Chemical and microphysical properties of wind-blown dust near an actively retreating glacier in Yukon, Canada

摘要

Airborne mineral aerosols emitted in high-latitude regions can impact radiative forcing, bio-geochemical cycling of metals, and local air quality. The impact of dust emissions in these regions may change rapidly, as warming temperatures can increase mineral dust production and source regions. As there exists little research on mineral dust emissions in high-latitude regions, we have performed the first study of the physico-chemical properties of mineral dust emitted from a sub-Arctic proglacial dust source, using a method tailored to the remote conditions of the Canadian North. Soil and aerosol samples (PM10 and deposited mineral dust) were collected in May 2018 near the A'ay Chu (Slims River), a site exhibiting strong dust emissions. WHO air quality thresholds were exceeded at several receptor sites near the dust source, indicating a negative impact on local air quality. Notably, temporally averaged particle size distributions of PM10 were very fine as compared to those measured at more well-characterized, low-latitude dust sources. In addition, mineralogy and elemental composition of ambient PM10 were characterized; PM10 elemental composition was enriched in trace elements as compared to dust deposition, bulk soil samples, and the fine soil fractions (d<53 mu m). Finally, through a comparison of the elemental composition of PM10, dust deposition, and both fine and bulk soil fractions, as well as of meteorological factors measured during our campaign, we propose that the primary mechanisms for dust emissions from the A'ay Chu Valley are the rupture of clay coatings on particles and/or the release of resident fine particulate matter.