Radium Isotopes in the Orinoco Estuary and Eastern Caribbean Sea

Optically stimulated luminescence dating of young sediments: A review

“…Using thick source alpha counting, Huntley and Clague (1996) detected what they presumed to be uranium uptake in the peat layers surrounding their tsunami sand layer, and they made a simple correction to their timeaveraged dose rate to account for this. It is also known that a large fraction (∼50%) of radium isotopes (half lives from 1600 years to less than 30 min) held on freshwater sediments can enter solution when encountering the salinity gradient found in estuaries (Hancock and Murray, 1996;Moore and Todd, 1993). These radium activities will then tend to return to equilibrium with their respective thorium parent isotopes when the estuarine sediment is buried sufficiently deeply that migration in pore water is no longer possible, giving rise to a time-dependent dose rate component.…”

Radium isotopes in the Ulsan Bay

“…This increase may be attributed to desorption of Ra from suspended particulate matter. In studies of the Hudson River (Li et al, 1977), the Pee Dee River (Elsinger and Moore, 1980), the Yangtze River (Elsinger and Moore, 1984), the Amazon River (Key et al, 1985), the Orinoco River (Moore and Todd, 1993), and Bega River (Hancock and Murray, 1996), the 226 Ra activity maximum occurred at salinities from 15 to 30. At salinities above 26.41, the 226 Ra activities decreased to the value of the oceanic end-member (1.34 mBq L ÿ1 ).…”

Signature of the Mekong River plume in the western South China Sea revealed by radium isotopes

“…However, the salinity signal can be altered by precipitation and evaporation, and the silica signal is sensitive to biological uptake. To circumvent these drawbacks, radium isotopes can be employed [ Moore and Krest , 2004; Moore et al , 1986; Moore and Todd , 1993; Rutgers van der Loeff et al , 2003]. Unlike salinity and silica, the 228 Ra/ 226 Ra activity ratio (AR) only changes by decay of 228 Ra and mixing.…”