PHYTOREMEDIATIONCONCEPTS AND

TECHNIQUESName: A. Ranga RaniID.NO:TAM-13-24

Phytoremediation

It is applied at sites with contamination of

Organic Chemicals –TCE, TNT,, PCBs etc Nutrient – Ammonia, Phosphate, Nitrate Metal pollutants – Lead, Cadmium, Zinc,

Arsenic, Chromium

Phytoremediation is a process that uses plants to remove, transfer, stabilize, and destroy contaminants in soil and sediment.

Pteris vittata

Brassica juncea

Thlaspi caerulescens

Alyssum serpyllifoliumHyperaccumulator plants

Poplar sps

PHYTOSTIMULATION

Phytoextraction

It is the uptake of contaminants,particularly toxic metals and radio

nuclei by plant roots and the translocate to the above ground parts.

Specially selected plants, known as hyperaccumulators, can extract and

accumulate exceptionally high levels of contaminants from soil.

Phytoextraction is achieved by two methods:

1. Continuous phytoextraction

2. Induced phytoextraction

1. Continuous phytoextraction

It is based on the phytological processes that allow plants

to accumulate metals over the complete growth cycle. It is

based on the genetic and physiological capacity of hyper

accumulators to accumulate,translocate and resist high

amount of metals

• The first hyper accumulators characterized were number of Brasicaceae. Eg: Thallium- Iberis intermedia and Biscutella laevigata of brassicaceae family,

• Zn in roots and shoots of Thalaspi arvense

• Brassica juncea in Pb, Zn and Cd

Chinese brake fern, P. vittata to hyperaccumulate arsenic

Remediation of saline soils

Salicornia (pickleweed) accumulates salt in vacuole.A form of table salt can then be extracted from plant.

Induced phytoextraction

• It is also known as chelate assisted phytoextraction. Synthetic

metal chelates such as EDTA addition to soil increase the heavy

metal accumulation by plants.

• Metal accumulation efficiency of plants is directly related to the

affinity of chelates for a particular metal.

• Eg. EDTA for Pb,Cd and citrate for U is normally recommended for

induced phytoextraction.

• Chelates applied at 5 and 10 mmol/kg to soil

Phytostabilization

Phytostabilization, also referred to as in place inactivation, is

primarily used for the remediation of soil, sediment, and

sludges

It is the use of plant roots to limit contaminant mobility and

bioavailability in the soil.

It is useful for the treatment of Pb as well as As, Cd, Cr, Cu

and Zn.

It is very effective when rapid immobilization is needed to

preserve ground and surface waters

Phytostabilization of mercury by willow roots

Yaodong Wang, 2004

Rhizofiltration

Rhizofiltration is primarily used to remediate extracted

groundwater, surface water, and wastewater with low contaminant

concentrations (Ensley, 2000).

It is defined as the filtering of water through a mass of roots to

remove toxic substances or excess nutrients.

Rhizofiltration can be used for Pb, Cd, Cu, Ni, Zn, and Cr, which

are primarily retained within the roots

Indian mustard

water hyacinthDuckweed (Lemna)

Azolla

Sunflower

Removal of substances from the

soil or water with release into the

air, possibly after degradation.

Indian mustard and canola

(Brassicanapus) may be effective

for phytovolatilization of

Selenium.

Enhancement of microbial activity for the degradation

of contaminants, typically around plant roots

PGPR bacteria produce heavy metal chelating agents

such as siderophores which results in sequestration of

metals and thus facilitates better crop growth in

polluted environment

Phytostimulation

PHYTOTRANSFORMATION

Uptake of substances from the environment, and

degradation occurring in the plant

Trichloroethylene (TCE), a prevalent groundwater

contaminant, transformed to less toxic

metabolites by using hybrid poplar tree

Phytoremediation of pesticides by a notorious pest plant

. This plant might be utilized as an efficient, economical and ecological alternative to accelerate the removal and degradation of agro-industrial wastewater polluted with ethion.

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

Multiple contaminants can be removed with the same plant.

Disadvantages Success is dependant on the tolerance of the

plant to the pollutant Long length of time is required for remediation Possibility of contaminated plants entering the food

chain. Depends on the climate. Possible spread of contaminant through falling leaves.

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