General Audience Oral Presentations Abstracts

TOPIC #1

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1. Semivolatile Organic Compound Emission Profiles–Effects of Sampling Artifacts

Lisa A. Graham
Environment Canada
Emissions Research and Measurement Division, Ottawa, Ontario, Canada

Jeff Brook
Environment Canada
Air Quality Research Branch, Downsview, Ontario, Canada

Emission profiles for semivolatile organic compounds that are used in a variety of source apportionment studies are often produced by normalizing individual compound emission rates to organic carbon emission rates. Organic carbon emission rates are determined using a variety of analytical methods, the most common of which are thermal optical transmittance and thermal optical reflectance (TOT and TOR respectively). Both of these methods require collection of PM samples on quartz sample media with additional samples collected for attempting to correct for various sampling artifacts such as adsorption of gas phase organic material during sample collection.

The practice of normalizing emission rates of the individual compounds to the organic carbon emission rate may produce emission profiles that are difficult to use outside the study for which they were developed due to large variability and large uncertainties in artifact correction for organic carbon emission rates and to variabilities due to conditions under which samples for organic speciation are collected.

PM2.5 samples were collected during the 2001 Cassiar Tunnel Study in Vancouver. Three-hour integrated samples were collected over each of the three daily sampling intervals for determination of organic and elemental carbon by the TOT method. These samples were collected on pre-fired quartz filters with the sample for artifact correction collected downstream of a Teflon membrane filter, rather than downstream of the primary quartz filter.

On six of the seven sampling days, 9-hour integrated samples were collected for organic compound speciation. These samples were collected by exposing the same 90mm diameter filter over the three 3-hour sampling periods. On one of the seven days, three separate 3-hour integrated samples were collected. These PM samples were analyzed for n-alkanes (C11-C36), petroleum biomarker compounds (65 hopanes and steranes), alkylcyclohexanes (C3-C20 alkyl groups) PAH, NO2-PAH and PAsH.

Significant differences in emission rates were obtained between the 3-hour and 9-hour integrated samples, so normalizing to organic carbon emission rates obtained over the 3-hour interval produced profiles with very different magnitudes but no difference in relative amounts of individual organic species. Similar differences may be expected depending on the sampling interval for organic carbon and the method by which the sampling artifacts are corrected. These results clearly add fuel to the debate of uncertainty estimates on emission profiles and the role sampling artifacts play, even when attempts to correct for them are made.

2. Rapid Sampling and High-Resolution Analyses of
Ambient Organic Species

William K. Modey and Paul V. Doskey
Environmental Research Division
Argonne National Laboratory
9700 South Cass Avenue
Argonne, IL 60439-4843

Work at Argonne National Laboratory supported by the U.S. Department of Energy, Office of Science, Office of Biological and Environmental Research, Climate Change Research Division, under contract W-31-109-Eng-38.

The submitted manuscript has been created by the University of Chicago as operator of Argonne National Laboratory under Contract No. W-31-109-ENG-38 with the U.S. Department of Energy. The U.S. government retains for itself, and others acting on its behalf, a paid-up, nonexclusive, irrevocable worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the government.

An improved technology for sampling vapor- and particle-phase ambient organic species based on the diffusion denuder, will be discussed. The multicapillary collection device (MCCD) consists of a very sharp cut size-selective cyclone for sampling particles with aerodynamic diameters less than 2.5 mm, plus a single-stage inline stainless steel filter holder that places a quartz fiber filter between two multicapillary diffusion denuders. Vapor-phase organic compounds are collected on the first denuder, and species that are volatilized from particles collected on the filter are trapped on the second denuder. Organic vapors are trapped in a multicapillary diffusion denuder that contains a total of 289 fused-silica capillaries (ZB-1, Phenomenex, Torrance, CA; 5-mm film thickness; 0.254 m x 0.53 mm ID) in a 1.6-cm-OD Silcosteel-coated stainless steel tube (Restek, Bellefonte, PA). An automated sampling system that holds 8 MCCDs has been constructed to examine diurnal variations in concentrations of ambient organic species. The analytes are recovered from the denuder and filters by thermal desorption or supercritical fluid extraction (SFE) and are transferred directly to fused-silica wool or Tenax-TA in the controlled-temperature vaporization inlet (Gerstel, Inc., Baltimore, MD) of a high-resolution gas chromatograph. Combining the sampling and analytical approaches avoids dilution of the sample by solvent and enables rapid sampling and analysis of the ambient atmosphere. In addition, sample contamination is minimized when intermediate sample-handling steps are eliminated. Preliminary data comparing the thermal desorption and SFE techniques and examining diurnal variations in the concentrations of ambient organic species will be presented.

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