Uranium series isotopes in the Avon Valley, Nova Scotia.
An U-series isotopic study was carried out in the waters of the Avon Valley, Nova Scotia. The fresh and acidic recharge waters flow rapidly through the watershed composed of a granitic highland and a sedimentary, largely carbonate, lowland plain, before draining to the sea. There is no significant anthropogenic pollution; but, naturally elevated U levels can be encountered within the bedrock. Nonetheless, the U concentrations of the surface and groundwater are low (generally within the range of several hundredths to several tenths of a microg l(-1)), except in the proximity to weathering of U mineralization. The dissolved U in the surface waters appears to be stabilized by organic rather than inorganic complexes. Both the groundwaters and surface waters have similar (234)U/(238)U activity ratios that rarely deviate from secular equilibrium by more than 20% throughout the watershed. The magnitude of the (234)U/(238)U activity ratio is not determined by lithology but rather by the weathering mechanism, the high rate of flushing, and the leaching of local U mineralization. Dissolved Ra is consistently absent. The dissolved Rn concentrations, though variable, are measurable even in surface waters. This may be due to a continual degassing from the U-enriched bedrock or release from local sites of U mineralization underlying the surface water sources.
Kronfeld
J
J
Department of Geophysics and Planetary Sciences, The Raymond and Beverly Sackler Faculty of Science, Tel Aviv University, Ramat Aviv 69978, Israel.
Godfrey-Smith
D I
DI
Johannessen
D
D
Zentilli
M
M
D004784:Environmental Monitoring; D055593:Geological Phenomena; D005844:Geology; D009674:Nova Scotia; D045483:Rivers; D012995:Solubility; D014501:Uranium / Q000032:analysis*; D014867:Water / Q000737:chemistry*
D014867:Water; D014501:Uranium