Phytoremediation: The power of plants to clean up the environment

The tsunami that struck Japan in 2011 not only caused extensive damage to the country’s infrastructure, but also poisoned the environment when it caused the Fukushima nuclear power plant to leak radiation into the surrounding area.  The cleanup of Japan’s radioactive water and land is expected to take decades and will require a variety of corrective methods.  One potential method for removing the poisonous material from the environment is to plant sunflowers.

Why sunflowers?  Because these plants are what environmental scientists call hyperaccumulators; that is, the plants have the ability to take up large amounts of toxic materials from their environment.  In fact, sunflowers were planted around the Chernobyl region to remove some of the radioactive isotopes released by a nuclear plant meltdown.  This use of plants to clean up contaminated areas is called phytoremediation.

Combining the Latin words for “plant” and “remedy,” phytoremediation uses special types of plants that are able to absorb or metabolize harmful chemicals such as radionuclides, inorganics, and heavy metals in the soil and ground water.  There are several types of phytoremediation processes, including:

From Krystofova, O., Adam, V., Opatrilova, R., Babula, P., Zehnalek, J., Kaiser, J., et al. (2009). Sunflower Plants as Bioindicators of Environmental Pollution with Lead (II) Ions. Sensors, 9(7), 5040-5058.

• Phytoextraction – (the most common method) uses hyperaccumulating plants, like sunflowers, to take up and store pollutants in roots, stems, and leaves.
• Phytometabolism – plants break down toxic material into non-toxic forms.
• Phytovolatization – plants convert pollutants to a gas released into the atmosphere.

 
In phytoextraction, although the contaminants are not neutralized, the plants and the stored pollution can be harvested and properly disposed of.  If this process is done on a large scale and for a long time – say, thousands of sunflowers planted near Fukushima for decades – phytoremediation can be an effective environmental solution.

As a naturally occurring process, phytoremediation offers several benefits.  Plants are both easily available and relatively cost-effective to grow and maintain.  Some researchers have estimated that the cost of phytoremediation is approximately 25% less than comparable clean-up efforts.  In addition to being cheaper, it is, compared to bulldozers and technicians in hazmat suits, a much more visually pleasant method as well.  The process is also much less disruptive to the local environment and helps to maintain the landscape.

But, even though it is a more environmentally-friendly and aesthetically-pleasing process, phytoremediation does have negative aspects as well.  First of all, it is a significantly longer clean-up process than using machines and manpower, often stretching into decades.  Second, phytoremediation has the potential to transfer contaminants from the water or ground to foraging animals, extending the toxic effect of the problem to an environment’s food chain.  Finally, the remediation zone of this process is limited by the reach of the plants’ roots, ranging from 12 inches to 15 feet, and cannot address contaminants at deeper levels.

The future of environmental clean up could certainly involve more phytoremediation with fields of plants becoming common at disaster sites.  For phytoremediation to gain greater acceptance, however, stakeholders have to be willing to discount some of the limitations of the process – like the length of time required – in favor of the many positives.  It is especially important that those communities affected by environmental contamination advocate for the use of plants in improving the situation.  One day you may see fields of flowers, like the sunflowers in the image above, silently working to make the land safer for us all.

To learn more:

– A Citizen’s Guide to Phytoremediation from the EPA

– Introduction to Phytoremediation also from the EPA

– Phytoremediation of Contaminated Groundwater, a USGS podcast interview with hydrologist Jim Landmeyer

– Cristina Negri Talks About Phytoremediation, a video of Argonne National Laboratory environmental engineer Cristina Negri discussing the process

Written by Eric Dillalogue

Eric Dillalogue holds a MS in Library and Information Science and a BA in English. He has worked in a variety of roles from service industry management, academic libraries, and grant administration. He has taught courses on information literacy, web research, and developmental reading. Eric joined the Visionlearning team as a project manager in 2014.