In groundwater

Groundwater. Nitrotoluenes have been detected in groundwater in some areas, and intrinsic remediation may be occurring at some sites by anaerobic degradation. Research into whether this can be stimulated with a net environmental benefit is in its very earliest stages, and no clear evidence for success has been presented. 

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. 

Limits of Detection. One reason for the concern about pesticides in groundwater has been the abiUty to detect trace amounts of these... 

Table 3. Pesticides in Groundwater from Normal Agricultural Use ...

The interaction of all these factors makes it difficult to predict an overall effect of conservation tillage on the potential leaching of a pesticide compared to that in a conventionally tilled field. However, it was found that a prolonged rain immediately after appHcation resulted in short-term levels of pesticide in groundwater to be greater under no-tiU than under conventional till plots, which suggested that preferential transport in no-tiU had occurred... 

Volatile organic contaminants occur primarily in groundwaters as a result of the disposal of industrial solvents on the ground or in soakage pits. The removal of these compounds has best been accompHshed by the use of air stripping or adsorption on activated carbon. 

Cumene is expected to exist almost entirely in the vapor phase in the atmosphere (13). In water, mixed cultures of microorganisms collected from various locations and depths in the Atiantic Ocean were all found to be capable of degrading cumene (14). A number of studies have examined the aerobic degradation of cumene in seawater and in groundwater (15,16). The results indicate that cumene would normally be naturally degraded to below detectable limits within a week to ten days. Cumene is tightly adsorbed by soil and is not significantly mobile in soil (17). 

Multiple pathways are a major concern since depostion of PIC would have occurred. Specific soil conditions determine attenuation rates of penta PIC leachate. Once penta reaches the water table, other transport and fate processes become important. Penta exists in two forms ionized and non-ionized. The ionized form is soluble in water, while the non-ionized form is not. The ratio of the two forms in water is dependent on the pH of the aquifer. In alkaline environments penta PIC tend to be more soluble and more susceptible to advective transport and biological decay. Half-lives of penta leachate in groundwater have been estimated ranging from 27 days to 58 years. 

Technology Description In-situ chemical treatment uses the same principles employed for above-ground chemical processes. Materials are added to neutralize, oxidize or remove contaminants in groundwater or soils in order to avoid digging or pumping of the contaminated waste above ground for... 

Concentration of the dissolved hydrocarbon fraction in groundwater near the dwelling... 

S. Lacorte and D. Barcelo, Determination of parts per trillion levels of organophospho-rus pesticides in groundwater by automated on-line liquid- solid extraction followed by liquid chr omatography/atmospheric pressure chemical ionization mass spectrometry using positive and negative ion modes of operation . Anal. Chem. 68 2464- 2470 (1996). 

Moreover, MTBE has been found in groundwater, lakes and resei voirs used for drinking water, and it has been linked to possible serious disease. The probable occurrence of cancerous tumors in labora-toiyi rats injected with MTBE alerted federal agencies as to its possible health hazards. In 1999, the EPA reversed itself, recommending the phasing out of MTBE as an additive to gasoline. 

Rain in equilibrium with atmospheric C02, but uncontaminated by industrial emissions, should have a pH of 5.7. However, atmospheric pollution from burning fossil fuels has resulted in acid rain of pH as low as 3.5 (24). If this condition continues for a long time, it may lead to a change in groundwater composition, which may considerably change the migration of plutonium in nature. 

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