Measuring low concentrations of {sup 234}Th in water and sediment

{sup 234}Th/{sup 238}U disequilibria have been used extensively in studies of particle dynamics and the fate and transport of particle-reactive matter in marine environments. Similar work in low salinity, estuarine, and freshwater systems has not occurred primarily because the lower concentrations of both parent and daughter nuclides that are typical of these systems often render established methods for the analysis of {sup 234}Th inadequate. The application of this radionuclide tracer technique to these systems, however, has great potential. To this end, we present a method for measuring low activities of {sup 234}Th in relatively small samples (