The Impact of Aerosols, Clouds, and Ozone on Surface UV and Photochemistry in Houston, TX

EPA Grant Number: R832837
Title: 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 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


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.


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.

Expected Results:

This project will result in: 1) a new methodology for characterizing the organic content in an aerosol, 2) a greater understanding of the compounds emitted from well-controlled combustion sources, and 3) real-time determination of the chemical composition of semi-volatile aerosols observed in Los Angeles.

Publications and Presentations:

Publications have been submitted on this project: View all 5 publications for this project

Journal Articles:

Journal Articles have been submitted on this project: View all 2 journal articles for this project

Supplemental Keywords:

ambient air, mobile sources, organics, 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, chemical characteristics, environmental measurement, source apportionment, emissions monitoring, air quality models, 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

Progress and Final Reports:

  • 2006 Progress Report
  • 2007 Progress Report
  • 2008 Progress Report
  • 2009 Progress Report
  • Final Report