plants on the land, like crops.This technique is most useful when the contaminant is within the plant root zone, typically 3 - 6feet (Black, 1997), or the tree root zone, typically 10-15 feet. The second technique is growingplants in water (aquaculture). Water from deeper aquifers can be pumped out of the ground andcirculated through a reactor of plants and then used in an application where it is returned tothe earth (e.g. irrigation). The third technique is growing trees on the land and constructingwells through which tree roots can grow. This method can remediate deeper aquifers in-situ. Thewells provide an artery for tree roots to grow toward the water and form a root system in thecapillary fringe (Black, 1997). The majority of current research in the phytoremediation field revolves arounddetermining which plant works most efficiently in a given application. Not all plant species willmetabolize, volatize, and/or accumulate pollutants in the same manner. The goal is to ascertainwhich plants are most effective at remediating a given pollutant. Research has yielded somegeneral guidelines for groundwater phytoremediation plants. The plant must grow quickly andconsume large quantities of water in a short time. A good plant would also be able to remediatemore than one pollutant because pollution rarely occurs as a single compound. Poplars andcottonwoods are being studied extensively because they can used as much as 25 to 350 gallonsof water per day, and they can remediate a wide variety of organic compounds (Ackerman,1996). Phytoremediation has been shown to work on metals and moderately hydrophobiccompounds such as BTEX compounds, chlorinated solvents, ammunition wastes, and nitrogencompounds. Yellow poplars are generally favored by Environmental Scientists for use inphytoremediation at this time. They can grow up to 15 feet per year and absorb 25 gallons ofwater a day. They have an extensive root system, and are resistant to everything ...
