Phytoremediation PDF

Phytoremediation M.K. Beals  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 technol...

Phytoremediation M.K. Beals  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,  Phytoremediation Phytoremediation can occur through a series of complex interactions 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. Phytoremediation  What is – the use Phytoremediation? of green plants to clean-up contaminated hazardous waste sites. – The idea of using metal-accumulating plants to remove heavy metals and other compounds – first introduced in 1983, but the concept has actually been implemented for the past 300 years on wastewater discharges. – A general, visual reference concerning plant-based mechanisms used to remediate the environment  What is Phytoremeditaion? – has the potential to clean an estimated 30,000 contaminated waste sites throughout the US according to the EPA’s Comprehensive Environmental Response Compensation Liability Information System (CERCLIS). – Sites included in this estimate are those that have either been owned or contaminated by: battery manufacturers, electroplating, metal finishing, and mining companies. Also included are producers of solvents, coated glass, paints, leather, and chemicals. What is Phytoremediation? – Phytoremediation is aimed at providing an innovative, economical, and environmentally-friendly approach to removing toxic metals from hazardous waste sites. – The foundation of phytoremediation is built upon the microbial community, and the contaminated soil/water environment. – Plants exudate from their roots a variety of organic compounds that support the microbial community and facilitate the uptake of some metals. – The complex interactions among the roots, microbes, metals, and soil make phytoremediation a highly site- specific technology.  Why phytoremediation ? – Various Remediation procedures – Conventional measures – Land filling and leaching – Excavation – Burial 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  Why phytoremediation? Cont’d – 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 occur 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  Pollution Classification A major distinction – Heavy metals between elemental and organic pollutants: Most – Phosphate organic pollutants can be mineralized, while – Arsenate elements cannot. – Nitrogen Source – Insecticides Agriculture (pesticides, – Herbicides herbicides, irrigation water), mining, transport, – PCBs, TCE,... spills (fuel, solvents), military activities – Radionuclides (explosives, chemical weapons), industry Because biological processes are ultimately solar-driven, phytoremediation is on average tenfold cheaper than engineering-based remediation methods such as soil excavation, soil washing or burning, or pump-and-treat systems. Phytoremediation is usually carried out in situ contributes to its cost-effectiveness and may reduce exposure Examples of the polluted substrate to in detail humans, wildlife, and the environment.  Phytoextraction (As/ H3PO4/ metals)  Phytodegradation/ Phytotransformation  Phytodegradation of explosives   Application of Phytoremediation It can be effectively carried out for remediation of – Heavy metals – Petroleum hydrocarbons – Chlorinated solvents – Pesticides – Radio nuclides – Explosives – Excess nutrients Phytoremediation  Phytostabilizati Phytoextraction on Phytodegredati Rhizodegredati on on Phytovolatilizat Rhizofiltration ion  Types of Phytoremediation Phytotransformation – uptake of contaminants from soil & groundwater by plants and their subsequent transformation in roots, stems, and leaves. Rhizosphere Bioremediation – occurs in the root-zone; also known as phytostimulation or plant-assisted bioremediation; results in increase of soil organic carbon, and bacterial and fungal populations. Phytostabilization – refers to holding of contaminated soils in place by vegetation, and immobilization (physically or chemically) of contaminants. Phytoextraction – use of metal-accumulating plants that translocate metals from the soil to their roots and concentrate the metals to aboveground stems and leaves. Rhizofiltration – use of plants to absorb, concentrate, and/or precipitate metal contaminants from surface waters(treatment wetlands) or groundwater  Types of Phytoremediation for Inorganic Compounds Type of Phytoremediation Process Involved Contaminant Treated* Phytostabilization Plants control pH, soil gases, Proven for heavy metals in and redox conditions in soil mine tailing ponds to immobilize contaminants. Humification of some organic compounds is expected. Rhizofiltration or Compounds are taken up or Heavy metals and contaminant uptake sorbed by roots (or sorbed to radionuclides algae and bacteria). Phytoaccumulation, Metals and organic Nickel, zinc, lead, phytoextraction, or chemicals are taken up by chromium, hyperaccumulation the plant with water, or cadmium, selenium, other by cation pumps, sorption, heavy metals; radionuclides and other mechanisms. Phytovolatilization Volatile metals are taken up, Mercury and selenium changed in species, and transpired. Phytoremediation Mechanics  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 Phytoremediation Mechanics  Hyper-accumulators Plants so called hyperaccumulators 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  Heavy metal hyperaccumulators Thlaspi montanum var. montanum, a Ni-hyperaccumulator plant that grows on Serpentine soils, research of Martha Palamino, IB graduate student (UC Berkeley).  Hyperaccumulator Alyssum serpyllifolium plants Brassica juncea Thlaspi caerulescens Pteris vittata  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.  Advantages of – WorksPhytoremediation 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 )  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 Future Research needs – Government and industry commitment to a multiyear field program. – Develop research strategies to address concerns with mixed contaminant systems.(petroleum hydrocarbons-salts-heavy metals) – Support for establishment of multiple use, controlled, field-scale phytoremediation research facility.  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.  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 own siblings (plants) by exploring the extrovert relationship between the roots and the Environment, aided by his Scientific Outlook to create economical