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Real-Time Monitoring of Dioxins and Other Ambient Air Trace Organics
Jet-REMPI Ion Source (courtesy of DLR Stuttgart).
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This project is part of EPA's EMPACT program which was begun in 1998. EMPACT is jointly administered by EPA's Office of Research and Development (ORD), National Center for Environmental Research and Quality Assurance (NCERQA), and the National Center for Environmental Assessment (NCEA). The program was developed to provide understandable environmental information on various research initiatives to the public in a timely manner on various issues of importance.
Objectives
The project objectives will be to develop the REMPI instrumental method into a tool that will be used for assessment of potential dioxin sources, control and prevention of dioxin formation in known sources, and communication of facility performance. This will be accomplished through instrument development, laboratory verification, thermokinetic modelling, equilibrium modelling, statistical determinations, field validation, program publication and presentation, regulatory office support, and development of data communication/presentation procedures.
Description
"Dioxin" is probably the most recognizable, scientifically studied, and toxic air pollution problem. Despite this dubious distinction, our understanding of how dioxin is formed in combustion systems and therefore, how to prevent dioxin from forming, is extremely limited. In addition, our awareness of dioxin sources and subsequent population exposure to dioxin emissions is limited by our inability to monitor this pollutant and assess exposure risk. Recently, scientific advances in analytical instrumentation have demonstrated the potential to monitor, in real-time, extremely trace concentrations of dioxin compounds and dioxin precursors. This new capability can significantly advance time-relevant pollutant monitoring, since current methods to get a single dioxin measurement require a lengthy and costly sampling effort followed by an equally lengthy and costly analytical effort. The infrequent (often annual, or less) facility sampling and delayed analytical results preclude efforts to understand and prevent emissions as well as assure the public that a facility is operating appropriately.
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During this research effort, an on-line, real time dioxin monitor that will enable timely measurements will be developed. Work will involve multiple tasks and participants, demonstrating the utility and usefulness of this new analytical method for control, monitoring, and compliance assurance.
Benefits
Expected benefits include: (1) demonstration of an analytical method that measures, in real time, dioxin compounds and dioxin precursors from industrial sources; (2) demonstration of a statistical/thermokinetic/equilibrium method that uses this information to provide real-time predictions of dioxin emissions and process feedback controls to prevent formation; and (3) development of an industry/public interface method that allows these data to be appropriately understood and communicated in terms of environmental hazard exposure.
The project will guide development of the first techniques for monitoring gas phase, trace concentrations of highly toxic chlorinated dioxins/furans (D/F or "dioxins") toward objectives of emission control, pollutant prevention, risk management, and understandable environmental impact communication. A newly enhanced analytical technique called Resonance Enhanced MultiPhoton Ionization (REMPI) will be adapted and used as a tool for source risk assessment, as a tool for process control to understand and prevent conditions that are crucial to D/F formation, and as a method of communicating facility operating performance.
Figure 1. Isotopomer selectivity of DLR's Jet-REMPI (Oser, et al., 1997)1
REMPI is an on-line method that combines compound-specific selectivity (see Figure 1) with high sensitivity. While REMPI has been recognized for years and is currently under development by multiple groups, recent geometric- and laser-based advances have improved sensitivity. The sharp resonances of target molecules require a tunable laser for ionization [See Photo 1], leading to a two-dimensional spectra (ion mass and wavelength, see Figure 2). The resulting sensitivity has improved by over three orders of magnitude, making REMPI measurements relevant to on-line measurement of trace organic toxics.
OPO Laser and Time of Flight Mass Spectrometer (Courtesy of SRI, International)
Figure 2. Wavelength dependent Jet-REMPI spectra for 2,7-DCDD.
Mass 252 is monitored (Inset: Parent ions at a wavelength of 305.6 nm).1
REMPI is capable of measuring concentrations of some dioxin compounds that exist in industrial applications (for some of the already-measured compounds, see Figure 3). However, the full range of 210 dioxin (and furan) compounds and, hence, the full dioxin toxicity measure which is comprised of seventeen 2,3,7,8-Cl-substituted dioxins is not accessible to REMPI due to spectroscopic and detection limitations.
Figure 3. Mass and wavelength map for hazardous air pollutants.
Relevant concentrations of these compounds are often in the parts per quadrillion levels and become even lower as emissions become cleaner. Thus it becomes expedient to search for compounds which are spectroscopically viable, are more abundant, and/or are more easily detected, such as dioxin formation precursors and chemically-related dioxins and furans which serve as indicators of the presence of the full range of toxic 2,3,7,8-Cl-substituted compounds. Some of these compounds include proven precursors such as chlorophenols and chlorobenzes2 as well as indicators, such as the mono- to tri-chlorinated dioxins and furans.3 These compounds are easily discerned within the resolution of the laser and mass spectrometer (see Figure 4). These indicator and precursor compounds can then easily be followed by REMPI instrumentation to discern, by correlation, the value of the dioxin toxicity. Establishment of this relationship is critical to the broad, successful application of the REMPI technology.
Figure 4. High resolution mass and wavelength map for two DCDD congeners.
The overall objective is to obtain the theoretical, mechanistic, statistical, and experimental data necessary to establish the relationship between REMPI-monitorable species and dioxin concentrations and to develop the methodology to use this relationship for industrial pollution prevention, regulatory guidance, and public assessment of risk exposure.
Project Team
Brian K. Gullett, Ph.D.Principal Investigator
U.S. Environmental Protection Agency
National Risk Management Research Laboratory (NRMRL)
Research Triangle Park, North Carolina 27711
gullett.brian@epa.gov
Jeff Ryan, Judy Ford, EPA/ORD/NRMRL
Lukas Oudejans, Ph.D., ORISE Post-Doctoral Fellow
Stephen J. Priebe, Ph.D., Idaho National Environmental Engineering Laboratory
Co-Investigators
Michael Coggiola, Ph.D., SRI, InternationalDavid Crosley, Ph.D., SRI, International
Barry Dellinger, Ph.D., Louisiana State University
James E. Dunn, Ph.D., University of Arkansas
Horst-Henning Grotheer, Ph.D., DLR Stuttgart, Germany
James Mulholland, Ph.D., Georgia Institute of Technology
Harald Oser, Ph.D., SRI, International
Advisory Council
Elmar Altwicker, Rensselaer Polytechnic InstituteBeth Antley, US EPA Region IV
R. Lane Brown, South Eastern Public Service Authority (SPSA)
Nina Bergan French, Sky+, Ltd.
Jill Engel-Cox, EPA/ORD/NCERQA, AAAS Fellow
Ken Froese, University of Alberta
Robert Giraud, Dupont
Mel Keener, Coalition for Responsible Waste Incineration
Catherine Koshland, UCLA
William Lamason, EPA/OAQPS/Emission Measurement Center
N. Scott Postma, US EPA Region VII
Dave Rejeski, US EPA, White House CEQ
Randy Seeker, GE, Energy & Environmental Research Corporation
Valerie Thomas, University of Princeton
Ed Timm, DOW Chemical
Additional Information
For more information on this project, please contact Brian Gullett at gullett.brian@epa.gov or by fax at (919) 541-0290. For additional information on the EMPACT program, please contact Denice Shaw at (202) 564-3234 or access the EMPACT web site.
__________________1 Oser, H., R. Thanner, and H.-H. Grotheer, B. K. Gullett, N. Bergan French, D. Natschke, "DLR Jet-REMPI as a Continuous Emissions Monitor: Measurements of Chlorinated Dibenzodioxins," In: Proceedings, 1997 International Conference on Incineration & Thermal Treatment Technologies, UC-Irvine/AWMA, Oakland, California, May 12-16, 1997.
2 Kaune, A., Lenoir, D., Nikolai, U., and Kettrup, A. (1994) Estimating Concentrations of Polychlorinated Dibenzo-p-dioxins and Dibenzofurans in the Stack Gas of a Hazardous Waste Incinerator from Concentrations of Chlorinated Benzenes and Biphenyls Chemos., 29, 2083.3 Gullett, B. K. and Wikström, E., "Use of Mono- to Tri-Chlorinated Dibenzodioxin (CDD) and Dibenzofuran (CDF) Congeners/Homologues as Indicators of Tetra- to Octa-CDD/CDF Emissions from Municipal Waste and Waste/Coal Combustion," In: Proceedings: Dioxin '98, August 17-21, 1998, Stockholm, Sweden and Organohalogen Compounds, V36, 179-182.