The use of plants in remediation of soil and unconfined groundwater contaminated with organic materials is appealing for a variety of reasons: (1) plants provide a remediation strategy that utilizes solar energy; (2) vegetation is aesthetically pleasing; (3) plant samples can be harvested and tested as indicators of the level of remediation; (4) plants help contain the region of contamination by removing water from soil; (5) rhizosphere microbial communities are able to biodegrade a wide variety of organic contaminants; and (6) many plants have mechanisms for transporting oxygen to the rhizosphere. However, before effective plant remediation strategies can be developed, an understanding is needed of the physical, biological, and chemical relationships that determine the fate of each organic contaminant in the rhizosphere. This review presents an overview of some factors required to understand and model the complex processes that determine the fate of the organic contaminants in plant remediation strategies. In addition, some planning and management criteria for the development of practical plant remediation strategies are presented.
Plants have the potential for aiding in situ remediation of contaminated soil and groundwater by promoting microbial growth in the rhizosphere. Microbial populations vary in response to the presence of oxygen, water and metabolizable carbon sources. Plants are able to provide a favorable environment for microbe growth by providing a plant pathway for oxygen transfer to the soil, transferring water from saturated to unsaturated soil, and supplying supplemental substrate in the form of root exudates and decaying root hairs. Models of the physical, chemical, and biological relationships in the rhizosphere are reported. Simulation results are presented for a hypothetical vegetative buffer zone over a shallow aquifer. The fate of atrazine is simulated in order to investigate the effects of rain fall, evapotranspiration, atrazine uptake by plants, and atrazine adsorption to root surfaces on atrazine concentration at the downstream edge of the vegetative buffer zone.
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