Water‐soluble organic compounds in biomass burning aerosols over Amazonia 1. Characterization by NMR and GC‐MS

Abstract

As part of the European contribution to the Large‐Scale Atmosphere‐Biosphere Experiment in Amazonia (LBA‐EUSTACH), aerosols were sampled at representative pasture and primary rainforest sites in Rondônia, Brazil, during the 1999 “burning season” and dry‐to‐wet season transition (September‐October). Water‐soluble organic compounds (WSOCs) within the samples were characterized using a combination of 1H Nuclear Magnetic Resonance (NMR) spectroscopy for chemical functional group analysis, and Gas Chromatography‐Mass Spectrometry (GC‐MS) for identification and quantification of individual low‐molecular‐weight compounds. The 1H NMR analysis indicates that WSOCs are predominantly aliphatic or oxygenated aliphatic compounds (alcohols, carboxylic acids, etc.), with a minor content of aromatic rings carrying carboxylic and phenolic groups. Levoglucosan (1,6‐anhydro‐β‐D‐glucose), a well‐known cellulose combustion product, was the most abundant individual compound identified by GC‐MS (0.04–6.90 μg m−3), accounting for 1–6% of the total carbon (TC) and 2–8% of the water‐soluble organic carbon (WSOC). Other anhydrosugars, produced by hemicellulose breakdown, were detected in much smaller amounts, in addition to series of acids, hydroxyacids, oxoacids, and polyalcohols (altogether 2–5% of TC, 3–6% of WSOC). Most correlated well with organic carbon, black carbon, and potassium, indicating biomass burning to be the major source. A series of sugar alcohols (mannitol, arabitol, erythritol) and sugars (glucose, fructose, mannose, galactose, sucrose, trehalose) were identified as part of the natural background aerosol and are probably derived from airborne microbes and other biogenic material. The bulk of the WSOCs (86–91% WSOC) eluded analysis by GC‐MS and may be predominantly high‐molecular weight in nature.

Diurnal and temporal variations of water-soluble dicarboxylic acids and related compounds in aerosols from the northern vicinity of Beijing: Implication for photochemical aging during atmospheric transport

“…Photochemical breakdown of C 9 , ωC 8 and ωC 9 may produce small dicarboxylic acids including C 4 , C 3 , and C 2 , as illustrated in Figure 6. Although oxalic acid is known to produce via fossil-fuel combustion, its relatively high abundance in the remote atmosphere, coupled with the estimated lifetime of 6-8 days, may demonstrate either a background presence or secondary production from anthropogenic and natural precursors (Graham et al, 2002;Myriokefalitakis et al, 2011).…”

“…Oxalic acid (C 2 ) is usually the dominant organic species in aerosols (Kawamura and Sakaguchi, 1999). Diacids are emitted primarily from combustion of fossil fuels, i.e., motor exhausts and coal burning, and biomass burning (Graham et al, 2002;Kawamura and Kaplan, 1987;Kundu et al, 2010a, b;Narukawa et al, 1999), but more importantly produced by the secondary oxidation of anthropogenic and biogenic volatile organic compounds (VOCs) in the atmosphere (Glasius et al, 2000;Kawamura et al, 1996a;Legrand et al, 2007). Aqueous-phase production of C 2 is also important in aerosol/cloud/fog droplets (Warneck, 2003).…”

Gas chromatography coupled to mass spectrometry for analyses of organic compounds and biomarkers as tracers for geological, environmental, and forensic research

“…Ergosterol is a primary fungal membrane sterol (C 28 ) and serves as a biomarker for determining fungal biomass in soil [e. g., 157] and aerosol [e. g., 158] samples. The disaccharide mycose is a known fungal metabolite [159,160] and has been detected in sediments [93], soils [161,162], and aerosols [e. g., 100,163,164]. Finally, usnic acid, which was detected in smoke samples from biomass burning [165], has been isolated from several species of lichen genera [166].…”

Characterisation of solvent extractable organic constituents in atmospheric particulate matter: an overview

“…Little is known about the type and abundance of water-soluble organic compounds (WSOC) in atmospheric particulate matter. The limited results available to date indicate that WSOC could account for 20-90% of total carbon in aerosols (Alves et al 2002, Decesari et al 2000, Facchini et al 1999, Graham et al 2002, Saxena and Hildemann 1996. Yang et al (2003) compared two methods for the determination of WSOC in ambient aerosols, one based on a total organic carbon analyser (TOC) and the other based on an aerosol carbon analyser (ACA).…”

“…Potential acid-catalysed hydrolysis of levoglucosan in atmospheric droplets was Table X presents the contribution of levoglucosan to OC in fine particles from different fuel types and distict burning conditions. Based on the average value between the OC/levoglucosan ratio of 12.3 measured for the fine dry season aerosol in Rhondonia (Graham et al 2002) and the ratio of 10.5 obtained for a pine forest fire in southeast USA (Lee et al 2005), it was found a smaller than expected contribution (11-36%) of wood combustion to the amount of OC throughout the summer of 2003, which was characterised by an intense heat wave and forest fires in Portugal ). Thus, unrealistically, its seems that the major fraction of OC measured in both fine and coarse aerosols during the Portuguese study was chiefly related to other primary anthropogenic and biogenic sources, as well secondary formation processes.…”