An integrated monitoring approach to evaluating the incidental remediation of VOC-contaminated groundwater

Volatile organic compounds (VOCs) have been identified as a major source of groundwater contamination worldwide. However, assessing the potential exploitation of a contaminated phreatic aquifer has been somewhat limited in the past, especially because integrated monitoring activities are required to elucidate the dynamics of vadose zone processes and their interactions with the atmosphere. The present paper presents and discusses the findings of a pilot study carried out in a contaminated site, where poplar trees were cultivated for phytoremediation purposes, to evaluate the efficacy of two irrigation systems in reducing VOC concentrations in groundwater exiting an irrigation well. The dynamics of unsaturated zone processes within a 1.0-m-deep soil profile were monitored by measuring soil-water contents and matric heads. Geophysical techniques provided high-resolution 2D and 3D time-lapse images of subsurface soil electrical resistivity, extending down to a depth of 10 m below ground. The monitoring of VOC concentrations in the aquifer and outgoing nozzle waters, as well as in the air above the study area, proved to be of the utmost importance. Vegetation responses during the experimental period were obtained indirectly through the use of an electronic dendrometer. The integrated monitoring activities presented in this study have demonstrated how valuable information can be obtained today at affordable costs, providing a comprehensive perspective of the complex contamination processes in an agroecosystem. The use of these datasets has been exemplified by their implementation in simulating the transport processes in soil associated with two growing seasons of maize irrigated with a drip system fed by groundwater contaminated with trichloroethylene (TCE). This simulation was performed using the Hydrus-1D model.