US EPA

3076741 

Journal Article 

Anthropogenic sulfur perturbations on biogenic oxidation: SO2 additions impact gas-phase OH oxidation products of α- and β-pinene 

Friedman, B; Brophy, P; Brune, WH; Farmer, DK 

2016 

1 

Environmental Science & Technology
ISSN: 0013-936X
EISSN: 1520-5851 

AMER CHEMICAL SOC 

WASHINGTON 

50 

3 

1269-1279 

English 

26735899 

10.1021/acs.est.5b05010 

WOS:000369471300023 

https://pubs.acs.org/doi/10.1021/acs.est.5b05010
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is supplemented by 3449560 : Supplementary materials

In order to probe how anthropogenic pollutants can impact the atmospheric oxidation of biogenic emissions, we investigated how sulfur dioxide (SO2) perturbations impact the oxidation of two monoterpenes, α-and β-pinene. We used chemical ionization mass spectrometry to examine changes in both individual molecules and gas-phase bulk properties of oxidation products as a function of SO2 addition. SO2 perturbations impacted the oxidation systems of α-and β-pinene, leading to an ensemble of products with a lesser degree of oxygenation than unperturbed systems. These changes may be due to shifts in the OH:HO2 ratio from SO2 oxidation and/or to SO3 reacting directly with organic molecules. Van Krevelen diagrams suggest a shift from gas-phase functionalization by alcohol/peroxide groups to functionalization by carboxylic acid or carbonyl groups, consistent with a decreased OH:HO2 ratio. Increasing relative humidity dampens the impact of the perturbation. This decrease in oxygenation may impact secondary organic aerosol formation in regions dominated by biogenic emissions with nearby SO2 sources. We observed sulfur-containing organic compounds following SO2 perturbations of monoterpene oxidation; whether these are the result of photochemistry or an instrumental artifact from ion-molecule clustering remains uncertain. However, our results demonstrate that the two monoterpene isomers produce unique suites of oxidation products.