Natural recovery

A short column of alumina may also be employed for decolorization. The colored solution is placed on the column and eluted with a dry hydrocarbon solvent. If the desired product is not highly polar in nature, recovery by the technique may be excellent. 

U.S. EPA defines MNA as the reliance on natural processes, within the context of a carefully controlled and monitored site cleanup approach, to achieve site-specific remediation objectives within a time frame that is reasonable compared to that offered by other more active methods. The natural processes include biodegradation, dispersion, dilution, sorption, volatilization, stabilization, and transformation. These processes reduce site risk by transforming contaminants to less toxic forms, reducing contaminant concentrations, and reducing contaminant mobility and bioavailability. Other terms for natural attenuation in the literature include intrinsic remediation, intrinsic bio-remediation, passive bioremediation natural recovery, and natural assimilation. 30... 

Natural recovery. The phenomenon whereby many people with drug problems are able to overcome those problems by themselves. 

McGeachy MJ, Stephens LA, Anderton SM Natural recovery and protection from autoimmune encephalomyelitis contribution ofCD4+CD25+ regulatory cells within the central nervous system. J Immunol 2005 175 3025-3032. 

Exploratory drilling in tundra or permafrost areas requires greater care because of the much slower natural recovery capability [68]. Wildcat wells in these areas require more precautions for the handling of warm drilling mud, etc., to avoid terrain collapse from the introduction of a thaw-susceptible area into permafrost [69]. 

The primary objective of cleanup operations is to minimize the effects of the stranded oil and accelerate the natural recovery of affected areas. Obviously, a... 

Some recommended shoreline cleanup methods are natural recovery, manual removal, flooding or washing, use of vacuums, mechanical removal, tilling and aeration, sediment reworking or surf washing, and the use of sorbents or chemical cleaning agents. 

Shoreline Type Condition of the Oil Natural Recovery Flooding Low-Pressure Cold Water Low-Pressure Warm Water Manual Removal Vacuums Mechanical Removal Sorbents Tilling/ Aeration Sediment Reworking/ Surf- Washing Cleaning Agents... 

Sometimes the best response to an oil spill on a shoreline may be to leave the oil and monitor the natural recovery of the affected area. This would be the case if more damage would be caused by cleanup than by leaving the environment to recover on its own. This option is suitable for small spills in sensitive environments and on a beach that will recover quickly on its own such as on exposed shorelines and with non-persistent oils such as diesel fuel on impermeable beaches. This is not an appropriate response if important ecological or human resources are threatened by long-term persistence of the oil. 

Forstner, U. and Apitz, S. (2007) Sediment remediation US focus on capping and monitored natural recovery, J. Soils and Sediments, 1, pp. 351-358. 

Monitored natural recovery, which is based on the assumption that, while sediments pose some risk, it is low enough that natural processes can reduce risk over time in a reasonably safe manner. 

The perceived placebo effect is defined as the total effect of the placebo medicine, which includes the true placebo effect and other effects, such as any physiological effect, and non-specific effects such as natural recovery from the disease. The perceived placebo effect is normally measured in a placebo-controlled clinical trial, but it is not possible to estimate the contribution of the true placebo effect to any changes in cough severity from this parameter, as the perceived placebo effect also includes the physiological effect and non-specific effect of treatment as shown in Fig. 3. 

Drake D. E. (1994) The natural recovery of contaminated effluent-affected sediment on the Palos Verdes Margin background information and results of the USGS natural recovery research. Southern CaUfomia Damage Assessment Witness Reports, 131 pp. 

As described in Section il, cationic peptides are very widely distributed in nature. Recovery from these sources involves a wide range of methods. One effective procedure is extraction with 30% acetic acid, which tends to solubilize cationic peptides and precipitate many globular proteins. This is usually followed by a variety of chroinatogra ic procedures often including reverse phase HPLC or FPLC as the final step in purification. However, purification from natural sources is rarely a practical ahemarive for commercial purposes, since yields tend to be relatively low. For example, a single rabbit will permit the recovery of only 200 mg of rabbit defensins. The one exception is the production of cationic lantibiotic peptides such as nisin from bacteria and commercial production of nisin by fermentation of Lnctococcus beds (see Chapter 15). 

The phrase natural attenuation as understood within the context of subsurface remediation of contaminated soil and water evolved over a period of several years. It has largely been accepted as the politically and scientifically appropriate term, however it is still frequently used synonymously with Intrinsic remediation , natural recovery , and natural assimilation . The phrases intrinsic bioremediation and passive bioremediation refer strictly to biologically mediated attenuation processes, which are obviously a less broad definition, not including all the physical and abiotically mediated processes that... 

Of all the processes that affect the exposure of aquatic systems to contaminated sediments, the deposition and resuspension processes reviewed in this chapter are probably most important in assessing the long-term fate of contaminants in the surface sediments of a system. As a result, these processes are important in the determination of a remediation plan for a contaminated site, because of the need to understand the stability of bottom sediments and the associated stability of contaminants in those sediments. A quantitative understanding of sediment deposition and resuspension processes is needed to address such management questions as What are the expected rate and extent of risk reduction at a site under natural recovery (no additional actions), with additional source controls, and/or with in situ remedial actions (i.e., dredging and/or capping) and Are risk reductions permanent in response to extreme events (i.e., floods, wind storms, low water level conditions) ... 

Winter, T.C. 2002. Subaqueous capping and natural recovery Understanding the hydrogeologic settings at contaminated sites. DOER Technical Notes Collection (TN DOER-C26), U.S. Army Engineer Research and Development Center, Vicksburg, MS. 

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