If you were to ask someone why they think plants are important, you may expect answers such as; “They provide the air we need to breathe”, “they serve as a food source for animals” and “they are great for making tea as well as pretty to have around”.
No matter the answer, I am sure everybody would be able to agree that plants are important as well as incredible! Even today we are still discovering new, exciting ways in which we could use plants so to help make our planet a better place to live in.
I am sure many people are aware that certain plants are able to grow in extremely unfavourable environments, such as in deserts, snowy mountaintops and salt marsh lands. Although what most people probably don’t know, is that certain plants are even able to survive in areas exposed to high radiation and chemical pollution.
Scientists have taken advantage of this incredible ability displayed by certain plants to live in highly polluted areas, by studying the effectiveness of these plants in removing a wide range of contaminants. They then pushed this further by using these plants to extract pollutants from areas laden with toxic, heavy metals.
Through this, a relatively new technology called phytoremediation was started. Phytoremediation involves the removal or extraction of certain metals through the plants’ root system. These metals then accumulate in the plants’ tissues, without damaging the plant. Pollutants are either removed from the soil and groundwater or they are transformed into less harmful forms.
Heavy metals pose many health risks to the environment as well as on human health. They are non-degradable and therefore just accumulate in the environment. Examples of two toxic, heavy metals are arsenic and mercury. Exposure to arsenic is known to cause skin and lung cancer as well as nausea, diarrhoea and vomiting. Mercury poisoning can lead to mental retardation, blindness and brain damage. One of the main ways that mercury poisoning occurs is through biomagnification (the build-up of metal concentration as the element passes from the lower to the higher trophic levels). Arsenic is found in the soil from smelters and pesticides.
The immobilisation and extraction of these toxic, heavy metals is therefore paramount for if we want to live in a safer, healthier and cleaner environment. Areas where smelting, mining and sludging occur as well as where pesticides and fertilizers are used are therefore high-risk areas.
Although phytoremediation has many benefits such as being low cost, environmentally friendly, as well as limiting the movement of these toxic metals within the soil and preventing soil erosion. There are also a number of problems associated with this technique. Firstly, the ideal plant characteristics for phytoremediation are for these plants to be tall, high yielding, fast growing and easy to harvest. But most of the 400 species identified as a bioaccumulator (an organism that is able to accumulate metals or other contaminants in it’s’ tissues) seem to exhibit a slow growth rate, therefore limiting the amount of metal taken up. Areas where the heavy metal concentration is too elevated also poses a threat as plants begin to become too stressed. So what is the solution?
In the paper written by Paz-Ferreiro and his colleagues, they suggest that the use of biochar combined with phytoremediation could vastly improve remediation efforts.
Biochar is simply charcoal, which comes in many different forms-depending on the waste material it is made from. Biochar has shown many benefits on soil properties, increasing the plant yield, as well as increasing the percentage of germinating seeds and root length.
In this paper, the authors provide a very comprehensive summary of these two techniques as well as a summary of the various studies performed using biochars and phytoremediation in differently polluted environments. They also stress the importance of further research into the combining of these two techniques for future soil remediation.
One example of phytoremediation in action is with using sunflowers to remove radiation. Since the tragedy of the Chernobyl nuclear reactor leak in 1986, sunflowers have been planted all around the region where the disaster took place. Effectively, sunflowers can removed up to 95% of the radiation in the soil as well as in the contaminated water. These sunflowers are then harvested, to which the radioactive material within the plant is properly disposed of.
Although, not all phytoremediation efforts have been as successful such as with the Chernobyl disaster. The survival of these plants depends greatly on the level of toxicity of the contaminated land as well as the general condition of the soil. This is where biochars can become of great value. Future phytoremediation efforts using biochars may prove to be a lot more effective in terms of heavy-metal accumulation as well as the long term survival of the plant. Phytoremediation combined with biochar is the way forward, especially in today’s’ world of massive corporations, industries and development.