Wintertime Aerosol Chemistry in Sub-Arctic Urban Air

<div><p>Measurements of submicron particulate matter (PM) were performed at an urban background station, in Helsinki, Finland during wintertime to investigate the chemical characteristics and sources of PM₁. The PM₁ was dominated by sulfate and organics. The source apportionment indicated that organic aerosol (OA) was a mixture from local sources (biomass burning (BBOA), traffic, coffee roaster (CROA)), secondary compounds formed in local wintertime conditions (nitrogen containing OA (NOA), semivolatile oxygenated OA (SV-OOA), and regional and long-range transported compounds (low volatile oxygenated OA, LV-OOA). BBOA was dominated by the fragments C₂H₄O₂⁺ and C₃H₄O₂⁺ (m/z 60.021 and 73.029) from levoglucosan, or other similar sugar components, comprising on average 32% of the BBOA mass concentration. The ratio between fragments C₂H₄O₂⁺/C₃H₄O₂⁺ was significantly lower for CROA (=1.1) when compared to BBOA (=2.1), indicating that they consisted of different sugar compounds. In addition, a component containing substantial amount of nitrogen compounds (NOA) was observed in a sub-arctic region for the first time. The NOA contribution to OA ranged from 1% to 29% and elevated concentrations were observed when ambient relative humidity was high and the visibility low. Low solar radiation and temperature in wintertime were observed to influence the oxidation of compounds. A change in aerosol composition, with an increase of LV-OOA and decrease in BBOA, SV-OOA and NOA was noticed during the transition from wintertime to springtime. Size distribution measurements with high-time resolution enabled chemical characterization of externally mixed aerosol from different sources. Aged regional long-range transported aerosols were dominant at around 0.5 μm (vacuum aerodynamic diameter), whereas traffic and CROA emissions dominated at around 120 nm.</p> <p>Copyright 2014 American Association for Aerosol Research</p> </div

Organic aerosol components derived from 25 AMS datasets across Europe using a newly developed ME-2 based source apportionment strategy

Organic aerosols (OA) represent one of the major constituents of submicron particulatematter (PM1) and comprise a huge variety of compounds emitted by different sources.Three intensive measurement field campaigns to investigate the aerosol chemical com-position all over Europe were carried out within the framework of EUCAARI and the intensive campaigns of EMEP during 2008 (May–June and September–October) and2009 (February–March). In this paper we focus on the identification of the main organicaerosol sources and we propose a standardized methodology to perform source ap-portionment using positive matrix factorization (PMF) with the multilinear engine (ME-2)on Aerodyne aerosol mass spectrometer (AMS) data. Our source apportionment procedure is tested and applied on 25 datasets accounting for urban, rural, remote andhigh altitude sites and therefore it is likely suitable for the treatment of AMS-relatedambient datasets. For most of the sites, four organic components are retrieved, im-proving significantly previous source apportionment results where only a separationin primary and secondary OA sources was possible. Our solutions include two primary OA sources, i.e. hydrocarbon-like OA (HOA) and biomass burning OA (BBOA)and two secondary OA components, i.e. semi-volatile oxygenated OA (SV-OOA) andlow-volatility oxygenated OA (LV-OOA). For specific sites cooking-related (COA) andmarine-related sources (MSA) are also separated. Finally, our work provides a largeoverview of organic aerosol sources in Europe and an interesting set of highly time resolved data for modeling evaluation purposes.ISSN:1680-7375ISSN:1680-736