Black willow (Salix nigra) use in phytoremediation techniques to remove the herbicide bentazon from shallow groundwater

Wetland environments have been impacted by the activities of man over the past several hundred years in North America. Industrialization into wetland areas has brought with it anthropogenic compounds that have been released into soils and groundwater. The use of phytoremediation to detoxify soil and groundwater began in the mid 1990's and has become a popular remediation technology. In 1994, a feasibility study for using phytoremediation in such an industrialized wetland area was conducted at a petrochemical facility at BASF Corporation, located about 20 kilometers south of Baton Rouge, Louisiana in Ascension Parish. The test site consisted of low level concentrations of the herbicide bentazon in the shallow soil and groundwater. In 1996, two test plots of 438 and 1000 black willow saplings were planted over the two shallow groundwater plumes of bentazon contamination.; Groundwater monitoring, which began five years prior to plantings, was continued for five additional years after plantings. An effectiveness study was concluded in 2001. This research included measuring plant water use, soil conditions, evapotranspiration rates. Groundwater and statistical modeling were used to evaluate phytoremediation effectiveness. Data support that phytoremediation at the test site was successful at reducing the concentration of bentazon from the shallow groundwater. Modeling studies demonstrated that effective remediation will continue to occur as the trees continue to grow. It is predicted that remediation will be completed within 22 years. This research demonstrates the first comprehensive phytoremediation approach to remove the herbicide bentazon from shallow groundwater.