The Effects of Organic Solvents on the Water Uptake of Organic Aerosols
Kotiba A. Malek, Nahin Ferdousi, Dewansh Rastogi, AKUA ASA-AWUKU, University of Maryland, College Park
Abstract Number: 81
Working Group: Aerosols, Clouds and Climate
Abstract
Organic solvents are atmospherically ubiquitous, yet their effects on cloud droplet formation have been poorly investigated. To elucidate on the effects of solvents on cloud formation, this work investigated the water uptake efficiencies of aerosols obtained from three organic isomers of different solubility namely, Phthalic acid (PTA), Isophthalic acid (IPTA), and Terephthalic acid (TPTA) in the presence of aqueous-phase and gas-phase ethanol (EtOH). The water uptake properties were investigated under supersaturated and subsaturated conditions using a Cloud Condensation Nuclei Counter (CCNC) and a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA), respectively. Under supersaturated environment, the presence of EtOH was shown to increase water uptake efficiency of partial and low solubility particles: IPTA and TPTA but not the water-soluble PTA particles. The intrinsic solubility of the aerosol particle governs its water uptake behavior in supersaturated conditions. Hence, since PTA exhibits a high-water solubility, the presence of EtOH exerted little to no influence on the dissolution of PTA particles. Conversely, the addition of EtOH to IPTA and TPTA aerosols enhanced the dissolution of these partial/low-water solubility particles; as a result, increasing their water uptake affinity. Our subsaturated results show that EtOH has the opposite effect relative to our supersaturated results. Under subsaturated environment, the water uptake affinity of PTA particles was enhanced by the presence of EtOH and diminished for IPTA and TPTA particles. This is attributed to the morphological properties of particles supported by TEM images and shape factor measurements. Hence, atmospheric organic solvents can readily coat aerosol particles and play a major role in the water uptake properties under sub- and supersaturated conditions.