2007 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: Oberd√∂rster, G√ľnter
Title: Characterization and Source Apportionment
Investigators: Hopke, Philip K. , Prather, Kimberly A.
Current Investigators: Hopke, Philip K. , Gelein, Robert , Prather, Kimberly A.
Institution: Clarkson University , University of California - San Diego
Current 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: October 1, 2006 through September 30,2007
RFA: Particulate Matter Research Centers (2004) RFA Text |  Recipients Lists
Research Category: Health Effects , Air

Objective:

This core will provide critical information on the physical and chemical properties of ultrafine and fine aerosols to be used by health effect researchers in the other research cores. We will link state-of-the-art measurements with data analysis methods that will permit apportionment of the major source types contributing to airborne particulate matter (PM). The core will apportion particulate mater mass apportionments to support epidemiologic, toxicological, and clinical studies. We will develop methods to characterize particulate compositional changes as they are processed in the atmosphere in transit from the source to the receptor site with a focus on the identification of the chemical species contributing to the measured reactive oxygen species. We will use the data characterizing the composition of the ambient aerosol being concentrated for animal and clinical exposures in Rochester and state-of-the-art receptor models to apportion the sources of these particles.

Progress Summary:

Exposure Assessments

The particle size distribution data from the Cardiac Rehabilitation Center (indoors and outdoors) and at the NYS DEC site are being collected to support the clinical studies of heart rate variability and inflammatory markers in the blood of rehabilitation patients. We have supplied hourly summaries of the particle number concentrations in three size bins: 11 to 50 nm, 50 to 100 nm, and 100 to 500 nm. In addition, we are obtaining the DEC criteria pollutant monitoring data at their Rochester site and providing them to the biostatistics group.

The ambient particle size distribution data collected at the NYS DEC site from the end of 2001 to the present will be used in a mortality study in conjunction with Prof. Joel Schwartz and his student at the Harvard School of Public Health. We have received mortality data for Monroe County from NYS Department of Health. One of Prof. Hopke’s students visited HSPH in early July to begin this joint center project and work will begin in earnest this fall.

In conjunction with the toxicological studies, filter samples were collected from the ultrafine concentrator. A 25 mm quartz fiber filter with a flow of 5 LPM was collected for OC/EC analysis and a 25 mm Teflon filter also at 5 LPM is collected for elemental analysis using XRF.

We are participating in the Centers measurement intercomparison exercise and are currently waiting for the samples collected by UC Davis to be analyzed by EPA. We will then analyze these samples by XRF and subsequently the same samples will be digested and analyzed by ICP/MS.

During the first period of the PM centers, a multicenter study measured in vitro responses to particle samples collected in various locations around the United States. The PM samples have been analyzed and provide particle composition data. These data will be analyzed using partial least squares (PLS) analysis to explore the relationships between the observed responses and the measured compositions. The data set is rather small to perform positive matrix factorization, but the PLS analysis should provide useful information about the combinations of particle species that have the largest effects in producing the observed responses.

Source Identification in Real Time.

Research Core 1 investigators have developed a library of major particle signatures for different ambient sources. We now can use this library to immediately identify the fractional contributions of different sources in the ambient air. Figure 1 shows an example from a site near a major freeway. The accomplishment of this step is a major one; we now have the only instrument capable of identifying aerosol sources in "on the fly" apportionment. The next step will be to link ambient sampling to specific sources that can be used for in vitro and – provided that enough material can be collected

- for in vivo studies by Cores 5 and 4 investigators. Plans to run field studies this summer have been developed where sample aerosols and simultaneously source apportionment will be performed. Particle size distributions, ozone, CO, NOx, and black carbon measurements will also be measured. Alongside the suite of aerosol and gas phase measurements, a High Vol sampler will collect samples near specific sources of interest. One major sampling study will focus on the aerosols near the Long Beach (Los Angeles) harbor region, an area known to have some of the highest air pollution related health effects in the nation.

Characterization of the Reactive Oxygen Species (ROS)

As an illustrative example of a reactive hydrocarbon species that will react with ozone to form reactive oxygen species, the α-pinene reaction with ozone has been studied. The alkene-ozone reaction is initiated by addition of ozone across the carbon-carbon double bond to form a primary ozonide, that rapidly decomposes to two Criegee biradicals. The two Criegee biradical intermediates can decompose or collisionally stabilize. The two main reaction channels proposed for the formation of SOA from α­pinene ozonolysis are the Stabilized Criegee intermediate (SCI) channel and the hydroperoxide channel (Tolocka et al., 2006). Docherty et al. (2005) probed the identity of SOA formed from reactions of monoterpenes such as α-pinene with ozone, and concluded that the SOA was predominantly organic peroxides. They estimated that organic peroxides contributed to almost half the total SOA mass formed from the α­pinene-ozone reaction. Thus, we have used our ROS aerosol generator to produce samples for LC/MS analysis.

Figure 2 shows the representative mass spectra of a direct mass spectrometer infusion of the extract solution. It is observed that species with a broad range of molecular masses are formed in the ROS Generator. For the purposes of this discussion, the terms “monomeric”, “dimeric” and “trimeric” are used, albeit loosely, to describe species with m/z ratios as shown in Figure 2.

Individual species formed in the ROS generator and collected on the Teflon® filters, have been identified by collision energy induced fragmentation of the molecular ion in the sample. The fragmentation produces daughter ions resulting from fragment-induced cleavage and rearrangement resulting in the loss of neutral molecules. The daughter ions are subsequently subjected to further fragmentation, and so on, until the structure can be definitively identified. In this study, second generation daughter ions were found to be sufficient to identify the “monomeric” species.

Figure 1.

Figure 2. Representative direct mass-spec of the filter extract solution

Figure 2. Representative direct mass-spec of the filter extract solution

The classes of ‘monomeric’ compounds identified from the LC/MSnanalyses of filters collected from the ROS Generator include, but are not limited to, organic hydroperoxides, peroxides, peroxo-acids, aldehydes, and carboxylic acids. Higher molecular weight, ‘dimeric’ and ‘trimeric’, compounds were also observed in the direct mass spectra of the filter extract (Figure 2). Specific compound assignments have been made in a number of cases.

At UCSD, we have helped rebuild an EPR spectrometer that will be available to analyze samples that are collected by different activities in the Center. The system is now fully functional with a new data acquisition system and electronics. We have run some particles collected in ambient studies, and are working on establishing the best protocols for trapping and stabilizing free radicals. To this end, we have developed a method which uses an impinger that samples particles directly into solution with the spin trap. We plan to start running ambient nanoparticles starting in July. The number of spins for different types of nanoparticle samples will be measured in preparation for toxicity studies by Core 5 and 4 investigators. As an inter-Center collaboration, we will also begin running samples for the UC Davis PM Center group this summer--they are making soot-metal particle combinations in a unique set of experiments and interested in measuring the number of spins they are producing.

References:

Hasson AS, Paulson SE.  An investigation of the relationship between gasphase and aerosol-bourne hydroperoxides in urban air.  Journal of Aerosol Science 2003;34: 459-468.
 
Hung H-F, Wang C-S.  Experimental determination of reactive oxygen species in Taipei aerosols.  Journal of Aerosol Science 2001;32:1201-1211.
 
Li N, Sioutas C, Cho A, Schmitz D, Misra C, Sempf J, Wang M, Oberley J, Froines J, Nel A.  Ultrafine particulate pollutants induce oxidative stress and mitochondrial damage.  Environmental Health Perspectives 2003;111(4):455-460.
 
Squadrito GL, Cueto R, Dellinger B, Pryor WA.  Quinoid redox cycling as a mechanism for sustained free radical generation by inhaled airborne particulate matter.  Free Radical Biology & Medicine 2001;31(9):1132-1138.
 
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 2008A;42:629–635.
 
Venkatachari P, Hopke PK.  Development and evaluation of a particle-bound reactive oxygen species generator.  Journal of Aerosol Science 2008b;39:168-174.
 
Venkatachari P, Hopke PK.  Characterization of Products Formed in the Reaction of Ozone with α-Pinene: Case for Organic Peroxides.  Journal of Environmental Monitoring (in press, 2008c).

Journal Articles:

No journal articles submitted with this report: View all 19 publications for this subproject

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

Progress and Final Reports:

Original Abstract
  • 2006 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report
  • 2010 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