Vertical Profiles of Fluorescent and Coarse Mode Particle Properties in the Colorado River Basin and Southeastern United States

MARIA ZAWADOWICZ, Chongai Kuang, Tamanna Subba, Shawn Serbin, Olga Mayol-Bracero, Darielle Dexheimer, Mirtha Salatti, Russell Perkins, Paul DeMott, Jessie Creamean, Zezhen Cheng, Gregory W. Vandergrift, Ashfiqur Rahman, Nurun Nahar Lata, Swarup China, Brookhaven National Laboratory

     Abstract Number: 472
     Working Group: Bioaerosols

Abstract
Bioaerosols—aerosols of biological origin—have wide-ranging atmospheric implications, including acting as ice-nucleating particles (INPs) to trigger ice formation in mixed-phase clouds. The potential impacts of bioaerosols on clouds depends on the vertical extent of biological material, yet vertical profiles of speciated aerosols can be difficult to measure without deploying dedicated bioaerosol samplers on airborne platforms such as an aircraft or a tethered balloon. This project investigates the vertical profiles of atmospheric bioaerosol concentrations during the ARM Surface-Atmosphere Integrated Laboratory (SAIL) campaign in the Colorado River basin and third ARM Mobile Facility (AMF3) deployment to Bankhead National Forest (BNF). During SAIL, we deployed a novel, small-footprint fluorescence sensor alongside a Size- and Time-resolved Aerosol Collector (STAC) sampler and a collector for off-line quantification of immersion ice nuclei concentrations (IcePuck) on ARM’s tethered balloon system (TBS) during spring and summer of 2023. We obtained simultaneous vertically resolved profiles of fluorescent aerosol concentrations, accumulation and coarse-mode size distributions, and samples of aerosol for subsequent analysis with high-resolution mass spectrometry and microscopy at the Environmental Molecular Sciences Laboratory (EMSL) for identification of specific particle morphologies. In addition, we also deployed a coarse-mode optical particle counter to measure vertically-resolved size distributions of particles up to 35 μm. At BNF, we have analyzed the available in-situ aerosol measurements to constrain possible influence of coarse-mode biological aerosol and classify characteristic regimes in preparation for TBS deployments that will take place later this year. Measurements of vertical profiles of coarse-mode particles are rare, yet essential to capture the vertical extent of surface-atmosphere interactions, as the coarse-mode particles tend to be limited to surface sources such as dust or pollen. These studies are designed for comprehensive characterization of spring and summertime aerobiome in the continental United States, its vertical extent, and its interactions with clouds as a potential source of INPs.