Grantee Research Project Results
2000 Progress Report: Characterization of Urban Air Toxics Sources in Support of HAPs Emission Control Strategies
EPA Grant Number: R827927Title: Characterization of Urban Air Toxics Sources in Support of HAPs Emission Control Strategies
Investigators:
Institution: Sri International
EPA Project Officer: Chung, Serena
Project Period: December 1, 1999 through November 30, 2002
Project Period Covered by this Report: December 1, 1999 through November 30, 2000
Project Amount: $506,742
RFA: Urban Air Toxics (1999) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Air
Objective:
This research project leverages SRI International's current development of a continuous emissions monitor (CEM) for dioxins and furans supported by the U.S. Department of Energy (DOE). The detector uses a pulsed nozzle gas inlet, resonance enhanced multiphoton ionization (REMPI), and time-of-flight mass spectrometry (TOF-MS). Using this jet-REMPI approach, detection limits in the low 20 ppt have been obtained. The extreme sensitivity and chemical specificity of this instrument and the nearly universal nature of REMPI and mass spectrometry provide a new analytical capability. With a single instrument, the spatial and temporal distribution of a majority of the most toxic organic hazardous air pollutants (HAPs) now can be concurrently measured at levels that are of toxicological interest.
This instrument provides direct detection and identification of the most HAPs and HAP mixtures in urban air in real time (i.e., 1 to several minutes of averaging). The objectives of this combined laboratory and pilot field study are to establish a viable means of measuring the emission rates and temporal and spatial distributions of urban air toxics and HAPs using an existing, ultra-sensitive CEM. Because our CEM is capable of directly measuring real-time concentrations of specific HAPs and urban air toxics at levels far below present analytical instruments, we will develop the capability to identify and characterize critical emission sources over a wide geographical area under a variety of ambient monitoring conditions. We will use this capability in a pilot field study to validate our approach to measurement and characterization of urban air toxics.
An important result of this effort will be the design of a field-deployable instrument based on our approach that can be used in a subsequent comprehensive field study of urban air toxics linked to epidemiological or health effects studies. These studies will provide the scientific basis for regional or national emissions control strategies and standards. Once these exposure levels are measured using the techniques established in this effort, they will contribute to a significant improvement in the ability to link exposure and risk associated with urban air toxics.
In addition to making HAPs concentration measurements, we also will study the temporal variation and interconversion of related chemical species with exposure to sunlight and other meteorological conditions. This will provide direct information on atmospheric transformations of emitted HAPs by photolytic processes. This aspect often is neglected in urban pollution studies, but is crucial to establishing the identity of those compounds actually causing toxic effects. Such transformation studies can be enhanced by correlating our real-time HAPs and transformed HAPs levels with short-term, local variations in oxidizing potential as indicated by ambient zone levels independently measured using off-the-shelf instrumentation.
Progress Summary:
During this reporting period, SRI International made numerous improvements in the jet-REMPI instrument. These improvements involved the characterization and optimization of the molecular cooling in the gas jet, implementation of a custom-fabricated four-pulsed valve assembly, new data acquisition and display software, preliminary development of a wavelength and mass calibration approach, and the acquisition and installation of a stable wavelength doubling option for our tunable laser. Together, these improvements have resulted in an instrument with superior detection capabilities and ease of use. Utilizing the improved instrument, we measured the REMPI excitation spectra of numerous organic compounds of interest to the air toxics community.
Future Activities:
The major objectives and focus for the subsequent reporting periods are to develop a spectral library for additional air toxic compounds, determine the optimized instrumental sensitivity for detecting these compounds in urban air samples, and ultimately, measure their concentrations in a limited-scope field study.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 8 publications | 4 publications in selected types | All 4 journal articles |
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Type | Citation | ||
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Oser H, Coggiola MJ, Faris GW, Young SE, Volquardsen B, Crosley DR. Development of a jet-REMPI (resonantly enhanced multiphoton ionization) continuous monitor for environmental applications. Applied Optics 2001;40(6):859-865. |
R827927 (2000) R827927 (2001) R827927 (Final) |
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Supplemental Keywords:
volatile organic compound, VOC, polycyclic aromatic hydrocarbon, PAH, polychlorinated biphenyl, PCB, polynuclear aromatic hydrocarbons, PNA, dioxin, furan, environmental chemistry, physics, risk assessment, chemical transformation, epidemiology., RFA, Scientific Discipline, Air, Toxics, air toxics, Environmental Chemistry, HAPS, Chemistry, chemical mixtures, tropospheric ozone, 33/50, ambient air quality, emission control strategies, urban air toxics, urban air, stratospheric ozone, air pollutants, Toluene, hydrocarbon, Xylenes, hazardous air pollutants, benzene, chemical composition, urban air pollutants, Cresols/Cresylic acid (isomers and mixture), furans, acute toxicity, hydrocarbons, Benzene (including benzene from gasoline), Xylenes (isomers and mixture), atmospheric chemistryProgress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.