Effect of soil type on the extractability of /sup 237/Np, /sup 239/Pu, /sup 241/Am and /sup 244/Cm as a function of pH

The extractability of /sup 237/Np, /sup 239/Pu, /sup 241/Am, and /sup 244/Cm from widely different kinds of soils as a function of pH was determined using an equilibrium batch technique. Hydrochloric acid or NaOH was used to adjust the pH. The sorption and extractability of the transuranics studied varied considerably with pH and the kind of soil. A general pattern of extractability that is common to all of the transuranics studied was exhibited to a varying degree by each mineral soil (except the calcareous soil). Typically the extractability was relatively high under strongly acidic condition, particularly below pH 2. Then, as the pH increased, there was a zone of rapid decrease, which was followed by a zone of relatively low extractability. Above the latter zone, there was an increase to a peak with increasing pH and then a decline. The organic soil used differed from this general pattern in that it showed a progressive increase of extractability in the alkaline pH range instead of peaking and declining. Among the mineral soils, the extractability of /sup 237/Np was markedly greater than those of /sup 239/Pu, /sup 241/Am, or /sup 244/Cm in the pH range below pH 6. Above this pH, the relative extractability of the radionuclides depended on the soil. The extractability of /sup 244/Cm was practically the same as that of /sup 241/Am over the entire pH range. The relative magnitudes of the distribution coefficient, K/sub d/, values around the pH levels of the soils were /sup 237/Np < /sup 239/Pu < /sup 241/Am, /sup 244/Cm. Soil organic matter and hydrous oxides of Al, Fe, and Mn appeared to influence the sorption and extractability of the transuranics studied.