Uptake of Halogenated Phenols by Aquatic Plants

Abstract

Reclamation of biologically treated wastewaters is frequently enhanced with the use of constructed wetlands and wastewater lagoons that remove nutrients and persistent organic pollutants. To better design systems utilizing uptake of persistent organic contaminants by aquatic plants, a quantitative description of partitioning of contaminants into aquatic plants is required. The uptake of halogenated phenols by Lemna minor was investigated to examine uptake of a family of closely related organic contaminants by a common aquatic plant. Batch experiments with L. minor (52h) and 14 halogenated phenols were operated at nontoxic concentration levels with >90% of aqueous-phase contaminant in the protonated form. Pseudo-first-order rate coefficients determined using nonlinear regression of time series concentration data described contaminant uptake. Changing halogen substituent or number of halogen substituents did not affect uptake rate, however halogen positioning did affect contaminant uptake rate. Uptake rate constants were not correlated with logKow , however, uptake rate was correlated with parameters related to rate of internal plant enzymatic transformation. Therefore, contaminant uptake rate appeared to proceed at a rate dependent on internal enzymatic transformation.