What are heavy metals? Heavy metals are elements having atomic weight between 63.54 and 200.59 , and a specific gravity greater than about 5.0 g/cc, especially that is poisonous such as lead(Pb),mercury(Hg), chromium(Cr), cadmium(Cd)… They can damage living things at low concentrations and tend to accumulate in the food chain .

Heavy metals are elements having atomic weight between 63.54 and 200.59 , and a specific gravity greater than about 5.0 g/cc, especially that is poisonous such as lead(Pb),mercury(Hg), chromium(Cr), cadmium(Cd)…

They can damage living things at low concentrations and tend to accumulate in the food chain .

Sources of heavy metals in the environment Municipal and industrial waste . Sediment from waste water treatment plant. Leachate from solid waste treatment plant. Mining waste.

Municipal and industrial waste .

Sediment from waste water treatment plant.

Leachate from solid waste treatment plant.

Mining waste.

Sources of heavy metal in the environment Municipal and Industrial waste Sediment from wastewater treatment plant

Leachate from solid waste treatment plant Mining wastes

Heavy metal toxicity in plants cause widespread toxicity due to following stress imposed on the plants. Oxidative stress caused by redox active transitional metal (eg. Fe 2+ , Cu 2+ ). Replace other essential metals in pigments and enzymes disrupting the functions of these molecules Some metal ions (Hg 2+ ,Cu 2+ ) are very reactive to thiol (-SH) groups and can interfere with protein structure and function. Some metals like ( 238 U & 137 Cs etc) occur in environment as radio active isotopes, posing an additional health risk.

cause widespread toxicity due to following stress imposed on the plants.

Oxidative stress caused by redox active transitional metal (eg. Fe 2+ , Cu 2+ ).

Replace other essential metals in pigments and enzymes disrupting the functions of these molecules

Some metal ions (Hg 2+ ,Cu 2+ ) are very reactive to thiol (-SH) groups and can interfere with protein structure and function.

Some metals like ( 238 U & 137 Cs etc) occur in environment as radio active isotopes, posing an additional health risk.

Heavy metal toxicity Excessive heavy metal accumulation can be toxic to many plants leading to Reducrd seed germination,biomass formation & root elongation. Inhibition of chlorophyll biosynthesis Disturbance in cellular metabolism & chromosome abberations. The heavy metals ger entry into the the human and animal food chain and cause various disorders.

Excessive heavy metal accumulation can be toxic to many plants leading to

Reducrd seed germination,biomass formation & root elongation.

Inhibition of chlorophyll biosynthesis

Disturbance in cellular metabolism & chromosome abberations.

The heavy metals ger entry into the the human and animal food chain and cause various disorders.

Heavy metals prevailing in soil and their regulatory limits Source – Salt et al ( 1995 ) Elements Conc. Range (mg/kg) Regulatory limit (mg/kg) Lead 1-6900 600 Cadmium 0.1-345 100 Arsenic 0.1-102 20 Chromium 0.005-3950 100 Mercury 0.001-1800 270 Copper 0.03-15500 600 Zinc 0.15-5000 1500

Why phytoremediation ? Various Remediation procedures Conventional measures Land filling and leaching Excavation Burrial or soil washing Soil flushing However these approaches are cost intensive, not economically viable, intrusive in nature and cause soil degradation, not bonafide decontamination measures but a temporary evasion of problem, destabilize natural ecosystem and aesthetically unacceptable

Various Remediation procedures

Conventional measures

Land filling and leaching

Excavation

Burrial or soil washing

Soil flushing

However these approaches are cost intensive, not economically viable, intrusive in nature and cause soil degradation, not bonafide decontamination measures but a temporary evasion of problem, destabilize natural ecosystem and aesthetically unacceptable

Microbial measures Decontamination of polluted land through application of immobilized microbial enzymes Use of resistant micro organisms like fungi, bacteria vesicular arbuscular mycorrhizae These microbial approaches are ecological and economically sound but physical removal / cleaning up of the contaminants does not occure as contaminants remain in the soil system.

Microbial measures

Decontamination of polluted land through

application of immobilized microbial enzymes

Use of resistant micro organisms like fungi, bacteria

vesicular arbuscular mycorrhizae

These microbial approaches are ecological and economically sound but physical removal / cleaning up of the contaminants does not occure as contaminants remain in the soil system.

Chemical extraction procedures have been suggested but they are not cost effective. So these constraints have forced the researchers to think of using plants for cleaning up their own support system ie phytoremediation which is ecofriendly and cost effective

Chemical extraction procedures have been suggested but they are not cost effective.

So these constraints have forced the researchers to think of using plants for cleaning up their own support system ie phytoremediation which is ecofriendly and cost effective

Phytoremediation “ Phyton” = Plant (in greek) “ Remediare” = To remedy (in latin). Phytoremediation can be defined as the use of green plants to remove the pollutants from the environment or to render them harmless . An innovative clean-up technology by use of various plants for treatment of contaminated soils and water . The Basic Principle behind Phytoremediation is that, plant roots either break the contaminant down in the soil, or suck the contaminant up, storing it in the stems and leaves of the plant.

“ Phyton” = Plant (in greek)

“ Remediare” = To remedy (in latin).

Phytoremediation can be defined as the use of green plants to remove the pollutants from the environment or to render them harmless .

An innovative clean-up technology by use of various plants for treatment of contaminated soils and water .

The Basic Principle behind Phytoremediation is that, plant roots either break the contaminant down in the soil, or suck the contaminant up, storing it in the stems and leaves of the plant.

Application of phytoremediation It can be effecively carried out for remediation of Heavy metals Petroleum hydrocarbons Chlorinated solvents Pesticides Radio nuclides Explosives Excess nutrients

Application of phytoremediation

It can be effecively carried out for remediation of

Heavy metals

Petroleum hydrocarbons

Chlorinated solvents

Pesticides

Radio nuclides

Explosives

Excess nutrients

Application of Phytoremediation

Types of phytoremediation Phytoextraction Rhizofiltration Phytostabilization Phytodegradation Rhizodegradation Phytovolatilization Hydraulic Control Riparian corridors Vegetative cover

Phytoextraction

Rhizofiltration

Phytostabilization

Phytodegradation

Rhizodegradation

Phytovolatilization

Hydraulic Control

Riparian corridors

Vegetative cover

Soil Remediation (Schnoor, 2002) Application Description Contaminants Types of Plants Phytotransformation Sorption, uptake, and transformation of contaminants Organics, including nitroaromatics and chlorinated aliphatics Trees and grasses Rhizosphere Biodegradation Microbial biodegradation in the rhizosphere stimulated by plants Organics; e.g., PAHs, petroleum hydrocarbons, TNT, pesticides Grasses, alfalfa, many other species including trees Phytostabilization Stabilization of contaminants by binding, holding soils, and/or decreased leaching Metals, organics Various plants with deep or fibrous root systems Phytoextraction Uptake of contaminants from soil into roots or harvestable shoots Metals, inorganics, radionuclides Variety of natural and selected hyperaccumulators, e.g., Thalaspi,

Water/Groundwater (Schnoor, 2002) Application Description Contaminants Types of Plants Rhizofiltration Sorption of contaminants from aqueous solutions onto or into roots Metals, radionuclides, hydrophobic organics Aquatic plants, (e.g., duckweed, pennywort) Brassica, sunflower Hydraulic Control Removal of large volumes of water from aquifers by trees Inorganics, nutrients, chlorinated solvents Poplar, willow trees Phytovolatilization Uptake and volatilization from soil water and groundwater; conversion of Se and Hg to volatile chemical species Volatile organic compounds, Se, Hg Trees for VOCs in groundwater; Brassica, grasses, wetlands plants for Se, Hg in soil/sediments Vegetative Caps Use of plants to retard leaching of hazardous compounds from landfills Organics, inorganics, wastewater, landfill leachate Trees such as poplar, plants (e.g., alfalfa) and grasses

. . . . Phytoremediation can occur through a series of complex intereactions between plants, microbes, and the soil, including accumulation, hyperaccumulation, exclusion, volatilization, and degradation. Plants also stabilize mobile contaminated sediments by forming dense root mats under the surface.

Plant response to heavy metals Metal excluders: prevent metal from entering their aerial parts . Metal indicators: actively accumulate metal in their aerial tissues and reflect metal level in soil . Metal accumulator plant species: concentrate metal in their aerial parts, to levels far exceeding than soil.

Metal excluders: prevent metal from entering their aerial parts .

Metal indicators: actively accumulate metal in their aerial tissues and reflect metal level in soil .

Metal accumulator plant species:

concentrate metal in their aerial parts, to levels far exceeding than soil.

Hyper-accumulators Plants, so called hyperaccumulator s are usually used, they take up 100 times the concentration of metals over other plants

Hyper-accumulators A plant is classified hyper accumulators when it takes heavy metals against their conc. Gradient between the soil solution and cell cytoplasm. Acquiring capacity of accumulating a very high metal conc. In tissues without much difficulty in carrying out growth and metabolic functions. A hyperaccumulator will concentrate more than: - 100 ppm for Cd -1,000 ppm for Co and Pb -10,000 ppm for Ni

A plant is classified hyper accumulators when it takes heavy metals against their conc. Gradient between the soil solution and cell cytoplasm.

Acquiring capacity of accumulating a very high metal conc. In tissues without much difficulty in carrying out growth and metabolic functions.

A hyperaccumulator will concentrate more than:

- 100 ppm for Cd

-1,000 ppm for Co and Pb

-10,000 ppm for Ni

Criteria for designating a plant as hyper accumulator for different metals Shoot metal conc.(oven dry basis) should be more than 1% for Mn & Zn;0.1% for Cu,Ni & Pb;and 0.01% for Cd & As. Should be fast growing with high rate of biomass production. Should be able to accumulate metals even from low external metal conc.. Should be able to transfer accumulated metals from root to shoot (above ground) quite efficiently (often more than 90%)

Shoot metal conc.(oven dry basis) should be more than 1% for Mn & Zn;0.1% for Cu,Ni & Pb;and 0.01% for Cd & As.

Should be fast growing with high rate of biomass production.

Should be able to accumulate metals even from low external metal conc..

Should be able to transfer accumulated metals from root to shoot (above ground) quite efficiently (often more than 90%)

Important and widely reported hyper accumulators used for metal remediation ELEMENTS Plant species Max. reported Conc . ( mg/kg) Cadmium Thlaspi caerulescens 500 Cupper Ipomoea alpina 12300 Cobalt Haumaniuastrum robertii 10200 Lead Thlaspi rotundifolium, Brassica juncea, Zea mays 8200 Nickel Alyssum lesbiacum, Sebertia acuminata 47500 Zinc Thlaspi caerulescens Brassica juncea, B. oleracea, B. campestris 51600 Selenium Brassica juncea, B. napus 900 Chromium Brassica juncea, Halianthus annus 1400

Disposal options Incineration Disposal as Hazardous Waste Direct burning or Ashing Phytomining - using hyperaccumulator plant biomass to produce a bio-ore for commercial use. - Li et al. look at using Ni as a possible bio-ore

Incineration

Disposal as Hazardous Waste

Direct burning or Ashing

Phytomining

- using hyperaccumulator plant biomass to produce a bio-ore for commercial use.

- Li et al. look at using Ni as a possible bio-ore

Enhancement Strategies Combining phytoremediation with other in situ technologies. ( eg. Electro-osmosis ) Enhancing phytoremediation process by using inducers. Screening to identify most suitable plant species or varieties. Enhancing plant growth & biomass accumulation by improved crop management practices. Creating improved plant through genetic engineering.

Combining phytoremediation with other in situ technologies. ( eg. Electro-osmosis )

Enhancing phytoremediation process by using inducers.

Screening to identify most suitable plant species or varieties.

Enhancing plant growth & biomass accumulation by improved crop management practices.

Creating improved plant through genetic engineering.

Chelate assisted or induced Phytoextraction Chelating agents desorb heavy metals from soil matrix and form water soluble metal complex. Within the plant cell heavy metal may trigger the production of oligopeptide ligandsknown as phytochelatins (PCs) and metallothioneins (MTs) These peptides bindand form stable complex with the heavy metal and thus neutralise the toxicity of the metal ion.

Chelating agents desorb heavy metals from soil matrix and form water soluble metal complex.

Within the plant cell heavy metal may trigger the production of oligopeptide ligandsknown as phytochelatins (PCs) and metallothioneins (MTs)

These peptides bindand form stable complex with the heavy metal and thus neutralise the toxicity of the metal ion.

Chelate assisted or induced Phytoextraction Chelators increases metal availability and uptake and their detoxification. Some reported chelating agents are: EDTA HEDTA DTPA EDDHA NTA Citric acid etc..

Chelators increases metal availability and uptake and their detoxification.

Some reported chelating agents are:

EDTA

HEDTA

DTPA

EDDHA

NTA

Citric acid etc..

Genetic Engineering to improve phytoremediation To breed plants having superior phytoremediation potential with high biomass production can be an alternative to improve phytoremediation. To implant more efficient accumulator gene into other plants. E.g. The γ-ECS transgenic seedlings showed increasedtolerance to cadmium and had higher concentrations of Phytochelatins, γ-GluCys,glutathione, and total nonprotein thiols compared to wild type seedlings.

To breed plants having superior phytoremediation potential with high biomass production can be an alternative to improve phytoremediation.

To implant more efficient accumulator gene

into other plants.

E.g. The γ-ECS transgenic seedlings showed increasedtolerance to cadmium and had higher concentrations of Phytochelatins, γ-GluCys,glutathione, and total nonprotein thiols compared to wild type seedlings.

Advantages of Phytoremediation Works on a variety of organic & inorganic compounds. Can be either In situ/ Exsitu Easy to implement & maintain. Low cost compared to other treatment methods . Environmental friendly & aesthetically pleasing to the public. Reduces the amount wastes to be landfilled High efficiency Easy operation ( large scale suitability ) Risk free or minimum

Works on a variety of organic & inorganic compounds.

Can be either In situ/ Exsitu

Easy to implement & maintain.

Low cost compared to other treatment methods .

Environmental friendly & aesthetically pleasing to the public.

Reduces the amount wastes to be landfilled

High efficiency

Easy operation ( large scale suitability )

Risk free or minimum

Costs * Jonathan Chappel 1997 Contaminant Phytoremediation Other Technologies Source Metals $80 per cubic yard $250 per cubic yard Black (1995) Site contaminated with petroleum hydrocarbons (site size not disclosed) $70,000 $850,000 Jipson (1996) 10 acres lead contaminated land $500,000 $12 million Plummer (1997) Radionuclides in surface water $2 to $6 per thousand gallons treated none listed Richman (1997) 1 hectare to a 15 cm depth (various contaminants) $2,500 to $15,000 none listed Cunningham et al. (1996)

Disadvantages of Phytoremediation Long length of time required for remediation. Depends on climatic condition. Restricted to sites with shallow contamination within rooting zone. Possible effect on the food chain. Consumption of contaminated plant tissue is also a concern. Possible uptake of contaminants into leaves and release during litter fall.

Long length of time required for remediation.

Depends on climatic condition.

Restricted to sites with shallow contamination within rooting zone.

Possible effect on the food chain.

Consumption of contaminated plant tissue is also a concern.

Possible uptake of contaminants into leaves and release during litter fall.

Future Research needs Government and industry commitment to a multiyear field programme. Develop research strategies to adress concerns with mixed contaminant systems.(petroleum hydrocarbons-salts-heavymetals) Support for estabilishment of multiple use,controlled,field-scale phytoremediation research facility.

Government and industry commitment to a multiyear field programme.

Develop research strategies to adress concerns with mixed contaminant systems.(petroleum hydrocarbons-salts-heavymetals)

Support for estabilishment of multiple use,controlled,field-scale phytoremediation research facility.

Technology Selection and Design Treatability conduct treatability studies prior to design to assure that the phytoremediation system will achieve desired results treatability studies provide the design information such as toxicity, transformation data and fate of the contaminant(s) in the plant system. Site Conditions sites with low to moderate soil contamination over large areas, sites with large volumes of groundwater with low levels of contamination that have to be cleaned to low (strict) standards

Treatability

conduct treatability studies prior to design to assure that the phytoremediation system will achieve desired results

treatability studies provide the design information such as toxicity, transformation data and fate of the contaminant(s) in the plant system.

Site Conditions

sites with low to moderate soil contamination over large areas,

sites with large volumes of groundwater with low levels of contamination that have to be cleaned to low (strict) standards

Technology Selection and Design (cont’d) Contaminant Considerations Type of Contaminants Inorganic or Organics compounds Contaminant Concentrations cannot be phytotoxic or cause unacceptable impacts on plant health or yield. preliminary laboratory or field plot screening study will be needed to determine

Contaminant Considerations

Type of Contaminants

Inorganic or Organics compounds

Contaminant Concentrations

cannot be phytotoxic or cause unacceptable impacts on plant health or yield.

preliminary laboratory or field plot screening study will be needed to determine

Technology Selection and Design (cont’d) Plant Considerations Plant Selection Plant species should have the appropriate characteristics for growth under site conditions Growth Rate A fast growth rate will minimize the time required to reach a large biomass A large root mass and large biomass increase the rate of remediation

Plant Considerations

Plant Selection

Plant species should have the appropriate characteristics for growth under site conditions

Growth Rate

A fast growth rate will minimize the time required to reach a large biomass

A large root mass and large biomass increase the rate of remediation

Technology Selection and Design (cont’d) Plant Considerations Root Type A fibrous root system has numerous fine roots spread throughout the soil and will provide maximum contact with the soil due to the high surface area of the roots. Root Depth most nonwoody plant : 1 or 2 feet tree roots : less than 10 or 20 feet Contaminant Uptake Rate and Clean-up Time Irregation, Agronomic Inputs and Maintenance Disposal Considerations

Plant Considerations

Root Type

A fibrous root system has numerous fine roots spread throughout the soil and will provide maximum contact with the soil due to the high surface area of the roots.

Root Depth

most nonwoody plant : 1 or 2 feet

tree roots : less than 10 or 20 feet

Contaminant Uptake Rate and Clean-up Time

Irregation, Agronomic Inputs and Maintenance

Disposal Considerations

Points to ponder May depend on climatic conditions. Time factor for obtaining results. Possible effect on the food chain.

May depend on climatic conditions.

Time factor for obtaining results.

Possible effect on the food chain.

SUMMARY Research and development of phytoremediation are just beginning . Advances in phytoremediation appear in several aspects:Theory,Research and Practice. Using natural green resources to tackle natural environment pollution will be encouraged.

Research and development of phytoremediation are just beginning .

Advances in phytoremediation appear in several aspects:Theory,Research and Practice.

Using natural green resources to tackle natural environment pollution will be encouraged.

Conclusion It is a fast developing field,since last 10 yrs lots of field application were initiated all over the world. Sustainable and inexpensive process is available alternative to conventional remediation method. Man has thus sought the aid of nature’s ownsiblings (plants) by exploring the extrovert relationship between the roots and the Environment, aided by his Scientific Outlook to create economical yet efficient Environment friendly technology called “Phytoremediation” Which would benefit humanity .

It is a fast developing field,since last 10 yrs lots of field application were initiated all over the world.

Sustainable and inexpensive process is available alternative to conventional remediation method.

Man has thus sought the aid of nature’s ownsiblings (plants) by exploring the extrovert relationship between the roots and the Environment, aided by his Scientific Outlook to create economical yet efficient Environment friendly technology called “Phytoremediation”

Which would benefit humanity .

Thank You..