Grantee Research Project Results

Organic aerosol formation in the humid, photochemically-active Southeastern US: SOAS experiments and simulations

EPA Grant Number: R835412
Title: Organic aerosol formation in the humid, photochemically-active Southeastern US: SOAS experiments and simulations
Investigators: Turpin, Barbara , Carlton, Annmarie
Institution: Rutgers
EPA Project Officer: Chung, Serena
Project Period: April 1, 2013 through March 31, 2015
Project Amount: $399,928
RFA: Anthropogenic Influences on Organic Aerosol Formation and Regional Climate Implications (2012) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Climate Change , Air

Objective:

Water is the most abundant fine particulate matter species in the eastern US, and yet its impact on ambient secondary organic aerosol formation is poorly understood. This proposal makes use of aqueous OH radical oxidation experiments conducted with ambient samples and evaluation of intermediate model products to improve mechanistic linkages between emissions and secondary organic species (gases and aerosol) in the humid, photochemically-active eastern United States (RFA Q#2). The proposed research is designed to be an integral part of the Southern Oxidant and Aerosol Study (SOAS), a collaborative field campaign taking place in a southeastern location influenced by biogenic emissions and with varying impacts from anthropogenic sources (RFA Q#1). We expect this work to ultimately lead to the development of more effective air quality management through models that better capture critical atmospheric processes. We hypothesize that chemistry that takes place in atmospheric waters has a substantial impact on the formation and properties of organic aerosol (note: we expect that gas-phase chemistry followed by aqueous chemistry will form SOA which is more hygroscopic and has higher O:C ratios). Gas phase photochemical reactions fragment and oxidize organic emissions, leading to the abundant formation of small, polar compounds (e.g., acetic acid, glyoxal, methylglyoxal, glycolaldehyde, acetone) that readily partition into cloud, fog and aerosol waters. Subsequent reactions in the aqueous phase can form low volatility products (e.g., organic acid salts, oligomers) that remain in the particle phase even after water evaporation. Thus, in an environment where photochemistry and abundant liquid water coexist, gas followed by aqueous chemistry could be the predominant source of secondary organic aerosol (SOA). The SOAS campaign is an ideal opportunity to test this.

Approach:

We will: 1) compare predicted and measured aerosol water concentrations during the SOAS campaign; 2) predict concentrations of total and selected water soluble gases for comparison with SOAS measurements and to link to ambient aqueous photooxidation experiments; 3) conduct ambient aqueous photooxidation experiments using water soluble gases scrubbed from the ambient air during the SOAS campaign and model reaction kinetics in these experiments. This will enable us to evaluate the degree to which aqueous photooxidation is captured by current aqueous chemistry models and identify key precursors and products of aqueous chemistry leading to SOA formation, 4) collaborate broadly to address SOAS science goals.

Expected Results:

A better understanding of SOA formation, properties and behavior in the humid eastern U.S. including dependence on anthropogenic emissions (RFA Q #1, 2). More accurate air quality prediction enabling more accurate air quality management (EPA Goal #1). Scientific insights communicated via peer-reviewed publications and other means.

Publications and Presentations:

Publications have been submitted on this project: View all 18 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 7 journal articles for this project

Supplemental Keywords:

ambient air, environmental chemistry, fine particles, PM2.5

Progress and Final Reports:

2013 Progress Report

Final Report