Relationship Between Tree-Core and Groundwater Trichloroethylene Concentrations for Groundwater Plume Delineation.

摘要

A 17-month field study designed to evaluate the feasibility of using trees as a cost-effective groundwater sampling and plume delineation tool was recently completed at site Operable Unit 4 at Hill Air Force Base (Ogden, UT). Using a hand-driven incremental borer, tree-core samples were collected monthly from cottonwood (Populus deltoides), russian olive (Elaeagnaceae elaeagnus), poplar (Salicaceae populus), apple (Malus pumila), and box elder (Acer negundo) trees located within and outside a trichloroethylene (TCE)-contaminated shallow groundwater plume. Concentrations of TCE in the core samples were determined using a headspace gas chromatography procedure. Variations to the headspace analysis method were made and results compared to other methods of TCE measurement for performance comparison. A relationship * between tree core (0. 001 to 32 mg/kg) and groundwater (0.2 to 4890 mg/L) TCE concentrations was observed (e.g., trees located above areas of high groundwater TCE concentration were found to contain high TCE concentrations). Stable isotopes of hydrogen were used to show that shallow TCE-contaminated groundwater is the most likely source of water used by the trees. Wood sorption isotherms (using site specific trees) were completed using C-14 TCE in a sealed batch process. Wood-water partitioning coefficient (K(sub wood)) values of 16.42 mL/g (cottonwood) and 11.51 mL/g (russian olive) were obtained from linear isotherms. When measuring TCE concentrations in water, these K(sub wood) values can now be used to estimate original concentrations of TCE within the tree tissues. Desorption coefficients were measured through sequential dilution steps and found to be reversible along the sorption isotherm.