Particle Sampler for On-Line Chemical and Physical Characterization of Particulate OrganicsEPA Grant Number: R831077
Title: Particle Sampler for On-Line Chemical and Physical Characterization of Particulate Organics
Investigators: Smith, Kenneth A. , Worsnop, Douglas R.
Institution: Massachusetts Institute of Technology , Aerodyne Research Inc.
EPA Project Officer: Chung, Serena
Project Period: October 1, 2003 through August 1, 2006 (Extended to September 30, 2007)
Project Amount: $410,000
RFA: Measurement, Modeling, and Analysis Methods for Airborne Carbonaceous Fine Particulate Matter (PM2.5) (2003) RFA Text | Recipients Lists
Research Category: Air , Air Quality and Air Toxics , Particulate Matter
Current research on atmospheric aerosols is focused on understanding their role in affecting the Earth's climate (including perturbations of direct radiative balance and cloud microphysics) and in causing serious human health effects. However, our understanding of aerosols is limited by the inability of existing instruments to provide real-time, size-resolved, quantitative measurements of aerosol mass and chemical composition, and especially of the organic species in/on aerosols. The most common current analytical technique to obtain information on individual compounds present on aerosols is to collect samples on filters followed by off-line techniques such as gas chromatography. Almost all filter analyses require long sampling times, can introduce artifacts due to evaporation and/or condensation from/to filters during sampling [Fine et al., 2001; Jeon et al., 2001; Solomon et al., 2001], are labor intensive, and are costly.
In this project, Massachusetts Institute of Technology (MIT) in collaboration with Aerodyne Research, Inc. (ARI) will design and construct a prototype innovative Particle Sampler (PS) system which can be coupled to most commercial or research-grade analytical instruments such as gas-chromatography (GC), gas chromatography-mass spectrometry (GC-MS) and also advanced techniques, like Proton-Transfer Reaction Mass Spectrometry (PTR-MS). This innovative Particle Sampler (PS) system will introduce for the first time an on-line measurement method that will deliver high-resolution chemical speciation of aerosol composition.
The PS system will use existing technology already in use at ARI to separate the particles from the gas phase, coupled with particle collection, thermal desorption, and injection into an appropriate analytical instrument. This approach will greatly minimize artifacts due to evaporation/condensation as compared with current filter collection and extraction techniques used for identifying and quantifying organic species in aerosols. A detection limit of about 1 ng m-3 may be achievable with the PS for a sampling time of less than 30 minutes.
The PS will be deployed in both an urban and a rural area. During these measurements, different groups of PM2.5 organics will be chemically analyzed. The PS system will be equipped with a thermal desorption unit that can reach a temperature of ~1500°C, allowing analysis of newly vaporized species. These studies will also focus on identifying signatures from different sources (anthropogenic, natural and secondary formation), and identify markers that can be used in source-oriented models to predict the composition and evolution of PM2.5 in the atmosphere.
At the end of this project, a commercial Particle Sampler system for on-line analysis of PM2.5 organics will be available for the research and regulatory communities. This PS system will operate unattended and will require only electrical power and carrier gas, and thus be suitable for continuous aerosol sampling campaigns.