What is Phytoremediation and how does it work?

 

What is Phytoremediation and how does it work?

What is Phytoremediation?

Imagine a field contaminated by an oil spill, by heavy metals or chemical products. The toxins have reached deposits of water, and fumes have overtaken the air, making of the site a natural wasteland. Sadly, situations like these are more than common all over the world, presenting hazards to both the environment and to human health.

Cleaning up such toxic sites can be very expensive and dangerous, however, over the last 30 years, researchers from all fields have been working on a new technique: letting plants do the work for us.

Phytoremediation refers to a part of the wider discipline called Bioremediation: the process of degrading waste through biological, living organisms. Phytoremediation focuses only on plants as primary organisms to dissolve waste and pollution.

phytoremediation graph

 

In a wider sense, people have been using the technique through all of human history, but bioremediation first became an official field of scientific study in the 1970s. But it wasn’t until the mid-1980s that plants were included in the roster of organisms used in bioremediation, mainly to restore fields contaminated with chemicals from intensive agriculture. Soon after, researchers started to explore a wider range of substances that could be cleaned from the environment, including petroleum derivatives, heavy metals, explosives, and volatile compounds from paints and refrigerants.

Adding plants to our spaces - both outdoors and indoor - has been proven to improve our overall health. When used indoors, plants can help with providing cleaner air and can even provide relief from depression and anxiety.

Choosing plants that purify the air through their roots and surrounding soil can improve the overall health of your home - and by extension - yourself. Follow along to learn more about how to effectively harness the process of phytoremediation for home health.

How does Phytoremediation Work?

Phytoremediation refers to a natural process occurring in any plant that has the ability to mitigate pollutants in the air, soil and water. There are a number a of ways in which certain plant species, together with microorganisms in their soil, are able to cleanse  their environment. They help remove contaminants in tandem with a number of different processes:

  • Phytostabilization - Plants are able to lock up contaminants in their roots, stems and leaves. This process aims to retain contaminants in the soil and prevent further dispersal by supporting existing elements within the soil. Phytostabilization involves adding plants to the soil that can provide additional microbes which can decrease toxic effects of contaminants in the soil.
  • Phytoextraction - Contaminated portions of plants can be removed and destroyed. In phytoextraction, plants are used to accumulate contaminants in the above-ground, harvestable biomass (leaves and stems). In this process, only certain plants that can hyper-accumulate toxins without any toxic effects are used. These plants are adapted to naturally occurring, metalliferous soils and can therefore naturally hyper-accumulate various metals.
  • Phytodegradation - Plants are able to attract certain bacteria to their root zone, where toxic substances in the soil are either reduced or absorbed. This involves breaking down organic contaminants directly, through the release of enzymes from roots, or through metabolic activities within plant tissues. Through phytodegredation, organic contaminants are converted to less harmful substances, thereby improving the health of the soil.
  • Phytovolatilization - Plants and organisms in the soil are able to convert toxic substances in the air into less toxic gases. This involves converting contaminants stored inside plants to a gaseous state. These contaminants are then released into the atmosphere via the evapotranspiration process. Large plants like trees are often involved in phytovolatilization as they are the most effective at converting VOCs into less harmful substances. Certain trees like hybrid poplars and tulip trees have even been genetically engineered to allow the plants to better “volatilize specific contaminants.”

Other ways in which plants can remove toxins, chemicals, and pollutants from the environment are normally referred to as:

  • Stabilization of the roots - Plants are able to fix toxic substances onto their roots, where microorganisms, break them down and convert them into less toxic substances.
  • Stabilization - Some plants draw polluted groundwater upwards, so that it cannot seep deeper into the soil.
  • Translocation - Plants and organisms in the soil are able to convert toxic substances into less toxic ones; this occurs either within the plants or in their roots.

In a recent article, we explained how scientists studying the air-purification capacities of indoor plants have demonstrated that plants can absorb many other gases in addition to carbon dioxide, including an extensive list of volatile organic compounds (VOCs).

How can Phytoremediation be used in “real life”?

Phytoremediation is used outdoors in a number of ways. It can be used to remove pollutants from air and drinking water in city centers. It can also be used in agricultural areas to remove toxins from soil and groundwater. Another use is to increase the health of residential properties through changes in the back- and front yards. In “Remediation Technologies” the author wrote “phytoremediation may be applied wherever water or air has become polluted." It can also be used wherever there are problem of ongoing – chronic – pollution like major industrial areas, ports, highways, airports, city parks and more.

In other words, the applications for phytoremediation are practically endless.

Phytoremediation has lessened the effects and concentrations of contaminants in thousands of civilian and industrial projects across the globe. Contaminants such as metals, pesticides, solvents, explosives, and crude oil can all be heavily mitigated with phytoremediation techniques. Some plants known to be extremely effective in doing so include mustard plants, alpine pennycress, hemp, and pigweed. These are especially sought after because they have proven to be successful at hyper-accumulating contaminants at toxic waste sites consistently in the past three decades.

Can Phytoremediation be helpful indoors?

According to EPA “phytoremediation is a low-risk and attractive cleanup method.” While you might imagine phytoremediation can only be effective outdoors with large plants, such as trees and shrubs, this is far from being the case. Several recent studies proved that some indoor houseplants can remove VOCs and other microorganisms from the air through phytoremediation quite effectively. In particular, a study published in the Journal of Air Quality, Atmosphere & Health found that indoor houseplants can remove various pollutants in the air. The study concluded that this result is to be attributed primarily to natural occurring phytoremediation.

who air pollution health effects air quality

If you aren’t sure about what plant might be the best for cleaning your home, check out our article about the 9 best air purifying plants:

  • Spider plants
  • Dracaenas
  • Golden pothos
  • Areca palms
  • Chrysanthemums 
  • English ivy
  • Rubber plants
  • Chinese evergreen
  • Peace Lilies

A conclusive note

Unfortunately, after over 30 years of research, phytoremediation is still largely ignored in commercial applications. An article from the National Academy of Sciences tried to cast some light on what might be the main reasons for that: phytoremediation takes a lot of time.

It may take years to completely clean an entire field. Even if phytoremediation is far cheaper and clearly more environmentally friendly, developers tend to prefer quicker methods like excavation. A lack of understanding about this natural process is another huge barrier to widespread adoption of this incredibly positive practice.

Even in its most basic form, phytoremediation possesses a ton of advantages compared with other methods of “remediation”. Plants are solar-powered and generate little to no air or water pollution (they actually help decrease it). In the case of heavy metals, plants allow for the recuperation of valuable products. As science invests more in toxin-absorbing plants, there is hope that phytoremediation will become a more common and frequently-used tool in the fight against water, air, and soil pollution.