2011 Progress Report: Sources, Composition, Variability and Toxicological Characteristics of Coarse (PM10-2.5) Particles in Southern California

EPA Grant Number: R833743
Title: Sources, Composition, Variability and Toxicological Characteristics of Coarse (PM10-2.5) Particles in Southern California
Investigators: Sioutas, Constantinos
Current Investigators: Sioutas, Constantinos , Cho, Arthur K. , Froines, John R. , Moore, Katharine F. , Nel, Andre E. , Schauer, James J.
Institution: University of Southern California
Current Institution: University of Southern California , University of California - Los Angeles , University of Wisconsin - Madison
EPA Project Officer: Chung, Serena
Project Period: November 1, 2007 through October 31, 2009 (Extended to October 31, 2012)
Project Period Covered by this Report: November 1, 2010 through October 31,2011
Project Amount: $1,120,641
RFA: Sources, Composition, and Health Effects of Coarse Particulate Matter (2006) RFA Text |  Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter

Objective:

The objective of this study is to provide the much-needed information on the relationships between coarse particulate matter (PM) sources, spatial and seasonal characteristics, and toxicity in Southern California. The multidisciplinary research currently under way combines ambient measurements, exposure assessment and toxicology. The results of this study – the Los Angeles Basin (LAB) Coarse PM Study – will be integrated with other major research efforts currently under way in Southern California, including the EPA-funded Southern California PM Center.

Progress Summary:

During Year 1, the LAB Coarse PM Study performed the following tasks: 

  • Designed, assembled, tested and deployed 10 outdoor coarse PM samplers to the field to collect the time-integrated filter samples across the Los Angeles Basin. Field sampling campaign commenced in April 2008 (Q2) and the weekly collection of coarse PM samples, each integrated 24 hours sampling time, continued uninterruptedly until May 2009 (the end of Q2).
  • Designed, assembled, tested and deployed two indoor coarse PM samplers to the field to collect the indoor filter samples in two indoor sites associated with their corresponding outdoor sites. Phase I of the indoor sampling started in mid-July 2008 (Q3) and continued successfully for 9 consecutive weeks through early September 2008 (Q4). Collection of a single 24-hour integrated weekly sample was carried out concurrently with the operation of the associated outdoor coarse PM sampler.
  • Following factory recalibration and testing at USC, three tapered element oscillating microbalance (TEOM) units modified to measure coarse PM only were deployed to sampling sites in Riverside, Lancaster and downtown Los Angeles to provide continuous hourly data of ambient coarse PM concentration. Deployment commenced during April and May 2008 (Q2) and measurements continued through the end of the campaign.
  • Detailed field sampling maintenance protocols were developed for the collection of both the time-integrated filter samples and continuous data for the regular weekly visit to each site.
  • Supporting hourly air quality data (e.g., meteorological parameters) were acquired for each coarse PM sampling site covering the period of concurrent time-integrated filter sampling from Q2 of 2008 through Q2 of 2009.
  • The mass concentration of each filter was determined by the gravimetric measurement of the filters in sampling each site on an ongoing basis.

During Year 2, the LAB Coarse PM Study performed the following tasks: 

  • Completed the collection of weekly 24-hr integrated filter samples starting from early-April 2008 (Q2) to the end of May 2009 (14 months). The coarse PM samplers at all of the sites except sites in Los Angeles, Lancaster and Riverside were disassembled. The three samplers in the aforementioned sites were modified and designated for the intensive coarse PM sampling campaign.
  • Designed, assembled, tested and deployed the coarse PM samplers to the field using an additional set of USC virtual impactor (VI) samplers for winter and summer intensive campaigns in 3 of the 10 sites representing distinct regions of Los Angeles Basin. The purpose of the intensive campaign is to collect samples in four distinct daily time periods to assess the diurnal variations in coarse PM concentrations and chemical composition. Phase 1 of the intensive campaign started in mid-July 2009 (Q3) and continued successfully for 5 consecutive weeks through late August 2009 at three locations. Phase 2 of the campaign will start in mid-January 2010 (Q1) and will continue until four successful consecutive data sets are obtained.
  • QA/QC was performed on the continuous and time-integrated measurements (including measurements from intensive campaign) based primarily on the mass concentration data reported for each filter. Comparisons between the continuous and time-integrated data also helped to identify problematic data. > 88% of all collected filter samples passed QA/QC and were submitted for chemical and biological analysis.

During Year 3, the LAB Coarse PM Study performed the following tasks: 

  • The second phase of intensive campaign started in mid-January 2010 (Q1) and continued for 6 consecutive weeks.
  • All sample substrates were distributed between University of California-Los Angeles and University of Wisconsin-Madison for chemical and biological analysis.
  • The data processing started promptly after a complete data for 1 year of the study was received.

During Year 4, the LAB Coarse PM Study performed the following tasks: 

  • Complete the analysis of chemical data of the intensive campaign in Q1. A technical paper titled “Diurnal trends in coarse particulate matter composition in the Los Angeles Basin” was submitted to the Journal of Environmental Monitoring in April 2011 (Q2) and published in August 2011 (Q3).
  • Examined the historical trend of CPM mass concentrations and chemical composition in LA Basin from 1987 to 2009, as well as their linkage to past, current and proposed air quality regulations. A technical paper titled “Historical trends in the mass and chemical species concentrations of coarse particulate matter (PM) in the Los Angeles Basin and relation to sources and air quality regulations” was submitted to the Journal of the Air and Waste Management Association In August 2011 (Q3) and is accepted for publication in January 2012.
  • Received and analyzed toxicity data to investigate the relationship between oxidative potential and sources of CPM in Q2. A technical paper titled “Diurnal trends on oxidative potential of coarse particulate matter in the Los Angeles Basin and their relation to sources and chemical composition” was submitted to Environmental Science and Technology in November 2011 (Q4).

The time-integrated mass concentration results indicate that ambient coarse PM varies from 0.5 µg/m3 to more than 35 µg/m3 at the 10 sites in the Los Angeles basin. Mean 24-hour coarse PM concentrations at all sites are typically 10 µg/m3 with the exception of Lancaster site, where the average concentration is about half (5 µg/m3). Summer concentrations were typically 2 to 4 times higher than the winter concentrations at most sites. However, summer concentrations in Long Beach were lower than in the winter. Concentrations derived from both of the samplers (PCIS and USC VI) were compared to each other at 9 of the 10 outdoor monitoring sites. Agreement in the coarse PM concentrations produced by these two samplers is very reasonable (within 15% on average) with PCIS concentrations typically lower.

CPM concentration correlations between different sites reveal similar trends of CPM concentrations in nearby sites. The Long Beach site, which is located in the “source” regions of Los Angeles basin, had weak correlations with other sites, while strong correlations were observed among the urban Los Angeles sites. Correlations between measured CPM and PM2.5 were investigated. PM2.5 particles are produced predominantly from vehicular emissions, and high correlations indicate that the dominant source of coarse particles is traffic-induced resuspended PM in urban areas, where correlations were relatively higher. The relatively lower correlations in rural sites indicate that wind-blown dust is the significant contributor to CPM concentrations. Correlation of CPM and PM2.5 concentrations are much higher during winter than summer, highlighting the increasing role of wind-blown dust in windier and dryer months in summer.

To characterize the chemical composition of coarse particles, chemical constituents are divided into five major categories: 1. crustal materials and trace elements; 2. organic matter; 3. elemental carbon; 4. sea salts and 5. secondary ions. Overall, crustal materials and trace elements were the most dominant sources of coarse PM in this Basin, followed by secondary ions and organic matter. In particular, nitrate was the most abundant inorganic specie, accounted more than 17% of total reconstructed mass. Concentrations of elemental carbon were low in the coarse mode, with an average mass fraction of less than 2% across sites. Higher concentrations of sea salt were observed at the coastal sites, while crustal materials became dominant inland. The two Riverside sites experienced higher levels of organic matter, probably generated from the nearby agricultural area. Interestingly, OC was found to be highly correlated with soil dust tracers, suggesting that organic materials and mineral dust might share common origins or that organic materials might be present on the surface of mineral dust particles in the coarse mode.

The abundance and the spatial and temporal behavior of metals in coarse fraction of atmospheric particulate matter (CPM, particles smaller than 10 and larger than 2.5 µm in diameter, PM10-2.5) were studied in the Los Angeles area. Major trace element and metal sources contributing to CPM may consist of (but not limited to) re-suspended road dust, industrial materials, brake linings, tire residues, catalytic converter tracers, sea salt spray, etc. Trace metals in CPM showed distinct seasonal and temporal variations depending on the particle source from which they originate. To identify the sources of trace metal content of CPM, a principal components analysis (PCA) was performed. Five principal components of inter-correlated trace metal species were identified (crustal metals, abrasive vehicular emissions, abrasive mechanical planarization, catalyst converter material and sea salt), explaining 78.3% of total variance of CPM metal content. Mineral material, closely correlated with some of the rare earth elements, were identified as the main contributor to overall CPM mass, which accounts for 33.2% total CPM metal content, followed by abrasive vehicular tracers and noble metals from catalytic converters. The concentration of the abrasive vehicular tracers were correlated closely across more than 2 orders of magnitude, which is seen as evidence that major portions of transition metals (Cu, Ba, Fe, Sb) are released through abrasive vehicular emissions, particularly the wear of brake linings. To better understand the sources of these metal species, their temporal and spatial variations (in each identified class), were investigated with regards to the proximity of each site to major CPM sources. This yields a comprehensive data set for Los Angeles metropolitan airborne trace metals and their sources.

To investigate how the atmospheric parameters (including wind speed and direction, temperature, relative humidity, mixing height, etc.) influence the ambient coarse PM concentrations and composition, three sampling sites were set up in the Los Angeles Basin to collect coarse PM in four distinct time periods of the day (morning, midday, afternoon and overnight) in summer 2009 and winter 2010. The diurnal profile of chemical components and constituents of coarse PM differs significantly in the two seasons examined. In summer, highest levels of CPM mass, crustal materials and trace elements, vehicle abrasion, and water soluble organic carbon were observed in mid-day and/or afternoon when the wind speed was higher at the three sampling sites. In winter, the basin was characterized by stagnation conditions with low atmospheric dilution, and vehicle-induced turbulence became an important particle re-suspension mechanism when mixing height was low, as highlighted by the high levels of coarse PM mass, as well as mineral and road dust in the winter overnight period at the near freeway sampling sites. Nitrate was predominantly formed by sea salt depletion in summer, while the reactions with mineral dust particles, as well as the condensation of ammonium nitrate on PM surfaces also contributed to the formation of nitrate in winter, when sea salt levels were low.

The generation of reactive oxygen species (ROS) was used to evaluate the toxic activity of coarse particles. The diurnal variability of coarse PM-induced oxidative potential and the specific coarse PM sources/species that drive the ROS activity was determined using data from the intensive study. Overall, the diurnal profile of ROS activity was different in summer and winter. ROS activity peaked in summer mid-day/afternoon when wind speed was higher, while higher ROS activity was observed overnight in winter when traffic-induced turbulence became the primary re-suspension mechanism. Although abundant, crustal materials experienced very low water solubility and were not highly correlated with ROS activity. On the other hand, elements of anthropogenic origins such as Ba, Zn and Cu showed moderate solubility. Although relatively low in mass fraction, water-soluble V, Pd, Cu and Rh, primarily of anthropogenic origins, experienced high associations (R2 > 0.60) with ROS activity.

Future Activities:

The major objectives for the next reporting period of the LAB Coarse PM project are:

  • Continue chemical analysis (organics) of the collected samples,
  • Continue biological analysis of the collected samples,
  • Continue data analysis,
  • Prepare and present preliminary results at technical conferences, and
  • Begin and complete the upcoming technical manuscript to be submitted for peer-reviewed publication.

Data analysis and the preparation of conference presentations and technical manuscripts will continue through all four quarters of Year 5.


Journal Articles on this Report : 6 Displayed | Download in RIS Format

Other project views: All 21 publications 12 publications in selected types All 12 journal articles
Type Citation Project Document Sources
Journal Article Cheung K, Daher N, Kam W, Shafer MM, Ning Z, Schauer JJ, Sioutas C. Spatial and temporal variation of chemical composition and mass closure of ambient coarse particulate matter (PM10-2.5) in the Los Angeles area. Atmospheric Environment 2011;45(16):2651-2662. R833743 (2010)
R833743 (2011)
R833743 (Final)
  • Full-text: ScienceDirect-Full Text HTML
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  • Abstract: ScienceDirect-Abstract
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  • Other: ScienceDirect-Full Text PDF
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  • Journal Article Cheung K, Daher N, Shafer MM, Ning Z, Schauer JJ, Sioutas C. Diurnal trends in coarse particulate matter composition in the Los Angeles Basin. Journal of Environmental Monitoring 2011;13(11):3277-3287. R833743 (2011)
    R833743 (Final)
  • Abstract from PubMed
  • Abstract: RSC Publishing-Abstract
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  • Journal Article Cheung K, Shafer MM, Schauer JJ, Sioutas C. Diurnal trends in oxidative potential of coarse particulate matter in the Los Angeles Basin and their relation to sources and chemical composition. Environmental Science & Technology 2012;46(7):3779-3787. R833743 (2011)
    R833743 (Final)
  • Abstract from PubMed
  • Full-text: ES&T-Full Text HTML
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  • Abstract: ES&T-Abstract
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  • Other: ES&T-Full Text PDF
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  • Journal Article Cheung K, Shafer MM, Schauer JJ, Sioutas C. Historical trends in the mass and chemical species concentrations of coarse particulate matter in the Los Angeles Basin and relation to sources and air quality regulations. Journal of the Air & Waste Management Association 2012;62(5):541-556. R833743 (2011)
    R833743 (Final)
  • Abstract from PubMed
  • Full-text: JAWMA-Full Text PDF
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  • Abstract: JAWMA-Abstract & Full Text HTML
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  • Journal Article Moore KF, Verma V, Minguillon MC, Sioutas C. Inter-and Intra-community variability in continuous coarse particulate matter (PM10-2.5) concentrations in the Los Angeles area. Aerosol Science and Technology 2010;44(7):526-540. R833743 (2009)
    R833743 (2010)
    R833743 (2011)
    R833743 (Final)
    R831697 (Final)
  • Full-text: Taylor&Francis-Full Text HTML
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  • Abstract: Taylor&Francis-Abstract
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  • Journal Article Pakbin P, Hudda N, Cheung KL, Moore KF, Sioutas C. Spatial and temporal variability of coarse (PM10-2.5) particulate matter concentrations in the Los Angeles area. Aerosol Science and Technology 2010;44(7):514-525. R833743 (2009)
    R833743 (2010)
    R833743 (2011)
    R833743 (Final)
    R831697 (2013)
    R831697 (Final)
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  • Abstract: Taylor&Francis-Abstract
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  • Supplemental Keywords:

    Air pollution, ambient air quality, monitoring, environmental exposure, toxicology, human health, sensitive populations, environmental monitoring, air sampling, airborne particulate matter, chemical characteristics, chemical speciation sampling, source apportionment, quarter (Q)., RFA, Scientific Discipline, Air, particulate matter, Health Risk Assessment, Biology, atmospheric particulate matter, PM10, atmospheric particles, cardiopulmonary responses, human health effects, bioavailability, cardiovascular vulnerability, cardiotoxicity, coarse pm, exposure assessment

    Relevant Websites:

    The USC Aerosol Laboratory website describing the ongoing activities of Dr. Sioutas’ research group is available at http://www.usc.edu/aerosol/ Exit

    Progress and Final Reports:

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