Atmos. Chem. Phys. Discuss., 12, 20311-20350, 2012
© Author(s) 2012. This work is distributed
under the Creative Commons Attribution 3.0 License.
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties
E. U. Emanuelsson1, M. Hallquist1, K. Kristensen2, M. Glasius2, B. Bohn3, H. Fuchs3, B. Kammer3, A. Kiendler-Scharr3, S. Nehr3, F. Rubach3, R. Tillmann3, A. Wahner3, H.-C. Wu3, and Th. F. Mentel3
1Department of Chemistry and Molecular Biology, University of Gothenburg, 412 96 Göteborg, Sweden
2Department of Chemistry, Aarhus University, 8000 Aarhus, Denmark
3Institut für Energie- und Klimaforschung: Troposphäre (IEK-8), Forschungszentrum Jülich, 52 428 Jülich, Germany

Abstract. Secondary organic aerosol (SOA) formation from mixed anthropogenic and biogenic precursors has been studied exposing reaction mixtures to natural sunlight in the SAPHIR chamber in Jülich, Germany. Several experiments with exclusively anthropogenic precursors were performed to establish a relationship between yield and organic aerosol mass loading for the atmospheric relevant range of aerosol loads of 0.01 to 10 μg m−3. The yields (0.5–9%) were comparable to previous data and further used for the detailed evaluation of the mixed biogenic and anthropogenic experiments. For the mixed experiments a number of different oxidation schemes were addressed. The reactivity, the sequence of addition, and the amount of the precursors influenced the SOA properties. Monoterpene oxidation products, including carboxylic acids and dimer esters were identified in the aged aerosol at levels comparable to ambient air. OH radicals were measured by Laser Induced Fluorescence, which allowed for establishing relations of aerosol properties and composition to the experimental OH dose. Furthermore, the OH measurements in combination with the derived yields for anthropogenic SOA enabled application of a simplified model to calculate the chemical turnover of the anthropogenic precursor and corresponding anthropogenic contribution to the mixed aerosol. The estimated anthropogenic contributions were ranging from small (≈8%) up to significant fraction (>50%) providing a suitable range to study the effect of aerosol composition on the aerosol volatility (volume fraction remaining at 343 K: 0.86–0.94). The anthropogenic aerosol had higher oxygen to carbon ratio O/C and was less volatile than the biogenic fraction. However, in order to produce significant amount of anthropogenic SOA the reaction mixtures needed a higher OH dose that also increased O/C and provided a less volatile aerosol. A strong positive correlation was found between changes in volatility and O/C with the exception during dark hours where the SOA volatility decreased while O/C did not change significantly. This change in volatility under dark conditions is likely due to chemical or morphological changes not affecting O/C.

Citation: Emanuelsson, E. U., Hallquist, M., Kristensen, K., Glasius, M., Bohn, B., Fuchs, H., Kammer, B., Kiendler-Scharr, A., Nehr, S., Rubach, F., Tillmann, R., Wahner, A., Wu, H.-C., and Mentel, Th. F.: Formation of anthropogenic secondary organic aerosol (SOA) and its influence on biogenic SOA properties, Atmos. Chem. Phys. Discuss., 12, 20311-20350, doi:10.5194/acpd-12-20311-2012, 2012.
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