Understanding regional oxidation capacity by comprehensive observations to constrain hydroxyl radical sources and sinks during the Southern Oxidant Aerosol Study (SOAS)

EPA Grant Number: R835400
Title: Understanding regional oxidation capacity by comprehensive observations to constrain hydroxyl radical sources and sinks during the Southern Oxidant Aerosol Study (SOAS)
Investigators: Kim, Saewung
Institution: University of California - Irvine
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2013 through March 31, 2016
Project Amount: $299,895
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 overall goal of this project is to improve our understanding of oxidation capacity in the Southeastern U.S. region where biogenic volatile organic compounds (BVOCs) play a significant role in regional photochemistry to produce photochemical ozone and secondary organic aerosols (SOA) with different anthropogenic pollution influences (especially, NOX). Our specific objectives include:

  • Providing high-resolution datasets of OH, HO2+RO2, H2SO4, NOx, and OH reactivity to the SOAS study participants and the entire scientific community.
  • Constraining OH sources including photolytic and recycling sources and OH chemical sinks by measurements
  • Understanding HOx budget and implications for SOA production by comparing measured OH ([OH]MEA), measurement constrained steady-state model calculated OH ([OH]SS) and University of Washington Chemical Mechanism (UWCM), which embedded the near-explicit chemical mechanism (MCM 3.2) calculated OH ([OH]UWCM) to assess our current HOx and SOA modeling capacity in isoprene rich environments for various NOX levels.

Approach:

deploy 1) a chemical ionization mass spectrometry system for OH/HO2+RO2/H2SO4, 2) an OH reactivity measurement system with a comparative reactivity method, and 3) a cavity ring-down spectroscopy system for NOx measurements for Southern Oxidant & Aerosol Study (SOAS). These measurements are a critical addition to the SOAS campaign comprehensive measurement suite that will provide constraints for radical and SOA sources and sinks for the highly constrained steady-state model and box-model calculations.

Expected Results:

The proposed field measurements and data analysis will provide an important constraint to understand oxidation capacity in the Southeastern U.S. that determines SOA and photochemical ozone formation. Unexpectedly high levels of OH determining oxidation capacity have been consistently reported in high isoprene environments. Therefore, the comprehensive dataset from this proposed study is needed to seamlessly constrain OH sources and sinks and improve our understanding of OH primary production and recycling mechanisms in the Southeastern U.S. These outcomes, eventually, will improve modeling capability to predict SOA and photochemical ozone in the Southeastern U.S. region.

Publications and Presentations:

Publications have been submitted on this project: View all 5 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 1 journal articles for this project

Supplemental Keywords:

ambient air, tropospheric OH, SOA, observation, Southeast

Progress and Final Reports:

2013 Progress Report
2014 Progress Report
Final Report