Aquifers, radioactive waste

Beyond these impacts, more advanced nanotechnology may allow active remediation of many environmental problems. For example, toxic wastes in contaminated aquifers may be neutralized by specially designed nano-robots (nanobots) that selectively capture undesirable molecules and then either sequester them for removal or break them down into harmless substances [114,118,119,124]. While nano-devices cannot, for example, render radioactive materials non-radioactive, they could capture molecules of radioactive waste and concentrate them into a form that would be easily removed [31-33]. 

Other point sources of groundwater pollution include both deep injection wells and shallower dry wells used to inject chemical wastes (including radioactive waste) directly into the subsurface environment. While it is customary to make waste injections into deep aquifers that are salty or otherwise unusable for potable water, it is not unusual for injection wells to leak, or to force the flow of water from one layer of aquifer into another, resulting in contamination of an otherwise usable source of groundwater. 

SIMULATION OF COUPLED THERMAL AND SOLUTE CONCENTRATION EFFECTS ON DENSE RADIOACTIVE WASTE MIGRATION IN DEEP AQUIFERS... 

Nuclear waste (Section II.A.2) presents even more serious problems than does chemical waste. No method of elimination is possible radioactive material must be sequestered from the environment until it decays, which for some common by-products of nuclear reactor operation will take thousands of years. Continual exposure to radiation promotes deterioration of materials, so nuclear wastes held in aboveground storage or in subsurface tanks must frequently be transferred to new containers. Burial of such wastes has frequently been discussed as a long-term solution to the problem of their disposal, but finding geological formations sufficiently stable and remote from aquifers into which the wastes might migrate has proven to be very difficult. At present, ahention is fo-... 

Water on and beneath the surface of the geosphere plays a strong role in pollution and the distribution of toxic substances. Toxic substances from wastes improperly disposed to the geosphere can leach into groundwater and contaminate water supplies. Radioactive radium resulting from the decay of uranium in aquifer formations has caused some groundwater sources of drinking water to be abandoned. 

In many low-level waste repositories, the small absolute size of the initial inventory prevents solubility limits from being exceeded. All waste repositories are subject to eventual transport of contaminant-laden fluids into the surrounding rock and soil, and dilution to levels below solubility limits (if not in the immediate nearfield, certainly in the far-field, see Brady Kozak, 1995). Radionuclide sorption is therefore a primary control over radionuclide movement. If sorption to aquifer material is strong, decay to less dangerous isotopes might occur before a potential receptor is impacted. Alternatively, lack of binding would result in more rapid groundwater transport of radioactive elements to the biosphere. 

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