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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-132
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
06 Mar 2018
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Atmospheric Chemistry and Physics (ACP).
Chemical characterization of laboratory-generated tar ball particles
Ádám Tóth1, András Hoffer2, Mihály Pósfai1, Tibor Ajtai3, Zoltán Kónya4,5, Marianne Blazsó6, Zsuzsanna Czégény6, Gyula Kiss2, Zoltán Bozóki3, and András Gelencsér1,2 1Department of Earth and Environmental Sciences, University of Pannonia, Veszprém, P.O. Box 158, 8201, Hungary
2MTA-PE Air Chemistry Research Group, Veszprém, P.O. Box 158, 8201, Hungary
3MTA-SZTE Research Group on Photoacoustic Spectroscopy, Szeged, Dóm tér 9, 6720, Hungary
4Department of Applied and Environmental Chemistry, University of Szeged, Szeged, Rerrich Béla tér 1, 6720, Hungary
5MTA-SZTE Reaction Kinetics and Surface Chemistry Research Group, Szeged, Rerrich Béla tér 1, 6720, Hungary
6MTA-TTK Institute of Materials and Environmental Chemistry, Budapest, P.O. Box 286, 1519, Hungary
Abstract. The chemical properties of tar ball (TB) particles generated from dry distillate (wood tars) of three different wood species in the laboratory were investigated by analytical techniques that had never been used before, for their characterization. The elemental composition of TB particles from three tree species were very similar to one another and to those characteristic for atmospheric tar balls (TBs) collected from savanna fire during the SAFARI 2000 sampling campaign. The O / C and H / C molar ratios of the generated TBs were at the upper limit characteristic for soot particles. The FT-IR spectra of the generated TBs were very similar to one another as well and also showed some similarity with those of atmospheric humic-like substances (HULIS). The FT-IR measurements indicated that laboratory-generated TBs have a higher proportion of aromatic structure than HULIS and the oxygen atoms of TBs are mainly found in hydroxyl and keto functional groups. Whereas the starting materials of the TBs (wood tars) were Raman inactive in the range of 1000–1800 cm−1, the Raman spectra of TBs were dominated by two pronounced bands with intensity maxima near 1580 (G band) and 1350 cm−1 (D band), indicating the presence of sp2-hybridised carbon structures and disorder in them, respectively. In the Py-GC-MS chromatograms of the laboratory-generated TBs mostly aromatic compounds (aromatic hydrocarbons, oxygenated aromatics and heterocyclic aromatics) were identified in accordance with the results of Raman and FT-IR spectroscopy. According to OC / EC analysis using EUSAAR_2 long thermal protocol, 22 % of the total carbon content of laboratory-generated TBs was identified as elemental carbon (EC), contrary to expectations based on the current understanding that negligible if any EC is present in this sub-fraction of the brown carbon family. Our results suggest that spherical atmospheric TBs with high C / O molar ratios are closer to BC in many of their properties than to weakly absorbing HULIS.
Citation: Tóth, Á., Hoffer, A., Pósfai, M., Ajtai, T., Kónya, Z., Blazsó, M., Czégény, Z., Kiss, G., Bozóki, Z., and Gelencsér, A.: Chemical characterization of laboratory-generated tar ball particles, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-132, in review, 2018.
Ádám Tóth et al.
Ádám Tóth et al.
Ádám Tóth et al.

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Short summary
Atmospheric tar balls are abundant particles in biomass smoke and were shown to be strongly light-absorbing. Being able to synthesize pure tar balls in the laboratory we deployed various analytical techniques to determine the chemical characteristics of tar balls and to compare them with those of other light-absorbing particle types such as soot (black carbon, BC). The results have relevance in better representing these specific smoke particles in global climate models.
Atmospheric tar balls are abundant particles in biomass smoke and were shown to be strongly...
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