Impacts of Anthropogenic Emissions in the Southeastern U.S. on Heterogeneous Chemistry of Isoprene-Derived Epoxides Leading to Secondary Organic Aerosol Formation

EPA Grant Number: R835404
Title: Impacts of Anthropogenic Emissions in the Southeastern U.S. on Heterogeneous Chemistry of Isoprene-Derived Epoxides Leading to Secondary Organic Aerosol Formation
Investigators: Surratt, Jason D.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Chung, Serena
Project Period: April 1, 2013 through March 31, 2016 (Extended to March 31, 2017)
Project Amount: $300,000
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Global Climate Change , Climate Change , Air

Objective:

The underlying hypothesis of this study is that anthropogenic emissions enhance isoprene SOA formation through the heterogeneous chemistry of isoprene-derived epoxides, possibly leading to light-absorbing SOA in the southeastern U.S. The specific objectives to evaluate this hypothesis include: (1) Leveraging our ongoing Look Rock, TN, field site during the community-led Southern Oxidant & Aerosol Study (SOAS) in summer 2013 to evaluate how isoprene SOA formation chemistry varies between regional and urban influenced air masses; (2) Evaluate the effects of relative humidity, aerosol acidity, and seed aerosol type on the heterogeneous chemistry of isoprene-derived epoxides leading to SOA and how this might yield light-absorbing aerosol constituents (i.e., brown carbon); (3) Evaluate gaseous yields of epoxides from isoprene oxidation under varying initial levels of nitric oxide.

Approach:

We will directly couple our capability in synthetic organic chemistry with our involvement in the SOAS field campaign and our pre- and post-campaign UNC smog chamber studies. We have established synthetic routes for the isoprene-derived epoxides and their selected SOA products. These key chemicals will be provided for advanced mass spectrometry techniques, such as a chemical ionization high-resolution time-of-flight mass spectrometry (CIHR- TOFMS) and an aerosol chemical speciation monitor (ACSM), that will be utilized to quantitatively measure in real-time the gas- and aerosol-phase constituents related to isoprene oxidation. Furthermore, we will chemically characterize PM2.5 samples collected onto filters during the SOAS campaign and from our smog chamber studies for known isoprene SOA tracers using gas chromatography/mass spectrometry (GC/MS) and ultra performance liquid chromatography/electrospray ionization high-resolution mass spectrometry (UPLC/ESI-HRMS). UPLC-diode array detection (DAD) will also be used to detect and characterize brown carbon (or light-absorbing) aerosol constituents.

Expected Results:

The proposed activities will yield the formulation of parameterizations that can be incorporated into SOA models that will lead to improvement in the ability to simulate isoprene SOA formation in the southeastern U. S. Specific results include: (1) characterization of reaction pathways that control the oxidation of isoprene in the southeastern U. S. and quantitative assessment of the impact of anthropogenic emissions on these pathways; (2) discover the links between isoprene oxidation, anthropogenic influences, and formation of isoprene-derived SOA; (3) determine the importance of RH, aerosol water content, pre-existing PM, and aerosol acidity on isoprene SOA formation enhanced by anthropogenic emissions; and (4) characterization of isoprene-derived SOA constituents leading to light-absorbing brown carbon. These results will provide improvements that are essential so that air quality models can be used with increased confidence in predicting organic PM2.5.

Publications and Presentations:

Publications have been submitted on this project: View all 36 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 16 journal articles for this project

Supplemental Keywords:

atmosphere, particulates, environmental chemistry, biogenic volatile organic compounds, terpenes

Progress and Final Reports:

2013 Progress Report
2014 Progress Report
2015 Progress Report
Final Report