Jaoui, Mohammed;
Docherty, Kenneth S.;
Lewandowski, Michael;
Kleindienst, Tadeusz E.
Yields and molecular composition of gas-phase and secondary organic aerosol from the photooxidation of the volatile consumer product benzyl alcohol: formation of highly oxygenated and hydroxy nitro-aromatic compounds
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Medientyp:
E-Artikel
Titel:
Yields and molecular composition of gas-phase and secondary organic aerosol from the photooxidation of the volatile consumer product benzyl alcohol: formation of highly oxygenated and hydroxy nitro-aromatic compounds
Beteiligte:
Jaoui, Mohammed;
Docherty, Kenneth S.;
Lewandowski, Michael;
Kleindienst, Tadeusz E.
Beschreibung:
<jats:p>Abstract. Recently, volatile chemical products (VCPs) have been increasingly
recognized as important precursors for secondary organic aerosol (SOA) and
ozone in urban areas. However, their atmospheric chemistry, physical
transformation, and impact on climate, environment, and human health
remain poorly understood. Here, the yields and chemical composition at the
molecular level of gas- and particle-phase products originating from the
photooxidation of one of these VCPs, benzyl alcohol (BnOH), are reported.
The SOA was generated in the presence of seed aerosol from nebulized
ammonium sulfate solution in a 14.5 m3 smog chamber operated in flow
mode. More than 50 organic compounds containing nitrogen and/or up to seven
oxygen atoms were identified by mass spectrometry. While a detailed
non-targeted analysis has been made, our primary focus has been to examine
highly oxygenated and nitro-aromatic compounds. The major components include
ring-opening products with a high oxygen-to-carbon ratio (e.g., malic acid,
tartaric acids, arabic acid, trihydroxy-oxo-pentanoic acids, and pentaric
acid) and ring-retaining products (e.g., benzaldehyde, benzoic acid,
catechol, 3-nitrobenzyl alcohol, 4-nitrocatechol, 2-hydroxy-5-nitrobenzyl
alcohol, 2-nitrophloroglucinol, 3,4-dihydroxy-5-nitrobenzyl alcohol). The
presence of some of these products in the gas and particle phases
simultaneously provides evidence of their gas–particle partitioning. These
oxygenated oxidation products made dominant contributions to the SOA
particle composition in both low- and high-NOx systems. Yields, organic mass
to organic carbon ratio, and proposed reaction schemes for selected
compounds are provided. The aerosol yield was 5.2 % for
BnOH/H2O2 at an SOA concentration of 52.9 µg m−3 and
ranged between 1.7 % and 8.1 % for BnOH / NOx at an SOA concentration of 40.0–119.5 µg m−3.
</jats:p>