Alyssa Shiel | Oregon State University (original) (raw)
Papers by Alyssa Shiel
PLOS ONE
The DeLong Mountain Transportation System (DMTS) haul road links the Red Dog Mine—one of the worl... more The DeLong Mountain Transportation System (DMTS) haul road links the Red Dog Mine—one of the world’s largest zinc mines—with a shipping port on the Chukchi Sea in northwest Alaska, USA. The road traverses 32 km of National Park Service (NPS) lands managed by Cape Krusenstern National Monument (CAKR). Fugitive dusts from ore concentrate transport and mining operations have dispersed zinc (Zn), lead (Pb), cadmium (Cd), and metal sulfides onto NPS lands since the mine began operating in 1989. This study assessed the effects of metal-enriched road dusts on the diversity and community structure of lichens, bryophytes, and vascular plants in dwarf-shrub tundra within CAKR. In a Bayesian posterior predictions model, lichen species richness (LSR) was highly correlated to distance from the haul road and was distributed on the landscape consistently with the spatial patterns of Zn, Pb and Cd patterns published earlier in this journal. The mean modeled LSR of the 3000–4000 m distance class was...
Geological Society of America Abstracts with Programs, 2020
Geological Society of America Abstracts with Programs, 2017
Uranium is a contaminant of interest due to its toxicity and mobility in groundwater. It is a red... more Uranium is a contaminant of interest due to its toxicity and mobility in groundwater. It is a redox active element in which the oxidation state can change by the addition or removal of electrons. In one method of groundwater remediation, mobile, hexavalent uranium (U(VI)) can be reduced to immobile, tetravalent uranium (U(IV)) by microbial or abiotic chemical reactions. Unfortunately, due to uranium's complex geochemistry, measuring concentrations does not reliably give an accurate indicator of the efficiency of removal. However, uranium isotope ratios can provide a direct way to track the extent of reduction. At the Old Rifle site (Colorado, USA), reduction of U(VI) to U(IV) was induced via injections of acetate to stimulate microbial activity. A decrease of ~1‰ in the 238 U/ 235 U ratio of the dissolved U(VI) was observed and correlated closely to the decrease in concentration (Bopp et al., 2010). However, the primary mechanism of chemical reduction, microbial or abiotic, is still not well understood. Microbial laboratory experiments observed a shift of 1-2‰ in 238 U/ 235 U during reduction experiments with multiple bacterial strains (Basu et al., 2014). Little work has been done to determine the isotopic fractionation induced by abiotic reduction. This study focuses on determining the isotopic fractionation of uranium during reduction with Fe(II). Time series experiments with aqueous Fe(II) and magnetite (Fe3O4) were conducted with samples analyzed by a MC-ICP-MS. We find aqueous Fe(II) has a limited ability to reduce U(VI) and no isotopic data is reported. Stoichiometric magnetite (χ=0.49) reduces U(VI) to U(VI) completely and rapidly as confirmed by XANES analysis, but induces no shift in 238 U/ 235 U. This finding matches iii results observed in three other studies (Rademacher et al, 2006; Stirling et al., 2007; Stylo et al., 2014) where abiotic reduction does not induce isotopic fractionation. I owe the success of this project to many individuals. I especially thank my advisor Dr. Tom Johnson for providing me the opportunity to pursue research in the field of isotope geochemistry and guide me through the many challenges faced while conducting these experiments. I would also like to thank Dr. Craig Lundstrom and Dr. Alyssa Shiel for their endless help and support while working in the lab and on the mass spectrometer. My gratitude goes to Dr. Maxim Boyanov from Argonne National Lab for the opportunity to conduct and analyze my experiments at the Advanced Photon Source. Additionally, I would like to thank the rest of our geochemistry group Gideon
Environmental monitoring and remediation require techniques to identify the source and fate of me... more Environmental monitoring and remediation require techniques to identify the source and fate of metals emissions. In this study, Cd and Zn isotopes were evaluated as tools for the identification of metal sources through (1) the assessment of metallurgical processing as a source of Cd and Zn isotopic fractionation and (2) the measurement of isotopic compositions in bivalves from sites receiving variable metal contributions from natural and anthropogenic sources. This study was facilitated by the successful development of a technique to measure Cd and Zn isotopes (MC-ICP-MS) in environmental and anthropogenic samples. Cadmium, Zn and Pb isotopic ratios were measured for samples from an integrated Zn–Pb smelting/refining complex in B.C. (British Columbia, Canada). Significant fractionation of Cd and Zn isotopes during processing is demonstrated by the total isotopic variation in δCd (1.04‰) and δZn (0.42‰) among smelter samples. Characterization of Cd and Zn isotopic compositions in emi...
Goldschmidt Abstracts, 2020
Ecosphere, 2020
The lead (Pb) lining of agriculture-related subsidies: enhanced Golden Eagle growth rates tempere... more The lead (Pb) lining of agriculture-related subsidies: enhanced Golden Eagle growth rates tempered by Pb exposure.
Anthropocene, 2019
Industrial lead (Pb) emissions have changed oceanic Pb concentrations and isotopic compositions s... more Industrial lead (Pb) emissions have changed oceanic Pb concentrations and isotopic compositions significantly over the last century. Asian industrial emissions are currently the dominant Pb sources in the northwest and central Pacific Ocean. This study investigated major Pb sources in the northeast Pacific Ocean (inland, coastal, and open ocean), where no comprehensive data exist currently. We measured Pb concentrations and isotopic compositions of a variety of shellfish and fish collected in British Columbia (BC) and used them for Pb source apportionment applications in the marine environment. We identified a clear trend in Pb isotopic compositions, from higher 206 Pb/ 207 Pb in inland fish to lower 206 Pb/ 207 Pb in open ocean fish, with coastal fish possessing mid-range values. These results indicate that natural sources of Pb dominate freshwater ecosystems in the central BC coast, whereas anthropogenic Pb sources prevail in western North America and the northeast Pacific. Pacific herring that forage along BC coast exhibit Pb isotopic composition that deviates toward the Chinese Pb regression line. We estimate an Asian origin for about one third of their total Pb. This study shows that Pb isotopes in aquatic organisms are valuable tools for assessing Pb sources across coastal and offshore regions of the northeast Pacific, with great potential for identifying primary foraging areas of marine organisms.
Nature Sustainability, 2019
Urban geochemistry is an emerging field in which key scientific and societal challenges, includin... more Urban geochemistry is an emerging field in which key scientific and societal challenges, including rapid urbanization and population growth, compel investigation of readily accessible biomonitors to determine the source, transport and fate of heavy metal pollutants in cities. Lead isotopic analyses of honey have recently proven its efficacy as a biomonitor for Pb source apportionment applications. We collected honey directly from hives in six geographical sectors in Vancouver, British Columbia (Canada) to investigate the presence of potential pollutants from varying zoning districts: urban, industrial, residential and agricultural. Systematic variations in trace element concentrations and Pb isotopic compositions of the honeys reflect proximity to anthropogenic land-use activities such as shipping ports and heavy traffic. Honey sampled from downtown hives, near the Port of Vancouver, shows elevated trace element concentrations compared with suburban and rural honey, and distinctly higher 208 Pb/ 206 Pb (that is, less radiogenic) compared with local environmental proxies (for example, oysters, Fraser River sediment and volcanic rocks), indicating possible input from Asian anthropogenic sources. This study presents the first Pb isotope data for North American honey, and supports the combined use of trace elements and Pb isotopic compositions in honey as a geochemical biomonitor.
Geochimica et Cosmochimica Acta, 2016
We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical inves... more We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical investigation during field-scale biostimulation and desorption experiments. This investigation was carried out in the uranium-contaminated alluvial aquifer of the Rifle field research site. In this well-characterized setting, a more comprehensive understanding of U isotope geochemistry is possible. Our results indicate that U isotope fractionation is consistently observed across multiple experiments at the Rifle site. Microbially-mediated reduction is suggested to account for most or all of the observed fractionation as abiotic reduction has been demonstrated to impart much smaller, often near-zero, isotopic fractionation or isotopic fractionation in the opposite direction. Data from some time intervals are consistent with a simple model for transport and U(VI) reduction, where the fractionation factor (ε = +0.65‰ to +0.85‰) is consistent with experimental studies. However, during other time intervals the observed patterns in our data indicate the importance of other processes in governing U concentrations and 238 U/ 235 U ratios. For instance, we demonstrate that departures from Rayleigh behavior in groundwater systems arise from the presence of adsorbed species. We also show that isotope data are sensitive to the onset of oxidation after biostimulation ends, even in the case where reduction continues to remove contaminant uranium downstream. Our study and the described conceptual model support the use of 238 U/ 235 U ratios as a tool for evaluating the efficacy of biostimulation and potentially other remedial strategies employed at Rifle and other uraniumcontaminated sites.
The Science of the total environment, 2018
Recharge of alluvial aquifers is a key component in understanding the interaction between floodpl... more Recharge of alluvial aquifers is a key component in understanding the interaction between floodplain vadose zone biogeochemistry and groundwater quality. The Rifle Site (a former U-mill tailings site) adjacent to the Colorado River is a well-established field laboratory that has been used for over a decade for the study of biogeochemical processes in the vadose zone and aquifer. This site is considered an exemplar of both a riparian floodplain in a semiarid region and a post-remediation U-tailings site. In this paper we present Sr isotopic data for groundwater and vadose zone porewater samples collected in May and July 2013 to build a mixing model for the fractional contribution of vadose zone porewater (i.e. recharge) to the aquifer and its variation across the site. The vadose zone porewater contribution to the aquifer ranged systematically from 0% to 38% and appears to be controlled largely by the microtopography of the site. The area-weighted average contribution across the site...
![Research paper thumbnail of {"__content__"=>"Field Application of U/U Measurements To Detect Reoxidation and Mobilization of U(IV).", "sup"=>[{"__content__"=>"238"}, {"__content__"=>"235"}]}](https://attachments.academia-assets.com/96879176/thumbnails/1.jpg)
](Environmental science & technology, Jan 20, 2018
Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective ... more Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the U/U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high U/U ratio into the aqueous U(VI) pool produces an increase in U/U of aqueous U(VI). During several injections of nitrate to induce U(IV) oxidation, U...
PLOS ONE, 2017
Spatial patterns of Zn, Pb and Cd deposition in Cape Krusenstern National Monument (CAKR), Alaska... more Spatial patterns of Zn, Pb and Cd deposition in Cape Krusenstern National Monument (CAKR), Alaska, adjacent to the Red Dog Mine haul road, were characterized in 2001 and 2006 using Hylocomium moss tissue as a biomonitor. Elevated concentrations of Cd, Pb, and Zn in moss tissue decreased logarithmically away from the haul road and the marine port. The metals concentrations in the two years were compared using Bayesian posterior predictions on a new sampling grid to which both data sets were fit. Posterior predictions were simulated 200 times both on a coarse grid of 2,357 points and by distance-based strata including subsets of these points. Compared to 2001, Zn and Pb concentrations in 2006 were 31 to 54% lower in the 3 sampling strata closest to the haul road (0-100, 100-2000 and 2000-4000 m). Pb decreased by 40% in the stratum 4,000-5,000 m from the haul road. Cd decreased significantly by 38% immediately adjacent to the road (0-100m), had an 89% probability of a small decrease 100-2000 m from the road, and showed moderate probabilities (56-71%) for increase at greater distances. There was no significant change over time (with probabilities all 85%) for any of the 3 elements in more distant reference areas (40-60 km). As in 2001, elemental concentrations in 2006 were higher on the north side of the road. Reductions in deposition have followed a large investment in infrastructure to control fugitive dust escapement at the mine and port sites, operational controls, and road dust mitigation. Fugitive dust escapement, while much reduced, is still resulting in elevated concentrations of Zn, Pb and Cd out to 5,000 m from the haul road. Zn and Pb levels were slightly above arctic baseline values in southern CAKR reference areas.
Geological Society of America Abstracts with Programs, 2016
PLOS ONE
The DeLong Mountain Transportation System (DMTS) haul road links the Red Dog Mine—one of the worl... more The DeLong Mountain Transportation System (DMTS) haul road links the Red Dog Mine—one of the world’s largest zinc mines—with a shipping port on the Chukchi Sea in northwest Alaska, USA. The road traverses 32 km of National Park Service (NPS) lands managed by Cape Krusenstern National Monument (CAKR). Fugitive dusts from ore concentrate transport and mining operations have dispersed zinc (Zn), lead (Pb), cadmium (Cd), and metal sulfides onto NPS lands since the mine began operating in 1989. This study assessed the effects of metal-enriched road dusts on the diversity and community structure of lichens, bryophytes, and vascular plants in dwarf-shrub tundra within CAKR. In a Bayesian posterior predictions model, lichen species richness (LSR) was highly correlated to distance from the haul road and was distributed on the landscape consistently with the spatial patterns of Zn, Pb and Cd patterns published earlier in this journal. The mean modeled LSR of the 3000–4000 m distance class was...
Geological Society of America Abstracts with Programs, 2020
Geological Society of America Abstracts with Programs, 2017
Uranium is a contaminant of interest due to its toxicity and mobility in groundwater. It is a red... more Uranium is a contaminant of interest due to its toxicity and mobility in groundwater. It is a redox active element in which the oxidation state can change by the addition or removal of electrons. In one method of groundwater remediation, mobile, hexavalent uranium (U(VI)) can be reduced to immobile, tetravalent uranium (U(IV)) by microbial or abiotic chemical reactions. Unfortunately, due to uranium's complex geochemistry, measuring concentrations does not reliably give an accurate indicator of the efficiency of removal. However, uranium isotope ratios can provide a direct way to track the extent of reduction. At the Old Rifle site (Colorado, USA), reduction of U(VI) to U(IV) was induced via injections of acetate to stimulate microbial activity. A decrease of ~1‰ in the 238 U/ 235 U ratio of the dissolved U(VI) was observed and correlated closely to the decrease in concentration (Bopp et al., 2010). However, the primary mechanism of chemical reduction, microbial or abiotic, is still not well understood. Microbial laboratory experiments observed a shift of 1-2‰ in 238 U/ 235 U during reduction experiments with multiple bacterial strains (Basu et al., 2014). Little work has been done to determine the isotopic fractionation induced by abiotic reduction. This study focuses on determining the isotopic fractionation of uranium during reduction with Fe(II). Time series experiments with aqueous Fe(II) and magnetite (Fe3O4) were conducted with samples analyzed by a MC-ICP-MS. We find aqueous Fe(II) has a limited ability to reduce U(VI) and no isotopic data is reported. Stoichiometric magnetite (χ=0.49) reduces U(VI) to U(VI) completely and rapidly as confirmed by XANES analysis, but induces no shift in 238 U/ 235 U. This finding matches iii results observed in three other studies (Rademacher et al, 2006; Stirling et al., 2007; Stylo et al., 2014) where abiotic reduction does not induce isotopic fractionation. I owe the success of this project to many individuals. I especially thank my advisor Dr. Tom Johnson for providing me the opportunity to pursue research in the field of isotope geochemistry and guide me through the many challenges faced while conducting these experiments. I would also like to thank Dr. Craig Lundstrom and Dr. Alyssa Shiel for their endless help and support while working in the lab and on the mass spectrometer. My gratitude goes to Dr. Maxim Boyanov from Argonne National Lab for the opportunity to conduct and analyze my experiments at the Advanced Photon Source. Additionally, I would like to thank the rest of our geochemistry group Gideon
Environmental monitoring and remediation require techniques to identify the source and fate of me... more Environmental monitoring and remediation require techniques to identify the source and fate of metals emissions. In this study, Cd and Zn isotopes were evaluated as tools for the identification of metal sources through (1) the assessment of metallurgical processing as a source of Cd and Zn isotopic fractionation and (2) the measurement of isotopic compositions in bivalves from sites receiving variable metal contributions from natural and anthropogenic sources. This study was facilitated by the successful development of a technique to measure Cd and Zn isotopes (MC-ICP-MS) in environmental and anthropogenic samples. Cadmium, Zn and Pb isotopic ratios were measured for samples from an integrated Zn–Pb smelting/refining complex in B.C. (British Columbia, Canada). Significant fractionation of Cd and Zn isotopes during processing is demonstrated by the total isotopic variation in δCd (1.04‰) and δZn (0.42‰) among smelter samples. Characterization of Cd and Zn isotopic compositions in emi...
Goldschmidt Abstracts, 2020
Ecosphere, 2020
The lead (Pb) lining of agriculture-related subsidies: enhanced Golden Eagle growth rates tempere... more The lead (Pb) lining of agriculture-related subsidies: enhanced Golden Eagle growth rates tempered by Pb exposure.
Anthropocene, 2019
Industrial lead (Pb) emissions have changed oceanic Pb concentrations and isotopic compositions s... more Industrial lead (Pb) emissions have changed oceanic Pb concentrations and isotopic compositions significantly over the last century. Asian industrial emissions are currently the dominant Pb sources in the northwest and central Pacific Ocean. This study investigated major Pb sources in the northeast Pacific Ocean (inland, coastal, and open ocean), where no comprehensive data exist currently. We measured Pb concentrations and isotopic compositions of a variety of shellfish and fish collected in British Columbia (BC) and used them for Pb source apportionment applications in the marine environment. We identified a clear trend in Pb isotopic compositions, from higher 206 Pb/ 207 Pb in inland fish to lower 206 Pb/ 207 Pb in open ocean fish, with coastal fish possessing mid-range values. These results indicate that natural sources of Pb dominate freshwater ecosystems in the central BC coast, whereas anthropogenic Pb sources prevail in western North America and the northeast Pacific. Pacific herring that forage along BC coast exhibit Pb isotopic composition that deviates toward the Chinese Pb regression line. We estimate an Asian origin for about one third of their total Pb. This study shows that Pb isotopes in aquatic organisms are valuable tools for assessing Pb sources across coastal and offshore regions of the northeast Pacific, with great potential for identifying primary foraging areas of marine organisms.
Nature Sustainability, 2019
Urban geochemistry is an emerging field in which key scientific and societal challenges, includin... more Urban geochemistry is an emerging field in which key scientific and societal challenges, including rapid urbanization and population growth, compel investigation of readily accessible biomonitors to determine the source, transport and fate of heavy metal pollutants in cities. Lead isotopic analyses of honey have recently proven its efficacy as a biomonitor for Pb source apportionment applications. We collected honey directly from hives in six geographical sectors in Vancouver, British Columbia (Canada) to investigate the presence of potential pollutants from varying zoning districts: urban, industrial, residential and agricultural. Systematic variations in trace element concentrations and Pb isotopic compositions of the honeys reflect proximity to anthropogenic land-use activities such as shipping ports and heavy traffic. Honey sampled from downtown hives, near the Port of Vancouver, shows elevated trace element concentrations compared with suburban and rural honey, and distinctly higher 208 Pb/ 206 Pb (that is, less radiogenic) compared with local environmental proxies (for example, oysters, Fraser River sediment and volcanic rocks), indicating possible input from Asian anthropogenic sources. This study presents the first Pb isotope data for North American honey, and supports the combined use of trace elements and Pb isotopic compositions in honey as a geochemical biomonitor.
Geochimica et Cosmochimica Acta, 2016
We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical inves... more We conducted a detailed investigation of U isotopes in conjunction with a broad geochemical investigation during field-scale biostimulation and desorption experiments. This investigation was carried out in the uranium-contaminated alluvial aquifer of the Rifle field research site. In this well-characterized setting, a more comprehensive understanding of U isotope geochemistry is possible. Our results indicate that U isotope fractionation is consistently observed across multiple experiments at the Rifle site. Microbially-mediated reduction is suggested to account for most or all of the observed fractionation as abiotic reduction has been demonstrated to impart much smaller, often near-zero, isotopic fractionation or isotopic fractionation in the opposite direction. Data from some time intervals are consistent with a simple model for transport and U(VI) reduction, where the fractionation factor (ε = +0.65‰ to +0.85‰) is consistent with experimental studies. However, during other time intervals the observed patterns in our data indicate the importance of other processes in governing U concentrations and 238 U/ 235 U ratios. For instance, we demonstrate that departures from Rayleigh behavior in groundwater systems arise from the presence of adsorbed species. We also show that isotope data are sensitive to the onset of oxidation after biostimulation ends, even in the case where reduction continues to remove contaminant uranium downstream. Our study and the described conceptual model support the use of 238 U/ 235 U ratios as a tool for evaluating the efficacy of biostimulation and potentially other remedial strategies employed at Rifle and other uraniumcontaminated sites.
The Science of the total environment, 2018
Recharge of alluvial aquifers is a key component in understanding the interaction between floodpl... more Recharge of alluvial aquifers is a key component in understanding the interaction between floodplain vadose zone biogeochemistry and groundwater quality. The Rifle Site (a former U-mill tailings site) adjacent to the Colorado River is a well-established field laboratory that has been used for over a decade for the study of biogeochemical processes in the vadose zone and aquifer. This site is considered an exemplar of both a riparian floodplain in a semiarid region and a post-remediation U-tailings site. In this paper we present Sr isotopic data for groundwater and vadose zone porewater samples collected in May and July 2013 to build a mixing model for the fractional contribution of vadose zone porewater (i.e. recharge) to the aquifer and its variation across the site. The vadose zone porewater contribution to the aquifer ranged systematically from 0% to 38% and appears to be controlled largely by the microtopography of the site. The area-weighted average contribution across the site...
Environmental science & technology, Jan 20, 2018
Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective ... more Biostimulation to induce reduction of soluble U(VI) to relatively immobile U(IV) is an effective strategy for decreasing aqueous U(VI) concentrations in contaminated groundwater systems. If oxidation of U(IV) occurs following the biostimulation phase, U(VI) concentrations increase, challenging the long-term effectiveness of this technique. However, detecting U(IV) oxidation through dissolved U concentrations alone can prove difficult in locations with few groundwater wells to track the addition of U to a mass of groundwater. We propose the U/U ratio of aqueous U as an independent, reliable tracer of U(IV) remobilization via oxidation or mobilization of colloids. Reduction of U(VI) produces U-enriched U(IV), whereas remobilization of solid U(IV) should not induce isotopic fractionation. The incorporation of remobilized U(IV) with a high U/U ratio into the aqueous U(VI) pool produces an increase in U/U of aqueous U(VI). During several injections of nitrate to induce U(IV) oxidation, U...
PLOS ONE, 2017
Spatial patterns of Zn, Pb and Cd deposition in Cape Krusenstern National Monument (CAKR), Alaska... more Spatial patterns of Zn, Pb and Cd deposition in Cape Krusenstern National Monument (CAKR), Alaska, adjacent to the Red Dog Mine haul road, were characterized in 2001 and 2006 using Hylocomium moss tissue as a biomonitor. Elevated concentrations of Cd, Pb, and Zn in moss tissue decreased logarithmically away from the haul road and the marine port. The metals concentrations in the two years were compared using Bayesian posterior predictions on a new sampling grid to which both data sets were fit. Posterior predictions were simulated 200 times both on a coarse grid of 2,357 points and by distance-based strata including subsets of these points. Compared to 2001, Zn and Pb concentrations in 2006 were 31 to 54% lower in the 3 sampling strata closest to the haul road (0-100, 100-2000 and 2000-4000 m). Pb decreased by 40% in the stratum 4,000-5,000 m from the haul road. Cd decreased significantly by 38% immediately adjacent to the road (0-100m), had an 89% probability of a small decrease 100-2000 m from the road, and showed moderate probabilities (56-71%) for increase at greater distances. There was no significant change over time (with probabilities all 85%) for any of the 3 elements in more distant reference areas (40-60 km). As in 2001, elemental concentrations in 2006 were higher on the north side of the road. Reductions in deposition have followed a large investment in infrastructure to control fugitive dust escapement at the mine and port sites, operational controls, and road dust mitigation. Fugitive dust escapement, while much reduced, is still resulting in elevated concentrations of Zn, Pb and Cd out to 5,000 m from the haul road. Zn and Pb levels were slightly above arctic baseline values in southern CAKR reference areas.
Geological Society of America Abstracts with Programs, 2016