As this is my first blog, I would like to introduce myself. Do not worry! I shall not begin with a 'My name is...' Rather, you should know a tad about me in every blog piece, still focusing on the core purpose of this site.
What is Phytoremediation?
I pursued my research on the phytoremediation of heavy metal-contaminated water. A lot of mumbo-jumbo words there? Let me simplify the terms; phytoremediation is the decontamination of a polluted source using living plants.
Heavy metals are toxic to any living organism beyond a particular concentration. You may wonder, I just said that plants are used to decontaminate a source. Hence, doesn't a plant, a living organism, get affected by the toxicity of heavy metals? Well, they are. However, some plants can tolerate higher heavy metal concentrations and are found growing with ease in such contaminated areas like it's no big deal. Let us refer to such plants as 'Super-plants!'
My Engagement with a 'Super-plant'
I chose to work with such a plant. However, the super-plant I selected wasn't any regular angiosperm (flowering plant) but a pteridophyte. Pteridophyte, what is that? You might have heard about ferns. Yes, those ornamental leaves in bouquets.
Non-flowering pteridophytes are the most primitive, well-developed plants that have withstood the test of time. Hence, terrestrial and aquatic ferns can endure various stresses, including high concentrations of heavy metals.
Historically, when was the superpower of the pteridophytes realised? Proceed, and you shall know.
The Superpower Called Pteris vittata
It's a Chinese brake... a Ladder brake... also called a Brake fern... YES! It's the 'Super metal absorbing fern,' Pteris vittata L.
The lush green treasure and its superpower were undiscovered until the beginning of the 21st century. It was first discovered by Lena Q. Ma and her teammates in 2001, growing abundantly on an abandoned site where wood preservation using chromated copper arsenate was carried out. Read the original report here.
When no other plant species in that region could grow in the soil, this super-plant grew to tolerate 1,442–7,526 p.p.m. of toxic arsenic. Due to this finding, this treasure was more worthwhile than anticipated and turned out to be a super-plant. Thus, the world was introduced to the super metal-hyperaccumulating plant.
What Makes Pteris vittata the Best for Phytoremediation?
Over the years, the worth of this treasure doubled as it was utilised in phytoremediation, i.e., decontaminating the heavy metal-polluted lands using Pteris vittata. The heavy metal accumulated Pteris vittata reduced the heavy metal concentration in the contaminated land. Researchers worldwide were thrilled to discover that accumulating and transforming the toxic metals to lesser toxic forms are a few of the many superpowers of these super-plants.
Dr Smitha Hegde, a well-established pteridologist (one who studies ferns) in India, expresses her fascination with the fern. She reiterates that the fern is indeed a super-plant with superpowers. Why? Because of its resilience, she says. Resilience to urbanisation and how it can thrive on very little. The nutrients are derived from the water from leaky drain pipes of buildings, lines of air conditioning units or leaking water taps.
Pteris vittata grows swiftly through spores (like seeds, but technically not seeds!) with the right amount of moisture, phosphorous and other nutrients throughout the year. She points out how the environmentalists and farmers worry about this super-plant taking over other vegetation. With Pteris vittata not having any nutritional significance and having a bitter taste (due to excessive alkaloids), herbivores do not prefer them. Hence, the mature ferns are not an active part of the food chain.
At this point, the super-plant might sound like an unstoppable alien that is taking over. However, it faces a different fate. A fate where the farmers conveniently destroy the super plants to make way for commercial crops.
Utilising Pteris vittata for Water Decontamination
In spite of the known superpowers, the super-plant is losing researchers' attention in the field of phytoremediation. To alter the destiny of the super plant, I, along with my mentors, set out to up-scale the super-plant.
The researchers gave it a new 'Avatar,' a biosorbent. So, what is a biosorbent? A biosorbent is a non-living biological material with an 'Adsorption' capacity. I have formatted the 'Ad' of adsorption to bold to highlight the principle. Adsorption involves binding an atom, ion or molecule via various bonds or forces of attraction to a surface.
With the new Avatar, the super-plant biosorbent was to decontaminate polluted water by adsorbing the pollutants, heavy metals, on them.
Transforming Pteris vittata into an Efficient Biosorbent
The excessive availability of the weedy super-plant growing on compound walls, courtyards, tiles, and buildings was another reason for the desperate need to find an additional application, as people feared its capacity to destroy man-made structures. While the people received free clean-up services, the research team got the super-plant with water decontamination power.
Plant foliate (leaf of the ferns) was collected, separated, and washed thoroughly to remove the extraneous, dried and then powdered. The powder obtained is the biosorbent, the new Avatar of the super-plant, Pteris vittata.
Experiments to Determine Biosorbent Effectiveness
The researchers conducted several experiments to standardise the best operating conditions, including the operating pH and temperature of the polluted water, the time required, the concentration of metals, the particle size of the super-plant biosorbent and the amount of biosorbent for a maximum metal uptake.
These experiments aimed to determine if the super-plant biosorbent was as effective as when living. With just 1 gram of the super-plant biosorbent in a litre of single-metal contaminated water, the super-plant removed 126.58 mg of Pb(II), 31.06 mg of Cd(II) and 166.67 mg of Cr(VI)!
Further examinations showed that the super-plant biosorbent's functional groups, texture, morphology, elemental composition, surface area, and porosity influenced its superpower to remove heavy metals from contaminated water. Thus, the research team was glad to have found the scorned super-plant.
Improving the Convenience of Pteris vittata as a Biosorbent
The researchers further explored the easy handling of the biosorbent, and pelleting the super-plant biosorbent was a more acceptable option. Though the path ahead was challenging, the researchers successfully pelletised the super-plant biosorbent.
The trick lay in finding the suitable particle size of the powder, the right binder, the right binder consistency, and the correct binder-to-powder ratio. Stable 'magic pellets' were obtained with the standardisation of the pelleting process.
With the stable 'magic' pellets, the researchers used them to decontaminate heavy metal-laden water. The superpower of the plant was still retained even in its pellet form.
The researchers aim to improve metal-laden groundwater's potability by adding the pellets into the water. The investigations have exposed a marvel in the non-living form of the super-plant. As planned, the researchers have altered the destiny of the super-plant. The superpowers of this 'ladder' plant have reached new heights in its ability to decontaminate water!
What are your thoughts on using plants for environmental remediation? Share your opinions in the comments below!
Wow, that was a very thorough investigation of how Pteris Vittata decontaminates water! I think whever we can use natural means to help the environment all life is better off.
It's a well written article highlighting the significance and utility of Pteris Vittata in decontaminating the polluted land and water. Appreciate the author for her effective writting and the concern she has for the environment. Blogs like this are really informative and I welcome more such information from her.
Nicely written. A non biology person like me could understand. Pl do write more blogs on such topics.