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In-Situ Capping (ISC) of Subaqueous Waste is a non-removal remediation technique for contaminated sediment that involves leaving the waste in place and isolating it from the environment by placing a layer of soil and/or material over the contaminated waste as to prevent further spread of the contaminant. In-situ capping provides a viable way to remediate an area that is contaminated. It is an option when pump and treat becomes too expensive and the area surrounding the site is a low energy system. The design of the cap and the characterization of the surrounding areas are of equal importance and drive the feasibility of the entire project. Numerous successful cases exist and more will exist in the future as the technology expands and grows more popular.〔〔 In-situ capping uses techniques developed in chemistry, biology, geotechnical engineering, environmental engineering, and environmental geotechnical engineering. ==Introduction== Contaminants located in sediments still pose a risk to the environment and human health. Some of the direct effects on aquatic life that can be associated with contaminated sediment include “the development of cancerous tumors in fish exposed to polycyclic aromatic hydrocarbons in sediments."〔Palermo, M., Maynord, S., Miller, J., and Reible, D. 1998. "Guidance for In-Situ Subaqueous Capping of Contaminated Sediments," EPA 905-B96-004, Great Lakes National Program Office, Chicago, IL.〕 These high-risk sediments need to be remediated. There are usually only four options for remediation: #Nonremoval technologies〔 ## Containment in-place (In-Situ Capping) ## Treatment in-place #Removal technologies〔 ## Removal and containment ## Removal and treatment The cap can be made up of many different things, including but not limited to sand, gravel, geotextiles, and multiple layers of these options.〔 There are many ways that a contaminant inside sediment can become introduced to the environment. These ways include but are not limited to advection, diffusion, benthic organisms mixing and reworking of the upper layer of the contaminated sediment, and sediment re-suspension by different subaquatic forces.〔 In-situ capping (ISC) can fix all of these adverse effects with three primary functions: # Isolation of the contaminated sediment from the benthic environment; this prevents the contaminant from spreading up the food chain.〔 This isolation of the contaminant is the most important factor in reducing exposure risks.〔 # Prevention of resuspension and transport of the contaminant, referred to as stabilization of the sediments.〔〔 # Reduction of the flux of dissolved contaminants into the water column, also known as chemical isolation.〔〔Reible, D. 2003. “In Situ Remediation Through Capping: Status and Research Needs,” Department of Civil Engineering, University of Texas. Austin, Texas.〕 A fourth, although not necessary, function of an in-situ cap should be the "encouragement of habitat values." This should not be made a primary goal except in extreme circumstances. This can be achieved by altering the superficial characteristics of the cap to "encourage desirable species or discourage undesirable species."〔 The obvious advantage of using in-situ capping is that the waste will not be disturbed, and it prevents further contamination of the surrounding area from movement of the contaminant by removal. Sadly, the long-term effects of ISC have not been studied since it is an emerging technology.〔 In-situ capping has been effective in numerous locations. For example, in several places in the interior of Japan “in-situ capping of nutrient-laden sediments with sand” has worked very well in preserving water quality by reducing “the release of nutrients (nitrogen and phosphorus)” and oxygen depletion by bottom sediments.〔Zeman, A. J., Sills, S., Graham, J. E., and Klein, K. A. 1992. Subaqueous Capping of Contaminated Sediments: Annotated Bibliography, NWRI Contribution No. 92-65, National Water Research Institute, Burlington, Ontario.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「In situ capping of subaqueous waste」の詳細全文を読む スポンサード リンク
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