The mechanism of Rn solution in groundwaters has been studied in both laboratory simulations and in field situations. The effect of sporadic and seasonal changes in rainfall patterns on the Rn contents of perennial springs in the Mendip Hills has been investigated. The separate contributions of surface streams, soil zone residence and percolation within the rock formation have been identified. The relative importance of fissure or conduit and percolation flow in the aquifer have been shown to determine the nature of the response of Rn content to rainfall patterns. An examination of the Rn contents of air in limestone caverns has established that intergranular diffusion of Rn from below the rock surface is the primary reason for Rn release into the air space. Rn transport and release from stream inflows is relatively unimportant. Experimental determinations of the Rn diffusion coefficient in rock sections have shown that such intergranular diffusion is much more significant than intragranular diffusion. Laboratory studies of Rn release from fragmented rock samples have been used to determine the efficiency of radon release for different rock types. These studies have also confirmed that intergranular diffusion is an important process by which groundwaters acquire high Rn contents. The Ra content of geothermal groundwaters from Iceland have been determined. The Ra and U contents of calcite deposits from various depths within these geothermal systems are discussed in relation to changes in the Ra geochemistry. Rn contents have also been determined for groundwaters from the Berkshire Chalk and are shown to be dependent upon the extent to which porewater mixing has occurred.
|Date of Award