GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 237-8
Presentation Time: 10:10 AM


KING, James1, HAYES, Patrick L.2, BACHELDER, Jill2 and BASTIEN-THIBAULT, Marie-Pierre1, (1)Géographie, Université de Montréal, C.P. 6128, Succursale Centre-ville, Montréal, QC H3C 3J7, Canada, (2)Chimie, Université de Montréal, C.P. 6128, Succursale Centre-ville, MONTREAL, QC H3C 3J7, Canada

Mineral aerosols emitted in high latitude regions can impact radiative forcing, biogeochemical cycling of metals, and local air quality. These mineral dust emissions produce some of the largest dust fluxes and are attributed to a deposition feature that can be several hundred meters thick (loess) as a relic of past climatic change. In the present climate, pro-glacial processes are globally reduced compared to the last glacial maximum and concentrated at higher latitudes, but contribute a non-negligible proportion of the global dust budget albeit with large uncertainty. The estimates of dust production from high-latitudes is from a combination of few field studies (remote locations), poor satellite retrieval (high cloud cover and non-coincident acquisition), and limited knowledge on the processes that augment the timing and production of dust emissions in these 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 actively emitted from a sub-Arctic proglacial dust source. Soil, aerosol, and deposition samples (PM 10 and deposited mineral dust) were collected in May 2018 near the Ä’äy Chù (Slims River), Yukon, a site that has exhibited strong dust emissions. Moreover, a recent change in the river hydrology from rapid glacier retreat has left this watershed without its major tributary leading to speculation of its fate. 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. Mineralogy of ambient PM10 comprised primarily clay mineral aggregates, while PM10 elemental composition was enriched in trace elements as compared to dust deposition, bulk soil samples, and the fine soil fractions (d < 53 µm). Finally, through analysis of the elemental composition as a function of the soils and the ambient PM 10 particle size distributions, as well as meteorological factors measured during our sampling campaign, we propose that the primary mechanisms for dust emissions from the Ä’äy Chù Valley are the rupture of clay coatings on particles and/or the release of resident fine particulate matter.