Near Real-Time Speciation of Organic Aerosols for Source ApportionmentEPA Grant Number: R832166
Title: Near Real-Time Speciation of Organic Aerosols for Source Apportionment
Investigators: Johnston, Murray V. , Tolocka, Michael P.
Current Investigators: Johnston, Murray V.
Institution: University of Delaware
EPA Project Officer: Chung, Serena
Project Period: January 1, 2005 through December 31, 2007 (Extended to December 31, 2008)
Project Amount: $450,000
RFA: Source Apportionment of Particulate Matter (2004) RFA Text | Recipients Lists
Research Category: Air Quality and Air Toxics , Particulate Matter , Air
This project includes five specific objectives: 1) Develop a photoionization aerosol mass spectrometer (PIAMS) for near real-time measurement of trace organic constituents in fine particles. 2) Couple PIAMS with an aerosol concentrator to reduce the sampling time of PIAMS to two minutes or less for ambient urban air. 3) Acquire improved PIAMS signatures (source profiles) for those sources where elemental data may be ambiguous or non-existent, for example secondary organic aerosols (SOA), highway traffic, and meat cooking operations. 4) Use the concentrator and PIAMS to measure trace organic constituents in fine particles in Wilmington, Delaware at the State of Delaware Department of Natural Resources and Environmental Control (DNREC) Air Quality Measurement Site; concurrent carbonaceous particulate matter measurements will include semi-continuous OC/EC, GC/MS of collected Hi-Vol aerosol samples, OC/EC on Federal Reference Method (FRM) Samplers for PM2.5, and particulate mass. 5) Develop and refine source apportionment models using the speciated organics data.
A new method of analysis will be developed and deployed that provides much shorter time resolution for trace organic constituents. The method is based on a photoionization aerosol mass spectrometer (PIAMS) that operates in an automated, unattended manner. Ambient aerosol is drawn directly into the instrument without the need for time or labor intensive sample preparation. Inside the mass spectrometer, particles are collected on a probe, vaporized with a desorption laser pulse and ionized with a second laser pulse. Sampling intervals of two minutes or less will be achieved by combining the PIAMS with a particle concentrator. After quantification procedures and source signatures are developed, the PIAMS will be deployed at a State of Delaware Air Quality Measurement Site for urban, ambient measurements.
Near real-time speciation of organic constituents in urban air should provide a foundation to estimate the source strengths of pollution sources that are not easily amenable using conventional elemental analysis. Adding this type of data (and the insights as to which organic species correlate well with the integrated measurements) to existing databases for airshed models will benefit the development of state implementation plans for other this and other sites.
Health effects researchers will benefit from an improved understanding of the time-dependent exposure to specific organic components. With PIAMS, it may be possible to distinguish exposure to particles that have undergone condensation of high concentration semi-volatile gas phase species near the point of emission (i.e. roadway) from particles that have moved further from the source where dilution has permitted re-evaporation.