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Phyto stabilisation

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Phyto stabilisation

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Phytostabilization refers to establishing a plant cover on the surface of the contaminated soils, which reduces their exposure to wind, water, and direct contact with humans or animals. Phytostabilization reduces the mobility, and therefore the risk, of inorganic contaminants without necessarily removing them from the site.

Phytostabilization refers to establishing a plant cover on the surface of the contaminated soils, which reduces their exposure to wind, water, and direct contact with humans or animals. Phytostabilization reduces the mobility, and therefore the risk, of inorganic contaminants without necessarily removing them from the site.

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Phyto stabilisation

  1. 1. PHYTOSTABILISATION By Elegbeleye Oladipo Ayodamope Cyprus International University
  2. 2. OUTLINE  Introduction  Role Of Plants In Phytostabilization  Phytostabilisation Role of Soil Amendments in Phytostabilization  Phytostabilization In Mine Tailings Advantages  Disadvantages  Bioavailability In Phytostabilization  Processes Involved In Phytostabilization  Enhancement Of Phytostabilization  Environmental Factors  Conclusion  Reference
  3. 3. INTRODUCTION Phytostabilization refers to establishing a plant cover on the surface of the contaminated soils, which reduces their exposure to wind, water, and direct contact with humans or animals. Phytostabilization reduces the mobility, and therefore the risk, of inorganic contaminants without necessarily removing them from the site.
  4. 4. Role of Plants in Phytostabilization • Protect the contaminated soil from wind and water erosion • Reduce water percolation through the soil to prevent leaching of the contaminants • Alter the chemical form of the contaminants by changing the soil environments (e.g. pH, redox potential) around plant roots • Accumulate and precipitate heavy metals in the roots or adsorb metals to the roots • Micro-organisms living in the rhizophere of plants may have an important role in these processes
  5. 5. Phytostabilisation
  6. 6. Role of Soil Amendments in Phytostabilization Convert the soluble and exchangeable metals to more geochemically stable solid phases resulting in a reduced biological availability of heavy metals reduction of trace element transfer to surface- and groundwater Use of soil amendments to lower metal uptake in crops
  7. 7. Phytostabilization In Mine Tailings Mine tailings, or mill tailings, are the materials remaining after extraction and beneficiation of ores. they are characterized by elevated concentrations of metals such as arsenic, cadmium, copper, manganese, lead, and zinc Furthermore, tailings contain no organic matter or macronutrients, and usually exhibit acidic pH
  8. 8. Phytostabilization In Mine Tailings Contd Autotrophic iron and sulfur-oxidizing bacteria dominate the microbial community in mine tailings and are associated with plant death in acidic tailings (Schippers et al. 2000). Today, surface containment of tailings within embankments remains a commonly used approach. In 1995 it was estimated that on an annual basis over 700 million kg of metals in mine tailings were disposed on land (Warhurst 2000).
  9. 9. Phytostabilization In Mine Tailings Contd Phytostabilization creates a vegetative cap for the long-term stabilization and containment of the tailings. The plant canopy serves to reduce eolian dispersion whereas plant roots prevent water erosion, immobilize metals by adsorption or accumulation, and provide a rhizosphere wherein metals precipitate and stabilize.
  10. 10. ORGANIC AMENDMENTS REDUCE METAL TOXICITY IN MINE TAILINGS
  11. 11. Advantages It may combine treatment with ecosystem restoration. The technology usually enhances the soil fertility. Stabilization reduces mobility. This may be a risk, of organic contaminants without removing them from their location. Material handling is limited compared to other remedial technologies, such as excavation. Therefore costs will be typically lower. inorganic contaminants such as heavy metal(loid)s in the soil are immobilized, thereby minimizing their transport in water or dust
  12. 12. Disadvantages If soil additives are used, they may need to be periodically reapplied. This is to maintain the effectiveness of the immobilization. The site must be monitored perpetually to make sure the stabilization conditions continue because the contaminants are left in place. Toxic effects may prevent plants from growing until extensive amendment application reduce their bioavailability to plants. This will occur if the contamination concentration elevate. Phytostabilization is useful at sites with shallow contamination and where contamination is relatively low. Metals that are readily translocated to leaves in plants may limit the applicability of phytostabilization due to potential affects to the food chain.
  13. 13. Bioavailability In Phytostabilization Bioavailability of contaminants in soil Is the fraction of the total metal(loid) in the interstitial pore water (i.e., soil solution) and soil particles that is available to the receptor organism (Naidu et al. (2008a) Bioavailability can also be defined as the potential for living organisms to take up metal(loid)s through ingestion or from the abiotic environment (i.e., external) to the extent that the metal(loid)s may become involved in the metabolism of the organism (NRC, 2003). More specifically, it refers to the biologically available fraction (or pool) that can be taken up by an organism and can react with its metabolic machinery, or it refers to the fraction of the total concentration that can interact with a biological target (Vangronsveld and Cunningham, 1998).
  14. 14. Processes Involved In Phytostabilization  uptake and sequestration of contaminants in the root system;  alteration of soil factors that influence the speciation and immobilization of contaminants (pH, organic matter, redox levels);  root exudates that regulate the precipitation and immobilization of the contaminants;  establishment of vegetation barrier that reduces the likelihood of physical contact with the soil by animals and humans;  mechanical stabilization of the site to minimize erosion by wind and water;
  15. 15. Enhancement Of Phytostabilization Phytostabilization can be enhanced by increasing plant growth using both organic and inorganic amendments. Fertilizer application increases plant growth thereby enhancing phytostabilization Therefore, organic amendments such as bio- solids and manures and biological inoculants such as plant growth-promoting bacteria (PGPB) are used to enhance plant growth.
  16. 16. Environmental Factors  Rainfall controls the leaching of contaminants and erosion of soil and sediments.  Temperature affects both the plant growth and soil surface characteristics such as cracking and crust formation.  While cracking increases the leaching of contaminants, loose, dry, and bare soil is susceptible to wind erosion by dispersion.
  17. 17. CONCLUSION Phytostabilization is primarily aimed at containing the mobility of contaminants through their immobilization within the root zone of plants and “holding” soil and sediments, thereby preventing off-site contamination through their migration via wind and water erosion and leaching, and soil dispersion. This technique is readily suited to monitor natural attenuation of contaminated sites which is employed within the context of a carefully controlled site-specific clean up strategy
  18. 18. REFERENCE Adriano, D. C., Wenzel, W. W., Vangronsveld, J., and Bolan, N. S. (2004). Role of assisted natural remediation in environmental cleanup.Geoderma122,121–142. Bolan, N. S., Adriano, D. C., and Naidu, R. (2003a). Role of phosphorus in (im)mobilization and bioavailability of heavy metals in the soil-plant system. Rev. Environ. Contam. Toxicol.177,1– 44. Bolan, N. S., Adriano, D. C., Mani, S., and Khan, A. R. (2003d). Adsorption, complexation and phytoavailability of copper as influenced by organic manure. Environ. Toxicol. Chem. 22,450– 456.
  19. 19. THANK YOU

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