Grantee Research Project Results
2013 Progress Report: 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
EPA Grant Number: R835402Title: 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: Chung, Serena
Project Period: April 1, 2013 through March 31, 2016
Project Period Covered by this Report: April 1, 2013 through March 31,2014
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 , Climate Change , Air , Early Career Awards
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.
Progress Summary:
In year one of this project, we completed development of a volatility and polarity separator (VAPS) for improved chemical characterization of organic aerosol and deployed it on two different field studies. We also built a custom multi-channel tandem differential mobility analyzer (MC-TDMA) for particle sizing, volatility, and hygroscopicity, and deployed it on a first field study. We completed an initial round of laboratory-based measurements of the oxidation of isoprene (the dominant biogenic emission globally and in the southeastern United States) under varying concentrations, oxidant exposures, and mixtures with NOx. A major lesson in the first round of lab studies was to improve the design and operation of the PAM reaction chamber to ensure stable mixing and oxidation of precursor gases, and development of improved methods of calibrating oxidant exposures for each individual experiment. Major observations from VAPS deployment to Centreville, AL, as part of the Southern Oxidant and Aerosol Study (SOAS) include observation of highly oxygenated aerosol and identification of several major types of oxygenated biogenic aerosol, the largest contribution coming from low-NOx isoprene oxidation. Very little anthropogenic (from human activity) aerosol was observed. VAPS did observe minor components of organonitrates and organosulfates, which will be investigated further and compared to observations from offline filter-based analyses.
Figure 1. VAPS data from volatility and polatiry mode
(highly oxygenated SOAS sample in top panel, and
hydrocarbon loaded St. Louis sample in bottom panel)
Each data point also contains high reslolution MS
information
Figure 2. VAPS data from volatility and oxidation mode (SOAS sample). High
resolution MS data allows determination fo exact O:C rations of molecules of
fragments (red dots, sized by abundance) separated by volatility. Volatility
separated average totao O:C also displayed here (in gray).
Future Activities:
In the next reporting period, we will continue to improve VAPS and MC-TDMA operation, including implementation of a miniature-GC on the VAPS and faster mode-switching on the MC-TDMA (especially as we switch to hygroscopicity mode that currently takes additional time to stabilize relative humidity settings). We are currently performing a second intensive lab study using our emissions/combustion chamber, PAM reaction chamber, and a wide variety of gas and particle characterization instrumentation (including aerosol chemical characterization by VAPS and aerosol volatility/hygroscopicity by MC-TDMA). Finally, we will begin planning of a second field deployment to the St. Louis region and will work to scale up the project with hopes of having at least two field sites, one that would be upwind of the urban area relative to the Ozark Mountains and another downwind of the urban area to compare differences with the addition of anthropogenic pollutants.
Journal Articles:
No journal articles submitted with this report: View all 36 publications for this projectSupplemental Keywords:
Air quality and air toxics, global climate change, atmospheric chemistry, organic aerosol, mass spectrometry, biogenic and anthropogenic emissions, atmospheric oxidationProgress and Final Reports:
Original AbstractThe 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.