Phytoremediation| Types, Applications, & Its Advantages

Key Concepts

• Phytoremediation

• Types of phytoremediation

• Application of phytoretnediation

• Advantages and disadvantages of phytoremediation

Introduction:

Phytoremediation: 

It’s a plant-based method that uses living plants to remove toxins from soil and water. 

Bioremediation with plants is known as phytoremediation.  

It is a natural biological process that degrades xenobiotic and recalcitrant substances that cause pollution in the environment. 

Because the name Phyto means ‘plant,’ the remediation is mediated by the plant system. 

The best plants for phytoremediation are: Indian mustard, white willow, poplar tree, Indian grass, and sunflower. 

These plants absorb heavy metals and remove toxins from the soil and water. 

1. Indian mustard: Brassicaceae species, particularly Indian mustard, are extremely useful for accumulating specific metals while also producing large amounts of biomass. 

When cultivated in contaminated soil with the addition of a chelating agent like EDTA, Indian mustard (Brassica juncea) has been demonstrated to be successful at accumulating high tissue concentrations of lead.  

An electromagnetic field around the plants can be used as an alternative method of increasing lead uptake. 

2. The roots of white willow plants accumulate lower levels of heavy metals than Brassicaceae, and they deal with Cd, Ni and Pb, and work even in mixed heavy metals like diesel fuel polluted sites. 

3. Poplar trees’ beneficial effects on soil and underwater have also been extensively researched. 

The secret to their success is their naturally well-designed root system, which can absorb vast amounts of water. 

Organic pollutants that hybrid poplars are more susceptible to include chlorinated solvents such as trichloroethylene and the well-known carcinogenic carbon tetrachloride (with 95% of the chemical removed). 

4. Phyto Pet (bioremediation of aquatic and terrestrial ecosystems) has discovered nine members of the Gramineae family, one of them, Indian grass, is capable of removing petroleum pollutants. 

Other grasses, such as Common buffalo grass or Western wheatgrass, are at the top of the list. 

5. Sunflowers are utilized in phytoremediation because they have a high resistance to heavy metals. 

Experiments like the influence of the sunflower rhizosphere on the biodegradation of PAHs in soil shows that sunflowers effectively reduce various PAH levels in soil, but what’s more unexpected is the wide range of contaminants they can absorb. 

Sunflowers are hyperaccumulators, or plants that can take in enormous concentrations of harmful compounds in their tissues, according to environmental scientists. Zinc, copper, and other common contaminants can be absorbed through a multitude of pathways in their genome. 

Explanation:

Phytoremediation is a type of bioremediation that uses plants to remove, transport, maintain, extract, or degrade pollutants from soil and groundwater. 

Different types of phytoremediation processes are used to remove contaminants from the soil and water. 

Types of phytoremediation 

• Phytodegradation 
• Phyto stabilization 
• Phytoextraction(phytoaccumulation) 

• Rhizofiltration 
• Phytovolatization 

Phytodegradation: 

Certain plants have the capacity to take up and break down pollutants within plant tissues through internal enzymatic activity. 

In phytodegradation, organic pollutants are degraded directly, through the release of enzymes from roots, or by metabolic activity inside plant tissues. 

Organic pollutants are taken up by roots and converted into plant tissues to less hazardous compounds during phytodegradation. 

The breakdown of pollutants taken up by plants through metabolic processes within the plant, or the breakdown of toxins in the environment by the action of enzymes produced by the plant, is known as phytodegradation. 

Plants can develop enzymes that catalyse and speed up the degradation process. As a result, organic pollutants are degraded into simpler molecular forms and incorporated into plant tissues to promote plant growth. 

Organic pollutants are broken down (degraded) by enzymes in plant roots. The fragments are combined with new plant material to create a new plant. 

Phytostabilization: 

Phytostabilization is a method in which particular plant species are utilized to immobilize pollutants in the soil and groundwater. 

Chemical substances secreted by the plant immobilize pollutants rather than decompose them in this process. 

Within the root zone, they are prevented from migrating through the soil, as well as being transported by erosion and deforestation. 

It is effective in immobilizing water-soluble pollutants and preventing migration. 

Phytoextraction (Phytoaccumulation): 

Phytoextraction is the process of pollutant uptake/absorption and translocation by plant roots into plant shoots, which can then be harvested and metabolized for energy and metal recycling from the ash. 

The rhizosphere of the plant roots absorbs the pollutants, as well as other nutrients and water, during this process. 

The pollutant is not detoxified and is instead stored in plant parts like shoots and leaves. This approach is most commonly used for metal-based trash. 

Water-soluble metals are taken up by plant species selected for their ability to absorb significant amounts of lead (Pb). 

Metals are stored in the plants’ aerial shoots, which are harvested and either produced for possible metal recovery or discarded as hazardous waste. 

Rhizofiltration: 

Rhizofiltration is a type of phytoremediation that removes hazardous chemicals and excess nutrients by filtering contaminated groundwater, surface water, and wastewater through a mass of roots. 

Rhizofiltration is similar to phyto-accumulation, except that the plants employed are cultivated in greenhouses with their roots in water rather than soil. 

Groundwater is drawn to the surface to irrigate these plants, and during that time, pollutants are trapped in various parts of the plants. 

A synthetic soil medium, like sand mixed with perlite or vermiculite, is typically used in hydroponic systems. 

The roots are gathered and disposed of as soon as they become contaminated. 

Phytovolitilization: 

Plants absorb water containing organic pollutants and release the impurities as volatile components into the air through their leaves. 

Phytovolatilization is defined as the uptake and removal of a pollutant by a plant, followed by the release of the contaminant or a changed version of the contaminant into the atmosphere by the plant during transpiration. 

It occurs when growing trees and other plants absorb water, as well as toxins in the water. 

At relatively low quantities, these pollutants travel through the plants to the leaves and evaporate out into the atmosphere. 

With the support of their root systems, plants also serve to physically stabilize the soil. 

This also helps to minimize erosion, protect the soil surface, and reduce the environmental impact. 

Application of phytoremediation: 

• Metals, radionuclides, pesticides, explosives, fuels, Volatile Organic Compounds (VOCs), and Semi Volatile Organic Compounds (SVOCs) are all treated by phytoremediation (SVOCs). 

• It has the potential to remove pollutants from soil and groundwater. 
• Flyash is a mixture of various heavy metals. It is generated by thermal power and coal energy driven industries. This flyash then becomes airborne and spreads everywhere around the production area and contaminates the ground water. To overcome this, seedlings of Eucalyptus and Melia are grown in abandoned flyash ponds. 
• Many plants, including mustard, alpine pennycress, hemp, and pigweed, have demonstrated their ability to hyperaccumulate toxins at toxic waste sites. 
• Metals, pesticides, solvents, explosives, and crude oil and its derivatives have all been lowered through phytoremediation processes around the world. 

Advantages of phytoremediation: 

• Phytoremediation is cost-effective as it does not require any huge equipment. 
• Planting trees on remediation sites makes the sites aesthetic. 
• Plants can be easily grown without much effort. 
• Because it utilizes naturally occurring organisms and protects the ecosystem in a more natural condition, it has the potential to be the least destructive strategy. 
• It protects the topsoil, ensuring the soil’s fertility. 

• It improves soil health, yield, and phytochemicals in plants. 
• No removal of biomass or hazardous material required. 
• It avoids excavation and transport of contaminated mass, hence reducing the risk of spreading contamination. 
• It has potential to treat more than one type of pollutant at polluted sites. 
• It does not require a disposal site. 

Disadvantages of phytoremediation: 

• Phytoremediation requires the growing conditions of plants such as climate, temperature, altitude, etc. 
• Success is dependent on the tolerance of plants to contaminants. 
• Contaminants that are collected in woody tissues are used as fuel making the fumes harmful. 
• It only relocates hazardous heavy metals rather than removing them from the environment. 

• It is restricted to the roots’ surface area and depth. 
• 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. 
• Development of extensive root-zone required-takes time. 
• Sometimes, contaminants may be toxic to plants. 
• Contaminants may enter the food chain and affect the ecological level of organization. 

• It is much slower than other mechanical methods.

Summary

• Phytoremediation is a new technology that helps to remove toxic contaminants from soil and water bodies.

• Phytoremediation can help developing countries improve their economy at a reasonable cost and over time.

• Phytoremediation is a plant-based method of extracting and removing elemental contaminants 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.

• The best plants for phytoremediation are: Indian mustard, white willow, poplar tree, Indian grass, and sunflower.

• Phytoremediation is a type of bioremediation that uses plants to remove, transport, maintain, extract, or degrade pollutants from soil and groundwater.

• In phytodegradation, organic pollutants are degraded directly, through the release of enzymes from roots, or by metabolic activity inside plant tissues.

• Phytostabilization is a method in which particular plant species are utilized to immobilize pollutants in the soil and groundwater.

• Phytoextraction is the process of pollutant uptake/absorption and translocation by plant roots into plant shoots, which can then be harvested and metabolized for energy and metal recycling from the ash.

• Rhizofiltration is a type of phytoremediation that removes hazardous chemicals and excess nutrients by filtering contaminated groundwater, surface water, and wastewater through a mass of roots.

• Phytovolatilization is defined as the uptake and removal of a pollutant by a plant, followed by the release of the contaminant or a changed version of the contaminant into the atmosphere by the plant during transpiration.

• Advantages of phytoremediation: It is a cost-effective method. Planting trees on remediation sites makes the sites aesthetic. No removal of biomass or hazardous material required. It avoids excavation and transport of contaminated mass.

• Disadvantages of phytoremediation: Phytoremediation requires the growing conditions of plants such as climate, temperature, altitude, etc. Success is dependent on the tolerance of plant to contaminants.

• It only relocates hazardous heavy metals rather than removing them from the environment. Contaminants may enter the food chain and affect the ecological level of organization.