Lignin and lipid impact on sorption and diffusion of trichloroethylene in tree branches for determining contaminant fate during plant sampling and phytoremediation.

Plants draw all they need from their surrounding environment and in doing so also draw anthropogenic contaminants from their surroundings. Several natural processes (e.g., active transport, diffusion, sorption, and degradation) occur within trees and affect chemical concentrations in tree samples. This study elucidates tree contaminant chemical interactions on equilibrium sorption and diffusion into branch tissue (i.e., wood core and bark), specifically the impacts of lipid and lignin content. Five tree species were selected to span a range of lignin and lipid contents. Linear isotherms were obtained for all sampled species over a limited concentration range (2 microg/ mL < C(gas) < 12 microg/mL), and equilibrium distribution coefficients (K(d)) were linearly correlated to lipid (R2 > 0.83) but not lignin (R2 < 0.4) content. Lipid content was generally higher in bark than in wood cores, so mass concentrated in this tissue. Diffusion into trees was modeled, showing mass transfer resistance in bark was different from wood cores. Diffusion coefficients for bark were 2-10 times less than those for wood cores for all species, and diffusion was linearly related to lipid content (R2 > 0.96) and sorption coefficients (R2 > 0.83). Data from this study and previous research were used to develop the following correlation between the diffusion coefficient and relevant plant and chemical parameters for branch samples: D = (-7 x 10(-11)) x [f(lipid) x 10 (l.48 x logKow+0.54)] + 4 x 10(-8).