Issue 2, 2023

Aqueous processing of water-soluble organic compounds in the eastern United States during winter

Abstract

Aqueous multi-phase processes are significant contributors to organic aerosol (OA) mass in the atmosphere. This study characterizes the formation of water-soluble organic matter during the winter in the eastern United States through simultaneous measurements of water-soluble organic carbon in the gas and particle phases (WSOCg and WSOCp, respectively). The formation of secondary WSOCp occurred primarily through two pathways: (1) absorptive partitioning of oxygenated organics to the bulk OA and (2) aqueous phase processes. WSOCp formation through the former pathway was evident through the relationship between the fraction of total WSOC in the particle phase (Fp) and the total OA concentration. Conversely, evidence for nighttime aqueous WSOCp formation was based upon the strong enhancement in Fp with increasing relative humidity, indicating the uptake of WSOCg to aerosol liquid water (ALW). The Fp–RH relationship was only observed for temperatures between 0–10 °C, suggesting conditions for aqueous multi-phase processes were enhanced during these times. Temperature exhibited an inverse relationship with ALW and a proportional relationship with aerosol potassium. ALW and biomass burning precursors were both abundant in the 0–10 °C temperature range, facilitating aqueous WSOCp formation. To assess the impact of particle drying on the WSOCp concentrations, the particle measurements alternated between ambient and dried channels. No change was observed in the concentration of particles before and after drying, indicating that the WSOCp formed through the uptake of WSOCg into OA and ALW remained in the condensed phase upon particle drying at all temperature ranges. This work contributes to our understanding of sources, pathways, and factors affecting aqueous aerosol formation in the winter.

Graphical abstract: Aqueous processing of water-soluble organic compounds in the eastern United States during winter

Supplementary files

Article information

Article type
Paper
Submitted
16 Mär 2022
Accepted
29 Jun 2022
First published
07 Jul 2022

Environ. Sci.: Processes Impacts, 2023,25, 241-253

Author version available

Aqueous processing of water-soluble organic compounds in the eastern United States during winter

M. M. H. El-Sayed and C. J. Hennigan, Environ. Sci.: Processes Impacts, 2023, 25, 241 DOI: 10.1039/D2EM00115B

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