Competitive uptake of trichloroethene and 1,1,1-trichloroethane by Eucalyptus camaldulensis seedlings and wood

The efficient use of trees for taking up volatile organic compounds (VOCs) from the subsurface for remedial and screening purposes is hampered because many poorly quantified co-occurring processes affect VOC concentrations in the tree, the most basic of which are VOC sorption and uptake by roots. Toward understanding the dominant sorption mechanisms, uptake of trichloroethene (TCE) and 1,1,1-trichloroethane (TCA) by Eucalyptus camaldulensis seedlings was studied in both single-solute and bi-solute experiments. Single-solute and bi-solute sorption experiments on wood from a mature Eucalyptus camaldulensis specimen were also carried out. Competition between TCE and TCA for sorption sites was found in both seedling uptake and wood sorption experiments, indicating that partitioning is not the sole mechanism governing compound interactions in these systems. The nonlinear single-solute sorption isotherms on wood were fit by a dual-mode model including partitioning and Langmuir terms. The dual-mode model calculated parameters were consistent with the results of the bi-solute sorption experiments. As a consequence of competitive sorption processes, uptake of individual compounds may be lower than expected when multiple VOC contaminants are present in the subsurface.