This document summarizes various phytoremediation processes. Phytoremediation uses plants to remove contaminants from soil, water, or sediment. It includes processes like phytoextraction where plants absorb and concentrate contaminants, phytostabilization where plants reduce contaminant mobility and uptake, and phytotransformation where plants or associated microbes break down organic contaminants. Specific examples are given of plants used to remediate heavy metals like arsenic, cadmium, and lead through phytoextraction. Processes like rhizodegradation, phytovolatilization, and rhizofiltration are also outlined. The document notes advantages of phytoremediation being more environmentally friendly and cost effective
2. Phytoremediation
• Bioremediation through the use of
plants which mitigate the
environmental problem without the
need to exacavate the contaminant
material and disposal of it else where.
• Phyto remediation consist of two
words i.e.
phyto – plant, and
remedium – restoring balance .
4. Phytoextraction
• Phytoextraction (or phytoaccumulation) uses plants and algae to remove
contaminants from soils, sediments or water into harvestable plant
biomass.
• Advantages
• Environmental friendly as traditional methods which are used for cleaning
up heavy metals contaminated soil disrupt soil structure and reduce soil
productivity, where as phytoextraction can clean up the soil without
causing any kind of harm to soil quality.
• Less expensive than any other clean up process.
• Disadvantages
• As this process is controlled by plants, it takes more time than traditional
soil clean up methods.
5.
6. Examples of phyto extraction
from soils
• Arsenic, using the Sunflower, or the Chinese Brake fern, a hyperaccumulator.
Chinese Brake fern stores arsenic in its leaves.
• Cadmium, using Willow. As willow has some specific characteristics like high
transport capacity of heavy metals from root to shoot, huge amount of biomass
production, can use also for production of bio energy in the biomass energy
power plant.
• Cadmium and zinc using Alpine pennycress, a hyperaccumulator of these metals
at levels that would be toxic to many plants. On the other hand, the presence of
copper seems to impair its growth.
• Lead, using Indian Mustard, Ragweed, Hemp Dogbane, or Poplar trees, which
sequester lead in its biomass.
• Uranium, using sunflowers, as used after Chernobyl accident.
• Mercury, selenium and organic pollutants such as polychlorinated biphenyls
(PCBs) have been removed from soils by transgenic plants.
7. Phytostabilization
• Refers to the immobilization of contaminants in the soil through:
absorption and accumulation by roots.
precipitation within the roots.
• Eventually, the mobility of the contaminant is reduced, migration to
ground water is prevented and thus bioavailability of metal into
food chain is reduced.
8.
9. Phytotransformation
• Also known as phyto degradation, it is the break down of
contaminants taken up by plants by metabolic processes with in the
plant.
• Remediate some organic contaminants, such as chlorinated
solvents, herbicides, and munitions.
• It can address contaminants in soil, sediment, or ground water.
10. Phytostimulation
(Rhizodegradation)
• Break down of contaminants within the plant root zone, or
rhizosphere.
• Carried out by bacteria or other microorganisms flourishing in the
rhizosphere.
• Microbes in rhizosphere transform contaminant to non toxic
product.
• Works well in the removal of petroleum hydrocarbons.
11.
12. Phytovolatalization
Involves plants taking up contaminants from soil transforming them
into volatile forms and transpiring them into atmosphere.
• Works on organic compounds and heavy metal contaminants, TCE as
well.
• Mercury is the primary metal contaminant that this process has
been used for.
13.
14. Rhizofiltration
Adsorption and precipitation onto plant roots or absorption of
contaminants in the solution surrounding the root zone.
• Used to remediate extracted ground water, surface water, and
waste water with low contaminants.
• Compared to phytoextraction, here the plants are used to address
the groundwater rather than soil.
15.
16. Advantages
• The cost of the phyto remediation is lower than that of traditional
processes both in situ and ex situ
• The plants can be easily monitored
• The possibility of the recovery and reuse of valuable metals (by
companies specializing in “phyto mining”)
• It is potentially the least harmful method because it uses naturally
occurring organisms and preserves the environment in a more
natural state.
17. Limitation
• Phyto remediation is limited to the surface area and depth occupied by
the roots.
• Slow growth and low biomass require a long term commitment.
• With plant based systems of remediation, it is not possible to completely
prevent the leaching of contaminants into the ground water
• The survival of the plants is affected by the toxicity of the contaminated
land and the general condition of the soil.
• Bio-accumulation of contaminants, especially metals, into the plants
which then pass into the food chain,from primary level consumers
upwards and/or requires the safe disposal of the affected plant material.
