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Grantee Research Project Results

NCER Grantee Research Project Results

Laboratory Studies of Tropospheric Air Pollution: Mechanism of Isoprene Oxidation

EPA Grant Number: FP917325
Title: Laboratory Studies of Tropospheric Air Pollution: Mechanism of Isoprene Oxidation
Investigators: Dodson, Leah
Institution: California Institute of Technology
EPA Project Officer: Just, Theodore J.
Project Period: September 1, 2011 through August 31, 2014
Project Amount: $126,000
RFA: STAR Graduate Fellowships (2011)
Research Category: Academic Fellowships , Fellowship - Clean Air

Description:

Objective:

This research will study the atmospheric fate of isoprene (the most prevalent non-methane hydrocarbon in the troposphere) in the presence of radicals such at OH, NO3 and Cl. Alkenes are oxidized in the presence of both radicals and oxygen to form a peroxy radical, which undergoes a suite of reactions that impact air quality. This study seeks to understand how the branching of these reaction pathways can lead to gas phase products that go on to form ozone and various secondary organic aerosol products.

Approach:

This study proposes to directly detect the peroxy radical intermediate in the gas phase using the high sensitivity analytical laser method, cavity ringdown spectroscopy (CRDS). CRDS is a spectroscopic method utilizing an optical cavity, a cell with two highly reflective mirrors (R > 99.9%) on each end, to substantially increase the effective pathlength (> km). Sensitivities of 10-6~10-8 fractional absorption per pass are achieved, magnitudes higher than traditional absorption methods (10-4). This project utilizes the fast response time, high sensitivity and large scanning range of CRDS to directly detect the peroxy radical intermediate.

Expected Results:

Direct spectroscopic detection of the isoprene peroxy radical intermediate will enable the measure of the kinetics of the peroxy radical reaction pathways. The data gained from this project will be used in atmospheric models to provide better predictions for air quality control and air pollutant regulation.

Potential to Further Environmental / Human Health Protection

This research is critical to understanding the fate of volatile organic compounds in the troposphere, particularly of isoprene. This knowledge will help to understand the formation of oxidized species and their contribution to secondary organic aerosol formation. Once a more accurate picture of the fate of isoprene and other alkenes is had, researchers can work with modelers to provide lawmakers with more information on the precursors, both anthropogenic and biogenic, of smog and aerosols that are a severe detriment to human health.

Supplemental Keywords:

isoprene, radical, nitrate, hydroxyl radical, chlorine radical, peroxy radical, oxidation, spectroscopy, air quality, atmospheric sciences, chemistry and physics, measurement, emissions standards, pollution, air, alkenes, air quality data, air pollution models, hydrocarbon oxidation,

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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