Interpreting particle size effects in the adsorption of 137Cs and unsupported 210Pb by mineral soils and sediments

The fallout radionuclides 137Cs and unsupported 210Pb have been widely used as environmental tracers for studying both sediment deposition in various environments and associated erosion and sediment delivery processes in drainage basins. Information on the adsorption of these radionuclides by different size fractions of soils and sediments is important for the interpretation involved in such studies. Laboratory experiments and empirical observations of natural soils and sediments were used to study grain size effects associated with the adsorption of 137Cs and 210Pb by mineral soils. Quantitative relationships between the concentrations of 137Cs and 210Pb adsorbed by individual size fractions in soils and their specific surface area were derived from the results obtained and these also provide a basis for estimating radionuclide enrichment ratios associated with suspended sediment.