Grantee Research Project Results
2009 Progress Report: The Impact of Aerosols, Clouds, and Ozone on Surface UV and Photochemistry in Houston, TX
EPA Grant Number: R832837Title: The Impact of Aerosols, Clouds, and Ozone on Surface UV and Photochemistry in Houston, TX
Investigators: Phares, Denis J.
Institution: University of Southern California
EPA Project Officer: Chung, Serena
Project Period: January 1, 2006 through December 31, 2010
Project Period Covered by this Report: January 1, 2009 through December 7,2009
Project Amount: $356,500
RFA: Continuous Measurement Methods for Particulate Matter Composition (2005) RFA Text | Recipients Lists
Research Category: Particulate Matter , Air , Air Quality and Air Toxics
Objective:
This proposal responds to the need for in situ measurements of size-resolved aerosol chemical composition, focusing on speciation of organics. A novel instrument will be developed and deployed in order to understand the formation of specific compounds found in ambient aerosols and to elucidate their health effects.
Approach: The proposed instrumentation combines the well-characterized techniques of electrostatic classification and thermal desorption/chemical ionization with a coupled ion mobility/mass spectrometer. The instrument is meant to provide a soft ionization to keep the molecules intact, and subsequently analyzing the mobility and mass of the resulting ions, thus providing a mobility/mass matrix of the aerosol rather than solely a mass spectrum. The extra dimension provided by the ion mobility measurement will facilitate identification of organics by resolving isomers and elucidating relative amounts of aromatics and aliphatics. The instrument is designed to be deployable and to operate with high temporal resolution. Initially the instrument will be tested in the laboratory using both test aerosols generated from solution and aerosols generated from well-controlled combustion sources operated at a variety of conditions. The latter is meant to provide a data set to compare with ambient measurements, in order to identify particulate matter that originated from combustion sources. The instrument will be deployed in the Los Angeles basin to examine the composition of particles near freeways and airports that have been observed to evaporate within several hundred yards of their source. Such particles may pose health risks to those who live in the vicinity of the sources. The instrument will also be deployed for longer durations to detect seasonal and diurnal variations in the organic content within the ambient aerosol, and to determine potential tracers for secondary organic aerosol formation and primary emissions, to which bulk methods may not be sensitive.
Progress Summary:
- An inlet has been designed and built for size-resolved collection of aerosols and its performance has been tested.
- Ion mobility spectra were obtained for a variety of organic compounds, including gas-phase compounds and aerosols. The ion mobility cell was able to detect nanogram quantities of aerosol collected on the heating filament in the aerosol inlet.
- Chemical ionization time-of-flight mass spectra were obtained for a variety of organic gas-phase and aerosol standards.
- Atmospheric aerosols were sampled from the University of Southern California campus in downtown Los Angeles. Although analysis is minimal at this point, there are several notable observations. There are a series of complex organic compounds having a characteristic spacing of 14 amu indicative of - CH2 – group additions. Larger peaks corresponding to masses over 350 Da are evident during certain times. At this point, these peaks are unidentified and may have resulted from polymerization of gas phase species in the atmosphere.
- The instrument is now capable of producing mobility spectra as well as mass spectra using the soft ionization technique, which allows for more definitive identification of organic molecules and these two techniques have been successfully coupled to produce spectra. However, there is currently work needed to improve the data acquisition for the coupled system.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
| Other project views: | All 5 publications | 2 publications in selected types | All 2 journal articles |
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Phares DJ, Collier S. Direct collection of aerosols by electrostatic classification for size-resolved chemical analysis. Aerosol Science & Technology 2010;44(3):173-181. |
R832837 (2008) R832837 (2009) R832837 (Final) |
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Supplemental Keywords:
Particulate organic carbon, atmospheric measurements, model-based analysis, chemical characteristics, environmental measurement, source apportionment, emissions monitoring, airborne particulate matter, air sampling, air quality model, analytical chemistry, speciation, particulate matter mass, modeling studies, monitoring of organic particulate matter, aerosol analyzers, atmospheric chemistry, chemical speciation sampling, real-time monitoring, RFA, Scientific Discipline, Air, Ecosystem Protection/Environmental Exposure & Risk, particulate matter, Air Quality, Environmental Chemistry, Monitoring/Modeling, Environmental Monitoring, Environmental Engineering, particulate organic carbon, atmospheric measurements, model-based analysis, source apportionment, chemical characteristics, emissions monitoring, environmental measurement, airborne particulate matter, air quality models, air quality model, air sampling, speciation, particulate matter mass, analytical chemistry, modeling studies, monitoring of organic particulate matter, real-time monitoring, aerosol analyzers, chemical speciation sampling, particle size measurementProgress 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.