Using green plants to clean the environment

Argonne is pioneering the use of Mother Nature's green plants to clean up environmental pollution. The technique, known as phytoremediation, is not only cheaper than traditional clean-up methods, but it is also a natural process that is aesthetically pleasing. The technique uses plants to take in contaminants along with water and nutrients from the soil.

Like many other government facilities, Argonne is cleaning up previously contaminated areas on its own site. In the late 1950s and 1960s, Argonne disposed of various chemicals in a French drain - a gravel-filled trench. This technique is no longer used at Argonne, but it was the environmentally accepted standard at the time. As a result, a 10-acre area of the Argonne site is now contaminated with volatile organic compounds and small amounts of tritium. Argonne has been cleaning up this area since the 1980s.

In 1999, approximately 770 hybrid poplars and willows were planted in this area, as part of a soil and groundwater cleanup project to use the special capabilities of phytoremediation for cleaning up this type of contamination. Argonne's Environmental Safety and Health Division is managing this cleanup with the expertise of phytoremediation experts in the Energy Systems Division.

Researchers have determined in the past few years that plants are like green livers because they remove impurities. Plantings of hybrid poplars in Washington state, for example, indicate that of the organic contaminants taken up by the trees, about 70 percent is converted to non-volatile compounds and held in the plant. The other 30 percent vaporizes from the leaves with the transpired water.

The process has several advantages over the traditional and often invasive clean-up techniques in which the soil is sometimes dug up and incinerated in a kiln to break down the compounds. Not only is phytoremediation all natural, but the plants can address many contaminants at one time. It is also low cost and low maintenance, because the trees do the bulk of the work.

Researchers and engineers will monitor the surrounding soil and plants to check the progress of the Argonne phytoremediation plantation. Although it could be four to ten years before the process is completed, they expect to reduce contamination in the groundwater and limit it to a smaller area in two to three years.

If all goes as well as expected, forests of trees could soon replace incinerators at some environmental clean-up projects around the nation.

For more information about Argonne's environmental research and cleanup work, visit the following pages on the World Wide Web: