2010 Progress Report: Characterization and Source Apportionment

EPA Grant Number: R832415C001
Subproject: this is subproject number 001 , established and managed by the Center Director under grant R832415
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Rochester PM Center
Center Director: Oberdörster, Günter
Title: Characterization and Source Apportionment
Investigators: Hopke, Philip K. , Gelein, Robert , Prather, Kimberly A.
Institution: Clarkson University , University of California - San Diego , University of Rochester
EPA Project Officer: Chung, Serena
Project Period: October 1, 2005 through September 30, 2010 (Extended to September 30, 2012)
Project Period Covered by this Report: June 30, 2009 through July 1,2010
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

Characterize the nature of the particle-bound reactive oxygen species resulting from major biogenic VOC reactions with ozone

Progress Summary:

The reactions of ozone with monoterpenes proceed via the formation of multiple oxygenand carbon-centered free radical species. These radical species are highly reactive and thus, have generally not been measureable. A method for their detection and characterization is needed to preserve these radicals for a sufficiently long time to permit analyzes to be performed. Radicaladdition reactions, also called spin trapping techniques, allow the detection of short-lived radicals. This approach has been applied to products from the α-pinene/ozone reaction. Secondary organic aerosol (SOA) from a reaction chamber was collected on quartz fiber filters and extracted. The extracts were then reacted with either 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) or diethyl-(2-methyl-1-oxido-3,4-dihydro-2H-pyrrol-2-yl) phosphonate (DEPMPO) followed by analysis with ion-trap tandem mass spectrometry (MSn) using electrospray ionization (ESI) in the positive scan mode. Tandem mass spectrometry (MS2) was performed to identify the radical species. The formation of α-pinene/ozone first generation products involves a number of intermediate species and some of these reactive radicals are seen in Figure 1. Characteristic fragments with m/z 114, m/z 130 and m/z 148 with the DMPO trap, and m/z 236, m/z 252, and m/z 270 with the DEPMPO trap indicate the existence of alkyl, alkoxyl and peroxyl radicals, respectively. Based on the tandem mass spectrometry results, chemical structures of these radicals were tentatively identified and found to be species with molecular formulas C9O2H13 (153 Da), C10O3H15 (183 Da), and C10O4H15 (199 Da), respectively Chemical structures of several organic radicals have been tentatively identified. Radicals with molecular masses 125 Da and 157 Da, detected in this study, have not been previously reported. Structures of these radicals and formation mechanisms have been elucidated.
 
 
Figure 1. Proposed reaction mechanism of α-pinene and ozone leading to the formation of observed radicals
 
This work provides a clearer picture of the nature of some short-lived but highly reactive species that are associated with freshly formed secondary organic aerosol. The work provides a better understanding of the mechanism of formation of SOA and ROS and the nature of the reactive species to which humans are exposed.
 
We hypothesized that particle-bound ROS might be an important contributor to the health effects resulting from oxidative stress. Thus, understanding the nature of the ROS components, their formation and their reactivity provides a better basis for understanding their potential role in inducing adverse effects.
 
Understanding this oxidative chemistry is important to a fuller understanding of the formation of SOA and associated ROS in the ambient atmosphere. It helps to provide additional insights into the role composition might play in inducing adverse health effects and provides additional information regarding the implications of controlling ozone, a criterion air pollutant.
 
If ROS associated with biogenic SOA is a driver of adverse health effects, then regulatory action would need to focus more on ozone control as a basis for controlling secondary particulate matter.
 
Sub-project: Core 1/UC San Diego
 
Ultrafine particles are too small to optically scatter light and thus the ATOFMS cannot detect and measure the chemistry of these particles, at least efficiently, at typical ambient concentrations. We have found a way to get around this impediment by growing ultrafine particles with a growth tube before ATOFMS analysis. A prototype growth tube developed by Dr. Susanne Hering at Aerosol Dynamics, Inc. had been used in previous years, however, the system was unable to run for extended periods of time.
 
Over the past year, the Prather group has worked with Dr. Hering a new design and focused on calibration, testing, and optimization of a new version of a growth tube used for particle detection. This system has been used to further characterize ultrafine particles in ambient air in several studies in California. The growth tube has also been used to capture ambient particles into a small volume of liquid that can then be used for in vitro studies conducted at Rochester. A range of aerosol sources of interest have been identified which include vehicles, biomass burning, and ships. We collected samples using the newly developed growth tube in two locations in close proximity to ships and a local freeway and these are now being tested in in vitro studies at Rochester.
 
The advantage to the growth tube is it can be used to efficiently collect ultrafine particles into small volumes of solution. This gets around the problems associated with filters where particles can be deposited but it is quite difficult to remove the material for in vitro studies. The limitation to the growth tube is the low air flow rates which limit the amount of material that can be collected in a short time period. With this in mind, we are now working with Dr. Hering on a higher flow rate growth tube that we plan to use to collect higher masses of aerosols for in vitro analysis. This system will allow aerosols to be collected in one-tenth the amount of time as the previous version of the flow tube. This year the goal will be to collect and study a broad range of aerosol sources. We also plan to react ambient aerosols collected into aqueous solutions with oxidants and photochemistry to age them to study the differences in the endpoint responses for aged ambient aerosols.

Future Activities:

We are working to determine if the formation of these free radical species influence the formation of low volatility oligomeric SOA that contributes to increased particle mass.


Journal Articles on this Report : 4 Displayed | Download in RIS Format

Other subproject views: All 19 publications 13 publications in selected types All 13 journal articles
Other center views: All 190 publications 156 publications in selected types All 143 journal articles
Type Citation Sub Project Document Sources
Journal Article Pavlovic J, Hopke PK. Technical note: detection and identification of radical species formed from α-pinene/ozone reaction using DMPO spin trap. Atmospheric Chemistry and Physics Discussions 2009;9(6):23695-23717. R832415 (2009)
R832415 (2010)
R832415 (2011)
R832415 (Final)
R832415C001 (2009)
R832415C001 (2010)
R832415C001 (2011)
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  • Journal Article Spencer MT, Shields LG, Prather KA. Simultaneous measurement of the effective density and chemical composition of ambient aerosol particles. Environmental Science & Technology 2007;41(4):1303-1309. R832415 (2010)
    R832415 (2011)
    R832415 (Final)
    R832415C001 (2006)
    R832415C001 (2010)
    R832415C001 (2011)
    R827354 (Final)
    R831083 (Final)
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  • Journal Article Venkatachari P, Hopke PK. Development and laboratory testing of an automated monitor for the measurement of atmospheric particle-bound reactive oxygen species (ROS). Aerosol Science and Technology 2008;42(8):629-635. R832415 (2007)
    R832415 (2008)
    R832415 (2010)
    R832415 (2011)
    R832415 (Final)
    R832415C001 (2008)
    R832415C001 (2010)
    R832415C001 (2011)
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  • Journal Article Yue W, Stolzel M, Cyrys J, Pitz M, Heinrich J, Kreyling WG, Wichmann H-E, Peters A, Wang S, Hopke PK. Source apportionment of ambient fine particle size distribution using positive matrix factorization in Erfurt, Germany. Science of the Total Environment 2008;398(1-3):133-144. R832415 (2007)
    R832415 (2008)
    R832415 (2010)
    R832415 (2011)
    R832415 (Final)
    R832415C001 (2008)
    R832415C001 (2010)
    R832415C001 (2011)
    R832415C002 (2006)
    R832415C002 (2008)
    R832415C002 (2010)
    R832415C002 (2011)
    R827354 (Final)
    R834797 (2016)
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  • Supplemental Keywords:

    RFA, Scientific Discipline, Air, particulate matter, Environmental Chemistry, Health Risk Assessment, Biochemistry, cardiopulmonary responses, chemical characteristics, fine particles, atmospheric particles, airway epithelial cells, airborne particulate matter, human exposure, aerosol composition

    Relevant Websites:

    None

    Progress and Final Reports:

    Original Abstract
  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report
  • 2011 Progress Report
  • Final Report

  • Main Center Abstract and Reports:

    R832415    Rochester PM Center

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R832415C001 Characterization and Source Apportionment
    R832415C002 Epidemiological Studies on Extra Pulmonary Effects of Fresh and Aged Urban Aerosols from Different Sources
    R832415C003 Human Clinical Studies of Concentrated Ambient Ultrafine and Fine Particles
    R832415C004 Animal models: Cardiovascular Disease, CNS Injury and Ultrafine Particle Biokinetics
    R832415C005 Ultrafine Particle Cell Interactions In Vitro: Molecular Mechanisms Leading To Altered Gene Expression in Relation to Particle Composition