Assessing the oxidative potential of isoprene-derived epoxides and secondary organic aerosol. (April 2016)

• Record Type: Journal Article
• Authors: Kramer, Amanda J.; Rattanavaraha, Weruka; Zhang, Zhenfa; Gold, Avram; Surratt, Jason D.; Lin, Ying-Hsuan
• Is Part Of: Atmospheric environment. Volume 130(2016)
• Page Start: 211
• Page End: 218
• Publication Date: 2016-04
• Subjects: PM2.5 -- DTT assay -- Oxidative stress -- Health effects; Air -- Pollution -- Periodicals; Air -- Pollution -- Meteorological aspects -- Periodicals; 551.51
• DOI: 10.1016/j.atmosenv.2015.10.018
• Languages: English
• ISSNs: 1352-2310

Abstract

Abstract: Fine particulate matter (PM2.5 ) is known to contribute to adverse health effects, such as asthma, cardiopulmonary disease, and lung cancer. Secondary organic aerosol (SOA) is a major component of PM2.5 and can be enhanced by atmospheric oxidation of biogenic volatile organic compounds in the presence of anthropogenic pollutants, such as nitrogen oxides (NOx ) and sulfur dioxide. However, whether biogenic SOA contributes to adverse health effects remains unclear. The objective of this study was to assess the potential of isoprene-derived epoxides and SOA for generating reactive oxygen species (ROS) in light of the recent recognition that atmospheric oxidation of isoprene in the presence of acidic sulfate aerosol is a major contributor to the global SOA burden. The dithiothreitol (DTT) assay was used to characterize the ROS generation by the isoprene-derived epoxides, trans -β-isoprene epoxydiol (trans-β-IEPOX) and methacrylic acid epoxide (MAE), and their hydrolysis products, the 2-methyltetrol diastereomers (2-MT), 2-methylglyceric acid (2-MG), their organosulfate derivatives, as well as an isoprene-derived hydroxyhydroperoxide (ISOPOOH). In addition, ROS generation potential was evaluated for total SOA produced from photooxidation of isoprene and methacrolein (MACR) as well as from the reactive uptake of trans -β-IEPOX and MAE onto acidified sulfate aerosol. The high-NOx regime, which yields 2-MG-, MAE- and MACR-derived SOA has a higher ROS generation potential than the low-NOx regime, which yields 2-MT, IEPOX- and isoprene-derived SOA. ISOPOOH has an ROS generation potential similar to 1, 4-naphthoquinone (1, 4-NQ), suggesting a significant contribution of aerosol-phase organic peroxides to PM oxidative potential. MAE- and MACR-derived SOA show equal or greater ROS generation potential than reported in studies on diesel exhaust PM, highlighting the importance of a comprehensive investigation of the toxicity of isoprene-derived SOA. Highlights: ROS potential tested for isoprene-, MACR-, IEPOX-, and MAE-derived SOA systems. ROS potential tested for synthetic IEPOX, MAE, 2-MT, 2-MG, organosulfates, and ISOPOOH. High-NOx conditions produce SOA that is more oxidizing compared low-NOx conditions. MACR SOA had a higher ROS potential than diesel PM + ozone and daytime diesel PM. Organic peroxides could be major contributors to observed oxidative potential.