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Hemp-Using Plants to Clean Soil


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February, 2000: Chernobyl (Ukraine)

On the morning of April 26, 1986, a small town in the former Soviet Union was the site of a nuclear explosion that literally shook the earth. The historic accident at Chernobyl Nuclear Plant Reactor 4 in the Ukraine caused severe radioactive contamination. Families within a 30-km zone of the power plant were evacuated, and in the months that followed, extensive contamination was discovered in areas up to 100 km from the site. Scientists are hopeful that plants may play a key role in cleaning up some of the contamination.

In 1989, three years after the explosion, the Soviet government asked the International Atomic Energy Agency (IAEA) to assess the radiological and health situation in the area surrounding the power plant. Among the most significant findings were radioactive emissions and toxic metals--including iodine, cesium-137, strontium, and plutonium--concentrated in the soil, plants, and animals. Such substances are potentially harmful to human health. For example, although iodine tends to disappear within a few weeks of exposure, it can be inhaled or ingested and then accumulated in the thyroid gland, where it delivers high doses of radiation as it decays. Since 1991, the Canadian Nuclear Association has noted a marked increase in the incidence of thyroid cancer in the area surrounding the nuclear accident. Cesium-137, radioactive cesium with a mass number of 137, can enter the food chain and deliver an internal dose of radiation before it is eliminated metabolically.

Apparently these toxic substances entered the food chain via grazers, such as cows and other livestock, that fed on plants grown in contaminated soils. The toxins then accumulated and concentrated in the meat and milk products eventually consumed by humans. Additionally, wild foods, such as berries and mushrooms, are expected to continue showing elevated cesium levels over the next few decades.

To prevent further spread of these toxins, it was determined that livestock should be allowed to feed only on uncontaminated plants and on plants not tending to accumulate toxic metals within their tissues. Then a soil cleanup method was employed using green plants to remove toxins from the soil. This technique is phytoremediation, a term coined by Dr. Ilya Raskin of Rutgers University's Biotechnology Center for Agriculture and the Environment, who was a member of the original task force sent by the IAEA to examine food safety at the Chernobyl site. Phytoremediation is a process that takes advantage of the fact that green plants can extract and concentrate certain elements within their ecosystem. For example, some plants can grow in metal-laden soils, extract certain metals through their root systems, and accumulate them in their tissues without being damaged. In this way, pollutants are either removed from the soil and groundwater or rendered harmless.

Today, many researchers, institutes, and companies are funding scientific efforts to test different plants' effectiveness at removing a wide range of contaminants. Raskin favors Brassica juncea and Brassica carinata, two members of the mustard family, for phytoremediation. In laboratory tests with metals loaded onto artificial soil (a mix of sand and vermiculite), these plants appeared to be the best at removing large quantities of chromium, lead, copper, and nickel. Several members of this family are edible and yield additional products such as birdseed, mustard oil, and erucic acid, which is used in margarine and cooking oil. Researchers at the DuPont Company have found that corn, Zea mays, can take up incredibly high levels of lead. Z. mays, a monocot in the Poaceae or grass family, is the most important cultivated cereal next to wheat and rice, yielding such products as corn meal, corn flour, cornflakes, cooking oil, beer, and animal feed. Phytokinetics, a company in Logan, Utah, is testing plants for their ability to remove organic contaminants such as gasoline from soil and water. Applied Natural Sciences in Hamilton, Ohio, is taking a slightly different route by using trees to clean up deeper soils, a process they call "treemediation." University researchers from the UK reported in the May 1999 issue of Nature Biotechnology that transgenic tobacco plants can play a role in cleaning up explosives.

In February 1996, Phytotech, Inc., a Princeton, NJ-based company, reported that it had developed transgenic strains of sunflowers, Helianthus sp., that could remove as much as 95% of toxic contaminants in as little as 24 hours. Subsequently, Helianthus was planted on a styrofoam raft at one end of a contaminated pond near Chernobyl, and in twelve days the cesium concentrations within its roots were reportedly 8,000 times that of the water, while the strontium concentrations were 2,000 times that of the water. Helianthus is in the composite, or Asteraceae, family and has edible seeds. It also produces an oil that is used for cooking, in margarine, and as a paint additive. H. tuberosus was used by Native Americans as a carbohydrate source for diabetics.

In 1998, Phytotech, along with Consolidated Growers and Processors (CGP) and the Ukraine's Institute of Bast Crops, planted industrial hemp, Cannabis sp., for the purpose of removing contaminants near the Chernobyl site. Cannabis is in the Cannabidaceae family and is valuable for its fiber, which is used in ropes and other products. This industrial variety of hemp, incidentally, has only trace amounts of THC, the chemical that produces the "high" in a plant of the same genus commonly known as marijuana.

Overall, phytoremediation has great potential for cleaning up toxic metals, pesticides, solvents, gasoline, and explosives. The U.S. Environmental Protection Agency (EPA) estimates that more than 30,000 sites in the United States alone require hazardous waste treatment. Restoring these areas and their soil, as well as disposing of the wastes, are costly projects, but the costs are expected to be reduced drastically if plants provide the phytoremediation results everyone is hoping for.

Meanwhile, of the original four reactors at Chernobyl, Reactors 1 and 3 are still operating today, providing 6,000 jobs and about 6% of the Ukraine's electricity. Reactor 2 was closed after a fire in 1991; the construction of Reactors 5 and 6 came to a grinding halt after the explosion.

References, Websites, and Further Reading

"Sunflowers Bloom in Tests to Remove Radioactive Metals from Soil and Water," Wall Street Journal, 29 February 1996.

International Atomic Energy Association

Environmental Protection Agency research and scientists page

From Plants Sites & Parks magazine, May/June 1996: Attacking the Root of the Problem.

Central Oregon Green Pages: Hemp "Eats" Chernobyl Waste

Stern, Introductory Plant Biology, 8th Edition

Chapter 2: The Nature of Life
Isotopes and radioactivity, p. 17

Chapter 5 : Roots and Soils
Phytoremediation, p. 79

Chapter 7: Leaves
THC (tetrahydrocannabinol), p. 123

Chapter 24: Flowering Plants and Civilization
The Mustard Family (Brassicaceae), pp. 442-43
The Sunflower Family (Asteraceae), pp. 453-54
The Grass Family (Poaceae), pp. 454-56

Chapter 25: Ecology
Ecosystems, pp. 464-66
Food web diagram, p. 465
Herbivores, pp. 466-67

NewsHawk: MedicalNeed:420 MAGAZINE
Contact: McGraw Hill Higher Education
Copyright: 2000 The McGraw-Hill Companies.


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Economic benefits from hemp bioremediation

Hemp for Bioremediation of contaminated soils

Contamination of land and water is a growing concern for the health of the environment. Conventional practices in the remediation of contamination usually involve expensive processes such as land filling or incineration of soil. Phytoremediation uses plants to accumulate certain metals in plant biomass or accelerate contaminant breakdown. Phytoremediation can be used to accumulate, immobilize and transform low levels of pollutants from soil and water and is more economically and environmentally sound than most other remediation practices (Vidali, 2001, Blaylock et al., 1999, Ha et al., 2009, Datta and Sarkar, 2005).
Hemp is a suitable crop for phytoremediation of contaminated soil because, although hemp is not considered a hyperaccumulator it is able to remove significant quantities of contaminants which are generally stored in its roots.-The stems and seeds of hemp plants can therefore be used for end products such as chemical and pharmaceutical products, biofuel, paper, building, furniture, insulation and more. (Citterio et al., 2003, Vandenhove and Van Hees, 2005)
Hemp was used in 1998 by Phytotech and Ukraine's Institute of Bast Crops for removing contaminants near Chernobyl. Many studies have been conducted since to determine the suitability of hemp for phytoremdiation. In many studies hemp has displayed a very high tolerance to contaminants. It also has a greater adaptability to different soils and climatic conditions and has added benefits of being a rotational crop which can improve soil quality (Vandenhove and Van Hees, 2005, Citterio et al., 2003, Angelova et al., 2004).
A study by (Shi and Cai) looked for potential energy crops which could be grown on cadmium-contaminated land. Plants which offer end products such as biodiesel offer great economic value for landholders of contaminated soils. Hemp was found to be highly cadmium-tolerant and very useful in bioaccumulation of cadmium due its ability to accumulate cadmium in shoots. Hemp was also noted for having a high capacity for phytostabilisation. Phytostabilisation-uses plant structure to stabilize contaminants reducing the bioavailability and mobility of the contaminants in the soil, preventing them from entering the food chain or groundwater (Prasad and Freitas, 2003, Schwitzguébel, 2001).
Hemp is tolerant to contaminants, has the ability to accumulate and stabilise contaminated areas and, unlike most plants used in bioremediation, it offers additional end uses. Hemp can provide both an economic and sustainable solution to the contamination of soils worldwide.


ANGELOVA, V., IVANOVA, R., DELIBALTOVA, V. & IVANOV, K. 2004. Bio-accumulation and distribution of heavy metals in fibre crops (flax, cotton and hemp). Industrial Crops and Products, 19, 197-205.
BLAYLOCK, M. J., ELLESS, M. P., HUANG, J. W. & DUSHENKOV, S. M. 1999. Phytoremediation of lead-contaminated soil at a New Jersey Brownfield site. Remediation Journal, 9, 93-101.
CITTERIO, S., SANTAGOSTINO, A., FUMAGALLI, P., PRATO, N., RANALLI, P. & SGORBATI, S. 2003. Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L. Plant and Soil, 256, 243-243-252.
DATTA, R. & SARKAR, D. 2005. Genetics of Metal Tolerance and Accumulation in Higher Plants, John Wiley & Sons, Inc.
HA, N. T. H., SAKAKIBARA, M. & SANO, S. 2009. Phytoremediation of Sb, As, Cu, and Zn from Contaminated Water by the Aquatic Macrophyte Eleocharis acicularis. CLEAN — Soil, Air, Water, 37, 720-725.
PRASAD, M. N. V. & FREITAS, H. M. O. 2003. Metal hyperaccumulation in plants - Biodiversity prospecting for phytoremediation technology. Electronivc Journal of Biotechnology, 6.
SCHWITZGUÉBEL, J. P. 2001. Hype or Hope: The Potential of Phytoremediation as an Emerging Green Technology. Remediation Journal, 11, 63-78.
SHI, G. & CAI, Q. Cadmium tolerance and accumulation in eight potential energy crops. Biotechnology Advances, 27, 555-561.
VANDENHOVE, H. & VAN HEES, M. 2005. Fibre crops as alternative land use for radioactively contaminated arable land. Journal of Environmental Radioactivity, 81, 131-141.
VIDALI, M. 2001. Bioremediation. An overview. Pure and Applied Chemistry, 73, 1163-1172.

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