The Influence of Inorganic Salts on the Gas-Aqueous Partitioning of Formic Acid and Acetic Acid

AMIR BABAEI GHAREHBAGH, Rose Taylor, Joy Kiguru, Alyssa Burns, Annmarie Carlton, Christopher Hennigan, University of Maryland, Baltimore County

     Abstract Number: 692
     Working Group: Aerosol Chemistry

Abstract
Formic and acetic acid (FA and AA) are the most abundant organic acids in the atmosphere. FA and AA are water-soluble and semi-volatile so they can partition to aqueous droplets and particles in the atmosphere. There is often a significant disparity between measurements and predictions of the abundance and gas-particle partitioning of both acids. Inorganic salts in aqueous aerosols and cloud droplets may alter the partitioning of organics, potentially contributing uncertainty to these predictions. To address this, we conducted experiments using a dual mist-chamber setup to investigate the effects of salt identity, concentration, and pH on the partitioning of FA and AA. The study encompassed various salts, including (NH₄)₂SO₄, NaCl, and mixed salt solutions, under pH conditions ranging from 1 to 6, and ionic strengths ranging from 0.01 to 3 mol/kg. Quantification of these measurements was achieved by applying Henry's constant, enabling us to predict the “salting-in” or “salting-out” effects on the partitioning of formic acid and acetic acid. The findings offer valuable insights into interactions between organic acids and inorganic salts in the atmosphere, enhancing our understanding of gas-aqueous partitioning processes.