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Factors in Geotropospheric Particle-Gas Transport of Semivolatile Organic Compounds

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Abstract:Semivolatile organic compounds (SVOCs) can exist in solid, liquid, or gas phases under ambient environmental conditions. The geotropospheric transport of SVOCs varies according to the particle type. Two classes of SVOCs and two types of particles were analyzed to determine possible transport mechanisms to the troposphere: dicarboximide compounds moving from a soil matrix to the troposphere and polycyclic aromatic hydrocarbons (PAHs) from airborne particles to the troposphere. Both classes of compounds are considered to be SVOCs since their vapor pressures under most environmental conditions range between 10-2 to 10-5 kP. The dicarboximide results were obtained from a laboratory chamber designed and used to determine the headspace flux of the dicarboximide fungicide, vinclozolin (3-(3,5-dichlorophenyl)-5-methyl-5-vinyl-oxzoli-dine-2,4-dione), and its three principal degradation products from chamber surfaces, sand, and sterilized and non-sterile North Carolina Piedmont aquic hapludult soils following dicarboximide applications. The PAH results were gathered from a high-volume air sampling system used to measure particle and gas phase concentrations of SVOCs in the plume downwind from the World Trade Center fire. The comparison indicates that SVOC transport from the soil matrix can be influenced by the type and size of particles, their chemical composition, pH, oxygen, and microbial action. The study indicates that in the troposphere, molecular weight and structure are the principal factors affecting the geotropospheric flux of SVOCs from the particle to gas phase. Although experimentally determined equilibrium constants are more robust predictors of phase distribution in the troposphere (r2 = 0.81), published Henry's Law and vapor pressure constants also relate to particle-gas phase distribution (r2 = 0.73 and 0.72, respectively).

This work has been funded in part by EPA. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.
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Citation:Vallero, D. A. Factors in Geotropospheric Particle-Gas Transport of Semivolatile Organic Compounds. ENVIRONMENTAL ENGINEERING SCIENCE. Mary Ann Liebert, Inc., Larchmont, NY, 22(1):109-125, (2005).
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Contact: Liz Hope - (919) 541-2785 or hope.elizabeth@epa.gov
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Division: Human Exposure & Atmospheric Sciences Division
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Branch: Exposure Measurements & Analysis Branch
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Product Type: Journal
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Published: 01/01/2005
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Bullet Item Factors in Geotropospheric Particle-Gas Transport of Semivolatile Organic Compounds
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Bullet Item Methods Development at the Near Lab Ecological Research Area (Nlera) Located in the Neuse River Basin.
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Last Updated on Monday, October 22, 2007
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