ABSTRACT
Plants can remediate various contaminated compartments of the environment (e.g., water, sediments, soil, and air). The technology involved is generally referred to as phytotechnology (Cunningham et al. 1995; Cunningham et al. 1996; Salt et al. 1998). These technologies can be implemented either in situ or ex situ. Typical organic contaminants that this technology can be used for include petroleum hydrocarbons, gas condensates, crude oil, chlorinated compounds, pesticides, and explosive compounds. Similarly, inorganic contaminants include salts of sodium, potassium (salinity), heavy metals, metalloids, and radioactive materials. In addition, several emerging applications of
6.1 Introduction .......................................................................................................................... 113 6.2 Basic Fate and Transport Processes of Contaminants in the Unsaturated Zone .................. 115
6.2.1 Transport Processes of Contaminants ...................................................................... 116 6.2.2 Chemical and Biological Processes that Affect Contaminants ................................ 116
6.3 Bioavailability of Contaminants ........................................................................................... 117 6.3.1 Factors In¬uencing Bioavailability ........................................................................... 119
6.3.1.1 Soil Structure, Texture, and Organic Matter Content ................................ 119 6.3.1.2 Weathering ................................................................................................. 119
6.4 Toxicity of Contaminants to Plants ...................................................................................... 120 6.4.1 Role of Microorganisms in Reducing Toxicity of Contaminants to Plants .............. 120
6.5 Ecological Exposures of Contaminants ................................................................................ 120 6.5.1 Ecological Risk Assessment: A Requirement for Phytoremediation ....................... 121
6.6 Uptake of Contaminants by Plants ....................................................................................... 123 6.6.1 Translocation of Contaminants to Shoots .................................................................124 6.6.2 Root Level Contaminant Chelation and Sequestration .............................................124 6.6.3 Leaf Level Contaminant Chelation and Compartmentation .................................... 125 6.6.4 Degradation and Fate of Trichloroethane ................................................................. 127 6.6.5 Transformation of Toxic Elements............................................................................ 127
6.7 Ecological Consequences of the Use of Transgenic Plants .................................................. 128 6.8 Conclusions ........................................................................................................................... 129 References ...................................................................................................................................... 130
phytotechnology are being developed, such as the capability of vegetation to utilize atmospheric carbon emissions for greenhouse-gas mitigation.
