Water-Soluble Oligomer Formation from Acid-Catalyzed Reactions of Levoglucosan in Proxies of Atmospheric Aqueous Aerosols

Abstract

Herein is reported the first laboratory observation of the oligomerization of levoglucosan studied under atmospherically relevant conditions. Oligomers up to 1458 Da (9-mer) were measured by matrix-assisted laser desorption ionization time-of-flight mass spectrometry. A rational mechanism is proposed based on both the acid-catalyzed cationic ring-opening of levoglucosan and nucleophilic attack of ROH from levoglucosan on the hemi-acetal carbon to produce pyranose oligomers through the formation of glycosidic bonds. Oligomer formation is further supported by attenuated total reflectance Fourier transform infrared spectroscopy. Levoglucosan is a viable tracer for biomass burning aerosols, and the observed products may serve as secondary tracers for these types of aerosols, possibly providing additional information to facilitate source apportionment and better understand atmospheric processing of the aerosol parcel. Also, the processes supported here may contribute to the saccharide character of humic-like substances, which are proposed to be formed through the atmospheric processing of biomass burning aerosols.

The formation, properties and impact of secondary organic aerosol: current and emerging issues

“…Oligomers have been identified in SOA produced from the atmospheric oxidation of cyclic alkenes including terpenes (Gao et al, 2004a, b;Iinuma et al, 2004Iinuma et al, , 2007aTolocka et al, 2004;Baltensperger et al, 2005;Heaton et al, 2007;Müller et al, 2008), small open-chain alkenes including isoprene Sadezky et al, 2006;Szmigielski et al, 2007a) and aromatic VOC precursors Sato et al, 2007). In addition to these classical SOA precursor systems, other compounds which are present in atmospheric aerosols have also been investigated as possible contributors to oligomers, such as levoglucosan (Holmes and Petrucci, 2006) and oleic acid, although the motivation for investigating the chemical processing of oleic acid is often the search for an appropriate model system for heterogeneous reactions (Hearn et al, 2005;Hung et al, 2005;Mochida et al, 2006;Reynolds et al, 2006;Zahardis et al, 2006;Zahardis and Petrucci, 2007).…”

Arctic smoke – record high air pollution levels in the European Arctic due to agricultural fires in Eastern Europe in spring 2006

“…Since aerosols do not seem to have been removed to any significant extent, we suggest that degradation of levoglucosan during transport is a possible reason for the relatively low levoglucosan/CO ER. In a recent laboratory study by Holmes and Petrucci (2006), it was suggested that levoglucosan could be subjected to oligomer- Sulfate and nitrate were also elevated in the BB plume, reaching 1.2 µg S m −3 (0.12 µg S m −3 of which are attributable to sea salt) and 0.71 µg N m −3 , respectively, in the sample taken on 2 May. Again, few (8 for sulfate, 11 for nitrate) higher values were found in the long-term (1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003) dataset.…”

Impacts of Siberian Biomass Burning on Organic Aerosols over the North Pacific Ocean and the Arctic: Primary and Secondary Organic Tracers

“…44 Degradation and oligomerization of LEVO were also discovered in the aqueous solutions. 45,46 SOA tracers could also undergo all of these processes, such as forming organosulfates under acidic environment. 47 Atmospheric aging of OA has indicated increasing O/C ratios in contrast to lowing H/C ratios.…”