Snowpack in the Colorado Rockies is a crucial source of fresh water, nutrients, and carbon for the arid Southwest United States. We have applied chemical imaging (CI) and molecular characterization techniques to investigate composition of airborne particles and snow samples collected during the Surface-Atmosphere Integrated Field Laboratory (SAIL) campaign. Our goals are (1) characterize aerosol regimes, mixing states, and atmospheric transformations through correlative analysis of CI and real-time records of other instruments; (2) quantify the optical and chemical properties of snowpack deposits to investigate how aerosols deposition influence snowpack lifetime; (3) link the chemical and optical properties of aerosols and snowpack deposits to determine impacts on RF from its atmospheric and surface components. An AE33 aethalometer was deployed at the SAIL field site to provide real-time monitoring of optical properties and sampling of light-absorbing aerosols. Obtained samples are analyzed by complementary high resolution mass spectrometry (HRMS) methods of analysis to assess the relationship between composition and optical properties. Bulks samples of snowpack aerosols deposited during a severe haze event originating in Phoenix, AZ are analyzed with CI, which show that the majority of light-absorbing properties are dominated by water soluble BrC, with minor contributions from insoluble BC particles. Inorganic components present was analyzed with ion chromatography, revealing additional contributions of mineral dust and aged salt. The molecular composition and optical properties of specific BrC chromophores was analyzed with liquid chromatography coupled with a photodiode array detector into an HRMS. A tethered balloon system (TBS) and an automated time-resolved aerosol collector (TRAC) has been deployed at the field site as well. Samples collected by the TBS are used to investigate the differences present in the vertical gradient during notable BrC episodes. CI techniques have been utilized to assess the internal chemical heterogeneity of individual particles. Correlating this data will inform particle resolved models that account for individual particle complexity and modeling of snow spectral albedo under different contamination scenarios in the Rocky Mountains.

Multimodal chemical characterization of brown carbon in atmosphere and snowpack from the Colorado Rockies

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