the school ground. Because lead concentrations results were below the toxic levels for lead, the Air Force concluded that no further action was needed. Further investigation for soil removal took part in 1992 and 2009. Under the Critical Removal Action field activities included site preparation, waste characterization, investigative sample chemical analysis, contaminated soil excavation, dust control, disposal, backfill and grading, and site restoration. Over the years the Air Force has been able to educate the military community on health hazards in the base facilities especially lead exposure and have been able to implement programs dedicated to prevent any lead overexposure.

Call number: LD2668 .T4 1978 M58 / Master of Science

Utilizing geochemical and geospatial data to explore the spatial variability of metals within streambed sediment of a local waterway may help to identify anthropogenic input of copper, lead, and zinc in urbanized streams. Utoy Creek is an urbanized stream located just southwest of downtown Atlanta. Baseline trace metal values and a reference site were used to determine if copper, lead, and zinc concentrations were higher or lower than baseline or reference site values. The Atlanta Metro Region (AMR) had over 2,100 miles of impaired streams listed on the 2008 303(d) list. This type of study can be used as a proxy to help determine how "impaired" local urbanized streams really are and to identify areas of interest for future studies. For this study, 42 sites were selected for streambed sediment collection, chemical analysis was preformed, and GIS and statistical analysis were preformed. This study shows that several areas in Utoy Creek show elevated metal concentrations of copper, lead, and zinc.

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Historic mine tailings pose a significant health risk to surrounding ecosystems and communities because of high residual concentrations of contaminant metals. The initial tailings mineral assemblage, metal sulfides, silicates, and carbonates are unstable at earth surface conditions and undergo oxidative and proton-promoted weathering. The weathering of metal sulfides generally produces acid that, if not balanced by protonconsuming dissolution of silicates and carbonates, leads to progressive acidification. The Klondyke State Superfund Site in Graham County, Arizona contains high concentrations of Pb (up to 13 g kg⁻¹) and Zn (up to 6 g kg⁻¹), and remains unvegetated 50 years after mining cessation. Field-scale investigation revealed a wide range of pH (2.5-8.0) and plant-available (DTPA-extractable) metals in the near surface of the tailings pile. Four samples were chosen for in-depth characterization ranging in pH, as denoted by subscript, from 2.6 to 5.4. The mineral transformations occurring in these four samples were investigated using a variety of techniques and the data indicated an increase in tailings weathering extent with increasing acidification (decreasing pH). Lead speciation, studied by a combination of chemical sequential extraction and X-ray absorption fine structure (XAFS) spectroscopy, was found to vary with tailings depth. The principle lead-bearing mineral was plumbojarosite (PbFe₆(SO₄)₄(OH)₁₂), with smaller amounts of anglesite (PbSO₄) and lead-sorbed iron-oxide. Anglesite, the most bioavailable mineral form of Pb in the tailings, was found to accumulate at the tailings surface, which has important implications for health risks. Total Zn content decreased by an order of magnitude (from 6 to 0.4 g kg⁻¹) and showed a change in molecular speciation with decreasing pH. Zinc-rich phyllosilicates and Zn-containing manganese oxides predominate at high pH, whereas low pH samples contained principally Zn-sorbed iron oxides. One of the overarching goals of the project is to remediate the Klondyke site using phytostabilization to keep contaminant metals from eroding offsite either by wind or water transport mechanisms. However, the impacts of plant growth on metal bonding environment are unknown. To address that gap in knowledge, we have developed a technique for the study of root-microbe-mineral-metal interactions that occur in the rhizosphere, the volume of soil surrounding, and affected by, plant roots. This technique involves the conjunctive use of fluorescence in-situ hybridization, X-ray fluorescence elemental mapping, XAFS and Raman micro-spectroscopies, and electron microscopy on single roots. Manganese and iron root plaques collocalized with elevated Pb, Zn, and Cr demonstrate that the rhizosphere can affect metal speciation. Metal speciation is an important factor in determining metal bioavailability, and thus is critical for understanding the health risk associated with mine tailings. The results of this research provides site-specific information about Pb and Zn speciation, which will be used to evaluate the effectiveness of site remediation within the context of metal toxicity.

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