Site Location: Edgewood, Maryland (Aberdeen Proving Grounds)

Contaminants: PCE/TCE/Heavy Metals in Soil and Ground water that is 5 to 15 feet below ground surface.

Project Objective: Prevention of off-site migration of contaminant plume into coastal wetlands.

Implementation Program: A TreeMediation site assessment was performed by collecting and evaluating soil and ground water data and reviewing previously developed site environmental data. Hybrid poplars were implemented to create a zone of influence that would limit the off-site migration of the contaminated ground water.

Results to Date: Sampling of leaf and stem tissues has been performed along with evaluation of upgradient and downgradient ground water. TCE levels were detected in leaf tissue midway through the first year of the program.

In year two of the study, soil gas measurements were taken to identify trees that were and were not exposed to TCE/PCE in the root zone. Branches of these trees were bagged and off-gases were collected and measured. TCE/PCE were detected in the bags of trees that were known to be exposed to TCE/PCE in the soil and not detected in the bags of trees known not to be exposed to soil TCE/PCE.

A transect of monitoring wells through the TreeMediation area is being used to evaluate the programís effect on the ground water TCE/PCE levels and are demonstrating a hydraulic effect on the groundwater by the trees.

The graph below depicts the residual content of TCE (as trichloroacetic acid, TCAA) in branches and leaves of trees exposed to TCE contamination and background trees.  The relatively high values reflect elevated TCAA values for trees exposed to TCE.  The lower values generally represent background levels.