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ISOTOPIC (14C) AND CHEMICAL COMPOSITION OF ATMOSPHERIC VOLATILE ORGANIC COMPOUND FRACTIONS - PRECURSORS TO OZONE FORMATION
Citation:
Klouda, G. A., C W. Lewis, R. A. Rasmussen, D. C. Stiles, W. D. Ellenson, AND J. L. Marolf. ISOTOPIC (14C) AND CHEMICAL COMPOSITION OF ATMOSPHERIC VOLATILE ORGANIC COMPOUND FRACTIONS - PRECURSORS TO OZONE FORMATION. Presented at Proceedings of the Third International Conference on Isotopes, Vancouver, Canada, September 6-10, 1999.
Impact/Purpose:
To use the tools of radiocarbon (14C) and gas chromatographic (GC) analysis combined with various receptor models to determine the contributions of sources to ambient VOC, and indirectly their contribution to tropospheric ozone via their role as sources of ozone precursors.
Description:
Atmospheric volatile organic compounds (VOCs) are an important factor in the production of ozone near ground level [3]. Many hydrocarbons originate from auto exhaust. However, a number of VOCs, e.g., isoprene, are known to be natural in origin. To develop reliable models for understanding how ozone levels might be controlled, it has been recognized that a key variable is the fractional amount of fossil vs. non-fossil (biogenic, uncontrollable) VOCs [1]. These two source categories are uniquely discriminated from each other based on the 14C abundance of VOC fractions. Combining isotopic measurements with chemical information will yield greater confidence in source estimates. Over the last 8 years, NIST, OGI and the U.S. EPA have explored sampling methods and analytical procedures to collect enough carbon from atmospheric non-methane VOC fractions to measure the 14C composition [4,9]. In doing so, this work also provided an opportunity to enhance the sensitivity of GC-FID and GC-MS for chemical identification and quantification. This paper will briefly describe the methods studied and present preliminary 14C and chemical results from Azusa, CA, Houston, TX, and Nashville, TN, USA.
This work was funded in part by the U.S. Environmental Protection Agency Interagency Agreement No. DW13937923 with the National Institute of Standards and Technology, and the Texas Natural Resources Conservation Commission (TNRCC). The paper has been reviewed in accordance with the U.S. Environmental Protection Agency's peer and administrative review policies and approved for presentation and publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.