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Air Research

PM Sources Science


Photo of trucks at a plant


Research to understand the chemical characteristics and different sources of air pollutants is important to the U.S. Environmental Protection Agency in developing effective policies and standards to protect the public and environment.

The science of source characterization involves measuring emissions from a pollution source, such as a diesel truck or other man-made or natural source, and determining the chemical properties of these emissions. Techniques commonly used to perform these analyses include gas chromatography, X-ray fluorescence, and ion chromatography.

While these tools are adequate for many purposes, more accurate emission-analysis methods are required to fully assess airborne particulate matter (PM), provide needed data to chemical emissions inventories, improve air toxics modeling, accurately determine the health risks from exposure, and better understand how to control and reduce emissions.

As new technologies are developed for engine design, industrial production, and even the combustion fuels themselves, advances in methods to evaluate and analyze their emissions are critical.  High-tech source characterization methods that provide real-time feedback and results are needed during short, transitional events such as engine startups, changes in power level, and changes in combustion output.  New methods with enhanced sensitivities are also required when analyzing sources that emit minute amounts of air pollutants over wide dispersion areas, such as motor vehicles.

Scientific Objective

Scientists in the Clean Air Research Program in EPA’s Office of Research and Development are dedicated to advancing the science to understand sources of air pollutants through the development of new technology and other tools.  Research is focused on:

  • Developing improved emissions measurement systems
  • Characterizing and profiling air pollution sources
  • Developing enhanced models to quantify and estimate emissions, concentrations, exposures, and health impacts. 

Research objectives are to:

  • Characterize emissions from open burning.
  • Develop and apply optical, remote-sensing technology for petroleum refineries, oil and gas fields, mobile emissions, and waste operations, among other sources.
  • Improve methods to characterize ammonia (including ammonia nitrate and ammonia sulfate) from natural sources.
  • Improve characterization of PM and air toxic emissions from aircraft engines.
  • Develop an enhanced chemical composition database from sources contributing to air pollutants.
  • Characterize emissions from light-duty vehicles powered with ethanol and other alternative fuels.

This and other related research will enable EPA to determine the “chemical fingerprints” of PM from emissions sources that include commercial jet engine turbines, on- and off-road diesel/biodiesel engines, and industrial-scale and residential oil-fired boilers.

In addition, more advanced source characterization methods will enable detailed analysis of particulate matter in the 2.5-micrometer size range, known as PM2.5. All of these results will further EPA’s goal to determine which air pollution sources pose the greatest exposure risks and threats to human health.

Application and Impact

The Clean Air Research Program has advanced understanding of source characterization by providing new data and technology for use by EPA, states, and tribes to determine which sources of air pollution pose the greatest exposure risks and most severely impact human health.

The use of more technologically advanced source characterization techniques has:

  • Improved emissions inventories for air pollutants.
  • Advanced computer models for predicting airborne aerosol dispersion, PM source/receptor relationships, and air quality impacts.
  • Improved the ability to assess air toxicity levels.
  • Provided critical knowledge to advance health effects studies.

ssisted the development and implementation of rules and regulations of air pollutants.  


Lavrich,R.L., Hays,M.D. Validation studies of thermal extraction-GC/MS applied to source emissions aerosols: 1. Semivolatile analyte-nonvalatile matrix interactions, Anal. Chem., 2007, 79, 3635-3645.

Hays,M.D., Vander Wal,R.L. Heterogeneous soot nanostructure in atmospheric and combustion source aerosols, Energy and Fuels, 2007, 21, (2), 801-811.


Carlos Nunez (nunez.carlos@epa.gov), National Risk Management Research Laboratory, EPA’s Office of Research and Development, 919-541-1156

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Control Technology


Scientists Develop and Test Multipollutant Control Tecnologies (PDF) (2 pp, 73KB, About PDF)

Historically, the U.S. Environmental Protection Agency’s approach to regulating air pollutant emissions has been to target pollutants individually. For example, an industrial source may be subject to separate control requirements for nitrous oxide, sulfur dioxide, and hazardous air pollutant emissions.  As a result of these requirements, controls may be implemented and updated by different schedules for each emission component.

These myriad regulations can yield inefficient control strategies. For example, the control technology that is most cost-effective for one particular pollutant may not be cost-effective in the context of other regulated pollutants. Thus, a more integrated, multipollutant regulatory approach may lead to more cost-effective and efficient control strategies.  

To this end, EPA is piloting an integrated, multipollutant approach that more comprehensively considers the various types of emissions, technology characteristics, and control options for specific source “sectors” such as cement production or power generation.

Ultimately, a multipollutant approach is expected to lead to more streamlined regulatory requirements that achieve environmental and health goals more cost-effectively than traditional, single-pollutant approaches. Research is needed, however, to support the development of multipollutant regulatory strategies and applications.

Scientific Objective

EPA’s Clean Air Research Program in the Office of Research and Development is developing and testing new technologies and strategies for the simultaneous control of multiple pollutants.  Research efforts are underway and planned to:

  • Evaluate the performance and benefits of various control technologies, including scrubbers and sorbents, in removing multiple air pollutants from coal-combustion systems.
  • Determine the co-benefit efficiency of existing technologies for the control of other air pollutants.
  • Develop modeling tools that will enable air quality managers to consider multipollutant reduction strategies and evaluate the economic and cost implications of various options.
  • Determine the performance of novel and existing technologies for multipollutant control that have been developed for application in coal-fired electricity generating units to other industrial sectors (e.g., cement kilns, pulp and paper, etc.)  

In addition, EPA is developing computer models that will assist EPA and regulated industries in identifying cost-effective strategies for complying with multipollutant regulations.

Key scientific questions being addressed include:

  • What known technologies can be used to reduce multiple pollutants and are reasonably amenable to field application?
  • How can existing technologies be modified to provide multipollutant control?
  • Are there novel approaches or technologies that can be used to manage multipollutant risks?
  • What are the relative costs, performance, and environmental implications of competing multipollutant reduction options?
  • What are cost-effective control strategies by which specific industries can comply with multipollutant control requirements? 

Application and Impact

EPA’s Clean Air Research Program has been a leader in advancing air pollution prevention and control technologies for key industries, utility power plants, waste incinerators, indoor environments and sources of greenhouse gases. 

As EPA moves to a sector-based, multipollutant regulatory approach, the expertise in the research program is being tapped to develop new models and tools that can be used by risk assessors and air quality managers to develop more effective strategies to reduce air pollution.

For example, EPA researchers have conducted bench- and pilot-scale work to provide multipollutant capacity to a wet-flue-gas desulfurization (FGD) scrubber used in coal-fired power plants.  Through the optimized introduction of an oxidant additive, the scrubber can be used to reduce emissions of nitrogen oxides, mercury, and sulfur dioxides.

EPA researchers have also developed a multipollutant, multi-sector emissions trading model to analyze and evaluate various air pollution reduction policy options for industrial sectors. An initial effort has focused on the U.S. cement sector. The model enables industries to evaluate their emissions during the various stages of the production process and determine how to keep operating costs down along with associated air emissions. The model is being expanded to include additional sectors, such as pulp and paper as well as iron and steel.


Hutson, N.D., Krzyzynska, R., Srivastava, S.K., Simultaneous Removal of SO2, NOX, and Hg from a Simulated Coal Flue Gas using a NaClO2-enhanced Wet Scrubber, Ind. Eng. Chem. Res., 2008, 47 (16), 5825.

Staudt,J.E., Jozewicz,W. Performance and Cost of Mercury and Multipollutant Emission Control Technology Applications on Electric Utility Boilers. US EPA Report EPA/600/R-03/110. 2003. Washington, D.C.


Douglas McKinney (mckinney.douglas@epa.gov), EPA’s Office of Research and Development, National Risk Management Research Laboratory, 919-541-3006.

Nick Hutson, Ph.D. (hutson.nick@epa.gov), EPA’s Office of Research and Development, National Risk Management Research Laboratory, 919-541-2968.

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Advanced Measurement Technique

US EPA: EPA Advances Technology To More Effectively Measure Air Pollution Sources (PDF) (2 pp, 74KB, About PDF)


Technological advances in measurement methods provide state-of-the-art capabilities to support both the research and outdoor (ambient) monitoring needed to protect public health and the environment. 

New methodologies developed by the U.S. Environmental Protection Agency enable air quality managers and regulators to measure pollutants in the air we breathe in real time; track pollutants as they move across continents and oceans using global positioning technology; and detect diffuse sources such as pollutants from landfills and wastewater lagoons.

Research is needed to improve the detection limits, response-time, and versatility of existing measurement technologies. For example, most standard methods approved by EPA for detecting emissions of air pollutants provide accurate results, but they do not provide real-time data. The data are integrated over a period of measurement that may be hours or days old. Relating these data to rapidly changing pollutant levels, emission profile changes, or short- term health outcomes is difficult and complex.

In addition, the lack of real-time information prevents process-control adjustments to emission and exhaust systems that might improve efficiency and reduce pollution. 

Scientific Objective

The Clean Air Research Program in EPA’s Office of Research and Development (ORD) strives to advance  emission and air measurement and monitoring technologies as well as improve emissions control or prevention capabilities. ORD’s research addresses both technology and methodologies that enhance sensitivity and selectivity for the many types of particulate and gaseous materials that end up in the air.

In recent years, technological advances have produced real-time (or near real-time) emission-detection methods and instrumentation that are highly accurate and yield improved datasets for use in various assessments. The field application of these technologies ranges from point sources, such as smokestacks, to non-point (diffuse) sources, such as industrial leaks and animal farm waste lagoons.

Among these advanced methods are both instruments and analysis systems, For example:

  • Jet Resonance Enhanced Multi-Photon Ionization-Time-of-Flight Mass Spectrometry (Jet REMPI-TOFMS), developed in collaboration with SRI International. This instrument allows for real-time and highly accurate measurements of individual particles and their composition.

  • Geospatial Monitoring of Air Pollution (GMAP).  This mobile monitoring capability uses networked fast-response instruments and a precise global positioning system to yield a map of air pollution patterns surrounding a source.

  • An area source measurement method, called OTM 10, uses Vertical Radial Plume Mapping (VRPM) and Horizontal Radial Plume Mapping (HRPM) for rapid analysis of optical measurements of emissions from non-point sources.

Application and Impact

Measurement technologies developed by EPA scientists offer air quality managers and risk assessors more reliable and useful tools to control and prevent air pollution. The methods noted above (Jet REMPI-TOFMS  and OTM 10) have significantly advanced the control of air pollution sources.  They have:

  • Supported the development of more advanced and efficient combustion systems
  • Improved the ability to characterize sources of air pollution, including non-point sources
  • Improved air quality models and emissions inventories

Jet REMPI-TOFMS has been used to measure the exhaust gas streams of several on-site combustion systems, including a municipal waste incinerator and specialized mobile vehicles used by the U.S. Department of Defense. The technology has been applied to identify air toxics associated with diesel generators, aircraft turbines, and industrial boilers.

The technology has also proven to be an exceptional instrument for studies to determine sources of air toxics from roadway vehicles and is being used in EPA’s studies on air pollution near roadways. Likewise, the new GMAP program has been used in a number of field studies to assess air pollution spatial patterns in close proximity to major roadways. 

The EPA method OTM 10 has similarly been used successfully for numerous monitoring efforts, including:

  • Emissions from landfills
  • Animal feeding operations, industrial facilities
  • Highways
  • Agricultural fields sprayed with biosolids as fertilizer
  • Contaminated site remediation
  • Homeland security research

New measurement technologies help to protect human health and the environment by providing the data required to develop and implement sound pollution control strategies.


Carlos Nunez (nunez.carlos@epa.gov), National Risk Management Research Laboratory, EPA’s Office of Research and Development, 919- 541-1156

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Emissions Characterization

US EPA: EPA Develops and Applies New technologies and Data to Characterize Air Pollutant Emissions (PDF) (2 pp, 175KB, About PDF)


Profiling or characterizing the many sources of air pollutants is critical to advancing pollution control and mitigation efforts.  The data collected can be used to improve understanding of the risks of exposure to human health and the environment, and to support the development of risk management strategies. 

To accurately evaluate air pollutants and their unique characteristics, new testing methodologies, models, and data are required. These tools support efforts by the U.S. Environmental Protection Agency and states to improve inventories of air pollution emissions. The inventories are important, because they help to advance air pollution abatement strategies and enhance forecasting of the impact of these strategies on air quality.   

Scientific Objective

EPA's Clean Air Research Program in the Office of Research and Development (ORD) is a leader in developing and applying a wide array of sophisticated emissions detection and analysis technologies to more accurately characterize air pollution. These technologies offer faster and more accurate data, including real-time data.

ORD research is currently focused on:

  • Light-duty diesel vehicles using conventional and alternative fuels
  • Industrial sectors, including oil and gas production as well as distribution
  • Large area sources, e.g. landfills
  • Aircraft and other off-road vehicles and engines
  • Emissions from wild and prescribed fires
  • Emissions from gases released by vegetation
  • Ammonia sources
  • Geographic allocated emissions

ORD scientists are measuring ammonia (a major precursor to fine PM2.5) from a variety of sources such as animal farms and congested roadways. High-tech emission characterization methods like Fourier Transform Infrared Spectroscopy (FTIR) and diode lasers are being used to measure methane emissions from landfills. Likewise, ultraviolet spectra technology is being used to determine mercury emissions from power plants.

ORD’s laboratory and field capabilities for emissions characterization are extensive. Field test equipment for sampling emissions includes a dilution sampler testing facility, a mobile field test laboratory, and several types of open-path optical remote sensing units.

ORD has also developed a portable laboratory for field testing of PM2.5 and gaseous emissions. Equipment in this laboratory trailer samples and analyzes emission plumes from a number of sources, including jet engines and locomotives.

The research program has developed a facility in EPA’s research laboratories in Research Triangle Park, N.C., to reproduce real-world emissions of a wide variety of trucks, using diesel and alternative fuels. With this capability, scientists can characterize emission profiles under a variety of driving patterns and artificial environmental conditions.

Application and Impact

The Clean Air Research Program provides the scientific tools needed by air quality managers and regulators to improve the fundamental information regarding emission profiles from a wide variety of sources, from diesel trucks to landfills.  This information is incorporated into air quality models and management decisions to control air pollutants.   

For example, research incorporating flow visualization, tracer gas measurements, and computational fluid dynamics modeling has improved characterizations of diesel exhaust plume dispersion.

Research has also led to:

  • Updated data on air emissions from municipal landfills
  • Development of improved emission factors for prescribed forest burns
  • New physical and chemical methods to identify and quantify components of PM and develop emission profiles for important sources of PM and air toxics

These improved methods allow EPA to identify sources of air pollution that pose significant exposure and human health risks.

Ultimately, this research will help to develop improved emissions-measurement systems that:

  • Profile air pollution sources
  • Develop enhanced models to estimate emissions and pollutant concentrations
  • Understand exposure and health impacts
  • Lead to better management approaches


Hays, M.D., Beck, L., Barfield, P., Lavrich, R.J., Dong, Y., and Vander Wal, R. L. (2008) Physical and chemical characterization of residential oil boiler emissions. Environ. Sci. and Technol., 42, (7), 2496-2502.  

Walker, J.T., Spence, P, Kimbrough, S., Robarge, W. (2008)  Inferential model estimates of ammonia dry deposition in the vicinity of a swine production facility.  Atmospheric Environment 42, pp. 3407 – 3418.

Wiedinmyer, C. And C. Geron. 2006. Estimating Emissions From Fires In North America For Air Quality Modeling. Atmospheric Environment.

Landfill Gas Emission Model (Landgem) - Software And Manual (EPA-600/R-05/047, May 2005)


Carlos Nunez (nunez.carlos@epa.gov), National Risk Management Research Laboratory, EPA’s Office of Research and Development, 919- 541-1156,

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