phytoremediation of contaminated soil and water pdf

Phytoremediation Of Contaminated Soil And Water Pdf

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Biotechnology in the Sustainable Environment pp Cite as. Over the past several years, scientists have discovered many examples of living plants that can remove heavy metals and other pollutants from soil and water.

Phytoremediation technologies use living plants to clean up soil, air, and water contaminated with hazardous contaminants. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed.

Soil contamination has led to serious land tenure problems, reduction in land usability for agricultural production; as a consequence, food insecurity is nowadays a global challenge. Indeed, with rapid population growth across the world, the food demand for consumption has drastically increased and traditional ways of producing food cannot meet with the actual demand. Industrialization has been acknowledged as a way out to sustain humanity with food. Unfortunately, the later has further turn into a threat to the environment. In effect, several potentially toxic elements PTE are being released in the environment and soil systems; and arable or agricultural lands are getting restraint, limited and scarce.


Phytoremediation technologies use living plants to clean up soil, air, and water contaminated with hazardous contaminants. Although attractive for its cost, phytoremediation has not been demonstrated to redress any significant environmental challenge to the extent that contaminated space has been reclaimed.

Phytoremediation is proposed as a cost-effective plant-based approach of environmental remediation that takes advantage of the ability of plants to concentrate elements and compounds from the environment and to detoxify various compounds. The concentrating effect results from the ability of certain plants called hyperaccumulators to bioaccumulate chemicals.

The remediation effect is quite different. Toxic heavy metals cannot be degraded, but organic pollutants can be and are generally the major targets for phytoremediation.

Several field trials confirmed the feasibility of using plants for environmental cleanup. Phytoremediation may be applied to polluted soil or static water environment. This technology has been increasingly investigated and employed at sites with soils contaminated heavy metals like with cadmium , lead , aluminum , arsenic and antimony.

These metal can cause oxidative stress in plants, destroy cell membrane integrity, interfere with nutrient uptake, inhibit photosynthesis and decrease plant chlorophyll. Phytoremediation has been used successfully include the restoration of abandoned metal mine workings, and sites where polychlorinated biphenyls have been dumped during manufacture and mitigation of ongoing coal mine discharges reducing the impact of contaminants in soils, water, or air.

Contaminants such as metals, pesticides, solvents, explosives, [5] and crude oil and its derivatives, have been mitigated in phytoremediation projects worldwide. Many plants such as mustard plants , alpine pennycress , hemp , and pigweed have proven to be successful at hyperaccumulating contaminants at toxic waste sites.

Not all plants are able to accumulate heavy metals or organics pollutants due to differences in the physiology of the plant. A range of processes mediated by plants or algae are tested in treating environmental problems: [ citation needed ]. Phytoextraction or phytoaccumulation or phytosequestration exploits the ability of plants or algae to remove contaminants from soil or water into harvestable plant biomass.

The roots take up substances from the soil or water and concentrate it above ground in the plant biomass [7] Organisms that can uptake high amounts of contaminants are called hyperaccumulators. Populus and Salix that take up lower levels of pollutants, but due to their high growth rate and biomass production, may remove a considerable amount of contaminants from the soil.

Typically, phytoextraction is used for heavy metals or other inorganics. After the process, the soil is remediated. Of course many pollutants kill plants, so phytoremediation is not a panacea. Mining of these extracted metals through phytomining , is a conceivable way of recovering the material. Induced or assisted phytoextraction is a process where a conditioning fluid containing a chelator or another agent is added to soil to increase metal solubility or mobilization so that the plants can absorb them more easily.

Phytostabilization reduces the mobility of substances in the environment, for example, by limiting the leaching of substances from the soil. The plant immobilizes the pollutants by binding them to soil particles making them less available for plant or human uptake. Pollutants become less bioavailable, resulting in reduced exposure. The plants can also excrete a substance that produces a chemical reaction, converting the heavy metal pollutant into a less toxic form.

Phytodegradation also called phytotransformation uses plants or microorganisms to degrade organic pollutants in the soil or within the body of the plant. The organic compounds are broken down by enzymes that the plant roots secrete and these molecules are then taken up by the plant and released through transpiration. Phytotransformation results in the chemical modification of environmental substances as a direct result of plant metabolism , often resulting in their inactivation, degradation phytodegradation , or immobilization phytostabilization.

In the case of organic pollutants, such as pesticides , explosives , solvents , industrial chemicals, and other xenobiotic substances, certain plants, such as Cannas , render these substances non-toxic by their metabolism.

These complex and recalcitrant compounds cannot be broken down to basic molecules water, carbon-dioxide, etc. This is known as Phase I metabolism, similar to the way that the human liver increases the polarity of drugs and foreign compounds drug metabolism. Whereas in the human liver enzymes such as cytochrome Ps are responsible for the initial reactions, in plants enzymes such as peroxidases, phenoloxidases, esterases and nitroreductases carry out the same role.

In the second stage of phytotransformation, known as Phase II metabolism, plant biomolecules such as glucose and amino acids are added to the polarized xenobiotic to further increase the polarity known as conjugation. This is again similar to the processes occurring in the human liver where glucuronidation addition of glucose molecules by the UGT class of enzymes, e.

UGT1A1 and glutathione addition reactions occur on reactive centres of the xenobiotic. Phase I and II reactions serve to increase the polarity and reduce the toxicity of the compounds, although many exceptions to the rule are seen. The increased polarity also allows for easy transport of the xenobiotic along aqueous channels.

In the final stage of phytotransformation Phase III metabolism , a sequestration of the xenobiotic occurs within the plant.

The xenobiotics polymerize in a lignin -like manner and develop a complex structure that is sequestered in the plant. This ensures that the xenobiotic is safely stored, and does not affect the functioning of the plant. However, preliminary studies have shown that these plants can be toxic to small animals such as snails , and, hence, plants involved in phytotransformation may need to be maintained in a closed enclosure.

Hence, the plants reduce toxicity with exceptions and sequester the xenobiotics in phytotransformation. Trinitrotoluene phytotransformation has been extensively researched and a transformation pathway has been proposed. Phytostimulation or rhizodegradation is the enhancement of soil microbial activity for the degradation of organic contaminants, typically by organisms that associate with roots.

In this process, contaminants are taken up by the plant and through transpiration, evaporate into the atmosphere. Rhizofiltration is a process that filters water through a mass of roots to remove toxic substances or excess nutrients. The pollutants remain absorbed in or adsorbed to the roots. Biological hydraulic containment occurs when some plants, like poplars, draw water upwards through the soil into the roots and out through the plant, which decreases the movement of soluble contaminants downwards, deeper into the site and into the groundwater.

Phytodesalination uses halophytes plants adapted to saline soil to extract salt from the soil to improve its fertility [7]. Breeding programs and genetic engineering are powerful methods for enhancing natural phytoremediation capabilities, or for introducing new capabilities into plants. Genes for phytoremediation may originate from a micro-organism or may be transferred from one plant to another variety better adapted to the environmental conditions at the cleanup site.

For example, genes encoding a nitroreductase from a bacterium were inserted into tobacco and showed faster removal of TNT and enhanced resistance to the toxic effects of TNT. Some natural, biodegradable compounds, such as exogenous polyamines , allow the plants to tolerate concentrations of pollutants times higher than untreated plants, and to absorb more pollutants.

A number of interactions may be affected by metal hyperaccumulation, including protection, interferences with neighbour plants of different species, mutualism including mycorrhizae , pollen and seed dispersal , commensalism, and biofilm.

As plants are able to translocate and accumulate particular types of contaminants, plants can be used as biosensors of subsurface contamination, thereby allowing investigators to quickly delineate contaminant plumes. From Wikipedia, the free encyclopedia.

This section needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. June Learn how and when to remove this template message. See also: Phytoextraction process.

See also: 'Table of hyperaccumulators'. Defence Life Science Journal. Environmental and Experimental Botany. Journal of Zhejiang University Science B. Bibcode : Chmsp.. And what makes them so interesting?

Plant Science. Annual Review of Plant Biology. Environment International. The New York Times. Retrieved 27 February August Kirkham Ecotoxicology and Environmental Safety. Science News.

Archived from the original on July 15, Retrieved Journal of Experimental Botany. Kudjo Bibcode : EnST Soil Remediation and Plants. Phytotechnology and Photosynthesis. Categories : Bioremediation Phytoremediation plants Environmental soil science Environmental engineering Environmental terminology Pollution control technologies Conservation projects Ecological restoration Soil contamination Biotechnology Sustainable technologies.

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Phytoremediation of contaminated soils using ornamental plants

The potential of Arundo donax L. The growth and physiology of plants were evaluated at the end of the experiment. Relatively low Cd uptake occurred during soil experiment with low translocation factor TF values. Consequent to global industrialization, heavy metal pollution is a widespread problem which has become a major environmental concern due to hazardous effects on human and environmental health. In industrialized societies, heavy metals are the world over environmental contaminants. Air or water pollution by metals varies from soil pollution, because heavy metals persevere in soil for a longer time period as compared with the other compartment of the biosphere [ 1 ].

Heavy metals are among the most important sorts of contaminant in the environment. Several methods already used to clean up the environment from these kinds of contaminants, but most of them are costly and difficult to get optimum results. Currently, phytoremediation is an effective and affordable technological solution used to extract or remove inactive metals and metal pollutants from contaminated soil and water. This technology is environmental friendly and potentially cost effective. This paper aims to compile some information about heavy metals of arsenic, lead, and mercury As, Pb, and Hg sources, effects and their treatment. It also reviews deeply about phytoremediation technology, including the heavy metal uptake mechanisms and several research studies associated about the topics.

Nuclear power reactors are operating in 31 countries around the world. Along with reactor operations, activities like mining, fuel fabrication, fuel reprocessing and military operations are the major contributors to the nuclear waste. Commonly high concentrations of cesium Cs and strontium 90 Sr are found in a nuclear waste. These radionuclides are capable enough to produce potential health threat due to their long half-lives and effortless translocation into the human body. Besides the radionuclides, heavy metal contamination is also a serious issue.

colonisers, growing in small isolated tufts (De Koe ). Consequently, erosion of the spoil heaps by wind and water. resulted in a permanent pollution of.

A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation

Heavy metal accumulation in soil has been rapidly increased due to various natural processes and anthropogenic industrial activities. As heavy metals are non-biodegradable, they persist in the environment, have potential to enter the food chain through crop plants, and eventually may accumulate in the human body through biomagnification. Owing to their toxic nature, heavy metal contamination has posed a serious threat to human health and the ecosystem. Therefore, remediation of land contamination is of paramount importance. Phytoremediation is an eco-friendly approach that could be a successful mitigation measure to revegetate heavy metal-polluted soil in a cost-effective way.

There are several different types of phytoremediation mechanisms. These are:. Rhizosphere biodegradation.

Heavy metal—contaminated agricultural soil is a complex and serious phenomenon that has hazardous effects on the environment and, consequently, on humans, animals, plants, and beneficial microorganisms by influencing and tainting food chains, soil, irrigation or potable water, aquifers, and the surrounding atmosphere Wuana and Okieimen,

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