Several large-scale human biomonitoring projects have been conducted in Canada, including the Canadian Health Measures Survey (CHMS) and the First Nations Biomonitoring Initiative (FNBI). However, ...neither of these studies included participants living in the Yukon. To address this data gap, a human biomonitoring project was implemented in Old Crow, a fly-in Gwich'in community in the northern Yukon. The results of this project provide baseline levels of contaminant and nutrient biomarkers from Old Crow in 2019. Samples of hair, blood, and/or urine were collected from approximately 44% of community residents (77 of 175 adults). These samples were analyzed for contaminants (including heavy metals and persistent organic pollutants (POPs)), and nutrients (including trace elements and omega-3 fatty acids). Levels of these analytes were compared to health-based guidance values, when available, and results from other human biomonitoring projects in Canada. Levels of lead (GM 0.64 μg/g creatinine in urine/24 μg/L blood), cadmium (GM 0.32 μg/g creatinine in urine/0.85 μg/L blood), and mercury (GM < LOD in urine/0.76 μg/L blood/0.31 μg/g hair) were below select health-based guidance values for more than 95% of participants. However, compared to the general Canadian population, elevated levels of some contaminants, including lead (approximately 2× higher), cobalt (approximately 1.5× higher), manganese (approximately 1.3× higher), and hexachlorobenzene (approximately 1.5× higher) were observed. In contrast, levels of other POPs, including insecticides such as dichlorodiphenyltrichloroethane (DDT), its metabolite, dichlorodiphenyldichloroethylene (DDE), and polychlorinated biphenyls (PCBs) were similar to, or lower than, those reported in the general Canadian population. This study can be used along with future biomonitoring programs to evaluate the effectiveness of international initiatives designed to reduce the contaminant burden in the Arctic, including the Stockholm Convention and the Minamata Convention. Regionally, this project complements environmental monitoring being conducted in the region, informing local and regional traditional food consumption advisories.
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•Human biomonitoring study was conducted in the community of Old Crow, Yukon.•Elevated levels of Pb, Co, Mn were observed compared to Canadian population.•Some POPs, including HCB, were elevated compared to Canadian population.•Levels of Pb, Cd, Hg were below available health-based guidance for majority of participants.
Investigations of the regional distribution of ice‐wedge polygons and wedge‐ice volume allow for the assessment of the vulnerability of permafrost landscapes to thaw‐induced disturbances and related ...ecological feedbacks. Ice‐wedge polygons have been described in multiple studies in flat terrain and low‐gradient hillslopes, but few studies have examined ice‐wedge polygons in mountainous terrain. This study investigates the distribution, morphometry, and wedge‐ice content of ice‐wedge polygons in Tombstone Territorial Park, a mountainous permafrost region in central Yukon. Results show that ice‐wedge polygons occupy 2.6% of the park and preferentially develop in woody sedge peat, glaciofluvial, and alluvial deposits along the lower reaches of the Blackstone and East Blackstone rivers on hillslopes ≤1°. The morphometry of five of six polygonal sites studied showed statistically similar polygon sizes and trough angles, while showing different development stages based on vegetation type, surface wetness, and spatial pattern. The estimation of wedge‐ice volumes in the ice‐wedge polygons is 8–22% and is comparable to that of other Arctic regions. However, the estimated wedge‐ice volume represents a minimum value because older generations of ice wedges are truncated 3–4 m below the surface with no evidence of surface polygons, and the polygonal network can be obscured by slope processes, vegetation, and ice‐wedge inactivity. This study provides insights into the application of morphometric and soil parameters for the assessment of ice‐wedge polygon distribution and development stages.
Nickel (Ni) and its stable isotope signature (δ60Ni) have recently gained momentum as a tracer of nutrient cycling in the modern and past oceans. A robust understanding of Ni isotope cycling in the ...ocean rests on an accurate understanding of the Ni sources and sinks to and from the oceans. In particular, rivers, which are the dominant Ni source to the oceans, show significant variation in Ni isotopes compared to rocks, thought to reflect variable extents of formation of secondary phases that scavenge light Ni isotopes. The current estimate of the global isotope composition of riverine Ni is based on a few large rivers in warm climates, thus preventing the assessment of a potential climatic control on the Ni isotope flux to the ocean. In this contribution, we investigate the Ni elemental and isotope signatures of river catchments in cold climates, namely the Mackenzie Basin tributaries (Canada) and two rivers, the Nass and Skeena, draining the Western Cordillera.
The river solid load in the Mackenzie Basin shows almost no resolvable variation in terms of Ni abundances and Ni isotopes, which are similar to silicate rocks. Furthermore, dissolved Ni and Ni isotopes do not show any relationship with source tracers. This suggests a minimal source control on variations in riverine Ni. This result is particularly intriguing as riverine chemistry in the Mackenzie Basin is often dominated by lithological controls, including rocks other than silicate, such as carbonate and black shale. Instead, the variations in dissolved Ni isotopes are related to the removal of dissolved Ni, reflecting the dominant control by secondary weathering processes. The Ni isotope fingerprint of these secondary weathering processes reflects Ni scavenging into metal oxides, consistent with the literature. The data presented here and literature data show that dissolved Ni and lithium isotopes (a tracer of clay formation) exhibit contrasting patterns between the Mackenzie and the Amazon basins. This suggests that climatic conditions might couple or decouple the formation of metal oxide and clay. In addition, the Ni isotope signatures of the river dissolved load vary with the specific weathering intensity of Ni (the fraction of riverine Ni exported as dissolved species). At high specific weathering intensity of Ni, the Ni isotope signature reflects that of silicate, consistent with the congruent release of Ni from the weathering of silicate. Lower specific weathering intensities of Ni are associated with heavier Ni isotope signatures, suggesting greater scavenging of Ni onto secondary metal oxide. Finally, at the lowest Ni weathering intensity, the dissolved Ni isotope composition is lower again, potentially implying limited metal oxide formation under such conditions. Therefore, and though more data are required to confirm the hypothesis from this initial data, while climate might play a role in the relative rate of Li- and Ni- scavenging phase formation, the specific weathering intensity of Ni may be more significant in controlling dissolved Ni isotope composition.
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•Identifies for the first time Pt, Pd, Re, Au and Mo host in HEBS from Yukon, Canada.•These elements are hosted in pyrite and not millerite (NiS).•There are three discrete HEBS layers ...within the stratigraphy at Peel River.
Middle Devonian Ni-Mo-Zn-Pt-Pd-Au-Re hyper-enriched black shales (HEBS) from Peel River in north Yukon have high abundances of platinum group elements (PGE; ca. 500 ppb), Au (40–130 ppb) and Re (8–55 ppm). Mineralization occurs in up to three thin (0.5–10 cm thick) layers that include the regionally extensive HEBS at the Road River Group-Canol Formation stratigraphic contact (e.g., correlative with the Nick Ni-Mo-Zn-PGE-Au-Re prospect, northwestern Yukon); two other previously undocumented HEBS layers stratigraphic layers underlie the upper layer. Although the three different layers have minor textural differences, they display marked mineralogical and geochemical similarities to each other. Millerite is the predominant Ni sulfide, and it postdates several textural varieties of pyrite.
A longstanding, unresolved question regarding this mineralization in Yukon is the mineralogical host of PGE, Mo, Au and Re. We analyzed the sulfide mineral assemblages using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). LA-ICP-MS analyses reveal that pyrite within all of the layers is the principal host of PGE, Re, Au and Mo, and that paragenetically late pyrite (spatially associated with millerite) contains the highest abundances, with up to 4 ppm Pd, 8 ppm Pt, 500 ppm Re, 1.5 ppm Au and 7000 ppm Mo. Rare, late pyrite-marcasite veins in the upper HEBS layer cross-cut all previous generations of sulfides and also postdate quartz cement. The late sulfide veins are devoid of Mo-Pd-Re-Pt-Au, indicating that mineralization coincided with early to late diagenesis and predates lithification. The high abundances of these elements in diagenetic varieties of pyrite suggests that hyper-enrichment occurred near the seafloor, and that this suite of elements was likely derived from ambient seawater.
•Historical trends in extreme streamflow for boreal Alaska rivers are presented.•Annual and spring maximum flow declines are observed for snowmelt and glacial rivers.•Snowmelt systems respond to the ...Pacific Decadal Oscillation climate index.•Spring air temperature drives maximum flows in glacial/high elevation snowmelt basins.•Winter precipitation drives maximum flows in snowmelt basins.
Climate change will shift the frequency, intensity, duration and persistence of extreme hydroclimate events and have particularly disastrous consequences in vulnerable systems such as the warm permafrost-dominated Interior region of boreal Alaska. This work focuses on recent research results from nonparametric trends and nonstationary generalized extreme value (GEV) analyses at eight Interior Alaskan river basins for the past 50/60years (1954/64–2013). Trends analysis of maximum and minimum streamflow indicates a strong (>+50%) and statistically significant increase in 11-day flow events during the late fall/winter and during the snowmelt period (late April/mid-May), followed by a significant decrease in the 11-day flow events during the post-snowmelt period (late May and into the summer). The April–May–June seasonal trends show significant decreases in maximum streamflow for snowmelt dominated systems (<−50%) and glacially influenced basins (−24% to −33%). Annual maximum streamflow trends indicate that most systems are experiencing declines, while minimum flow trends are largely increasing. Nonstationary GEV analysis identifies time-dependent changes in the distribution of spring extremes for snowmelt dominated and glacially dominated systems. Temperature in spring influences the glacial and high elevation snowmelt systems and winter precipitation drives changes in the snowmelt dominated basins. The Pacific Decadal Oscillation was associated with changes occurring in snowmelt dominated systems, and the Arctic Oscillation was linked to one lake dominated basin, with half of the basins exhibiting no change in response to climate variability. The work indicates that broad scale studies examining trend and direction of change should employ multiple methods across various scales and consider regime dependent shifts to identify and understand changes in extreme streamflow within boreal forested watersheds of Alaska.
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•Cross-scale analytical techniques are utilized to delineate mechanisms of sphalerite weathering in a mine waste-rock pile.•Oxidation causes congruent dissolution of ...sphalerite.•Secondary sequestration of Cu occurs locally on the surfaces of sphalerite.•Zinc and Cd migration is controlled by pH-dependent reactions on the surfaces of Fe-oxhydroxides.•Continuous release of Zn and Cd is expected in the seepage in absence of remedial efforts.
Degraded water quality and environmental impacts caused by weathering of sulfide-bearing mine wastes are a legacy remaining at many historical mine sites. Release and mobilization of toxic metals (e.g., Zn and Cd) in mine drainage are often associated with weathering of primary sulfide minerals and precipitation and dissolution of secondary minerals. This study aims to couple field-scale measurements of physicochemical parameters with μm- and nm-scale mineralogical characterization to investigate sphalerite weathering and controls on Zn and Cd migration in an uncovered mine waste-rock pile. Elevated concentrations of Zn and Cd, potentially harmful to the receiving environment, were detected in waste-rock pore water and seepage. A suite of analytical techniques, including scanning electron microscopy – energy dispersive X-ray spectroscopy (SEM-EDS), scanning transmission electron microscopy (STEM) with EDS, electron microprobe analysis (EMPA), and synchrotron-based micro X-ray fluorescence (μ-XRF) mapping and micro X-ray absorption near edge structure (μ-XANES) spectroscopy were utilized in a high-resolution investigation of elemental- and secondary-mineral associations with sphalerite grains. EMPA and μ-XRF elemental maps and STEM investigations show depletion of Zn, Fe, S, and Cd, local enrichment of Cu, and distinct dissolution pits at the margins of sphalerite grains. Using μ-XANES, the speciation of solid phases containing Zn, Cu, Fe, and S indicates the dominance of primary sphalerite with microscopic inclusions of chalcopyrite, along with sparse occurrence of secondary Cu-bearing sulfides formed during weathering. These results suggest sphalerite oxidation leads to congruent dissolution without formation of distinct secondary-mineral coatings. Sphalerite weathering significantly contributes to elevated aqueous concentrations of Zn and Cd. Field-scale observations and mineralogical investigations indicate common occurrence of Fe-oxyhydroxides in the waste-rock pile. Seepage chemistry and surface complexation modeling results suggest that pH-dependent variations in reactions on the surfaces of the Fe-oxyhydroxides control aqueous concentrations of Zn and Cd, and the Zn/Cd ratio in the seepage. This work highlights the importance of understanding the mechanisms of sulfide-mineral oxidation and subsequent surface precipitation and adsorption, such that appropriate remediation action can be implemented to limit mobilization of metals to sensitive ecosystems.
Past emissions of the toxic metal mercury (Hg) persist in the global environment, yet these emissions remain poorly constrained by existing data. Ice cores are high-resolution archives of atmospheric ...deposition that may provide crucial insight into past atmospheric Hg levels during recent and historical time. Here we present a record of total Hg (HgT) in an ice core from the pristine summit plateau (5340 m asl) of Mount Logan, Yukon, Canada, representing atmospheric deposition from AD 1410 to 1998. The Colonial Period (∼1603–1850) and North American “Gold Rush” (1850–1900) represent minor fractions (8% and 14%, respectively) of total anthropogenic Hg deposition in the record, with the majority (78%) occurring during the 20th Century. A period of maximum HgT fluxes from 1940 to 1975 coincides with estimates of enhanced anthropogenic Hg emissions from commercial sources, as well as with industrial emissions of other toxic metals. Rapid declines in HgT fluxes following peaks during the Gold Rush and the mid-20th Century indicate that atmospheric Hg deposition responds quickly to reductions in emissions. Increasing HgT fluxes from 1993 until the youngest samples in 1998 may reflect the resurgence of Hg emissions from unregulated coal burning and small-scale gold mining.
Owyheeite Cu0.09 (1)Ag2.77 (4)Pb10.23 (4)Sb10.89 (5)S28.00 (5) crystallizes as a twofold superstructure with P21/n symmetry and pseudo‐orthorhombic metrics a = 8.1882 (3) Å, b = 27.2641 (7) Å, c = ...22.8679 (7) Å, β = 90.293 (3)°, V = 5105.0 (3) Å3, Z = 4. Owyheeite is systematically twinned by reflection at (021) or equivalently (021). Twinning is explained by describing a simplified Pmcn archetype structure as polytype built of two kinds of rods, which contact via electron‐pair micelles. A procedure of generating hypothetical polytypes by tiling space with partially overlapping equivalent regions is described.
Owyheeite crystallizes as a twofold superstructure. The systematic twinning is due to the rod‐polytype character of the structure.
Alpine headwaters in subarctic regions are particularly sensitive to climate change, yet there is little information on stream thermal regimes in these areas and how they might respond to global ...warming. In this paper, we characterize and compare the hydrological and thermal regimes of two subarctic headwater alpine streams within an empirical framework. The streams investigated are located within two adjacent catchments with similar geology, size, elevation and landscape, Granger Creek (GC) and Buckbrush Creek (BB), which are part of the Wolf Creek Research Basin in the Yukon Territory, Canada. Hydrometeorological and high‐resolution stream temperature data were collected throughout summer 2016. Both sites exhibited a flow regime typical of cold alpine headwater catchments influenced by frozen ground and permafrost. Comparatively, GC was characterized by a flashier response with more extreme flows, than BB. In both sites, stream temperature was highly variable and very responsive to short‐term changes in climatic conditions. On average, stream temperature in BB was slightly higher than in GC (respectively 5.8 and 5.7°C), but less variable (average difference between 75th and 25th quantiles of 1.6 and 2.0°C). Regression analysis between mean daily air and stream temperature suggested that a greater relative (to stream flow) groundwater contribution in BB could more effectively buffer atmospheric fluctuations. Heat fluxes were derived and utilized to assess their relative contribution to the energy balance. Overall, non‐advective fluxes followed a daily pattern highly correlated to short‐wave radiation. G1enerally, solar radiation and latent heat were respectively the most important heat source and sink, while air–water interface processes were major factors driving nighttime stream temperature fluctuations.
The study provides insights on the processes governing the hydrological and thermal regimes in poorly studied subarctic alpine headwater catchments. It identifies the key thermal fluxes controlling summer stream temperature. Furthermore, it highlights the important role played by small scale variability and groundwater contribution on the hydrological and thermal responses and how this can either enhance or moderate flow and stream temperature extremes. Counterintuitively, the study suggests that the more erratic (flashier hydrological response) headwater might be more resilient to a potential exacerbation of summer dry conditions caused by global warming.
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