Granite, 502 well waters

Radon gas is formed in the process of radioactive decay of uranium. The distribution of naturally occurring radon follows the distribution of uranium in geological formations. Elevated levels have been observed in certain granite-type minerals. Residences built in these areas have the potential for elevated indoor concentrations of radon from radon gas entering through cracks and crevices and from outgassing from well water. 

Chemical analyses and related information for some well waters from uranium deposits and two unmineralized granites (Aspo and Stripa,... 

Table II summarizes analytical data for dissolved inorganic matter in a number of natural water sources (J3, 9, J 9, 20, 21). Because of the interaction of rainwater with soil and surface minerals, waters in lakes, rivers and shallow wells (<50m) are quite different and vary considerably from one location to another. Nevertheless, the table gives a useful picture of how the composition of natural water changes in the sequence rain ->- surface water deep bedrock water in a granitic environment. Changes with depth may be considerable as illustrated by the Stripa mine studies (22) and other recent surveys (23). Typical changes are an increase in pH and decrease in total carbonate (coupled), a decrease in 02 and Eh (coupled), and an increase in dissolved inorganic constituents. The total salt concentration can vary by a factor of 10-100 with depth in the same borehole as a consequence of the presence of strata with relict sea water. Pockets with such water seem to be common in Scandinavian granite at >100 m depth.

A general conclusion from the review of the distribution of plutonium between different compartments of the ecosystem was that the enrichment of plutonium from water to food was fairly well compensated for by man s metabolic discrimination against plutonium. Therefore, under the conditions described above, it may be concluded that plutonium from a nuclear waste repository in deep granite bedrock is not likely to reach man in concentrations exceeding permissible levels. However, considering the uncertainties in the input equilibrium constants, the site-specific Kd-values and the very approximate transport equation, the effects of the decay products, etc. — as well as the crude assumptions in the above example — extensive research efforts are needed before the safety of a nuclear waste repository can be scientifically proven. 

The acidity of rains — due both to S04 and NO3 — formed in the atmosphere — which may bring the pH of lakes to figures of 5-6 and even 4.5 is not the sole factor responsible for the toxicity of water for fishes, phytoplankton and zooplankton. In effect there are several chemical processes due to the interaction of acid rains and the soil, as well as the water of lakes. First of all it may occur that in the water, owing to the presence of carbonic acid system HC03"/(Na) (C03 ) may act as buffer in many lakes. This is not the case of the lakes in Scandinavia because the soil is mainly constituted by granites. 

Evolved granites may contain uranium and thorium in very high concentrations and hence may account for a large fraction of their total content in the crust. One difficulty is that they are open to water circulation in the near-surface environment, which leads to uranium depletion (Oversby, 1976 Jaupart et al., 1981 A. Forster and H.-J. Forster, 2000). These effects are well documented and have been demonstrated even in... 

Recently, it has been possible to collect pore fluids from the unfractured granite rock matrix using upward-sloping boreholes at the 420 m level of the URL. These waters are highly saline (—90gL ) CaCl2 fluids that have a unique isotopic signature. Both and values are about — 15%o, a composition that places them well to the left of the meteoric water line and also above and to the left of the most saline Canadian Shield mine waters. 

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