Chemical Characterization of Brown Carbon in Atmosphere and Snowpack from the Rocky Mountains

STEVEN SHARPE, Felipe Rivera-Adorno, Jay Tomlin, Erik Hulm, Ryan Moffet, Alexander Laskin, Purdue University

     Abstract Number: 411
     Working Group: Remote and Regional Atmospheric Aerosol

Abstract
Snow fall is a crucial source of fresh water, nutrients, and carbon for land ecosystems, especially in mountain regions. Deposits of atmospheric aerosols within snowpack are high photochemically active, which influences the local land-atmosphere interactions. In terms of climate effects, snowpack is one of the highest light reflecting surfaces on Earth, and a key factor in Earth’s radiative balance. The deposition of light-absorbing particles composed of brown carbon (BrC), black carbon (BC), and mineral dust significantly impacts the absorption of solar radiation. This results in decreased snow albedo and accelerates the rate of snow melt, which in tern influences the regional and global climate. Our study uses microscopy, optical measurements, and molecular characterization to investigate the radiative properties of carbonaceous aerosols in regard to snow albedo, assess the relationships between composition of airborne BrC and that deposited on the snowpack. The study incorporates real time aerosol sampling and monitoring at a Colorado field site using an aethalometer coupled with a CO₂ probe. Particle and snow samples are collected for bulk composition analysis utilizing chemical imaging and molecular characterization techniques. These analyses will be able to differentiate between anthropogenically and naturally generated carbonaceous aerosols and how they impact Colorado alpine snowpack. We have found that the majority of light absorption comes from BrC with only minor absorption from BC and mineral dust.