Dust emission enrichment of bioavailable arsenic as measured in the stress response of wild snowshoe hares (Lepus americanus)

Abstract:

The dust emission process is highly selective, emitting sediment with mean diameters of less than 10 microns in a high collision environment known to abrade and disaggregate soil particles at the surface. Within the A’ąy Chù (Slims River) proglacial valley in southwest Yukon, the dust emission frequency induced by a river piracy event in 2016 induced by glacier retreat has recently increased considerably, from spring and summer dust storms limited by river discharge and precipitation to dust storms only limited by precipitation. The dust emission process within the A’ąy Chù valley is shown to enrich arsenic concentrations in the long-range transported dust fraction by over three-fold compared to soil concentrations and two-fold over short-term transported sediments. To investigate the bioavailability of the transported arsenic from the emitted dust, snowshoe hares were trapped and their winter hair sampled from within the valley region each February from 2014 to 2019, representing growth from September and October the previous year. Arsenic concentrations measured in snowshoe hare fur displays a significant increase due to the river piracy event with a maximum in the same year as the piracy event, correlating with the dust emission frequency. Other trace metals (e.g., Fe, Se, St, Ba) measured similar significant increases after the piracy event linked to the increased dust emissions. The increase in arsenic within snowshoe hares is known to impact oxidative stress response and, in this study, we also demonstrate a correlation between the stress response increase via hair cortisol concentration and an increase in hair arsenic concentration, from the same specimens after the river switch, hypothesized to be partly a direct result of the increased arsenic exposure from dust loading. In conclusion, we can demonstrate a significant and causal link between local dust emission increases with increased arsenic concentration that causes a significant increase in stress response of local snowshoe hare population, confirming the bioavailability of the arsenic in this environment.