Reactive Uptake of an Isoprene-Derived Epoxydiol to Submicron Aerosol Particles

Abstract

The reactive uptake of isoprene-derived epoxydiols (IEPOX) is thought to be a significant source of atmospheric secondary organic aerosol (SOA). However, the IEPOX reaction probability (γIEPOX) and its dependence upon particle composition remain poorly constrained. We report measurements of γIEPOX for trans-β-IEPOX, the predominant IEPOX isomer, on submicron particles as a function of composition, acidity, and relative humidity (RH). Particle acidity had the strongest effect. γIEPOX is more than 500 times greater on ammonium bisulfate (γ ∼ 0.05) than on ammonium sulfate (γ ≤ 1 × 10(-4)). We could accurately predict γIEPOX using an acid-catalyzed, epoxide ring-opening mechanism and a high Henry's law coefficient (1.7 × 10(8) M/atm). Suppression of γIEPOX was observed on particles containing both ammonium bisulfate and poly(ethylene glycol) (PEG-300), likely due to diffusion and solubility limitations within a PEG-300 coating, suggesting that IEPOX uptake could be self-limiting. Using the measured uptake kinetics, the predicted atmospheric lifetime of IEPOX is a few hours in the presence of highly acidic particles (pH < 0) but is greater than 25 h on less acidic particles (pH > 3). This work highlights the importance of aerosol acidity for accurately predicting the fate of IEPOX and anthropogenically influenced biogenic SOA formation.

Rapid deposition of oxidized biogenic compounds to a temperate forest

“…More likely, the low observed mixing ratios of IEPOX at SOAS may be due to error in its production rate or because heterogeneous loss reactions, such as conversion to organic aerosols in anthropogenically impacted particle liquid water (64), were not accounted for in the model. IEPOX uptake clearly involves hydronium-catalyzed ring opening in aerosol liquid water (62,65,66). However, field results suggest that more factors than acid catalysis govern the chemistry (67).…”

In vitro exposure to isoprene-derived secondary organic aerosol by direct deposition and its effects on &lt;i&gt;COX-2&lt;/i&gt; and &lt;i&gt;IL-8&lt;/i&gt; gene expression

“…Ozone exposure studies have shown that comparable dose and effect measurements for IL-8 and COX-2 can be found between in vivo and in vitro exposures, which adds promise to extrapolating effects seen in vitro to effects in vivo (Hatch et al, 2014). In vivo effects associated with isoprene SOA exposure in vitro cannot be inferred as it is a different system from ozone, so further in vitro studies exploring the health implication of the elevation of IL-8 and COX-2 due specifically to isoprene SOA exposure are necessary and may in turn justify further extension to in vivo work.…”

“…to particle acidity, which enhances isoprene SOA formation through acid-catalyzed reactive uptake and multiphase chemistry of IEPOX and MAE (Surratt et al, 2007Gaston et al, 2014;Riedel et al, 2015), while NO x determines whether the oxidation pathway leading to IEPOX or MAE/HMML predominates (Lin et al, 2013b;. Isoprene SOA comprises a large portion of global atmospheric fine particles (PM 2.5 , aerosol with aerodynamic diameters ≤ 2.5 µm) (Carlton et al, 2009;Henze et al, 2008), but few studies have focused on its health implications .…”

“…Isoprene SOA comprises a large portion of global atmospheric fine particles (PM 2.5 , aerosol with aerodynamic diameters ≤ 2.5 µm) (Carlton et al, 2009;Henze et al, 2008), but few studies have focused on its health implications . Evaluating the health effects of SOA from isoprene oxidation is important from a public health perspective, not only because of its atmospheric abundance but also because the anthropogenic contribution is the only component amenable to control (Pye et al, 2013;Gaston et al, 2014;Xu et al, 2015;Riedel et al, 2015).…”

A framework for expanding aqueous chemistry in the Community Multiscale Air Quality (CMAQ) model version 5.1

“…A large fraction of the total increase in SOA IEPOX/MPAN (red line) is due to increases in 2-MG production (grey line) even though 2-methyltetrols dominate the concentration of total SOA IEPOX/MPAN in most of the domain. If the Henry's law coefficient for IEPOX is much higher than used here (for example, 1.7 × 10 8 ; Gaston et al, 2014), then aqueous processing of IEPOX would lead to even higher methyltetrol concentrations than predicted here.…”