Radium, radon and inert gases in groundwaters and rocks as geochemical tracers

Natural radioelements and inert gases in solution in groundwaters have been applied to problems of groundwater flow and age measurement. The 4He content of groundwaters generally increases with age and in the Bunter Sandstone, Nottinghamshire, the 4He contents of groundwaters have been linearly related to 14C ages. In the Lincolnshire Limestone, the 4He contents have been used to indicate mixing of recharge water and interstitial water. In the other study areas, 4He and 40Ar in groundwaters have been used as qualitative indicators of age. The amounts of non-radiogenic gases dissolved in groundwaters have been used to estimate groundwater recharge temperatures. These have been related to seasonal recharge, changes in the altitude of recharge and variations in the hydrogen and oxygen isotopic ratios. Variation of the 222Rn contents of groundwaters has been used as an indicator of aquifer variability. The relative importance of intergranular and fissure flow and the variation in efficiency of 222Rn release into groundwaters has been investigated. Variability of the 226Ra contents of groundwaters has been explained in terms of the relative importance of the recoil and etch mechanisms of solution and the solubility of 226Ra salts in groundwaters. (author)