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description about the phytoremediation of heavy metals & pollution causing substances....


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PHYTOREMEDIATION OF HEAVY METALS Submitted by:- Nitish Ranjan BSA-10-240

What are environmental contaminants?:

What are environmental contaminants? Pollutants naturally-occurring compounds in the environment that are present in unnaturally high concentrations. Examples: crude oil refined oil heavy metals Xenobiotics chemically synthesized compounds that have never occurred in nature. Examples: pesticides herbicides plastics

PowerPoint Presentation:

What is phytoremediation ? -The use of plants to reduce the risks of pollutants in soil, sediments and water -encompasses microbial degradation in rhizosphere as well as uptake, accumulation and transformation in the plant . - It is an emerging technology . This can be achieved by: -removing the pollutants -otherwise reducing their effects on the environment

PowerPoint Presentation:

plants can be used to treat most classes of contaminants, including petroleum hydrocarbon, pesticides, metals, radionuclides , explosives, and excess nutrients. Plant species are selected for phytoremediation based on their potential to evapotranspirate groundwater, the degradative enzymes they produce, their growth rates and yield, the depth of their root zone, and their ability to bioaccumulate contaminants.

PowerPoint Presentation:

phytoremediation of heavy metals in soils: - Phytoextraction - Phytostabilisation (or re-vegetation )

Phytoextraction :

Phytoextraction Uptake of chemical by the plant. Works well on metals such as lead, cadmium, copper, nickel etc. Detroit lead contaminated site was removed with Sunflower and Indian Mustard . - recently researchers at the University of Florida have determined that a species of fern, native to the south east, stores high concentrations of arsenic in its fronds and stems more than 200 times the concentration in the soil.


Phytostabilization Vegetation holds contaminated soils in place - root system and low growing vegetation prevent mechanical transportation of pollutants from wind and erosion. - Trees transpire large quantities of water (more than 15 gal/day) so pumping action prevents contaminants from migration into the water table.


Rhizofiltration Use of the extensive root system of plants as a filter . 1995, Sunflowers were used in a pond near Chernobyl - approx. 1 week they had hyper-accumulated several thousand times the concentration of cesium and strontium. - hyper-accumulation can contain 100 times or more of contaminant than normal plant.

PowerPoint Presentation:

P hytoextraction – plant removal of: water nitrates, phosphates heavy-metals some organic nasties Phytodegradation and stabilisation enhanced by: soil aeration plant exudates soil microbiota stimulated by plant exudates Water and metals out of the soil - Phytoextraction Sugars and organic material into the soil - Phytodegradation/stabilisation Biopumps

The phytoextraction operation :

The phytoextraction operation Biopump grown Ni Au Cu Pd 2+ 2+ 2+ + Chemicals added Plant material harvested and burnt to produce bio- ore Bio-ore smelted Bio-ore landfilled


Advantages Cost effective when compared to other more conventional methods. “nature” method, more aesthetically pleasing. minimal land disturbance. reduces potential for transport of contaminants by wind, reduces soil erosion hyper- accumulaters of contaminants mean a much smaller volume of toxic waste. multiple contaminants can be removed with the same plant.


Disadvantages Slow rate and difficult to achieve acceptable levels of decontamination. Possibility of contaminated plants entering the food chain. Possible spread of contaminant through falling leaves . Trees and plants require care. Contaminant might kill the tree. Degradation product could be worse than original contaminant. Only surface soil (root zone) can be treated Cleanup takes several years


Conclusions Phytoremediation is land-management technology Where suitable, phytoremediation is a low-cost, sustainable solution for contaminated land and waste-streams Making the technology work relies on the ‘intelligent’ synergy of botany, microbiology and geochemistry Revegetation , land stabilisation and phytoextraction are all working scenarios of phytoremediation


Limitations Phytoremediation -- work at sites that are well suited for plant growth. Concenteration means that the concentration of pollutants cannot be toxic to the plants Reaching the pollution cannot be so deep in the soils or groundwater that plant roots cannot reach it. As a result, phytoremediation may be a good strategy for sites conducive to plant growth with shallow contamination, it may be a good secondary or tertiary phase in a treatment train for highly polluted sites, or it may not be a viable option for a site.



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