Geochemistry of natural radionuclides in uranium-enriched river catchments

摘要: Radionuclides from natural U-series in sediments two river catchments the UK have been studied. The aim was to gain insight into behaviour of 238U, 234U, 230Th and 226Ra real systems enriched uranium. A radiochemical method for radium separation followed by alpha spectrometric measurement has developed. allowed use 225Ra, equilibrium with parent 229Th, as a yield determinant, applied concentrations measurements selected areas study.U-series progeny, 226Ra, totally dissolved valley River Noe fraction leached aqua regia, measured. Total sediment contents ranged 9 � 2 184 8 Bq.kg-1 uranium, 3 200 13 thorium 18 1 179 radium. activity fractions, compared total, were 46% 54% 56% radium, on average. radionuclides showed extensive disequilibrium this suggested complex leaching/accumulation uranium well an impact organic matter secondary minerals.Uranium geochemically characterised near South Terras abandoned mine, Cornwall. Background concentration levels 290 14 Bq.kg-1, 42 4 424 23 Bq.kg-1. Elevated measured samples, S3 1820 36 940 53 radium; S7 4350 1765 48 Sequential chemical extraction samples revealed that both associated carbonate 25 % resistant phase S7. 234U/238U ratios sequential fractions different trends sediments, linked and/or exchange between water sediment. Uranium-bearing minerals association potassium, calcium, iron, manganese arsenic identified these sediments.