SINGLE PARTICLE INDUCTIVELY COUPLED PLASMA-TIME OF FLIGHT MASS SPECTROMETRY CHARACTERIZATION OF ATMOSPHERIC PM2.5 ENTRAPPED IN THE UPPER FREMONT GLACIER OVER THE PAST 20 YEARS

Anthropogenic emission of PM_2.5 has increased exponentially since the onset of the Industrial Revolution resulting from increases in factory emissions, transportation emissions, deforestation, wildfires, and urban processes. Large influxes of atmospheric PM_2.5 have been shown to influence Earth's radiative balance (increased backscattering of incoming shortwave radiation, increased absorption of outgoing longwave radiation, decreased albedo of snow and ice, and modification of clouds properties) and human health (increased rates of ischaemic heart disease, stroke mortality, chronic respiratory diseases, and lung cancer). Therefore, as anthropogenic emissions of PM_2.5 continue to increase in the coming decades it will be crucial to geochemically characterize these particles.

We focus on the Upper Fremont Glacier, located in the Wind River Range of the Rocky Mountains, Wyoming, which provides a unique century-scale archive of natural atmospheric particles and anthropogenic atmospheric pollutants such as mercury, lead, bismuth, and thallium occurring within interior North America. In this study, we utilized a manual hand auger to collect a shallow 15 m ice core (representing approximately the last 20 years of ice accumulation) from the Upper Fremont Glacier. PM_2.5 recorded in this ice core was analyzed using a single particle Inductively Coupled Plasma-Time of Flight Mass Spectrometer (spICP-TOFMS) which allows us to rapidly measure the elemental composition, size, and number concentration of hundreds of thousands of individual particles (PM_2.5) occurring within the collected ice core samples. Minerals consistent with the elemental chemical composition of each particle can also be inferred.

To our knowledge, this study is the first to measure the elemental composition, size, and number concentration of hundreds of thousands of individual particles (PM_2.5) deposited within an interior North American glacier. These data will complement previous Coulter Counter measurements of PM_2.5 in the Upper Fremont Glacier by providing the elemental composition of each detectable particle allowing us to understand the contribution of natural and anthropogenic atmospheric PM_2.5 over the last ~20 years.