Article

Fossil and non-fossil sources of organic carbon (OC) and elemental carbon (EC) in Göteborg, Sweden

Atmospheric Chemistry and Physics (Impact Factor: 4.88). 08/2008; 8:16255-16289. DOI: 10.5194/acpd-8-16255-2008
Source: DOAJ

ABSTRACT

Particulate matter was collected at an urban site in Göteborg (Sweden) in February/March 2005 and in June/July 2006. Additional samples were collected at a rural site for the winter period. Total carbon (TC) concentrations were 2.1–3.6 μg m−3, 1.8–1.9 μg m−3, and 2.2–3.0 μg m−3 for urban/winter, rural/winter, and urban/summer conditions, respectively. Elemental carbon (EC), organic carbon (OC), water-insoluble OC (WINSOC), and water-soluble OC (WSOC) were analyzed for 14C in order to distinguish fossil from non-fossil emissions. As wood burning is the single major source of non-fossil EC, its contribution can be quantified directly. For non-fossil OC, the wood-burning fraction was determined independently by levoglucosan and 14C analysis and combined using Latin-hypercube sampling (LHS). For the winter period, the relative contribution of EC from wood burning to the total EC was >3 times higher at the rural site compared to the urban site, whereas the absolute concentrations of EC from wood burning were elevated only moderately at the rural compared to the urban site. Thus, the urban site is substantially more influenced by fossil EC emissions. For summer, biogenic emissions dominated OC concentrations most likely due to secondary organic aerosol (SOA) formation. During both seasons, a more pronounced fossil signal was observed for Göteborg than has previously been reported for Zurich, Switzerland. Analysis of air mass origin using back trajectories suggests that the fossil impact was larger when local sources dominated, whereas long-range transport caused an enhanced non-fossil signal. In comparison to other European locations, concentrations of levoglucosan and other monosaccharide anhydrides were low for the urban and the rural site in the area of Göteborg during winter.

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    • "CC in airborne particulates originates mostly from re-suspension of mineral dust by natural or anthropogenic processes (Karanasiou et al. 2011). EC arises basically from incomplete combustion processes , and thus, traffic and other mobile sources (especially diesel engines), industry (engines and boilers) and biomass burning are its major sources (Bond 2007; Ramanathan and Carmichael 2008; Szidat et al. 2009; Ulevicius et al. 2010; Minguillón et al. 2011; Viana et al. 2012). The origin of primary OC may be biological (plant debris, biological particles). "
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    • "EC is directly emitted from incomplete combustion of biomass and fossil fuels, while OC has either a primary or secondary origin. Primary organic carbon (POC) is emitted from a variety of sources, including combustion processes and biogenic emissions (Bond et al. 2007; Szidat et al. 2009). On the other hand, secondary organic carbon (SOC) is produced by the oxidation of volatile and semivolatile organic species (Kroll and Seinfeld 2008; Robinson et al. 2007). "
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    • "Biomass burning is very important in winter in Switzerland (Lanz et al. 2010) but is difficult to separate from other non-fossil emissions based on 14 C measurement of TC alone. Recent works have attempted to measure 14 C in OC and EC separately (Szidat et al. 2009; Zhang et al. 2012), which allows a direct discrimination of the contributions from biomass and fossil fuel burning to EC and also enables a distinction of biogenic from biomass-burning sources of OC under certain conditions (Szidat et al. 2006). The challenge of 14 C measurement of OC and EC lies in the chemical separation of both, which is a prerequisite for unbiased source apportionment. "

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