%0 Journal Article
%A Randy L Maddalena
%A Thomas E McKone
%A Norman Y Kado
%B Environmental Science & Technology
%D 2002
%G eng
%N 16
%P 3577-3585
%R 10.1021/es0255554
%T Exposure chamber measurements of mass transfer and partitioning at the plant/air interface
%V 36
%1 <p>7.2</p>
%8 08/2002
%X <p>Dynamic measures of air and vegetation concentrations in an exposure chamber and a two-box mass balance model are used to quantify factors that control the rate and extent of chemical partitioning between vegetation and the atmosphere. A continuous stirred flow-through exposure chamber was used to investigate the gas-phase transfer of pollutants between air and plants. A probabilistic two-compartment mass balance model of plant/air exchange within the exposure chamber was developed and used with measured concentrations from the chamber to simultaneously evaluate partitioning (<em>K</em><sub>pa</sub>), overall mass transfer across the plant/air interface (Upa), and loss rates in the atmosphere (<em>R</em><sub>a</sub>) and aboveground vegetation (<em>R</em><sub>p</sub>). The approach is demonstrated using mature <em>Capsicum annuum</em> (bell pepper) plants exposed to phenanthrene (PH), anthracene (AN), fluoranthene (FL) and pyrene (PY). Measured values of log <em>K</em><sub>pa</sub> (<em>V</em><sub>[air]</sub>/<em>V</em><sub>[fresh&thinsp;plant]</sub>) were 5.7, 5.7, 6.0, and 6.2 for PH, AN, FL, and PY, respectively. Values of <em>U</em><sub>pa</sub> (m d<sup>-1</sup>) under the conditions of this study ranged from 42 for PH to 119 for FL. After correcting for wall effects, the estimated reaction half-lives in air were 3, 9, and 25 h for AN, FL, and PY. Reaction half-lives in the plant compartment were 17, 6, 17, and 5 d for PH, AN, FL, and PY, respectively. The combined use of exposure chamber measurements and models provides a robust tool for simultaneously measuring several different transfer factors that are important for modeling the uptake of pollutants into vegetation.</p>