the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 14 Aug 2025
Emerging Mineral Dust Source in ’A’ą̈y Chù’ Valley, Yukon, Canada Poses Potential Health Risk via Exposure to Metal and Metalloids Enriched in PM10 and PM2.5 Size Fractions
Abstract. The ’A’ą̈y Chù’ Valley in Kluane National Park, Yukon, Canada has undergone significant hydrological change in the past decade due to climate-driven glacial recession. This has reverted the ’A’ą̈y Chù’ to a major source of sediment-derived mineral dust, representing an environmental change for the region. Mineral dust influences climatic radiative forcing and impacts human health, both of which depend on its concentration, size distribution, and composition. This work discusses results from a field campaign conducted in the ’A’ą̈y Chù’ Valley in 2021 aimed at understanding and quantifying these parameters, with comparison to a previous campaign in the same location to evaluate the evolution of the dust emissions between 2018 and 2021. An optical particle counter (OPC) instrument measured a mean volume diameter of airborne dust of 4.43 µm at 3.3 m above ground, with Coulter Counter measurements being used for comparison and validation. The concentration of many metal(loid)s in the dust were also studied: Al, Ag, As, Ba, Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, Ni, Pb, Rb, Tl, U, V, and Zn. It was found that 24-hour ambient air quality criteria for exposure to several metal(loid)s were surpassed. Significant enrichment of several metal(loid)s was observed for both the PM10 and PM2.5 size fractions relative to the Total Suspended Material (TSP) fraction of the mineral dust. This suggests that the mineral dust in the ’A’ą̈y Chù’ Valley possesses compounding characteristics that are detrimental to human health due to exposure to potentially toxic metal(loid) concentrations.
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Status: final response (author comments only)
- RC1: 'Comment on egusphere-2025-3485', Ian Burke, 25 Sep 2025
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RC2: 'Comment on egusphere-2025-3485', Pavla Dagsson Waldhauserova, 10 Oct 2025
This study presents a valuable investigation of high-latitude dust (HLD) observations, focusing on the concentrations of metals and metalloids in airborne dust. It is a rare study that explains the mechanisms and significance of the detrimental impacts of HLD storms on human health. The study provides important evidence supporting the need for exposure limits to potentially toxic particulate matter (PM) components, such as metals and metalloids, each with distinct toxicological properties. The direct relationship between the metallic composition and particle size of HLD has rarely been characterized. This research presents additional breakthrough results by comparing TSP, PM₁₀, and PM₂.₅ concentrations at a height of 3.3 m, and by providing dust concentration ratios between 3 and 6 m — offering insights into the vertical dust gradient. Including measurements at 1–2 m height would further strengthen the analysis by capturing the full dust gradient from the surface upwards.
The hourly PM₂.₅ and PM₁₀ dust concentrations recorded at Kluane Lake are among the highest measured at high latitudes. The comparison between two measurement methods — optical particle counters (OPC) and gravimetric techniques — with respect to PM₁₀ and PM₂.₅ concentrations is also highly valuable. The study offers a clear daily temporal resolution of dust activity and provides a thorough explanation of particle size distributions in this unique environment, allowing comparisons with other HLD sources. It would be useful to highlight whether similar studies exist and add them to the discussion.
Furthermore, this research fills a critical gap in in-situ observations of particle number, surface area, and volume concentrations during active dust storms — particularly in ice-proximal regions. The comparative analysis of mean particle diameters is especially noteworthy. The enrichment of metalloids in finer-sized particles is an important finding for understanding the health impacts of dust exposure.
The paper is clearly written, and the figures effectively support the analyses. I highly recommend this work for publication in EGUsphere, pending minor revisions as outlined below.
Specific comments:
L 78 – Year is missing after the reference
L88, 98 – Please delete Meinander et al. before the actual reference in the brackets
L100-101 – Maybe the study of Panta et al. (2025) could be stated here:
Panta et al. (2025): Unveiling single-particle composition, size, shape, and mixing state of freshly emitted Icelandic dust via electron microscopy analysis, EGUsphere, https://doi.org/10.5194/egusphere-2025-494, 2025.
L134, 275, 346, 447 – Move the dot behind the bracket please
L139-141 – There are also specific conditions when dust storms occur during wet, moist and low-wind conditions. Please see here for examples:
Dupont, S., Klose, M., Irvine, M., González-Flórez, C., Alastuey, A. Bonnefond, J.-M., Dagsson-Waldhauserova, P., Gonzalez-Romero, A., Hussein, T., Lamaud, E., Meyer, H., Panta, A., Querol, X. Schepanski, S. Vergara Palacio, Wieser, A., Diez, J., Kandler, K., and Pérez García-Pando, C., 2024. Impact of dust source patchiness on the existence of a constant dust flux layer during aeolian erosion events. Journal of Geophysical Research: Atmospheres 129(12), e2023JD040657
Dagsson-Waldhauserova, P., Arnalds, O., Olafsson, H., Skrabalova, L., Sigurdardottir, G.M., Branis, M., Hladil, J., Skala, R., Navratil, T., Chadimova, L., von Lowis of Menar, S., Thorsteinsson, Th., Carlsen, H.K., and Jonsdottir I., 2014. Physical properties of suspended dust during moist and low wind conditions in Iceland. Icelandic Agricultural Sciences 27: 25 – 39.
Dagsson-Waldhauserova, P., Arnalds, O., Olafsson, H., Hladil, J., Skala, R., Navratil, T., Chadimova, L., Meinander, O., 2015. Snow-dust storm A case study from Iceland, March 7th 2013. Aeolian Research 16, 69–74.
L152 – remove ‘et al.’
L271 – Results in this chapter could be compared to results in Dupont et al. (2024)
Dupont et al. (2024). Impact of dust source patchiness on the existence of a constant dust flux layer during aeolian erosion events. Journal of Geophysical Research: Atmospheres 129(12), e2023JD040657
L333 – RH seems to be quite low for the glacial and ice-proximal environment. Can you also explain the general RH conditions in this area? Is it normally 40-60% or was this exceptionally dry period?
L468- Please change dot to comma
L472 – Add IPCC in the brackets of reference
L663 – Please correct the ending of the reference
Citation: https://doi.org/10.5194/egusphere-2025-3485-RC2
Data sets
Concentrations of Select Metals and Metalloids in Air in ’A’ą̈y Chù’ Valley Mineral Dust Spring/Summer 2021 Arnold Ross Downey http://dx.doi.org/10.5683/SP3/Y4CTDC
Diurnal Statistics for Temperature, Relative Humidity, Wind Speed, PM10, and PM2.5 Concentrations at ’A’ą̈y Chù’ Valley in Kluane National Park, Yukon, Canada for June 2021 Arnold Ross Downey http://dx.doi.org/10.5683/SP3/1WHR3P
Raw Optical Particle Counter (OPC) Data for 3.3 and 6.3 meters off ground in ’A’ą̈y Chù’ Valley in Yukon, Canada Late Spring Early Summer 2021 Arnold Ross Downey http://dx.doi.org/10.5683/SP3/FKSRWL
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This study investigates the emergence of a high-latitude mineral dust source in the ’A’äy Chù’ Valley, Yukon, Canada, following climate-driven glacial recession. The authors focus on the size distribution, elemental composition, and health implications of particulate matter (PM), particularly PM₁₀ and PM₂.₅, enriched with PTEs. The work builds on previous campaigns and expands the scope of elemental analysis. The study addresses a newly intensified dust source in a high-latitude region, which is underrepresented in global dust budgets but disproportionately affects snow albedo and local air quality, linking climate change, glacial recession, and public health. Dual instrumentation (Optical Particle Counter and Coulter Counter) provides cross-validation of particle size distributions. Elemental analysis is well-detailed, including digestion protocols, calibration, and recovery corrections. The study also includes some diurnal variation analysis and comparisons with WHO and Ontario air quality standards.
The study is a nice case study in one valley, it would be interesting to see how the authors would scale up these implications to the wider regional impacts (is this just a health impact in one valley?). how many similar sites have emerged due to glacial recession. Can this data be reflected in dispersion models to elucidate local / regional impacts.
Air quality standards are normally considered for urban and industrial dust sources – do these natural source dusts contain materials that are similarly bioaccessible in e.g. oral or lung fluids.
Minor comments -
L114 – check if ‘Mcmurry’ should be ‘McMurry’. (again at L125 Mctainsh – best check all Scottish names cited).
L275 Typo - ‘respectively.(World Health Organization, 2021)’
L346 Typo ‘and 1.68.(Bachelder et al., 2020; Mukherjee, 2013; Smart and Willis, 1967)’
Fig. 8 – check the units of number, SA and volume, seems odd to me (not an atmospheric scientist), but they don’t match Table1 either.
Table 2 – why is Variance of distribution in brackets
L389 – ‘Shilts et al.’ needs a date.
L447 Typo - basis.(Human Toxicology and Air Standards Section, 2020)
Table 3 - enrichment of PTEs in the fine fraction material is commonly reported – it would be good to see the total enrichment versus the parent material (sediments) so that it could be potentially be predicted the relationship between bulk sediment concentrations and PM concentrations (measurement of sediment concentrations is much easier and much more commonly collected than PM concentrations).