Groupe du Prof. Patrick Hayes
Title: Mineral Dust in the Ä’äy Chù Valley, Yukon: An assessment of sizedistribution characteristics and potentially toxic elements
Abstract: The Ä’äy Chù Valley has undergone dramatic environmental changes due to the diversion of the Ä’äy Chù in 2016 resulting from the recession of the Kaskawulsh Glacier. The changes have led to elevated mineral dust activity in the region. With mineral dust affecting regional air quality, an understanding of its relevant properties pertinent to its human health effects is desirable. The impact that dust, or any aerosol, has on human health is directly related to its concentration, size, composition, and the bio-accessibility of toxins. Excluding bio-accessibility, these properties are relevant to the effect aerosol has on climatic radiative forcings as well, in addition to the basic optical properties dictating how radiation is absorbed or scattering upon interaction with the aerosol. To better understand these critical properties for the Ä’äy Chù Valley an intensive field measurement campaign was carried out in late Spring and early Summer of 2021. PM2.5, PM10, and TSP concentrations, as well as optically-derived size distribution data for the mineral dust, were measured. Furthermore, off-line chemical analysis has been performed for determining the metal and metalloid concentrations in the dust for the PM2.5, PM10, and TSP size fractions. Strong dust emissions were measured among all size fractions, particularly in late June of the campaign. Dust concentrations of all size fractions exhibit a diurnal cycle, dictated by ambient temperature, RH, and particularly the wind speed in the valley, resulting in maximum daily dust concentrations occurring in late afternoon/early evening, around 7pm local time. Size distributions were measured at both 3.3 m and 6.3 m off the ground, and a marked shift in the size distributions is noted with height. The number mean diameter of the particle number distribution shifts from 1.432 to 0.911 μm between 3.3 and 6.3 m. Total metal(loid) analysis reveals that there is an enhancement in metal(loid) concentrations with smaller size class. The bio-accessibility of the metals and metalloids present in the mineral dust was also assessed using an inhalation-ingestion assay procedure, which provides a better understanding of the potential toxicity of the dust due to the presence of various metals and metalloids. The bio-accessibility of As and Mn in the pulmonary phase was determined to be 48 ± 22 % and 52 ± 12 %, respectively.
