Uptake, accumulation, phytotoxicity, and removal of 2,4-dichlorophenol in willow trees

The relation between uptake, accumulation, toxicity and removal of 2,4-dichlorophenol (2,4-DCP) in willow trees (Salix viminalis) and the feasibility of implementing phytoremediation as a treatment method for 2,4-DCP contamination in wastewater and soil were investigated. Willows were exposed to various 2,4-DCP concentrations between 5 and 150 mg/L in hydroponic solution and between 9.1 and 44.4 mg/L in sand under constant illumination. The transpiration of the trees was used to determine toxic effects. In both hydroponic solution and sand, severe inhibition of transpiration started approximately at 2,4-DCP concentrations of 20 mg/L. Accumulation in willows was increased with higher concentrations. In surviving trees, the loss of chemical from the system was above 65%. In experiments performed without trees, the mass loss of 2,4-DCP was only 8 to 14%. For trees with detached roots, there was a significantly higher amount of 2,4-DCP remaining in the nutrient solution at the end of the experiment compared to experiments with the intact trees. The results indicate that degradation in the root zone, either by root cells or associated microorganisms, is the main reason for the removal of 2,4-DCP from the media. Phytoremediation of 2,4-DCP with willow trees does not seem to be a remediation option because of its high toxicity to trees and the limited removal efficiency.