Source apportionment of the carbonaceous aerosol in Norway – quantitative estimates based on ¹⁴C, thermal-optical and organic tracer analysis

• Main Authors: K. Stenström, H. Puxbaum, D. Simpson, K. E. Yttri, T. Svendby
• Format: Article
• Language: English
• Published: Copernicus Publications 2011-09-01
• Series: Atmospheric Chemistry and Physics
• Online Access: http://www.atmos-chem-phys.net/11/9375/2011/acp-11-9375-2011.pdf

In the present study, source apportionment of the ambient summer and winter time particulate carbonaceous matter (PCM) in aerosol particles (PM₁ and PM₁₀) has been conducted for the Norwegian urban and rural background environment. Statistical treatment of data from thermal-optical, ¹⁴C and organic tracer analysis using Latin Hypercube Sampling has allowed for quantitative estimates of seven different sources contributing to the ambient carbonaceous aerosol. These are: elemental carbon from combustion of biomass (EC_bb) and fossil fuel (EC_ff), primary and secondary organic carbon arising from combustion of biomass (OC_bb) and fossil fuel (OC_ff), primary biological aerosol particles (OC_PBAP, which includes plant debris, OC_pbc, and fungal spores, OC_pbs), and secondary organic aerosol from biogenic precursors (OC_BSOA). <br><br> Our results show that emissions from natural sources were particularly abundant in summer, and with a more pronounced influence at the rural compared to the urban background site. 80% of total carbon (TC_p, corrected for the positive artefact) in PM₁₀ and ca. 70% of TC_pin PM₁ could be attributed to natural sources at the rural background site in summer. Natural sources account for about 50% of TC_p in PM₁₀ at the urban background site as well. The natural source contribution was always dominated by OC_BSOA, regardless of season, site and size fraction. During winter anthropogenic sources totally dominated the carbonaceous aerosol (80–90%). Combustion of biomass contributed slightly more than fossil-fuel sources in winter, whereas emissions from fossil-fuel sources were more abundant in summer. <br><br> Mass closure calculations show that PCM made significant contributions to the mass concentration of the ambient PM regardless of size fraction, season, and site. A larger fraction of PM₁ (ca. 40–60%) was accounted for by carbonaceous matter compared to PM₁₀ (ca. 40–50%), but only by a small margin. In general, there were no pronounced differences in the relative contribution of carbonaceous matter to PM with respect to season or between the two sites.