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Home arrow Impacts arrow Heavy Metals and Radionuclides Impacts
Heavy Metals and Radionuclides Impacts Print

In his December 2007 article Nuking Ontario: Standoff at Sharbot Lake, Dr. Gordon Edwards declared uranium ore bodies to be among the deadliest mineral deposits on earth. “They harbour large quantities of dangerous radioactive materials. Exploration and mining activities liberate these poisons into the air we breathe, the water we drink, and the food we eat.”

Many heavy metals and radionucides (radioactive contaminants) occur naturally in the earth’s soil. While trace amounts of heavy metals are not harmful to humans, some even being necessary in our diet, accumulation over time can cause serious illnesses. Heavy metals can have toxic effects on humans when they contaminate the soil or they enter groundwater as a water pollutant. Likewise, most natural occurring radionuclides are at low levels and are not a public health concern. However, at higher levels, long-term exposure to radionuclides and uranium in drinking water can have toxic effects on the kidneys and/or cause cancer. Unnatural and dangerous concentrations of these elements are a by-product of uranium mining.

Because the geological make-up at every uranium-mining site is unique, it is difficult to know exactly what elements will present a problem, especially when foreign chemicals are introduced into the aquifer as they are in the ISL process. Selenium, vanadium, radium, molybdenum, nickel, cadmium, arsenic, and polonium-210 are found in the tailings of open-pit uranium mines and uranium mills. While the British Columbia Medical Association has given the title of “Superb Carcinogen” to radium, mining companies continue to discard large quanties of radium in uranium tailings piles where it can migrate into the food chain and ground water (pacificfreepress.com/content/view/2064/81/). Polouium-210, a billion times more toxic than cyanide, is dumped into uranium tailings piles as well.

These elements also create a chronic problem in the in-situ leaching (ISL) process. Water that has been chemically treated for the ISL process and pumped into the aquifer not only releases the uranium from its rock formation; metals and radionuclides are also mobilized in the ground water. These mobilized elements are a common cause of plugging and mechanical failures during the ISL uranium mining process, which can result in pollutants entering the aquifer. (See In-Situ Leaching (ISL) Impacts.)

“Due to the nature of In Situ Leach mining, quite large volumes of waste waters are created, which are often highly saline and contain toxic levels of heavy metals, process chemicals and radionuclides. The bleed solution (the excess water pumped out over that injected) is often the most significant component.” (See Page 20 of An Environmental Critique of In Situ Leach Mining: The Case Against Uranium Solution Mining PDF.)

One method of dealing with this toxic bleed solution is to retain it in a holding pond where radon is released into the atmosphere while the evaporation of water dries the elements into a powder. This toxic powder can be transported to a hazardous waste dump, ideally before interference from atmospheric conditions occur such as wind storms, tornados, or torrential rains (see Impact of Weather on Uranium Mine Tailings). Even ignoring northern Colorado’s volatile weather conditions, engineered holding ponds leak and cause contamination to earth and aquifers (see In-Situ Leaching (ISL) Impacts). A cheaper way to handle the bleed solution where human populations are not in close proximity to the mine and where aquifers not needed for human use, is to inject the toxic water back into the ground/aquifer where damages are not immediately recognized (see Deep Well Injection).

When the in-situ leaching of an area has been completed, all remaining chemicals that were pumped into the aquifer to dissolve the uranium should be removed and heavy metals, uranium, and other radionuclides mobilized in the aquifer should be returned to their original, pre-mining concentrations. In theory, this seems a plausible expectation. However, metals are often at concentrations in the aquifer a thousand times higher than before mining began. Uranium mining companies are faced with the impossible task of returning those concentrations to pre-mining levels in the aquifer when aquifer restoration is not fully understood.

The methods developed and used in an attempt to return aquifers to pre-mining conditions are ion exchange, reverse osmosis, ground water sweeping and clean water injection. More than one of these methods might be used on a site to successfully reduce some of the concentrations to baseline levels, while other elements are left at their elevated levels or even at higher levels. Doctoring the aquifer becomes an impossible balancing act. PH reactions that decrease one element may increase another. “The exact geochemical reactions that occur following the completion of ISL uranium mining will depend greatly on the influence of the above types of reactions on overall groundwater chemistry. Often it might be possible to predict the overall trend in pH or salinity, or for particular trace elements, but in general it is simply not possible to control the chemistry for every environmentally significant trace and heavy metal and radionuclide.” (See Page 24 of An Environmental Critique of In Situ Leach Mining: The Case Against Uranium Solution Mining PDF.)

Mix into to an already complicated mixture of metals and radionuclides any organic matter, and the ISL process in the aquifer becomes even more unpredictable and reactive. Organic matter may occur naturally in the aquifer or be introduced by unsanitatiry drill bits or pipes. “Many trace elements, including radionuclides, attach themselves preferentially (or form soluble chemical complexes) to organic compounds in solution such as humic and fulvic acids formed by the degradation of vegetation (Fetter, 1993). Thus the presence of organic matter within groundwater can lead to conditions where many trace metals and radionuclides, which would not otherwise would be soluble and affect groundwater quality, are soluble and therefore have the potential for migration in the direction of groundwater flow.” (See Page 29 of An Environmental Critique of In Situ Leach Mining: The Case Against Uranium Solution Mining PDF.)

In-situ leaching for uranium is proposed to take place in the Laramie-Fox Hills aquifer. Organics create problems for ILS operations, causing additional clogging of filters and plugging of pipes resulting in spills and leaks of toxic waters into the groundwater. (See In-Situ Leaching (ISL) Impacts.)

“The presence of organic matter in groundwater systems can thus lead to significant difficulties with an In Situ Leach mine, since many trace elements and radionuclides are potentially mobilised from a mineral to soluble state, and hence if complexed by organic matter, can remain soluble after ISL has finished.” (An Environmental Critique of In Situ Leach Mining: The Case Against Uranium Solution Mining PDF)

After mining operations have ceased, there is no method of cleanup that has proven to return the aquifer to pre-mining conditions. Even where large quantities of water are available to flush parts of the aquifer, chemical processes that took place during ISL may have caused clays, once a protective layer for the aquifer, to have soaked up some of the metals and held them during the flushing process, only to release the metals into the aquifer months or years after restoration is completed. “Despite nearly 25 years of commercial ISL uranium mines in the United States (all using alkaline leaching solutions), regulators are yet to review or approve a report on the full scale restoration of groundwater at these sites” (See Page vii of An Environmental Critique of In Situ Leach Mining: The Case Against Uranium Solution Mining PDF).

Since it is costly, time consuming, and almost impossible to return a uranium mine site to its pre-mining condition, a common mode of operation for uranium mining companies is to request and to receive lowered ground water standards. At the time of restoration, mining companies argue the standards they agreed to restore to before mining began have become unrealistic and unnecessary. The growing list of these sites includes but is not limited to: Bear Creek (Wyoming); Boots/Brown, (Texas); Burns/Moser (Texas); Christensen Ranch (Wyoming); Clay West (Texas); Gas Hills Uranium Mill (Wyoming); Highland (Wyoming); Holiday - El Mesquite, Duval County (Texas); Lucky Mc Uranium Mill Site (Wyoming); O'Hern (Texas); Palangana (Texas); Shirley Basin Uranium Mill (Wyoming); West Cole (Texas); Western Nuclear Split Rock uranium mill site (Wyoming); Zamzow (Texas). For specific details, please see these WISE Uranium Project links:

Once restoration is completed it is difficult to verify the uranium mining company has actually met their restoration requirements. Months after a mining site has been reclaimed, surface vegetation can appear green and lush. Closer studies reveal plants growing on uranium mining tailings have a high uptake of radionuclides. A 1988 study published in the Journal of Radioanalyical and Nuclear Chemistry found that grass-like plants growing on abandoned uranium tailings showed the uptake of high levels of radionuclides in the above ground parts, while woody plants had high uranium accumulation in their roots. This plant uptake would result in the spread of radioactive material from the site. (See A study of radionuclides in vegetation on abandoned uranium tailings.)

An example of toxic elements spreading, although not a result of uranium mining, can be seen at the Kesterson National Wildlife Refuge. There humans created an unnatural concentration of selenium in the water which resulted in an entire food chain carrying high levels of selenium and causing death and deformities in all animal populations and infestation of selenium loving plants. (See Selenium Case Study: Kesterson National Wildlife Refuge PDF.)

Uranium miners in northern Colorado will have a significant problem with selenium concentrations. Northern Coloradoan farmers and ranchers are already familiar with the plants toxic to livestock that thrive in soil with high selenium content (see Selenium Contamination).

In situ leaching for uranium in our area of the state will create hot spots of selenium that we may never be able to restore. Covered tailings can leach, protective barriers leak, and elements mobilized in the aquifer migrate. Mining companies used the common defense when water wells becomes contaminated following the introduction of uranium mining: the water well was drilled near the uranium ore-body so there is no legal proof uranium mining caused contaminates to appear in the well water. Counties, landowners, and Native American nations are mired in legal wranglings with uranium mining companies, trying to hold them accountable for environmental damages left when the prices of uranium fell or the uranium was mined out of a site, and the companies abandoned their mines.




        
 

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