Reishi, a Chinese mushroom, has long been recognized as promoting health and detoxifying the human body. Now this same species, Agaricus, offers hope in cleaning up soil pollutants. The process, referred to as bioremediation or phytoremediation, relies on phytoextraction -- a process by which biological organisms like mushrooms and plants take up toxins without getting sick or keeling over dead the way people do.
The discovery of phytoremediation dates back to the 1980s. One of the first examples occurred at the Oak Ridge National Laboratory, in Tennessee (USA). Workers found that an oak tree had penetrated an underground radioactive storage dump and was pulling the toxins through its roots and into its leaves. The tree remained unaffected, while the radioactive components were sequestered in the leaves, in much the same way carbon dioxide (CO2) -- the prime cause of global warming -- is sequestered. Eventually, the tree had to be cut down because its radioactive leaves presented a hazard, but the lesson was not lost on some.
Phytoremediation, currently one of the most unique approaches to resolving pollution, is being readily adopted by ecologists to treat environmental problems like leftover toxic wastes from manufacturing, or radiological hazards. At Chernobyl, site of the Ukranian nuclear plant failure in 1986, genetically altered sunflowers are being grown to clean up two ponds contaminated with both cesium and strontium, radioactive isotopes emitted when the reactor failed. The soil surrounding Chernobyl is also being cleaned of contaminants with hemp plants, which are naturally vigorous and appear capable of sequestering vast quantities of toxins while producing fibers that can be made into long-lasting paper, rope, or even clothing. Unfortunately, hemp is illegal in the U.S. due to its association with marijuana.
In fact, phytoremediation appears to be one of the most natural, most attractive and least destructive remediation techniques to come along in several decades, and promises relief to the more than 40,000 U.S. sites in need of cleanup, according to the EPA. While not always as fast or complete as more technologically advanced methods, phytoremediation has the advantage of being environmentally beneficial, and its branches (phytoextraction, or removal of toxins; phytotransformation, breaking down toxins; phytostimulation, enhancing microbial activity; and phytostabilization, preventing leaching of contaminants in the first place) provide completely natural ways to sequester, dilute, or prevent chemical contamination at less cost than other technologies.
Wikipedia has an entire wiki devoted to phytoremediation, and provides actual tables of remediative plants for removing various toxins, from PCBs to heavy metals and radioactive isotopes. These plants are called hyperaccumulators, and include botanical families like Brassicaceae (mustard and cabbage family), Poaceae (flowering grasses), Fabaceae (legumes), and Asteraceae (asters, daisies and sunflowers) – many of which also attract butterflies, bees and birds, add nitrogen to the soil, and are more attractive than ionized sheets of plastic laid on the soil to "soak up" pollutants, and less destructive than scraping topsoil for disposal elsewhere - a practice that sometimes leads to the spread of the very pollutants one is trying to contain.
Phytoremediation is far from a cure-all, but considerations of temperature and precipitation, combined with a careful selection of the appropriate plants, can provide remedial benefits over time at surprisingly affordable costs. In Fort Bragg, California, residents are already considering using mushrooms to remove soil dioxins left behind as a result of Georgia Pacific’s wood-burning project which produced and sold power to Pacific Gas & Electric in 2001-02. Georgia Pacific is financing the pilot remediation project, which will begin with 10 cubic yards of dioxin-laced soil at the company’s greenhouse site and a least one bioremediation expert. Citizens are hopeful this non-tech, non-invasive form of remediation will deliver them from the effects of dioxins, which the EPA in 1994 recognized as a serious public health threat, rivaling only DDT in its potential toxicity.