Browsing by Author "Dwyer, Gary S"

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    Boron and strontium isotopic characterization of coal combustion residuals: validation of new environmental tracers.
    (Environ Sci Technol, 2014-12-16) Ruhl, Laura S; Dwyer, Gary S; Hsu-Kim, Heileen; Hower, James C; Vengosh, Avner
    In the U.S., coal fired power plants produce over 136 million tons of coal combustion residuals (CCRs) annually. CCRs are enriched in toxic elements, and their leachates can have significant impacts on water quality. Here we report the boron and strontium isotopic ratios of leaching experiments on CCRs from a variety of coal sources (Appalachian, Illinois, and Powder River Basins). CCR leachates had a mostly negative δ(11)B, ranging from -17.6 to +6.3‰, and (87)Sr/(86)Sr ranging from 0.70975 to 0.71251. Additionally, we utilized these isotopic ratios for tracing CCR contaminants in different environments: (1) the 2008 Tennessee Valley Authority (TVA) coal ash spill affected waters; (2) CCR effluents from power plants in Tennessee and North Carolina; (3) lakes and rivers affected by CCR effluents in North Carolina; and (4) porewater extracted from sediments in lakes affected by CCRs. The boron isotopes measured in these environments had a distinctive negative δ(11)B signature relative to background waters. In contrast (87)Sr/(86)Sr ratios in CCRs were not always exclusively different from background, limiting their use as a CCR tracer. This investigation demonstrates the validity of the combined geochemical and isotopic approach as a unique and practical identification method for delineating and evaluating the environmental impact of CCRs.
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    Evaluating salinity sources of groundwater and implications for sustainable reverse osmosis desalination in coastal North Carolina, USA
    (Hydrogeology Journal, 2011-08-01) Vengosh, A; Vinson, David S; Schwartz, Haylee G; Dwyer, Gary S
    The natural and pumping-induced controls on groundwater salinization in the coastal aquifers of North Carolina, USA, and the implications for the performance of a reverse osmosis (RO) desalination plant have been investigated. Since installation of the well field in the Yorktown aquifer in Kill Devil Hills of Dare County during the late 1980s, the groundwater level has declined and salinity of groundwater has increased from ∼1,000 to ∼2,500 mg/L. Geochemical and boron isotope analyses suggest that the salinity increase is derived from an upflow of underlying saline groundwater and not from modern seawater intrusion. In the groundwater of four wells supplying the plant, elevated boron and arsenic concentrations were observed (1.3–1.4 mg/L and 8–53 μg/L, respectively). Major ions are effectively rejected by the RO membrane (96–99% removal), while boron and arsenic are not removed as effectively (16–42% and 54–75%, respectively). In coming decades, the expected rise of salinity will be associated with higher boron content in the groundwater and consequently also in the RO-produced water. In contrast, there is no expectation of an increase in the arsenic content of the salinized groundwater due to the lack of increase of arsenic with depth and salinity in Yorktown aquifer groundwater.
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    Isotopic imprints of mountaintop mining contaminants.
    (Environ Sci Technol, 2013-09-03) Vengosh, Avner; Lindberg, T Ty; Merola, Brittany R; Ruhl, Laura; Warner, Nathaniel R; White, Alissa; Dwyer, Gary S; Di Giulio, Richard T
    Mountaintop mining (MTM) is the primary procedure for surface coal exploration within the central Appalachian region of the eastern United States, and it is known to contaminate streams in local watersheds. In this study, we measured the chemical and isotopic compositions of water samples from MTM-impacted tributaries and streams in the Mud River watershed in West Virginia. We systematically document the isotopic compositions of three major constituents: sulfur isotopes in sulfate (δ(34)SSO4), carbon isotopes in dissolved inorganic carbon (δ(13)CDIC), and strontium isotopes ((87)Sr/(86)Sr). The data show that δ(34)SSO4, δ(13)CDIC, Sr/Ca, and (87)Sr/(86)Sr measured in saline- and selenium-rich MTM impacted tributaries are distinguishable from those of the surface water upstream of mining impacts. These tracers can therefore be used to delineate and quantify the impact of MTM in watersheds. High Sr/Ca and low (87)Sr/(86)Sr characterize tributaries that originated from active MTM areas, while tributaries from reclaimed MTM areas had low Sr/Ca and high (87)Sr/(86)Sr. Leaching experiments of rocks from the watershed show that pyrite oxidation and carbonate dissolution control the solute chemistry with distinct (87)Sr/(86)Sr ratios characterizing different rock sources. We propose that MTM operations that access the deeper Kanawha Formation generate residual mined rocks in valley fills from which effluents with distinctive (87)Sr/(86)Sr and Sr/Ca imprints affect the quality of the Appalachian watersheds.
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    Legacy of Coal Combustion: Widespread Contamination of Lake Sediments and Implications for Chronic Risks to Aquatic Ecosystems.
    (Environmental science & technology, 2022-10) Wang, Zhen; Cowan, Ellen A; Seramur, Keith C; Dwyer, Gary S; Wilson, Jessie C; Karcher, Randall; Brachfeld, Stefanie; Vengosh, Avner
    Elevated concentrations of toxic elements in coal ash pose human and ecological health risks upon release to the environment. Despite wide public concerns about water quality and human health risks from catastrophic coal ash spills and chronic leaking of coal ash ponds, coal ash disposal has only been partially regulated, and its impacts on aquatic sediment quality and ecological health have been overlooked. Here, we present a multiproxy approach of morphologic, magnetic, geochemical, and Sr isotopic analyses, revealing unmonitored coal ash releases over the past 40 to 70 years preserved in the sediment records of five freshwater lakes adjacent to coal-fired power plants across North Carolina. We detected significant sediment contamination and potential chronic ecological risks posed by the occurrence of hundreds of thousands of tons of coal ash solids mainly resulting from high-magnitude stormwater runoff/flooding and direct effluent discharge from coal ash disposal sites. The proximity of hundreds of disposal sites to natural waterways across the U.S. implies that such contamination is likely prevalent nationwide and expected to worsen with climate change.
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    The strontium isotope fingerprint of phosphate rocks mining.
    (The Science of the total environment, 2022-12) Vengosh, Avner; Wang, Zhen; Williams, Gordon; Hill, Robert; M Coyte, Rachel; Dwyer, Gary S
    High concentrations of metal(loid)s in phosphate rocks and wastewater associated with phosphate mining and fertilizer production operations pose potential contamination risks to water resources. Here, we propose using Sr isotopes as a tracer to determine possible water quality impacts induced from phosphate mining and fertilizers production. We utilized a regional case study in the northeastern Negev in Israel, where salinization of groundwater and a spring have been attributed to historic leaking and contamination from an upstream phosphate mining wastewater. This study presents a comprehensive dataset of major and trace elements, combined with Sr isotope analyses of the Rotem phosphate rocks, local aquifer carbonate rocks, wastewater from phosphate operation in Mishor Rotem Industries, saline groundwater suspected to be impacted by Rotem mining activities, and two types of background groundwater from the local Judea Group aquifer. The results of this study indicate that trace elements that are enriched in phosphate wastewater were ubiquitously present in the regional and non-contaminated groundwater at the same levels as detected in the impacted waters, and thus cannot be explicitly linked to the phosphate wastewater. The 87Sr/86Sr ratios of phosphate rocks (0.707794 ± 5 × 10-5) from Mishor Rotem Industries were identical to that of associated wastewater (0.707789 ± 3 × 10-5), indicating that the Sr isotopic fingerprint of phosphate rocks is preserved in its wastewater. The 87Sr/86Sr (0.707949 ± 3 × 10-6) of the impacted saline groundwater were significantly different from those of the Rotem wastewater and the background saline groundwater, excluding phosphate mining effluents as the major source for contamination of the aquifer. Instead, the 87Sr/86Sr ratio of the impacted water was similar to the composition of brines from the Dead Sea, which suggests that the salinization was derived primarily from industrial Dead Sea effluents with distinctive Sr isotope and geochemical fingerprints.