Editorial Feature

Toxin Eating Trees

Surprisingly, the whole global warming frenzy revolves more around inert gas CO2, rather than mercury, lead, and cadmium, which are constantly polluting the air, water and soil. Cleaning up these toxic wastes can be a quite expensive task.

Thanks to a group of researchers from the University of Washington, now we have genetically modified poplar trees that can suck up and destroy toxic chemicals from air and water. Even though Toxin Eating Trees sounds like a 1960s B Movie it is actually a proven way to save the environment, which may appear revolutionary but actually use a similar method that is age old. Seems unreal? Read on.

What are Toxin Eating Trees?

Toxin eating trees are reported to be able to absorb 91% of the trichloroethylene toxin from contaminated water than the regular trees, which can only remove about 3% of the toxins. Now that’s a much cheaper way to tackle pollution!

The researchers are still a long way from moving these trees from the lab to a practical scenario of an actual contaminated site. However, the encouraging fact is that in the lab, these super trees destroyed toxics such as TCE 53 times faster, chloroform nine times faster, and benzene 10 times faster than the regular trees. The toxin eating trees were only a few inches tall and grown in solutions in the lab.

Many more similar research studies are ongoing with some interesting results coming up. For example, genetically modified trees and plants such as cottonwoods have been found to have an unusual attraction for mercury, and Indian mustard plants display the ability to soak up selenium.

Trees from the Genes of Rabbits

When the genetic material of an organism is altered by addition of foreign genes, it is called a transgenic organism. This concept worries many people as no one can really predict the possible side effects of a new gene on a host plant or other plants and animals. The UW researchers used a gene from a rabbit and added it to the DNA of a poplar tree. The gene codes for an enzyme designed to break down pollutants. Although a similar enzyme is naturally present in the plant, scientists have not been able to isolate it to enhance its production.

These engineered trees will prevent the need for digging up tons of soil or pumping out millions of gallons of water for treatment and disposal. What is more beneficial is that these trees can naturally alter so many of the cancer-causing pollutants such as trichloroethylene (TCE), vinyl chloride, benzene, and chloroform, into non-toxic compounds.

One possible draw back may be that the enzyme is unusually flexible and can attack multiple chemicals thus increasing the chances that it could affect other trees and organisms in unforeseen ways.

Phytoremediation

Phytoremediation is a concept that is age old. It promotes planting of forests in order to clean up a polluted land. Phytoremediation is energy efficient, and feasible method of treating sites with low to medium levels of contamination. This concept is being developed in a more scientific way these days.

Phytoremediation has been estimated to be a lot cheaper alternative and costs about $25 - $100/t of soil, and $0.60 - $6.00/1000 gallons of polluted water. This system offers many options of dealing with pollution using plants. For example, plants can be used to break down or degrade organic pollutants, or they can be used to eliminate and stabilize metal contaminants.

Phytoremediation involves several processes as detailed below:

  • Phytodegradation — the decomposition of organic contaminants by internal and external metabolic processes by the plant.
  • Phytoextraction — a process where plant roots suck metal contaminants from the soil and translocate them to their tissues above soil.
  • Phytotransformation — chemical degradation or inactivation of toxins
  • Phytostabilisation — the use of specific plants to prevent movement of soil and water contaminants.
  • Phytovolatilization — uses plants to suck up contaminants, which are water soluble and release them into the atmosphere as they vaporize the water.
  • Rhizofiltration — handles remediation of contaminated groundwater rather than polluted soils. The contaminants in water are either adsorbed into the root surface or absorbed by roots of the plant.

Phytoextraction has been performed in Upton, NY to remove radionuclides from soil using Indian mustard and cabbage. Similar tests have been done in many places.

USDA plant physiologist Leon V. Kochian has been promoting the use of plants to clean up or remediate soils contaminated with heavy metals and radioisotopes. He talks about a vacuum cleaner effect of plants on contaminants. He uses plants to "vacuum" heavy metals from the soil through their roots. He terms these plants as metal hyperaccumulators.

For example, plants like Thlaspi possess genes that control the amount of metals sucked up from the soil by roots and deposited at other locations within the plant. The everyday plant probably can collect about 100 ppm zinc and 1 ppm cadmium. But super plant Thlaspi can collect up to 30,000 ppm zinc and 1,500 ppm cadmium in its shoots, and hardly exhibit any toxicity symptoms.

Just as most concepts have some drawbacks, phytoremediation also has its share. These are listed below:

  • Phytoremediation works only at the surface and at the depth occupied by the roots
  • Slow growth and low biomass require years of commitment and monitoring
  • Plant-based systems of remediation cannot do the entire job of removing contaminants from entering groundwater
  • Survival of the plants affected by the toxicity of the contaminated land is questionable
  • Bio-accumulation of contaminants, especially metals, into the plants which then pass into the food chain, requires very responsible and safe disposal of the affected plant material.

Summary

The earth certainly needs to be taken care of, the sooner the better. The efforts made by several scientists and researchers are taking us closer to making things better. Although many ideas are questionable, in order to find solutions and achieve progress, experiments need to be carried out.

Toxin eating trees and plants are an incredible concept that has immense potential. Planting these super trees would be a whole lot easier and cheaper than other waste disposal methods, not to mention that these plants are simpler to maintain and monitor. An immediate solution that has come up to prevent the spread of these engineered trees is to harvest the first few crops containing the most contamination. If this concept becomes a reality, instead of abandoned toxic pits, there could be lush green forests that remove toxins too.

One of the common concerns is that the mutant trees could put forest ecosystems at risk. These ecological and ethical concerns will have to be addressed in a better manner in the coming years to achieve the overall success in this concept.

References

Kris Walker

Written by

Kris Walker

Kris has a BA(hons) in Media & Performance from the University of Salford. Aside from overseeing the editorial and video teams, Kris can be found in far flung corners of the world capturing the story behind the science on behalf of our clients. Outside of work, Kris is finally seeing a return on 25 years of hurt supporting Manchester City.

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