Groundwater contaminated, migration

Several application methods are available for enzymatic reduction and precipitation of uranium. These include bioreactors, placement of the microorganisms on solid substrates for filtration, or placement in groundwater to create precipitation zones through which the contaminated groundwater migrates. 

Groundwater. One approach to minimizing the environmental impact of excess nitrogen in groundwater migrating into rivers and aquifers is to intercept the water with rapidly growing trees, such as poplars, that will use the contaminant as a fertilizer. 

To prevent migration of contaminated groundwater that may enlarge the size of the contaminated area and lead to the contamination of clean groundwater... 

Continued contamination is curtailed by use of cap. Continued migration of contaminated groundwater is allowed... 

Migration of the gasoline free product and the contaminated groundwater plumes should be controlled. The containment of a plume prevents its further migration and the enlargement of contaminated areas. The most effective method is to pump so as to cause a depression of the water... 

Wherever contaminated groundwater must be recovered or prevented by migrating by hydraulic control, the expense of a valid field investigation is always recouped. Efficient hydraulic control or recovery is based on the principle of handling (and treating) the smallest volume of water containing the highest concentration of dissolved chemicals as possible. 

Aqueous solubility (see Sect. 2.1.1) controls the loss of PCBs via surface and groundwater migration and transport, and is a major factor in understanding the environmental fate of PCB contaminants. The solubility of PCB isomers decreases as the degree of chlorination increases, as shown in Fig. 5. It should be noted that solubility data included in Table 7 and shown in Fig. 5 are based upon pure isomers. When an isomer is part of a mixture such as the Aroclors, solubility is reduced. Figure 6 shows the relationship between the solubility of the pure... 

Goerlitz DF, Troutman DE, Gody EM, et al. 1985. Migration of wood-preserving chemical in contaminated groundwater in a sand aquifer at Pensacola, Florida. Environ Sci Technol 19 955-961. 

Many refineries unintentionally release, or have released, liquid hydrocarbons to groundwater and surface waters. At some refineries contaminated groundwater has migrated off-site and resulted in continuous seeps to surface waters. Although the actual volume of hydrocarbons released in such a manner is relatively small, there is the potential to contaminate large volumes of groundwater and surface water, possibly posing a substantial risk to human health and the environment. 

The use of open pits or ponds for evaporation of brine is widely practiced in southwestern states where evaporation exceeds precipitation [23]. For example, about 75% of all oil and gas waste fluids are disposed of by evaporation pits in New Mexico [30]. Evaporation ponds require large land areas, and they may contaminate groundwater. Today regulators view evaporation pits with disfavor because faulty pond design and operation have allowed salts to migrate into usable groundwater reservoirs [9]. 

Hering, 2006 Campos, 2002 Reynolds, Naylor and Fendorf, 1999). Once the As(V) is mobilized, it may migrate deeper into the subsurface and contaminate groundwater. 

Migration of contaminated groundwater has been identified as the principal mechanism for radionuclide transport from a repository to the biosphere. Over the lifetime of the repository, it is assumed that groundwater will become contaminated as the result of hydrothermal reactions and interactions within and near waste packages. 

Because actual exposure measurements are often unavailable, exposure models may be used. For example, chemical emission and air dispersion models are used in air quality studies to predict the air concentrations for down-wind residents. Residential wells located down-gradient from a site may not currently show signs of contamination, but they may become contaminated in the future as chemicals in the groundwater migrate to the well site. In these situations, groundwater transport models may estimate the period of time that chemicals of potential concern will take to reach the wells. 

A primary directive of CERCLA is the protection of public health. Because the hazards that exist at Superfund sites tend to be quite variable, it has not been possible to establish specific cleanup criteria for the hazardous substances regulated under CERCLA potential human health effects must be evaluated by quantitative risk assessment on a site-by-site basis. Each Superfund site is assessed individually to determine how clean is clean. The rationale is that the hazard of a contaminant is a function of its potential to reach a receptor (e.g., groundwater, population) and the potential harm to the exposed receptor. The ability of a contaminant to migrate, its potential to degrade, and its distance to a receptor of concern (i.e., the risk), all are site-specific. Only on the basis of such individualized risk assessment is it possible to achieve efficient and cost-effective cleanup of the thousands of hazardous waste sites throughout the US. 

Pump-and-treat systems can be installed to remove contaminated groundwater from areas, beneath the landfill. This will control the migration of the leachate away from the landfill but the pump-and-treat system must be maintained as long as the landfill is a threat to the groundwater. Pump and treat at source is not very different than that in the leachate plume except that the volume is likely to be less and the concentrations of contaminants are likely to be higher when used for source control. 

Petroleum distillates that are spilled onto the ground may migrate to, and contaminate, groundwater supplies. Because they are volatile chemicals, however, most environmental releases will ultimately end up migrating to the atmosphere. 

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