2003 Progress Report: Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB

EPA Grant Number: R827352C013
Subproject: this is subproject number 013 , 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: Particle Size Distributions of Polycyclic Aromatic Hydrocarbons in the LAB
Investigators: Miguel, Antonio , Cho, Arthur K. , Froines, John R. , Sioutas, Constantinos
Current Investigators: Miguel, Antonio , Eiguren-Fernandez, Arantza , 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


The objective of this research project is to measure polycyclic aromatic hydrocarbons (PAHs) from 10 nm to 2.5 μm obtained by combining a microorifice uniform deposit impactor (MOUDI) with a nano-MOUDI and using a fluorescence detector under excitation and emission conditions optimized for groups of PAHs separated by high performance liquid chromatography (HPLC). These measurements include, to the best of our knowledge for the first time, PAH measurements in the Aitken size range.

Particles with diameters (dp) in the 3-10 nm size range—formed by photochemical nucleation—have been measured in urban air and in remote locations (McMurry, et al., 2000; Kulmala, et al., 2004). Combustion-generated particles in the 10 to approximately 40 nm range have been observed in tunnel-diluted diesel exhaust and in motorway measurement studies (Collings and Graskow, 2000). Observations in tunnels and ambient air reported around the world since the mid-1960s revealed that the size distribution of elemental carbon (EC) and PAHs measured down to 50 nm showed similar shape and form. This association has been hypothesized as being the result of: (1) adsorption of PAHs on the surface of EC and/or; (2) absorption onto the liquid organic carbon (OC) layer associated with the aerosol particles. To date, limited information is available on the composition of chemical species that make up the Aitken size range (1 < dp < 50 nm); only major species, including ammonium sulfate, EC, and OC have been observed (McMurry, personal communication, 2004). Until recently, the size resolution of PAH measurements was limited to 50 nm. Recent improvements in sampling instrumentation and analytical protocols, however, permit the examination of PAHs down to 10 nm.

This is one of the projects conducted by the Southern California Particle Center and Supersite (SCPCS). The progress for the other projects is reported separately (see reports for R827352C001 through R827352C019 and R827352C021).

Progress Summary:

In the present report, we examine and analyze the results of size distribution measurements of PAHs collected during five 11.5-hour periods (August 26-30, 2002), from 7:00 p.m. to 6:30 a.m., in Riverside, located approximately 70 km downwind from central Los Angeles. Samples were composited together to allow sufficient mass on each size bin for accurate PAH quantification by HPLC with selective fluorescence detection (Eiguren-Fernandez and Miguel, 2003). The sampling system consisted of a nano-MOUDI impactor (10 nm < dp < 180 nm) behind a MOUDI impactor (180 nm < dp < 2.5 mm).

A significant fraction of the target PAH mass is found in the Aitken size range (10-32 nm), regardless of molecular weight or vapor pressure (see Figure 1). The distribution of individual PAH mass in the 10-18, 10-32, and 10-56 nm size range as a percentage of the total PAH mass measured in the 10 nm-2.5 μm size range, and the species log subcooled liquid vapor pressures (atm), are shown in Figure 2. It is interesting to note that for phenanthrene (PHE), anthracene (ANT), and fluoranthene (FLT), up to approximately 45 percent of their mass is found in the narrow 10-56 nm size range, an observation consistent with their absorption in the liquid OC layer and possibly adsorption on the surface of entrained EC. For the remaining PAHs, most of the mass in the Aitken range is found in the narrow 10-18 nm range. A reasonable hypothesis is that similar to the ultrafine mode, these PAHs are adsorbed on the surface of EC. It is noteworthy to mention that among the PAHs found mostly in the particle phase (benzo[k]fluoranthene [BKF] to benzo [g,h,i]perylene [BGP]), a comparatively larger fraction of dibenz [b]anthracene (DBA) is found in the 10-32 nm size range (see Figure 2). This behavior may explain why DBA concentrations observed in PM2.5 collected in six Children’s Health Study sites (Eiguren-Fernandez, 2004) are generally lower than we would expect, based on its subcooled liquid vapor pressure. Such a large fraction of DBA (an International Agency for Research on Cancer class 2a and U.S. Environmental Protection Agency class B2 toxic species) would be expected to be lost to a large extent to cyclones and the tubing walls that lead the aerosol to a filter or impactor stage. If fractal-like agglomerates (see Figure 3) produced by spark ignition and diesel engines contain PAHs, it may be argued that these particles could eventually end up in brain cells, mitochondria, and other eukaryotes. Finally, collection and chemical analysis of source and ambient nanoparticles with 1- to 4-hour time resolution, using an electrostatic (non-MOUDI) sampling system and a higher sensitivity analytical method considered by McMurry and Miguel (proposal in preparation, 2004), may provide further insights into the mechanism of formation of PAHs in the Aitken size mode.

Our observations suggest that if fractal-like particles contain PAHs and other air toxics, they may have increased deposition efficiency in the upper region of the respiratory tract. Furthermore, consideration of aerosol dynamics on the behavior of particles of 10 nm or smaller suggests that these particles may be lost to the walls of denuders, commonly used to remove vapor-phase species. When such sampling artifacts occur, interpretation of partitioning data could suffer from severe sampling artifacts, as PAHs present in the particle phase could be assigned erroneously to the vapor phase.

Nighttime PAH Size Distributions Measured in Riverside, California

Figure 1. Nighttime PAH Size Distributions Measured in Riverside, California. Samples are 5-Day 11.5-Hour Composites Taken August 26-30, 2002. Nighttime temperatures ranged from 13 to 28°C, a variation of 15°C. PAH abbreviations: PHE = phenanthrene; ANT = anthracene; FLT = fluoranthene; PYR = pyrene, BAA = benz [a]anthracene; CRY = chrysene; BBF = benzo[b]fluoranthene; BKF = benzo[k]fluoranthene; BAP = benzo[a]pyrene; IND = indeno [c-d,1,2,3]pyrene; DBA = dibenz [b]anthracene; BGP = benzo [g,h,i]perylene.

Distribution of Individual PAH Mass in the 10-56 nm Dp Size Range

Figure 2. Distribution of Individual PAH Mass in the 10-56 nm Dp Size Range as a Percent of the Total PAH Mass Measured in the 10 nm-2.5 μm Size Range. Also shown are the log subcooled liquid vapor pressures (atm) for the target PAHs.

Transmission Electron Microscopy (TEM) of Fractal-Like Particles

Figure 3. Transmission Electron Microscopy (TEM) of Fractal-Like Particles Collected at the University of California at Los Angeles’ SPH Loading Dock During Deliveries by Spark Ignition and Diesel Vehicles. The samples were collected in December 2003 on Formvar®-coated grids using a TSI Model 3089 nanometer aerosol sampler operated at 1 LPM and -10 Kev after passing through a TSI Model 3080 electrostatic classifier. TEM pictures courtesy of Sheldon K. Friendlander and Abert Chong (2004).


Kulmala M, Vehkamäki H, Petäjä T, Dal Maso M, Lauri A, Kerminen VM, Birmili W, McMurry PH. Formation and growth rates of ultrafine atmospheric particles: a review of observations. Journal of Aerosol Science 2004;35(2):143-176.

McMurry PH, Woo KS, Weber R, Chen DR, Pui DYH. Size distributions of 3-10 nm atmospheric particles: implications for nucleation mechanisms. Philosophical Transactions of the Royal Society of London Series A-Mathematical Physical and Engineering Sciences 2000;358(1775):2625-2642.

Collings N, Graskow BR. Particles from internal combustion engines - what we need to know. Philosophical Transactions of the Royal Society of London Series A-Mathematical Physical and Engineering Sciences 2000;358(1775):2611-2622.

Journal Articles:

No journal articles submitted with this report: View all 14 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, Scientific Discipline, Air, Geographic Area, HUMAN HEALTH, particulate matter, Environmental Chemistry, Health Risk Assessment, Air Pollutants, State, mobile sources, Environmental Monitoring, Health Effects, ambient aerosol, asthma, engine exhaust, epidemiology, human health effects, motor vehicle emissions, particulate emissions, automotive emissions, air pollution, automobiles, automotive exhaust, children, human exposure, diesel exhaust particles, indoor air quality, California (CA), allergens, PM characteristics, aerosols, atmospheric chemistry

Relevant Websites:

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

Progress and Final Reports:

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