Abstract
ABSTRACT Water-soluble organic compounds are important constituents of atmospheric aerosols and have been recognized as unique fingerprints to identify atmospheric processes. Fine aerosol samples (PM2.5) were collected at Ambikapur (23.1°N and 83.2°E) in eastern central India from March to June 2017. The samples were analyzed for water-soluble dicarboxylic acids (C2–C12), glyoxylic acid (ωC2), glyoxal (Gly), methylglyoxal (MeGly), organic carbon (OC), elemental carbon (EC) and water-soluble OC (WSOC). Oxalic acid (C2) was detected as the most abundant species, followed by succinic (C4) and malonic (C3) acids. Temporal variation in concentrations of C2 diacid and related compounds was pronounced from early to late April when biomass burning (BB) was dominant in eastern central India. Strong positive correlations of C2 diacid and related compounds with levoglucosan (r = 0.83–0.99) further demonstrate that organic aerosols (OAs) were affected by BB in eastern central India. Strong positive correlations of C2 with saturated diacids (C3–C9: r = 0.78–0.97), ωC2 (r = 0.98), Gly (r = 0.96) and MeGly (r = 0.84) suggest that their sources and formation processes were similar and oxalic acid might be produced via the photochemical degradation of precursor compounds. The relatively high ratios of WSOC to OC (avg. 0.69) and C3 to C4 diacid (avg. 0.95) suggest that water-soluble OAs were photochemically processed during the campaign. The total water-soluble organic compounds detected in Ambikapur PM2.5 samples accounted for an average of 1.9% (1.1–3.1%) of OC. Our results demonstrate that BB and photochemical processing caused high levels of water-soluble organic compounds over eastern central India.
Highlights
Organic aerosols (OAs) are abundant in the troposphere and are crucial determinants of air quality and climate (Decesari et al, 2001; Kanakidou et al, 2005)
These variations are similar to those of organic carbon (OC) and water-soluble OC (WSOC). Their concentrations decreased towards the end of the campaign. These results further suggest that diacids and related compounds were closely linked with biomass burning emission in eastern central India
Water-soluble dicarboxylic acids, glyoxylic acid and α-dicarbonyls were detected in PM2.5 aerosol samples collected from March to June 2017 in the city of Ambikapur
Summary
Organic aerosols (OAs) are abundant in the troposphere and are crucial determinants of air quality and climate (Decesari et al, 2001; Kanakidou et al, 2005). They are secondarily produced in Dicarboxylic acids and related polar compounds, including oxocarboxylic acids and α-dicarbonyls, are known to be ubiquitous in atmospheric aerosols and comprise a significant fraction of OAs (Kawamura and Yasui, 2005; Pavuluri et al, 2010; Tsai et al, 2015) They are directly released to the Deshmukh et al, Aerosol and Air Quality Research, 19: 2625–2644, 2019 atmosphere from primary sources such as fossil fuel combustion and biomass burning (Kundu et al, 2010; Tsai et al, 2013; Cong et al, 2015). Diacids are an important organic compound class of secondary organic aerosol (SOA) because of their high abundance in the water-soluble organic carbon (WSOC) fraction of atmospheric aerosols (Decesari et al, 2006; Kawamura et al, 2013). Claeys et al (2004) and Fu et al (2008) have proposed that anthropogenic VOCs are rather a minor source of SOA precursors compared to those of biogenic VOCs on a global scale
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