Improved Approaches for Modeling the Sorption of Phenanthrene by a Range of Plant Species.

Equilibrium sorption of phenanthrene and its relationship with plant lipid contents were investigated using roots and shoots of alfalfa, ryegrass, tomato, potato, carrot, cucumber, zucchini, and pumpkin. Lipid extractions using chloroform and hexane were compared, and the influence of dechlorophyllization on lipid determinations was evaluated. The sorption isotherms were close to linear (R2 > 0.923, P < 0.05) and the plant-water partition coefficients (Kpl) of phenanthrene obtained from the isotherms exhibited significant and positive correlations with plant lipid contents (R2> 0.664, P < 0.05). The correlations were more significant (R2 > 0.906, P < 0.001) when dechlorophyllization was included in the lipid extraction. The measured sorption was higher than that estimated using the octanol-water partition coefficient (Kow) but was very close to the estimate using the triolein-water partition coefficient (Ktw). This study leads us to conclude that dechlorophyllization is necessary for plant lipid determination and that Ktw is more accurate as a substitute for the lipid-water partition coefficient (Klip) than Kow. These novel approaches may provide substantial improvements in the application of partition-limited models for the estimation of plant uptake of organic contaminants. [ABSTRACT FROM AUTHOR]