Organosulfates as Tracers for Secondary Organic Aerosol (SOA) Formation from 2-Methyl-3-Buten-2-ol (MBO) in the Atmosphere

Abstract

2-Methyl-3-buten-2-ol (MBO) is an important biogenic volatile organic compound (BVOC) emitted by pine trees and a potential precursor of atmospheric secondary organic aerosol (SOA) in forested regions. In the present study, hydroxyl radical (OH)-initiated oxidation of MBO was examined in smog chambers under varied initial nitric oxide (NO) and aerosol acidity levels. Results indicate measurable SOA from MBO under low-NO conditions. Moreover, increasing aerosol acidity was found to enhance MBO SOA. Chemical characterization of laboratory-generated MBO SOA reveals that an organosulfate species (C5H12O6S, MW 200) formed and was substantially enhanced with elevated aerosol acidity. Ambient fine aerosol (PM2.5) samples collected from the BEARPEX campaign during 2007 and 2009, as well as from the BEACHON-RoMBAS campaign during 2011, were also analyzed. The MBO-derived organosulfate characterized from laboratory-generated aerosol was observed in PM2.5 collected from these campaigns, demonstrating that it is a molecular tracer for MBO-initiated SOA in the atmosphere. Furthermore, mass concentrations of the MBO-derived organosulfate are well correlated with MBO mixing ratio, temperature, and acidity in the field campaigns. Importantly, this compound accounted for an average of 0.25% and as high as 1% of the total organic aerosol mass during BEARPEX 2009. An epoxide intermediate generated under low-NO conditions is tentatively proposed to produce MBO SOA.

A critical evaluation of proxy methods used to estimate the acidity of atmospheric particles

“…The ion balance proxy method assumes that conditions of high aerosol H + loading (in nmol m −3 ) correspond to an aerosol distribution with a low (acidic) pH (e.g., Feng et al, 2012;Zhang et al, 2012a). Figure 6 shows the relationship between predicted aerosol pH and the H + concentration inferred from the ion balance.…”

Atmospheric oxidation of isoprene and 1,3-butadiene: influence of aerosol acidity and relative humidity on secondary organic aerosol

“…Analysis by Chan et al (2011) confirmed the presence of organosulfate compounds in β-caryophyllene SOA formed under these conditions. Zhang et al (2012) performed acidity experiments for 2-methyl-3-buten-2-ol (MBO), a compound structurally related to isoprene. MBO was shown to be less influenced by acidity than isoprene or β-caryophyllene, but more affected than α-pinene.…”

“…In addition, this study attempts to extend the analysis over a broader range of humidities in an effort to assess the impact of aerosol water content on acidity-influenced SOA formation. In the previous studies by Surratt et al (2007) and Offenberg et al (2009), all measurements were conducted at a single humidity level (30 % relative humidity), while Zhang et al (2012) examined only dry conditions. Extending these studies to a wider range of hydrocarbons and across a more realistic range of humidities should provide data of greater atmospheric relevance and contribute to further development of acidity-influenced SOA chemistry in air quality models.…”

“…All data from experiments with isoprene, α-pinene, and β-caryophyllene are from prior studies in this laboratory (Surratt et al, 2007;Offenberg et al, 2009) and use a chamber relative humidity of 30 %. Table 3 also includes data for the MBO experiment described by Zhang et al (2012), where SOA was produced under conditions of low NO x with the aerosol generated through RO 2 + HO 2 and RO 2 + RO 2 reactions. Unlike the other experiments presented in Table 3, the MBO experiment was conducted under dry conditions (less than 3 % relative humidity).…”

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

“…The authors further found that organonitrates could easily be transformed to organosulfates during hydrolysis in the presence of sulfate. Some studies also showed that 2-methyl-3-buten-2-ol (MBO), due to its emissions that are larger than isoprene in some regions (Baker et al, 1999), is an important precursor for organosulfates and SOA in the atmosphere through its reactions with OH under NO and aerosol acidity conditions and from acid-catalysed reactive uptake of MBO-based epoxides formed during MBO photooxidation (Mael et al, 2015;Zhang et al, 2012Zhang et al, , 2014. Organosulfate formation was also found from oxidation of hydroxyhydroperoxides (Riva et al, 2016) and from heterogeneous reactions of SO 2 with selected long-chain alkenes and unsaturated fatty acids (Passananti et al, 2016).…”