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Leaves as Indicators of Exposure to Airborne Volatile Organic Compounds

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Abstract:The concentration of volatile organic compounds (VOCs) in leaves is primarily a product of airborne exposures and dependent upon bioconcentration factors and release rates. The bioconcentration factors for VOCs in grass are found to be related to their partitioning between octanol and air equivalent to a relationship previously determined for PCBs. The rate that leaves release VOCs is dependent upon meteorological conditions and the enthalpy of phase change between air and plant. The enthalpy of phase change ( H pa ) for a compound in leaves is closely related to its enthalpy of vaporization. The BCF and H pa for a compound vary among plants but are highly correlated to each other. The change in BCF by plant (and correlated change in H pa ) is likely due to differences in the amount of octanol-equivalent matter contained in their leaves. The concentration of airborne VOCs is predicted to maximize near dawn simultaneous with natural inversion patterns. A model incorporating this phenomenon with other meteorological data, H pa, and BCF is a useful tool predicting concentrations of VOCs in leaves. Vegetation can be especially useful in capturing VOCs at the critical time that air exposures are greatest. How long a leaf might retain a compound after uptake is dependent on the compound, the leaf type, and the magnitude of the wind and temperature. During calm weather, leaves can be used as a record of these early morning exposures. However, windy conditions quickly clear leaves of their VOC content.
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Citation:Hiatt, M. H. Leaves as Indicators of Exposure to Airborne Volatile Organic Compounds. ENVIRONMENTAL SCIENCE & TECHNOLOGY 33:4126-4133, (1999).
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Environmental Chemistry Branch
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Product Type: Journal
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Published: 12/19/1999
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