Remediation of polluted sites

PCBs are extremely stable to heat, chemical, and biological decomposition. They are excellent insulating and cooling fluids, extensively used for many years in manufacture of transformers and capacitors. PCBs are also used in hydraulic fluids, lubricating oils, paints, adhesive resins, inks, fire retardants, wax extenders, and numerous other products. The chemical and physical properties of PCBs make the remediation of polluted sites difficult. They resist degradation and absorb into soils and colloidal materials in water. Some persist with half-lives of 8-15 years in the environmental compartments. This stability contributes to their dispersion in the environment and long-range air pollution. Because they are lipophilic, these species are stored in fatty tissues and accumulate in the food webs (see Section 2.2). 

Overall, the field applications demonstrate that the electrokinetic treatment is an adequate tool for the remediation of polluted sites with heavy metals. However,... 

As a response, a policy framework was developed and introduced in 1986, with an update for the remediation of contaminated sites in 1994, the so-called Soil Protection Act (SPA). The main purpose was to establish the accountability of individuals in contributing to soil and sediment pollution, and to include the question of financial responsibility. In the SPA, the aim to preserve soil quality has a functional basis the quality of the soil is important due to the functional properties of soil. It is not stated explicitly but it can be assumed that the organisms responsible for soil functions have to be protected. In the SPA, soil and freshwater sediment are considered to be closely linked environmental compartments that require a uniform framework for protection and remediation. 

Many detailed descriptions have been made about the new statutory regime for CONTAMINATED LAND in the UK, and the reader can refer to these or preceding chapters of this publication to obtain a detailed description of the provisions. All that I would like to stress is that the system is essentially one that is likely to be used as a last resort in circumstances where land is a real environmental problem and remedial works need to be undertaken in a timely manner. The provisions should not be taken out of context and should not be considered as if they apply to all areas of contamination, since they are reserved for only the most serious of polluted sites. 

Several classes of priority pollutants can undergo abiotic reductive transformation reactions in anoxic aqueous environments. Such reactions may be environmentally benign since they often lead to products which are more bioavailable and more easily to degrade. In certain cases, however, the products of such reactions are more toxic than the parent compounds. Thus, knowledge of the reductants and processes involved in the reductive transformation of pollutants is essential to evaluate the risk of pollution and the need for remediation of contaminated sites. 

Because of their intrinsically persistent nature, heavy metal ions (As, Cd, Cr, Cu, Hg, Ni, Pb, Se, V and Zn) are major contributors to pollution of the biosphere (1). These metals when discharged or transported into the environment may undergo transformations and can have a large environmental, public health, and economic impact (2). The increasingly restrictive Federal regulation of allowable levels of heavy metal discharge and accelerated requirements for the remediation of contaminated sites make necessary the... 

One of the most important elements in the remediation of existing waste sites is early detection and actiom As an example, the cost of cleanup at Stringfellow, California, increased from an estimated 3.4 million to 65 million because of pollutant dispersal during a decade of inaction after the first identification of the problem. The opportunities for innovative sampling strategies responsive to this need are discussed in the following section. 

Phytoremediation is considered a low-cost remediation alternative for low-depth contamination, offering a permanent solution and improving the aesthetics of the polluted site. It is well-suited for use in the following situations ... 

Limitations need to be carefully considered before selecting this method for site remediation. These include the depth of contamination, the total length of time required for cleanup to below accepted limits, potential contamination of vegetation and the food chain, and difficulty in establishing and maintaining vegetation at some polluted sites.8... 

Following this, the duration for phytoremediation was calculated. For this purpose, we took the activity of the soil in Mydlovary to be 21.75Bq Ra/g DW, the amount of polluted soil at Mydlovary to be lOOOt, and the annual Lupinus dry matter production on the polluted soil to be 1 Ot. The site contains about 21.8GBq of Ra and the target post-remediation level is... 

Bacteria indigenous to Cr(VI)-polluted areas are Cr(VI) tolerant and/or resistant and have been considered as potential candidates for bioremediation of Cr(VI)-contaminated sites.16 However, the ability of bacteria to reduce Cr(VI) to the less-toxic Cr(III) compounds may produce reactive intermediates (such as Cr(V), Cr(IV), radicals), which are known to be active genotoxins and are likely to be carcinogenic.17 Therefore, the formation and lifetimes of Cr(V) intermediates, produced via bacterial reduction of Cr(VI), need to be evaluated carefully if microorganisms are to be employed as a means for remediation of chromium-polluted subsurface environments. Similarly, Cr(V) accumulation should first be monitored when considering plants and algae as biosorption materials for the bioremediation in the event of chromium pollution.18... 

It has become clear over the past ten years that the 1980s demonstration of anaerobic microbial dechlorination of PCBs is probably the most important discovery in the field of PCB biotransformations since Ahmed and Focht first demonstrated in 1973 that PCBs were biodegradable. Many new anaerobic microbial activities have been enriched and characterized from anaerobic fresh water and marine environments and heavily polluted industrial sediments. These anaerobic cultures are capable ofdechlorinating PCBs, thereby transforming highly chlorinated Aroclors to lower-chlorinated mixtures. This natural attenuation process is an important contributor to PCB degradation and detoxification in the environment and can form the basis for intrinsic remediation of many PCB-contaminated sites. 

Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA). This is an attempt to deal with the many waste sites that exist across the nation. It covers remedial action, including the establishment of a National Priorities List to identify those sites that should have a high priority for remediation. This act authorizes the cleanup of hazardous waste sites, including those containing pesticides, that threaten human health or the environment. If they can be identified, the US EPA is authorized to recover cleanup costs from those parties responsible for the contamination. CERCLA provides a fund to pay for the cleanup of contaminated sites when no other parties are able to conduct the cleanup. The Superfund Amendments and Reauthorization Act (SARA) (1986) is an amendment to CERCLA that enables the US EPA to identify and cleanup inactive hazardous waste sites and to recover reimbursement of cleanup costs. One section of CERCLA authorizes the EPA to act whenever there is a release or substantial threat of release of a hazardous substance or any pollutant or contaminant that may present an imminent or substantial danger to the public health or welfare into the environment. 

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