Multi-Modal Chemical Characterization of Brown Carbon in Atmosphere and Snowpack from the Colorado Rockies

Snowpack in the Colorado Rockies is a crucial source of fresh water, nutrients, and carbon for the arid Southwest United States. The lifetime and evolution of alpine snowpack is influenced by the deposition of light absorbing particles (LAPs), principally black carbon (BC), brown carbon (BrC), and mineral dust (MD). Deposition of LAPs decreases snow albedo, which lead to a positive feedback loop of rapid snowmelt. We have applied chemical imaging (CI) and molecular characterization techniques to particle and snow samples collected at Gothic, CO as part of the Surface-Atmosphere Integrated Field Laboratory (SAIL) campaign in order to [1] characterize aerosol regimes; [2] quantify optical and chemical properties of LAPs within snowpack; and [3] link the optical and chemical properties of LAPs deposited in snowpack to model the impacts of RF from its atmospheric and surface components. We deployed an AE33 aethalometer and a time-resolved aerosol collector (TRAC) to provide real-time monitoring and sampling of light-absorbing aerosols. Aethalometer filters were analyzed with Direct Analysis in Real Time (DART) high resolution mass spectrometry aided with temperature programed desorption (TPD) to assess the relationship between the optical and chemical properties. We have also analyzed bulk snow sampled from a 2022 haze event with CI and HPLC-PDA-HRMS, where the bulk of the light-absorbing properties are dominated by BrC and mineral dust. Additionally, a tethered balloon system (TBS) has been deployed at Gothic to investigate differences in aerosol composition at various altitudes with CI. Correlating the CI and HRMS data will inform particle resolved models that account for individual particle complexity and modeling of snow spectral albedo under different contamination scenarios in Colorado.