Physico-chemical characterization of SOA derived from catechol and guaiacol – a model substance for the aromatic fraction of atmospheric HULIS

Abstract

Abstract. Secondary organic aerosol (SOA) was produced from the aromatic precursors catechol and guaiacol by reaction with ozone in the presence and absence of simulated sunlight and humidity and investigated for its properties as a proxy for HUmic-LIke Substances (HULIS). Beside a small particle size, a relatively low molecular weight and typical optical features in the UV/VIS spectral range, HULIS contain a typical aromatic and/or olefinic chemical structure and highly oxidized functional groups within a high chemical diversity. Various methods were used to characterize the secondary organic aerosols obtained: Fourier transform infrared spectroscopy (FTIR) demonstrated the formation of several carbonyl containing functional groups as well as structural and functional differences between aerosols formed at different environmental conditions. UV/VIS spectroscopy of filter samples showed that the particulate matter absorbs far into the visible range up to more than 500 nm. Ultrahigh resolved mass spectroscopy (ICR-FT/MS) determined O/Cratios between 0.3 and 1 and observed m/z ratios between 200 and 450 to be most abundant. Temperature-programmedpyrolysis mass spectroscopy (TPP-MS) identified carboxylic acids and lactones/esters as major functional groups. Particle sizing using a condensation-nucleus-counter and differentialmobility-particle-sizer (CNC/DMPS) monitored the formation of small particles during the SOA formation process.Correspondence to: H. Grothe (grothe@tuwien.ac.at) Particle imaging, using field-emission-gun scanning electron microscopy (FEG-SEM), showed spherical particles, forming clusters and chains. We conclude that catechol and guaiacol are appropriate precursors for studies of the processing of aromatic SOA with atmospheric HULIS properties on the laboratory scale.

Photooxidation of cyclohexene in the presence of SO<sub>2</sub>: SOA yield and chemical composition

“…The peaks at 1622 and 1278 cm −1 show good correlation and both are assigned to the -ONO 2 stretching (Liu et al, 2012;Jia and Xu, 2014). The characteristic absorption band at 1500-1350 cm −1 is the C-O stretching and O-H bending of the COOH group (Ofner et al, 2011), and the absorption peak of sulfate exists in the range of 1200-1000 cm −1 (Wu et al, 2013). The band at 1100 cm −1 in the IR spectra can be attributed to the sulfate group in organic compounds and sulfate.…”

“…There are three possible explanations for this phenomenon. (1) SOA formation is closely related to the oxidation capacity in the photooxidation experiments and, therefore, is affected by the ratio of [VOC] (Pandis et al, 1991). Experiments performed with different SO 2 concentrations indicate that the SOA formation is partly controlled by the ability of the system to oxidize cyclohexene and contribute to the particle mass.…”

Halogenation processes of secondary organic aerosol and implications on halogen release mechanisms

“…Physicochemical characterization of SOA from α-pinene has been reported by Ofner (2011). SOA formation from catechol and guaiacol is described in detail by Ofner et al (2010Ofner et al ( , 2011.…”

Climate engineering by mimicking natural dust climate control: the iron salt aerosol method

“…The sources of SOA are biogenic VOCs such as terpenes (Fry et al, 2014). HULISs contain polyphenolic redox mediators such as catechol and nitro-catechols (Claeys et al, 2012;Hoffer et al, 2004;Ofner et al, 2011;Pillar et al, 2014).…”