Physical and Chemical Research on Particulate Matter

This page updated July 17, 2003.


Source Apportionment of Fine and Ultrafine Particles in California
  This project is a statistical source apportionment study of airborne fine and ultrafine particles in California. Airborne particle samples collected with filter-based samplers and Micro Orifice Uniform Deposit Impactors (MOUDIs) will be analyzed for the quantity of unique chemical tracers that can be used in a source apportionment analysis. The final stage of the MOUDI collects particles exclusively in the ultrafine particle size range. Apportionment of the particulate matter collected on this stage will effectively reveal the contribution that different sources make to ultrafine particle concentrations. Three major parts of research are proposed: 1) characterize ultrafine particles at the source, 2) characterize fine particles collected during SCOS97 and 3) perform source apportionment analysis for collected fine and ultrafine particles.


Determination of the Contributions of Light-Duty and Heavy-Duty Vehicle Emissions to Ambient Particles in California
  Diesel exhaust particles, a significant fraction of total motor vehicle PM emissions, are classified as a Toxic Air Contaminant. Developing plans to reduce human exposure to these air pollutants requires data on the origins of ambient aerosols, both to identify source-specific concentrations of primary particles, and to understand the processes that form secondary particles in the air. Real-time single particle analysis using aerosol time-of-flight mass spectrometry (ATOFMS) is capable of discriminating among sources based on characteristic particles and particle populations that are irretrievably mixed in conventional filter and impactor samples.
  The objective of this project is to demonstrate source-specific (diesel vs. gasoline) detection of ambient particles emitted by motor vehicles. The approach involves limited new source sampling to better characterize "fresh" diesel exhaust particles, reanalysis of existing ambient monitoring data, and new field sampling along roadways, in a tunnel, and in a complex urban setting. The expected results are techniques to perform time-resolved (possibly real-time) source apportionment for motor vehicle particulate emissions.


The Physical and Chemical Characterization of Ultrafine and Nanoparticle Particulate Matter Emissions from Gasoline and Diesel On-Road Motor Vehicles
  The objective of this project was to characterize number concentrations and gross chemical composition of ultrafine particles (<.1 mm) near a freeway. Simultaneous measurements were made of vehicle activity and particle number concentration and size distributions near a major interstate in Northern California (I-80). Continuous measurements were made in the morning and evening at a distance of 5 m from the freeway shoulder. Two summer and two winter sampling campaigns were completed. Heavy-Duty vehicle traffic volumes ranged from 10 percent to 15 percent of total volume during the study. Size-segregated mass was collected using impactors and IMPROVE samplers for organic chemical analysis. UCD researchers found particle concentrations at least one order of magnitude above background concentrations near a freeway dominated by light-duty traffic. The lack of correlation between particle concentrations and traffic volume, however, was unexpected. Researchers hypothesize that vehicle wakes may have affected the SMPS measurements; a larger sampling distance from the freeway was recommended. Chemical analysis results are pending.


Concentrations and Size Distribution of Ultrafine Particles Near a Major Highway and Study of Ultrafine Particles and Other Vehicular Pollutants Near a Highway with Heavy-Duty Diesel Traffic
  The objective of these studies was to characterize particle number and size distributions (6-220 nm) in the vicinity of two highways, 405 and 710. Freeway 405 is dominated by gasoline vehicles, >95 percent, and freeway 710 contains a large fraction of heavy-duty diesel vehicles, >25 percent. Measurements were taken at six distances downwind and at a reference location 200 m upwind of the freeways. Ultrafine particle number concentration measured at 300m downwind was indistinguishable from upwind background concentration. The size distributions at 30 m downwind of the freeways were very similar: three modes were observed; the first mode 10-20 nm was slightly higher near the highway 405 (gasoline vehicles), the second mode ~30 nm is approximately 30 percent higher near the diesel influenced highway, 710, and the last mode ~70nm is comparable to background concentrations.


Oxygenated Organics in Gas and Fine Particle Diesel Emissions for Source Apportionment
  The objective of this project is to characterize the oxygenated organic compounds found in "real world" diesel emissions and to assess whether such oxygenated compounds or patterns of them may be used as tracers of diesel emissions in source apportionment studies. The focus of the study will be on sampling, identification and quantification of aliphatic and aromatic carbonyls, including oxo-polyaromatic hydrocarbons (PAH), multifunctional carbonyls and mono  and di-organic acids. Preliminary PM2.5 data indicate that certain carbonyls and multifunctional carbonyls may be unique tracers of diesel exhaust.
  The present research will: 1) develop a new annular denuder filter sampler in which the denuder is coated with derivatizing reagents that selectively sample carbonyls, multifunctional carbonyls and carboxylic acids and 2) use this method to sample gaseous and fine particulate matter from emissions in the Caldecott tunnel and from heavy-duty diesel vehicles.


Initial Exploration of Advanced Data Analysis Methods to Assist Air Quality Management
  The objective of this project is to demonstrate the usefulness of the data analysis tool - positive matrix factorization (PMF) - to resolve the sources of ambient aerosols. This objective will be realized through two major data analysis tasks. The first task is to perform PMF on three sets of Interagency Monitoring of Protected Visual Environments (IMPROVE) data. Two IMPROVE sites are at high altitude and the objective is to separate and quantify the influence of Asian dust on observed mass concentrations. The third site is downwind of Los Angeles and the primary objective is to determine if gasoline and diesel emissions can be separately identified and quantified using the chemically speciated data.
  The second task is to apply factor analysis to Aerosol Time-of-Flight Mass Spectrometry data and ascertain the ability of this method to separate diesel from gasoline motor vehicle emissions. As part of this second task, test calibration models will be developed that permit estimation of the composition of the bulk ambient aerosol composition from single particle ATOFMS data.


Research on Background Aerosols in California
  This project is "in-house," involving cooperative data analysis by ARB staff for public data (IMPROVE) and new measurements from intensive field programs over the Pacific Ocean (UC Davis). This has already resulted in a paper to be published later this month in JGR identifying Asia as the major source of PM2.5 soil aerosol in the Sierra Nevada and Cascade ranges.
  Work in progress is developing speciated PM2.5 aerosol data for other material coming over the Pacific (primarily from China), including urban and industrial aerosols (sulfate, carbon, etc.). A final report covering the concentration, chemical composition, frequency and spatial distribution of fine aerosols coming over the Pacific is planned for 2003.


Methods Development for Advanced Multivariate Aerosol Receptor Analysis
  This project is a contract with Dr. Philip Hopke of Clarkson University. The project involves analysis of IMPROVE samples to develop profiles of emissions from upwind source areas, and analysis of single-particle data collected during the CRPAQS field program to develop enhanced source identification techniques for use in receptor analysis.


Lake Tahoe Atmospheric Deposition Study (LTADS)
  The spectacular clarity of Lake Tahoe has been diminishing for several decades, driven by increasing amounts of algal nutrients and fine-grained sediment. Measurements of lake water chemistry and limited atmospheric data in the basin indicate that a significant fraction of the input of nutrients and fine particles may be transported to the lake through the air.
  The ARB is cooperating with water quality and land management agencies in the Lake Tahoe basin and scientific researchers from Nevada and California in a coordinated study of the sources of material impacting the lake. The ARB's LTADS' study will assess atmospheric inputs to the lake from all sources, including transport from outside the basin and locally pollutants generated within the basin. This requires full characterization of the size, concentration and chemical composition of all aerosols in the Tahoe region. Field work is just starting and intensive data collection will run for at least the next year. The ARB will report findings to Lahontan Regional Water Quality Control Board and the Tahoe Regional Planning Agency, who have lead responsibilities for protecting water quality in the basin.


Methods Validation for Soil Stabilization for Abandoned Farmland
  The Antelope Valley Dustbusters Project is a cooperative effort of ARB, local air pollution control agencies, local government, federal agencies and private industry to develop effective means to control dust from abandoned irrigated farmland. The major effort is focused on reducing PM10 impacts to nearby residents and to develop techniques that may be useful in other localities.
  Secondary benefits accrue from learning about soil dust processes, since fine-grained soils can produce significant amounts of PM2.5 and contribute to long range transport and regional PM2.5 loadings. This latter effect may have particular significant for Regional Haze analysis for some Class I areas in California.