2003 Progress Report: Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)

EPA Grant Number: R827352C003
Subproject: this is subproject number 003 , established and managed by the Center Director under grant R827352
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: Southern California Particle Center and Supersite
Center Director: Froines, John R.
Title: Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)
Investigators: Friedlander, Sheldon , Sioutas, Constantinos
Institution: University of California - Los Angeles , University of Southern California
EPA Project Officer: Chung, Serena
Project Period: June 1, 1999 through May 31, 2005 (Extended to May 31, 2006)
Project Period Covered by this Report: June 1, 2002 through May 31, 2003
RFA: Airborne Particulate Matter (PM) Centers (1999) RFA Text |  Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air


A major contribution to the atmospheric aerosol surface area comes from the ultrafine (UF) particle size range; in certain cases, much of the surface area is associated with fractal-like aggregates. The large surface area allows this aerosol size range to carry high concentrations of adsorbed compounds that may be biochemically active and likely to cause adverse health effects. Surface areas of fractal structures cannot be estimated accurately using electrical mobility or aerodynamic diameters alone. Better estimates are possible using electron microscopy, but current techniques are tedious and faster methods are being sought.

The objective of this research project is to provide new data on the surface area, primary particle size, and effective density of ambient UF particulate matter (PM). The methodology permits direct comparison of the electrical mobility diameter measured with the differential mobility analyzer (DMA) and the aerodynamic diameter measured with an impactor. New measurements of aggregate morphology and surface area were made in conjunction with a comparative study of indoor and outdoor aerosols by Professors Hinds and Sioutas.

This is one of the research projects of the Southern California Particle Center and Supersite (SCPCS). The progress for the other projects is reported separately (see reports for R827352, R827352C001 through R827352C014, and R827352C016 through R827352C021).

Progress Summary:

A workshop entitled “Emerging Issues in Nanoparticle Aerosol Science and Technology” was held at the University of California at Los Angeles (UCLA). It was chaired by the Principal Investigator, and more than 30 leading researchers in the nanoparticle aerosol field worked together at the workshop to write a 120-page report that included recommendations (National Science Foundation, 2003). Southern California Particle Center and Supersite (SCPCS) investigators who participated in this effort include Professors Sioutas, Hinds, and Turco. The workshop report is available on the SCPCS Web Site.

Aim 1: Comparison of Aerodynamic and Electrical Mobility Diameters for Atmospheric Aerosols

In this study, a comparison was made of the aerodynamic and electrical mobility diameters. The goal was to relate data from impactors and mobility analyzers that provide complementary information on aerosol characteristics.

Atmospheric aerosol was sampled using a DMA followed by an eight-stage low-pressure impactor (LPI). All samples were collected on October 17, 2003, between 1 p.m. and 4 p.m., during three 30-minute sampling periods. Each sampling period was followed by 15 minutes of measurement of the particle size distribution with the DMA and condensation particle counter and an additional 15 minutes of experimental setup. An important finding was that atmospheric UF particles with a narrow range of electrical mobility diameters can have a correspondingly wide range of aerodynamic diameters—articles in each narrow electrical mobility diameter range had aerodynamic diameters in the range of 50 to 500 nm. For particles with an electrical mobility diameter of 60, 90, or 180 nm, the count mode of particles measured was in the aerodynamic range of 75-120 nm, 240-500 nm, or 50-75 nm, respectively. Therefore, the aerodynamic diameter of the count mode of particles was larger than the electrical mobility diameter for particles of 60 and 90 nm. The aerodynamic diameter, however, was smaller than the electrical mobility diameter for particles of 180 nm. These results agree with the findings of Maricq, et al. (2000) in which aerodynamic size distributions were obtained for mobility size-selected diesel exhaust particles.

Aim 2: Comparison of Morphology and Surface Area of Indoor/Outdoor UF Aerosols

As part of the collaborative study with Professors Sioutas and Hinds, indoor and outdoor aerosols were sampled with the LPI in parallel with a scanning mobility particle sizer (SMPS) at a graduate housing complex located a few miles south of UCLA, close to the I-10 and I-405 junction. Sampling was conducted during the morning of January 14, 2004, in one of the unit’s bedrooms, which had its windows shut and doors closed off to the rest of the living area. The sampling port led to the LPI, an eight-stage LPI, with 50 percent aerodynamic diameter cutoff points of 4.0, 2.0, 1.0, 0.5, 0.26, 0.11, 0.075, and 0.05 mm for stages one through eight.

The impactor samples were analyzed by transmission electron microscopy (TEM) in the morphology studies. Twenty aggregates were analyzed on each stage for a total of 80. Each aggregate was analyzed for fractal dimension, number of primary particles, primary particle size distribution, and total and projected surface area. Particle counts for the LPI samples were made from the TEM images for the LPI samples and compared to SMPS measurements. The fraction of the total particles sampled that consisted of aggregates was determined for the LPI samples. The average primary particle size was about the same for the indoor and outdoor samples. For a given aerodynamic diameter, indoor aggregates had a higher fractal dimension and were composed of more primary particles than outdoor aggregates. Indoor and outdoor particles deposited on stage eight were composed of the same percentage of aggregates (65 to 70 %), whereas indoor particles deposited on stage seven consisted of a higher percentage of aggregates (63 %) than outdoor particles (46 %). These were the first morphological studies of their kind to our knowledge.

Journal Articles:

No journal articles submitted with this report: View all 1 publications for this subproject

Supplemental Keywords:

particulate matter, PM, quinones, polycyclic aromatic hydrocarbons, PAHs, aldehydes, ketones, metals, allergic airway disease, human exposure studies, asthma, cardiovascular effects, aerosol sampling, atmospheric aerosol, environmental monitoring, environmental statistics, California, CA, acute exposure, aerosols, air pollution, air quality, air toxics, airway disease, allergen, allergic response, ambient aerosol, assessment of exposure, asthma triggers, atmospheric chemistry, bioaerosols, biological response, childhood respiratory disease, children, dosimetry, environmental hazard exposures, environmental health hazard, environmental triggers, environmentally caused disease, epidemiology, exposure assessment, health effects, home, household, human exposure, human health effects, indoor air quality, inhaled particles, lead, outdoor air, particle concentrator, particle transport, particulate exposure, particulates, sensitive populations, toxicology, toxics,, RFA, Health, Scientific Discipline, Air, HUMAN HEALTH, particulate matter, Environmental Chemistry, Air Pollutants, Risk Assessments, Biochemistry, Health Effects, Atmospheric Sciences, ambient aerosol, asthma, particulates, morphometric analyses, human health effects, toxicology, quinones, airway disease, ambient measurement methods, allergic airway disease, air pollution, PAH, human exposure, toxicity, particulate exposure, aerosol composition, allergens, breath samples, aerosols, atmospheric chemistry, human health risk, genetic susceptibility, particle transport, particle concentrator, particle size measurement

Relevant Websites:

http://www.nano.govexit EPA
http://www.scpcs.ucla.edu/exit EPA

Progress and Final Reports:

Original Abstract
  • 1999
  • 2000
  • 2001
  • 2002 Progress Report
  • 2004
  • Final Report

  • Main Center Abstract and Reports:

    R827352    Southern California Particle Center and Supersite

    Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
    R827352C001 The Chemical Toxicology of Particulate Matter
    R827352C002 Pro-inflammatory and the Pro-oxidative Effects of Diesel Exhaust Particulate in Vivo and in Vitro
    R827352C003 Measurement of the “Effective” Surface Area of Ultrafine and Accumulation Mode PM (Pilot Project)
    R827352C004 Effect of Exposure to Freeways with Heavy Diesel Traffic and Gasoline Traffic on Asthma Mouse Model
    R827352C005 Effects of Exposure to Fine and Ultrafine Concentrated Ambient Particles near a Heavily Trafficked Freeway in Geriatric Rats (Pilot Project)
    R827352C006 Relationship Between Ultrafine Particle Size Distribution and Distance From Highways
    R827352C007 Exposure to Vehicular Pollutants and Respiratory Health
    R827352C008 Traffic Density and Human Reproductive Health
    R827352C009 The Role of Quinones, Aldehydes, Polycyclic Aromatic Hydrocarbons, and other Atmospheric Transformation Products on Chronic Health Effects in Children
    R827352C010 Novel Method for Measurement of Acrolein in Aerosols
    R827352C011 Off-Line Sampling of Exhaled Nitric Oxide in Respiratory Health Surveys
    R827352C012 Controlled Human Exposure Studies with Concentrated PM
    R827352C013 Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB
    R827352C014 Physical and Chemical Characteristics of PM in the LAB (Source Receptor Study)
    R827352C015 Exposure Assessment and Airshed Modeling Applications in Support of SCPC and CHS Projects
    R827352C016 Particle Dosimetry
    R827352C017 Conduct Research and Monitoring That Contributes to a Better Understanding of the Measurement, Sources, Size Distribution, Chemical Composition, Physical State, Spatial and Temporal Variability, and Health Effects of Suspended PM in the Los Angeles Basin (LAB)