Sorption of selected aromatic compounds by vegetables

The sorption equilibrium and uptake kinetics of toluene, p-xylene, and 4-chlorophenol in Chinese cabbage, lettuce, scallions, and peanut were examined. The kinetic experiment revealed that faster uptake rates were observed for plant with higher lipid content and for chemicals with higher log K_ow, the octanol-water coefficient, consistent with that expected from the first order theory. Equilibrium was established in 12h. The resulting isotherms were strongly linear (R²=0.89-1.00), indicating that the sorption was primarily dominated by chemical partitioning between bulk phases/components. Plant lipid dominated over carbohydrates or proteins in sorption and accounted for 50-98% of the sorbed chemicals. Regression analysis showed that log K_lip, the lipid-water partition coefficient, and log K_ow for aromatic compounds were linearly related as follows: log K_lip=1.12 log K_ow (n=9, R²=0.998). The correlation allows sorption capacity of vegetation for a chemical to be estimated when the plant composition and the K_ow of the chemical are available. These findings have implications for the management and the remediation of lands polluted by organic chemicals as well as the assessment of their fate in the environment. © 2013 Elsevier B.V.