Phytoremediation is a plant-based method of extracting and removing elemental pollutants from the environment or lowering their bioavailability in soil. Plants have the ability to absorb ionic substances from the soil through their root system, even at low concentrations. Plants extend their root systems into the soil matrix, forming a rhizosphere ecosystem, which collects heavy metals and modulates their bioavailability, reclaiming damaged soil and regulating soil fertility. This article will explain to you about Phytoremediation which will be helpful in preparing the Environment syllabus for the UPSC Civil Service exam.

Phytoremediation- Concept

• Living plants are used in phytoremediation technologies to clean up soil, air, and water that have been contaminated with dangerous pollutants.
• It's defined as "the employment of green plants and associated microbes, as well as appropriate soil amendments and agronomic techniques, to either contain, remove, or render harmful environmental toxins harmless."
• Many plants, including mustard, alpine pennycress, hemp, and pigweed, have demonstrated their ability to hyperaccumulate toxins at toxic waste sites.
• Phytoremediation has been used successfully to recover abandoned metal mine workings, sites where polychlorinated biphenyls were deposited during manufacturing, and mitigation of continuing coal mine discharges, decreasing pollutants in soils, water, and air.
• Metals, pesticides, solvents, explosives, and crude oil and its derivatives have all been reduced through phytoremediation operations around the world.

Phytoremediation

Phytoremediation- Types

Phytoextraction / Phytoaccumulation

• Phytoextraction / phytoaccumulation is the process by which plants accumulate pollutants in their roots, shoots, or leaves above ground.
• The roots absorb elements from the soil or water and concentrate them in the plant biomass above ground.
• Hyperaccumulators are organisms that have a high capacity for absorbing pollutants.
• For the past twenty years or so, phytoextraction has been rapidly gaining popularity around the world. Heavy metals and other inorganics are commonly extracted via phytoextraction.
• Contaminants are often concentrated in a significantly smaller volume of plant matter at the time of disposal than in the initially contaminated soil or silt.
• Because a lesser level of pollutant remains in the soil after harvest, the growth/harvest cycle must normally be repeated over several crops in order to achieve a meaningful cleanup. The soil is then remediated as a result of the procedure.

Phytoextraction

Phytotransformation/ Phytodegradation

• Phytotransformation, also known as phytodegradation, is the transformation of organic pollutants from soil, sediments, or water into a more stable, less hazardous, and less mobile form.
• The plant roots secrete enzymes that break down the organic chemicals, which are subsequently taken in by the plant and expelled by transpiration.
• Herbicides, trichloroethylene, and methyl tert-butyl ether are among the organic pollutants that this method works best with.
• The chemical change of environmental compounds as a direct result of plant metabolism is known as phytotransformation, and it frequently results in their inactivation, degradation (phytodegradation), or immobilization (phytostabilization).
• Organic pollutants, such as pesticides, explosives, solvents, industrial chemicals, and other xenobiotic compounds, are rendered non-toxic by the metabolism of certain plants, such as Cannas.
• In other cases, these compounds may be metabolized in soil or water by microbes living in close proximity to plant roots.

Phytodegradation

Phytostabilization

• Phytostabilization is a process in which plants limit contaminated soil movement and migration.
• Adsorbed and bonded into the plant structure, leachable elements form an unstable mass of plant from which toxins cannot re-enter the environment.
• By attaching contaminants to soil particles, the plant immobilizes them, making them less available for plant or human uptake.
• Phytostabilization, unlike phytoextraction, concentrates on sequestering contaminants in the soil near the roots rather than in plant tissues.
• As pollutant bioavailability decreases, exposure decreases.
• Plants can also excrete a material that causes a chemical reaction, resulting in the heavy metal pollution being converted to a less harmful form.
• Stabilization reduces erosion, runoff, and leaching while also lowering the contaminant's bioavailability.
• The use of a vegetative cap to stabilize and contain mining tailings is an example of phytostabilization in action.

Phytostabilization

Rhizodegradation/ Phytostimulation

• Rhizodegradation, also known as phytostimulation, is the breakdown of pollutants through rhizosphere activity.
• The presence of proteins and enzymes produced by plants or soil organisms such as bacteria, yeast, and fungi is responsible for this action.
• These bacteria may degrade dangerous contaminants like fuels and solvents into benign and harmless products.
• Plants release natural carbon-containing compounds such as sugar, alcohols, and acid, which provide additional nutrition to microbes and increase their activity.
• Transgenic plants with better plant-microbe interactions have potential to produce.
• The plant's ability to release natural chemicals that drive microbial activity would be improved.

Rhizodegradation

Rhizofiltration

• Rhizofiltration is a method of removing harmful chemicals and surplus nutrients from water by filtering it through a mass of roots.
• Pollutants are absorbed by the roots or transferred on them.
• This method is frequently used to clean up contaminated groundwater by either planting directly in the contaminated area or extracting the contaminated water and delivering it to these plants off-site.
• Plants are normally grown in a greenhouse under controlled conditions in either situation.
• This technique is used for reducing pollution in wetlands and estuaries.

Rhizofiltration

Mycoremediation

• Mycoremediation is a type of bioremediation in which fungi are utilized to clean up a site.
• Fungi have been shown to be a cost-effective, ecologically friendly method of eliminating a wide range of toxins from contaminated settings or wastewater.
• In land, fresh water, and marine ecosystems, these contaminants include heavy metals, organic pollutants, textile dyes, leather tanning chemicals and wastewater, petroleum fuels, polycyclic aromatic hydrocarbons, pharmaceuticals and personal care products, pesticides, and herbicides.
• Byproducts of the remediation process, such as enzymes, edible or medicinal mushrooms, can be valuable resources in and of themselves, making the remediation process even more profitable.
• Some fungus can help with the biodegradation of pollutants in extremely cold or radioactive situations, where typical cleanup procedures are either too expensive or impossible to utilize due to the severe conditions.

Mycoremediation

*To know more about the topic, click this link Mycoremediation

Mycofiltration

• Mycofiltration is a similar method that filters harmful waste and germs from water in soil using fungus mycelium.
• In the remediation of pollutants/xenobiotics, fungal mycelium is reported to use methods such as biosorption, bioaccumulation, and biodegradation.
• Several fungus species have been examined and found to have outstanding ability to absorb and remove metals and other contaminants from waste and/or runoff water.
• Fungal species, whether alive or as dried biomass, have a high biosorption capacity for metals like Cu, Zn, Fe, and Mn, as well as the ability to change resistant medicinal compounds and break down insecticides.

Phytoremediation- Advantages

• Environmental Friendly Option: It is an environmentally friendly approach as it can limit pollution exposure to the environment and ecosystem.
• Applicability And Easy Disposal: This method can be applied over a large-scale field and easily disposed of.
• Prevents Erosion And Spreading: It prevents erosion and metal leaching by stabilising heavy metals, reducing the risk of contaminants spreading.
• Improve Soil Fertility: It can also improve soil fertility by releasing various organic matter to the soil.

Phytoremediation- Disadvantages

• Relocation And Not Removal: Phytoremediation relocates hazardous heavy metals rather than removing them from the environment.
• Limited Scope: The surface area and depth occupied by the roots are the only areas where phytoremediation can occur.
• Slow Growth And Limited Biomass: Because of the slow growth and limited biomass, a long-term commitment is required.
• Cannot Totally Avoid Pollutants: It is impossible to totally avoid pollutant leaching into groundwater using plant-based remediation techniques.
• Impact On Plant Survival: The toxicity of contaminated land and the general quality of the soil have an impact on plant survival.
• Metal Bonding to Organic Stuff: When taking up heavy metals, the metal might become bonded to the organic stuff in the soil, making it impossible for the plant to remove.

Phytoremediation- Applications

• Soil And Water: Phytoremediation is typically used in stable contaminated soil or aquatic ecosystems.
• Abandoned Mine Sites: Restoration of abandoned metal mine workings and sites where polychlorinated biphenyls were deposited during the manufacturing process, as well as mitigation of active coal mine, discharges decreasing the impact of contaminants in soils, water, or air, are just a few examples.
• Pesticides, Crude Oil And Derivatives: Metals, pesticides, solvents, explosives, and crude oil and its derivatives have all been reduced through phytoremediation operations around the world.
• Toxic Waste Sites: Many plants, including mustard, alpine pennycress, hemp, and pigweed, have demonstrated their ability to hyperaccumulate toxins at toxic waste sites.

Conclusion

In phytoremediation, heavy metal detoxification is a necessary step in the phytoremediation process. Plants thus employ one of two defense methods to deal with heavy metal toxicity: avoidance or tolerance. Plants use these two methods to keep heavy metal concentrations in their cells below the toxicity threshold levels. Through a variety of mechanisms such as root adsorption, metal ion precipitation, and metal exclusion, it acts as the first line of defense at the extracellular level.