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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-273
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
19 Mar 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Chemical composition of isoprene SOA under acidic and non-acidic conditions: Effect of relative humidity
Klara Nestorowicz1, Mohammed Jaoui2, Krzysztof Jan Rudzinski1, Michael Lewandowski2, Tadeusz E. Kleindienst2, Witold Danikiewicz3, and Rafal Szmigielski1 1Environmental Chemistry Group, Institute of Physical Chemistry Polish Academy of Sciences, 01-224 Warsaw, Poland
2US Environmental Protection Agency, 109 T.W. Alexander Drive, RTP NC, 27711, USA
3Mass Spectrometry Group, Institute of Organic Chemistry, Polish Academy of Science, 01-224 Warsaw, Poland
Abstract. The effect of acidity and relative humidity on bulk isoprene aerosol parameters has been investigated in several studies, however few measurements have been conducted on individual aerosol compounds. While the focus of this study has been the examination of the effect of acidity and RH on secondary organic aerosol (SOA) chemical composition from isoprene photooxidation in the presence of NOx, a detailed characterization of SOA at the molecular level have been also conducted. Experiments were conducted in a 14.5 m3 smog chamber operated in flow mode. Based on a detailed analysis of mass spectra obtained from GCMS of silylated derivatives in EI and CI modes, and UPLC/ESI/QTOF HRMS, and collision-induced dissociation in the positive and negative ionization modes, we characterized not only typical isoprene products, but also new oxygenated compounds. The analysis showed the presence of methylthreonic acids (mTr) and methyltartaric acids (mTA), proposed recently by our groups as isoprene aging SOA markers. Furthermore, a series of organosulfates (OSs) were tentatively identified including 2mTr-OS, 2mTA-OS and 2mTA nitroxy-OS. Under acidic conditions, the major identified compounds include 2-methyltetrols (2mT), 2-methylglyceric acid (2mGA) and 2mT-OS. Other products identified include epoxydiols, mono- and dicarboxylic acids, OSs, and nitroxy- and nitrosoxy-OSs. The contribution of SOA products from isoprene oxidation to PM2.5 was investigated by analyzing ambient aerosol collected at rural sites in Poland. mTs, mGA and several organosulfates and nitroxy-OS were detected in both the field and laboratory samples. The influence of RH on SOA formation was modest in non-acidic seed experiments. Total SOC decreased with increasing RH. The yields of most compounds decreased, but the concentrations of 2mTA, IEPOX-OS, 2mGA-OS and 2mTr-OS increased with increasing RH. Some components followed this pattern while other were more abundant in non-acidic experiments or behaved in a mixed way, depending on RH.
Citation: Nestorowicz, K., Jaoui, M., Rudzinski, K. J., Lewandowski, M., Kleindienst, T. E., Danikiewicz, W., and Szmigielski, R.: Chemical composition of isoprene SOA under acidic and non-acidic conditions: Effect of relative humidity, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-273, in review, 2018.
Klara Nestorowicz et al.
Klara Nestorowicz et al.
Klara Nestorowicz et al.

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