By Anita B. Stone – America’s priceless natural resource, land, has often been used as a natural, free dispose-all for toxic compounds. For many of us, it seemed to be a harmless practice, using the out of sight, out of mind idea. But, as a result, the damage to soil can be long term leaving areas of land that were once productive to lie fallow and become a wasteland. The surprising solution comes from phytoremediation plants — living green plants that can help clean and mitigate soil damage.
Just as there are best houseplants for clean air indoors, there are best plants that can be used outdoors for cleaner soil. Good soil lacks contaminants and provides trace minerals and key components for plant growth. But good soil is not always easy to find. And many contaminants can be expensive and require a great deal of time to remove from toxic soil. Good soil will result when phytoremediation plants clean contaminated soil. This problem is not just an occasional issue concerning a variety of news-worthy events. Homesteaders and farmers can face these same issues. For instance, disposing of petroleum products such as machine oil, asphalt, lead, tar or certain agricultural chemicals can pose problems. In order to reclaim the soil and get rid of contaminants, phytoremediation plants can be used to reduce these issues.
Phytoremediation plants refer to the use of living plants to reduce, degrade or remove toxic residue from the soil. Using green plants to decontaminate soil is a progressive and sustainable process, greatly reducing the need for heavy machinery or additional contaminants. Familiar plants such as alfalfa, sunflower, corn, date palms, certain mustards, even willow and poplar trees can be used to reclaim contaminated soil – a cheap, clean and sustainable process. The term, phytoremediation, can be best understood by breaking the word into two parts: “phyto” is the Greek word for plant. “Remediation” refers to a remedy, and in this case, a remedy for soil contamination whether it be located in the garden or across a large landscape area.
Here is where plants used in phytoremediation enter the area. These special plants are known as superplants, which readily absorb toxins from the very soil where they are growing. For phytoremediation plants to work effectively, the specific plant must be able to tolerate the toxic material it is absorbing from the soil. We cannot just plant any vegetation in contaminated soil and hope for the best. The history of the concept of phytoremediation plants is interesting and can be traced to earlier studies of the relationship between soil-plant systems and the nutritional quality of food.
In 1940, studies of compounds within edible plants and their ability to absorb additional nutrition from the soil became big news. Early research on soil contamination testing proved the ability of soil to increase a given plant’s nutrition beyond what was thought to be their ultimate level. Soil testing research led to further tests of a plant’s ability to absorb less desirable elements from the soil; that is, toxins released through industrial waste, sewage and agricultural chemicals. Eventually, phytoremediation plants became an additional clean-up technique to remove harmful chemicals from the soil, such as cadmium, zinc, iron, and manganese. One plant used in phytoremediation for cleaner soil is Alpine Pennygrass because it was found to be able to remove 10 times more cadmium than any other known soil cleaning plant. Another plant used in phytoremediation for cleaner soil is Indian mustard, which removes lead, selenium, zinc, mercury, and copper from the soil.
In 1980, R.L. Chanely published a paper on the subject of what makes good soil and how to establish it through the use of phytoremediation plants. Plants such as mustard and canola thrive in contaminated soils, absorbing and therefore reducing the level of toxic accumulation. A native phytoremediation plant for cleaner soil, known as Indian Grass, has the ability to detoxify common agrochemical residues such as pesticides and herbicides. Indian Grass is one of nine members of grasses that assist in phytoremediation plants. When planted on farmland, the reduction of pesticides and herbicides is significant. This list also includes Buffalo grass and Western wheatgrass, both capable of absorbing hydrocarbons from the land.
Since any plant used as a phytoremediator must be able to tolerate any toxins it absorbs, researcher David W. Ow has been investigating which genes are key to increased plant tolerance. When identified, these genes can then be moved to other plant species to absorb high levels of certain metals. More research proves genetic movement. During testing into the nutritional value of broccoli, it was found that the plant worked well to deplete the soil of several metals. In California, some farmers who had been irrigating with recycled water discovered that their soil became overloaded with either selenium or boron.
Other plants used in phytoremediation for cleaner soil include species that reduce levels of organic compounds found in coal and tar, which are present in pitch, creosote, and asphalt. These include the very popular sunflower, which has the ability to absorb heavy metals, such as lead. Homesteaders, farmers, and agriculturalists have been practicing “intercropping” for several years. By simply employing the intercropping method, the above-mentioned plants can be effectively used as excellent choices. For example, sunflower plants were demonstrated to have removed 95 percent of uranium from a contaminated area in a 24-hour period. This highly successful crop is a powerful tool for the environment because of its ability to remove radioactive metals from superficial groundwater.
The willow is being used as a phytoremediation plant for cleaner soil. It not only beautifies the landscape but the roots have the capability of accumulating heavy metals in sites polluted with diesel fuel. A tree that is being studied for use as phytoremediation for cleaner soil is the poplar tree. Poplar trees have a root system that absorbs large quantities of water. Carbon tetrachloride, a well-known carcinogen, is easily absorbed by poplar tree roots. They can also degrade petroleum hydrocarbons like benzene or paint thinners that have accidentally spilled onto the soil. This has been a fantastic discovery. Besides their usefulness in controlling and absorbing toxic soil materials, poplar trees can be easily integrated into any type of landscape for aesthetic appeal.
With ongoing research and new toxin-absorbing plant life being discovered each year, we can expect phytoremediator choices for pollutant cleanup projects to increase. The process appears simple, but the research is slow, complicated and painstaking. But, compared to the process of soil removal, soil disposal, or physical extraction of contaminants, phytoremediation plants are a useful and working alternative that pinpoints toxic materials in the soil. We can remove quite a bit of soil contamination by using this process.
Some enthusiasts consider this process a low-cost “green” technology for soil cleanup, which can be used anywhere without specialized training or equipment. Planting a few additional plants, attractive to the landscape, can certainly enhance the soil on any land area. A variety of grasses, sunflowers, trees and other plants work in a positive way, helping farmers, homesteaders and agriculturalists rid levels of toxic materials found in our soil. These plants, themselves, are used in the restoration of healthy soils as they become their own ready-made storage containers for removal and subsequent treatment. The future of phytoremediation plants continues to move forward in creating clean soil. It is being used by industrial groups. With the help of farmers, homesteaders, and landowners, future research could create a system that will continually absorb contaminants, free up useless soil, and clean the environment on a continuous, constant and self-renewing basis.
Have you used phytoremediation plants to clean contaminated soil? If so, what plants did you use? Was the process successful? Let us know in the comments below.