Abstract
Abstract. The formation of oxalic acid and its mixing state in atmospheric particulate matter (PM) were studied using a single-particle aerosol mass spectrometer (SPAMS) in the summer and winter of 2014 in Heshan, a supersite in the rural area of the Pearl River Delta (PRD) region in China. Oxalic-acid-containing particles accounted for 2.5 and 2.7 % in total detected ambient particles in summer and winter, respectively. Oxalic acid was measured in particles classified as elemental carbon (EC), organic carbon (OC), elemental and organic carbon (ECOC), biomass burning (BB), heavy metal (HM), secondary (Sec), sodium-potassium (NaK), and dust. Oxalic acid was found predominantly mixing with sulfate and nitrate during the whole sampling period, likely due to aqueous-phase reactions. In summer, oxalic-acid-containing particle number and ozone concentration followed a very similar trend, which may reflect the significant contribution of photochemical reactions to oxalic acid formation. The HM particles were the most abundant oxalic acid particles in summer and the diurnal variations in peak area of iron and oxalic acid show opposite trends, which suggests a possible loss of oxalic acid through the photolysis of iron oxalato-complexes during the strong photochemical activity period. In wintertime, carbonaceous particles contained a substantial amount of oxalic acid as well as abundant carbon clusters and BB markers. The general existence of nitric acid in oxalic-acid-containing particles indicates an acidic environment during the formation process of oxalic acid. The peak areas of nitrate, sulfate and oxalic had similar temporal change in the carbonaceous type oxalic acid particles, and the organosulfate-containing oxalic acid particles correlated well with total oxalic acid particles during the haze episode, which suggests that the formation of oxalic acid is closely associated with the oxidation of organic precursors in the aqueous phase.
Highlights
IntroductionTypically a large fraction of fine particles, contains thousands or more of organic compounds and contributes to visibility reduction, photochemical smog, climate9520 C
Organic aerosol, typically a large fraction of fine particles, contains thousands or more of organic compounds and contributes to visibility reduction, photochemical smog, climatePublished by Copernicus Publications on behalf of the European Geosciences Union.9520 C
Oxalic acid was measured in particles classified as elemental carbon (EC), organic carbon (OC), elemental and organic carbon (ECOC), biomass burning (BB), heavy metal (HM), secondary (Sec), sodium-potassium (NaK), and dust
Summary
Typically a large fraction of fine particles, contains thousands or more of organic compounds and contributes to visibility reduction, photochemical smog, climate9520 C. Typically a large fraction of fine particles, contains thousands or more of organic compounds and contributes to visibility reduction, photochemical smog, climate. DCAs normally have high water solubility and low vapor pressure. They play important roles in controlling the hygroscopic properties of organic aerosols (Prenni et al, 2003; Ma et al, 2013) and activating cloud condensation nuclei (Booth et al, 2009). High concentrations of DCAs have been observed in biomass burning plumes (Kundu et al, 2010; Kawamura et al, 2013), with more than 70 % of DCAs produced from photochemical oxidation of water-soluble organic compounds, and only a small contribution from direct biomass burning (BB) emission (van Pinxteren et al, 2014)
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