Novel Measurements of Volatility- and Polarity-Separated Organic Aerosol Composition and Associated Hygroscopicity to Investigate the Influence of Mixed Anthropogenic-Biogenic Emissions on Atmospheric Aging ProcessesEPA Grant Number: R835402
Title: Novel Measurements of Volatility- and Polarity-Separated Organic Aerosol Composition and Associated Hygroscopicity to Investigate the Influence of Mixed Anthropogenic-Biogenic Emissions on Atmospheric Aging Processes
Investigators: Williams, Brent
Institution: Washington University
EPA Project Officer: Hunt, Sherri
Project Period: April 1, 2013 through March 31, 2016
Project Amount: $298,747
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:Coupling of anthropogenic and biogenic emissions and subsequent atmospheric aging processes are hypothesized to be the leading single contribution to global organic aerosol (OA) mass concentrations, and is also perhaps the least understood single contribution to OA. Improved understanding of this coupling is a high priority topic in the field of atmospheric chemistry in order to determine mitigation strategies for OA control, a pollutant that alters climate and causes detrimental health effects. The primary objective of this proposed work is to better characterize the controlling factors in enhanced secondary organic aerosol (SOA) formation from combined anthropogenic and biogenic emission sources through innovative laboratory and field studies using novel instrumentation.
Approach:The proposed project consists of four key components: 1) Development of new instrumentation to obtain new insights on the inherent complex chemistry and composition of SOA formation and evolution, 2) Deployment to a large field study (Southern Oxidant & Aerosol Study), 3) Controlled laboratory studies using a custom emissions/combustion chamber, a flow-tube Potential Aerosol Mass (PAM) reaction chamber, and a large suite of chemical and physical measurement systems, and 4) A second field study (East St. Louis) which incorporates key lessons from the initial field study and extensive laboratory studies to perform in-field controlled oxidation experiments (utilizing the PAM reaction chamber) to test the sensitivity of ambient SOA formation and transformation to perturbations in oxidation intensity and precursor composition. Both proposed field studies have the advantage of being in regions of mixed biogenic and anthropogenic emissions, and are at locations with sufficient infrastructure and supporting measurements. The infrastructure for proposed laboratory measurements already exists in the PI's laboratory, so will require limited setup time and cost. The proposed instrument development is focused on two measurement methods: 1)Volatility and Polarity Separator (VAPS) for in-situ, high time-resolution, volatility-and polarity-separated OA composition, and 2) a modified Hygroscopicity-Tandem Differential Mobility Analyzer (HTDMA) for measurement of particle hygroscopicity, particle volatility, and size-dependent oxidation effects.
Through the proposed study, novel measurements of compositional and hygroscopic changes during SOA formation and transformation under various mixtures of biogenic- anthropogenic sources will be obser\led: 1) under unperturbed conditions, allowing meteorology to deliver various emission mixtures (SOAS), 2) in a laboratory setting, with complete control over oxidant levels, emission types, specific particle coatings, etc., and 3) with ambient emissions of gases/particles, but having the option to perturb the oxidation level, or add specific biogenic or anthropogenic gases/particles to the photochemical reaction mixture (East St. Louis). This study design will lead to many new insights on the formation processes and atmospheric transformations of SOA produced from mixed biogenic-anthropogenic emissions, and the associated potential for climate interactions.