Chapter One

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Castor Plant Intro
  CHAPTER ONE INTRODUCTION At many hazardous waste sites requiring cleanup, the contaminated soil, groundwater, and/or wastewater contain a mixture of contaminant types, often at widely varying concentrations. These may include salts, organics, heavy metals, trace elements, and radioactive compounds. The simultaneous cleanup of multiple, mixed contaminants using conventional chemical and thermal methods is both technically difficult and expensive; these methods also destroy the biotic component of soils . Phytoremediation, an emerging cleanup technology for contaminated soils, groundwater, and wastewater, is both low-tech and low-cost. We define  phytoremediation as the engineered use of green plants, including grasses, forbs, and woody species, to remove, contain, or render harmless such environmental contaminants as heavy metals, trace elements, organic compounds, and radioactive compounds in soil or water. This definition includes all plant-influenced  biological, chemical, and physical processes that aid in the uptake, sequestration, degradation, and metabolism of contaminants, either by plants or by the free-living organisms that constitute the plant's rhizosphere. Phytoremediation takes advantage of the unique and selective uptake capabilities of plant root systems, together with  the translocation, bioaccumulation, and contaminant storage/degradation abilities of the entire plant body. Plant-based soil remediation systems can be viewed as  biological, solar-driven, pump-and-treat systems with an extensive, self extending uptake network (the root system) that enhances the below-ground ecosystem for subsequent productive use. Examples of simpler phytoremediation systems that have been used for years are constructed or engineered wetlands, often using cattails to treat acid mine drainage or municipal sewage. Some work extends to more complicated remediation cases: the phytoremediation of a site contaminated with heavy metals and/or radionuclides involves farming the soil with selected plants to biomine the inorganic contaminants, which are concentrated in the plant biomass (Ross 1994, Salt et al. 1995). For soils contaminated with toxic organics, the approach is similar, but the plant may take up or assist in the degradation of the organic (Schnoor et al. 1995). Several sequential crops of hyperaccumulating plants could  possibly reduce soil concentrations of toxic inorganics or organics to the extent that residual concentrations would be environmentally acceptable and no longer considered hazardous. The potential also exists for degrading the hazardous organic component of mixed contamination, thus reducing the waste (which may  be sequestered in plant biomass) to a more manageable radioactive one.   Though it is not a panacea, phytoremediation is well suited for applications in low-permeability soils, where most currently used technologies have a low degree of feasibility or success, as well as in combination with more conventional cleanup technologies (electromigration, foam migration, etc.). In appropriate situations, phytoremediation can be an alternative to the much harsher remediation technologies of incineration, thermal vaporization, solvent washing, or other soil washing techniques, which essentially destroy the biological component of the soil and can drastically alter its chemical and physical characteristics as well, creating a relatively nonviable solid waste. Phytoremediation actually benefits the soil, leaving an improved, functional, soil ecosystem at costs estimated at approximately one-tenth of those currently adopted technologies. AIMS AND OBJECTIVES The aim of this project is to experiment on the phytoremedial capabilities of castor  plant. The main objectives of this project includes; 1.   To identify the plant capabilities of degrading specific contaminants and evaluate these species in controlled laboratory experiments. 2.   To elucidate the physical, chemical, physiological and metabolic mechanisms of contaminant uptake, translocation,  sequestration/detoxification, partitioning and bioaccumulation in  phytoremediation plants. 3.   This research is focusing on heavy metal, radionuclide, and organic contaminants. 4.   To demonstrate that plant-based cleanup systems using castor plant for heavy metals and organics are low-cost, low tech, environmentally friendly, and will operate economically at actual contaminated sites.
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