Jump to main content
Jump to site search


Investigation on the hygroscopicity of oxalic acid and atmospherically relevant oxalate salts under sub- and supersaturated conditions

Abstract

Oxalic acid (OxA) is an end product in the oxidation of many organic compounds before CO2 and therefore is ubiquitous in the atmosphere and the most abundant organic species in aerosols. To better understand the hygroscopic properties of OxA under sub- and supersaturated conditions in the atmosphere, we investigated the hygroscopic growth and cloud condensation nuclei (CCN) activation ability of pure OxA and its salts using a hygroscopic tandem differential mobility analyzer (HTDMA) and cloud condensation nuclei counter (CCNC), respectively. OxA particles absorb water under >45% RH, suggesting that initial phase state might be an amorphous solid. The measured hygroscopic growth (HGF) of OxA at 90% RH was 1.47. We found that HGF of ammonium oxalate (NH4-Ox) was larger than OxA, whereas HGFs of sodium, calcium, and magnesium oxalates (Na-Ox, Ca-Ox, and Mg-Ox) showed smaller than OxA particles. Potassium oxalate (K-Ox) behaved like a typical water-soluble inorganic salt, exhibited deliquescence and efflorescence transitions at around 85% and 50% RH, respectively. Na-Ox exhibited strong activation capabilities among all the investigated salts, followed by NH4-Ox and K-Ox as inferred from the activation ratios (CCN/CN) against supersaturations (SS). On the other hand, Ca-Ox showed moderate and Mg-Ox showed poor CCN activation abilities. We also observed significantly higher κCCN values compared to κHTDMA for pure OxA and its salts (NH4-Ox, Na-Ox), suggesting that condensation of OxA to aqueous-phase occurs during water-uptake. These findings improve the fundamental understanding of hygroscopic behaviors and phase state of oxalic acid and its salts under sub- and supersaturated conditions in the atmosphere and impacts of hygroscopicity on the direct and indirect effects of aerosol particles.

Back to tab navigation

Publication details

The article was received on 05 Feb 2018, accepted on 27 May 2018 and first published on 29 May 2018


Article type: Paper
DOI: 10.1039/C8EM00053K
Citation: Environ. Sci.: Processes Impacts, 2018, Accepted Manuscript
  •   Request permissions

    Investigation on the hygroscopicity of oxalic acid and atmospherically relevant oxalate salts under sub- and supersaturated conditions

    S. K. R. Borredy and K. Kawamura, Environ. Sci.: Processes Impacts, 2018, Accepted Manuscript , DOI: 10.1039/C8EM00053K

Search articles by author

Spotlight

Advertisements