27ATCHEM Exploring Organic Acid Contributions to Cloud Water Chemistry and Aqueous Processing of Organics within Clouds: Insights from Whiteface Mountain Measurements

Organic compounds in the atmosphere play a pivotal role in atmospheric chemistry, and clouds are significant in the genesis and alteration of these compounds. Di-carboxylic organic anions such as oxalate serve as tracers for aqueous processing. This presentation details our findings from summer measurements of three major organic acids (formic acid, acetic acid, oxalic acid), as well as inorganic anions (sulfate, chloride, nitrate) and cations (sodium, potassium, ammonium, calcium, magnesium) in cloud water, aerosol, and cloud droplet residual samples collected at the summit of Whiteface Mountain (WFM) in the Adirondack Mountains, northern New York State. We also evaluate the contribution of these organic acids to dissolved organic carbon (DOC) concentrations. Previous studies have explored the oxalate: DOC ratio with ozone levels, aiming to deduce the influence of biogenic Volatile Organic Compounds (VOCs) on Secondary Organic Aerosol (SOA) formation from nearby forest ecosystems. Our study presents new observations that significantly broaden this understanding by analyzing both cloud water and aerosol phases. Additionally, we introduce oxalate: sulfate ratios from our dataset, proposed by other researchers as a key indicator of aqueous processing due to the enhanced production rates of these ions by liquid water content (sulfate ion) or droplet surface area (oxalate ion). We compare the observed range of oxalate: sulfate ratios with those from field campaigns conducted in other regions. Moreover, for the first time, we investigate the relationship between ammonium and organic acids in cloud water, aerosols, and droplet residuals from 2023, while also exploring the impact of wildfire smoke on these interactions.