Phytoremediation

Phytoremediation /ˌfaɪtəʊrɪˌmiːdɪˈeɪʃən/ (from Ancient Greek φυτό (phyto), meaning 'plant', and Latin remedium, meaning 'restoring balance') refers to the technologies that use living plants to clean up soil, air, and water contaminated with hazardous contaminants.

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1. PHYTOREMEDIATION SUBMITTED BY, GAYATHRY SATHEESAN

2. INTRODUCTION Refers to the mechanism in which fast growing plants are used to eliminate, hold or provide non-toxic contaminants in soil or water. It is also known as agro-remediation. It is an aesthetical, economical and environmental friendly way to detoxify contaminants.

3. Best approach to deal with low to average metal contaminated soils Can be applied in combination with other traditional soil remediation approaches for efficient removal of contaminants.

4. Involves growing plants in a contaminated matrix, for a required growth period, to remove contaminants from the matrix, or facilitate immobilization or degradation of the pollutants. The plants can be subsequently harvested, processed and disposed.

5. ADVANTAGES The cost of the phytoremediation 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 re-use of valuable metals . It is potentially the least harmful method.

6. It preserves the topsoil , maintaining the fertility of the soil. Increase soil health, yield and plant phytochemicals . The use of plants also reduces erosion and metal leaching in the soil.

7. DISADVANTAGES Limited to the surface area and depth occupied by the roots. Slow growth and low biomass require a long-term commitment. Contaminants may be mobilized to the ground water. Influenced by soil and climatic conditions .

8. The survival of the plants is affected by the toxicity of the contaminated land and the general condition of the soil. Requires the safe disposal of the affected plant material. When taking up heavy metals, sometimes the metal is bound to the soil organic matter, which makes it unavailable for the plant to extract .

9. MECHANISM

10. Factors to be considered where phytoemediation is done are; category of contaminant plant species levels of contamination; contaminated area - size and depth site conditions type and number of plants required

11. Types of Phytoremediation

12. PHYTOEXTRACTION Fig 3. Phytoextraction (Source ; https://watershedbiodiversity.wordpress.com )

13. Phytoextraction also called phytoaccumulation. In phytoextraction, fast growing plants are implemented to remove heavy metals from the environment. Involves two approaches that include continuous or natural and chemically induced phytoextraction.

14. Continuous phytoextraction : Approach which includes the removal of heavy metals by network of roots and then directed to upper plant tissues above ground. Harvested plant biomass can be used for biogas production and also combusted.

15. Different process in Phyroextraction Some metals fraction get sorbed at roots. Bioavailable metals enter roots through cellular membrane. Mobile metals in roots enter the xylem. Metals are translocated from roots to tissues of stem and leaves. Small fraction of metals taken by roots become immobilized in vacuole.

16. Metals such as nickel, zinc and copper are the best candidates for removal by phytoextraction. Fig 4. Phytoextraction of Ni from contaminated soil. (Source; https://watershedbiodiversity.wordpress.com)

17. ADVANTAGES The cost is fairly inexpensive when compared to conventional methods. T he contaminant is permanently removed from the soil. T he amount of waste material to be disposed is decreased. T he contaminant can be recycled from the contaminated plant biomass. DISADVANTAGES Time consuming. Controlled by plants.

18. PHYTOSTABILIZATION Fig: 5 Phytoextraction of Ni from contaminated soil. Source; https://watershedbiodiversity.wordpress.com

19. Phytostabilisation is plant based inactivation approach to deal with metal contaminated soil. Objective is the reduction in mobility and bioavailability of heavy metals and limits their leaching and entry into ground water and food chain. Involves physical and chemical immobilization of metal contaminants by their sorption onto roots.

20. ADVANTAGES Does not produce secondary waste that needs treatment. The technology enhances the soil fertility . Improved aesthetic . Impact on aquatic life will be greatly reduced due to lesser sediment deposition DISADVANTAGES If the contaminant concentrations increase to a high level, toxic effects may prevent plants from growing. Mandatory monitoring required.

21. APPLICABILITY Efficient in lowering levels of Pb in sand. Low level radionuclides may be stabilized. Reduces leaching by converting metals from a soluble oxidation state to an insoluble oxidation state.

22. PHYTOTRANSFORMATION Also known as phytodegradation. Break down of organic compounds either by metabolic processes of plants or enzymes produced by plants. It does not depend upon microbial community.

23. It results in a chemical modification of environmental substances. Fig:6 The roots secrete enzymes that degrade (breakdown) organic pollutants in the soil. Source; https://watershedbiodiversity.wordpress.com

24. APPLICABILITY Employed to remediate sites contaminated with organic compounds. Can be used to remove contaminants from petrochemical sites, fuel spills, agricultural chemicals and landfill leachates . They may be used in combination with other remediation technologies or as a polishing treatment.

25. ADVANTAGES Both economical and environmental friendly . DISADVANTAGES Requires more than one season to become efficient. Contaminants may re-enter the food chain through animals or insects that et the plant material.

26. PHYTOSTIMULATION (rhizodegradation) It Involves the disintegration of organic pollutants in rhizosphere with enhanced microbial activity. Microbial activity is enhanced by different ways; Roots ensure the supply of oxygen in rizhosphere for aerobic transformation.

27. Roots biomass enhance the availability of organic carbon. Mycorrhizae fungi cause degradation of compounds that cannot be break down by bacteria. Plants provide habitat for enhanced microbial population.

28. Phytostimulation (Source ; https://www.the-scientist.com )

29. ADVANTAGES No disposal of hazardous waste material required. Very effective when rapid immobilization is needed to preserve ground and surface waters . DISADVANTAGES Contaminant remain in soil. Mandatory monitoring required.

30. PHYTOVOLATIZATION The process in which plants take up contaminants from soil and release them as volatile form into the atmosphere through transpiration. The process occurs as growing plants absorb water and organic contaminants. Phytovolatilization has been primarily used to remove mercury.

31. There are two different type of phytovolitization: Direct Indirect phytovolitization . (Source ; https://www.the-scientist.com/ )

32. ADVANTAGES The mercuric ion is converted into less toxic elemental mercury.   DISADVANTAGES The mercury released into the atmosphere is likely to be recycled by precipitation and then re-deposited back into lakes and oceans; repeating the prodution of methyl anaerobic bacteria.

33. RHIZOFILTRATION ( phytofiltration) Use of plant roots for reclamation of surface, ground water and wastewater with low level of contaminants. Here the contaminants become absorbed, adsorbed or precipitated and leaching to groundwater reduces. Can be used for the removal of Cd, Cr, Cu, Ni and Zn.

34. Some of the most common plant species that have shown the ability to remove toxins from water via rhizofiltration Sunflower Indian Mustard Tobacco Rye Spinach Corn Parrot's Feather

35. ADVANTAGES Ability to use both terrestrial and aquatic plants for either in situ or ex situ applications. Contaminants do not have to be translocated to shoots. DISADVANTAGES Constant need to adjust pH. Plants may first need to be grown in greenhouse or nursery.

36. APPLICABILITY It is applicable to the treatment of surface water and ground water, Industrial and residential effluents. It can effectively remove toxic metals from a solution using rapid growth root system. Low level radio active contaminants can be successively removed from liquid streams.

37. CONCLUSION

38. Phytoremediation is an emerging technology that employs the use of higher plants for the cleanup of contaminated environment. Phytoremediation, which makes use of vegetation to remove, detoxify, or stabilize persistent pollutants, is a green and environmentally-friendly tool for cleaning polluted soil and water. The advantage of high biomass productive and easy disposal makes plants most useful to remediate heavy metals on site.

39. Thank you…