year and absorb 25 gallons of water a day. They have an extensive root system, and are resistant to everything from gypsy moths to toxic wastes. Partial listing of current remediation possibilities. Plant Chemicals Clean-up numbers Pondweed TNT & RDX 0.016-0.019 mg of TNT / L per day Poplar Trees Atrazine 91% of the Atrazine taken up in 10 days Poplars Nitrates from fertilizers From 150 mg/L to 3 mg / L in under 3yrs. Mustard Greens Lead 45% of the excess was removed Pennycress Zinc & Cadmium 108 lb./acre per year & 1.7 lb./acre per yr. Halophytes Salts reduced the salt levels in the soils by65% Advantages and Disadvantages to Phytoremediation: Advantages: ( www.rtdf.org/genlatst.htm) 1.Aesthetically pleasing and publicly accepted. 2.Solar driven. 3.Works with metals and slightly hydrophobic compounds, including many organics. 4.Can stimulate bioremediation in the soil closely associated with the plant root. Plants can stimulate microorganisms through the release of nutrients and the transport of oxygen to their roots. 5.Relatively inexpensive - phytoremediation can cost as little as $10 - $100 per cubic yard whereas metal washing can cost $30 - $300 per cubic yard. 6.Even if the plants are contaminated and unusable, the resulting ash is approximately 20-30 tons per 5000 tons soil (Black, 1997). 7.Having ground cover on property reduces exposure risk to the community (i.e. lead). 8.Planting vegetation on a site also reduces erosion by wind and water. 9.Can leave usable topsoil intact with minimal environmental disturbance. 10.Generates recyclable metal rich plant residue. 11.Eliminates secondary water or air-borne wastes. Disadvantages: 1.Can take many growing seasons to clean up a site. 2.Plants have short roots. They can clean up soil or groundwater near the surface in-situ, typically 3 - 6 feet (Ecological Engineering, 1997), but cannot remediate deep aquifers without further design work. 3.Trees have longer roots and can clean up sl...
