Adsorption of actinides by marine sediments: effect of the sediment/seawater ratio on the measured distribution ratio

The effect of the solid/solution ratio on distribution ratios measured was investigated, focusing on two different deep sea sediments and the actinides americium, neptunium, and plutinium. The apparent drop in distribution ratio with increasing sediment concentration can frequently be explained by the presence of a small amount of nonseparable or low distribution coefficient species. By measuring the coefficient at different solid/solution ratios it is possible to estimate the proportion of nonseparable species present. Pu exhibited anomalous behavior with the high-carbonate sediment, and the distribution ratio dropped from greater than 1000 to 100 ml/g as the solid/solution ratio increased from 2 to 20 g/l.