Plutonium Colloid-Facilitated Transport in the Environment-Experimental and Transport Modeling Evidence for Plutonium Migration Mechanisms

摘要

Natural inorganic colloids (< 1 micron particles) found in groundwater can absorb low-solubility actinides and may provide a pathway for transport in the subsurface. For example, Kerting et al. found that Pu, associated with colloids fraction of the groundwater, was detected over 1 km away from the underground nuclear test at the Nevada Test Site (NTS) where it was originally deposited 28 years earlier. However, laboratory experiments have not identified the mechanisms by which Pu may absorb to colloids or exist as its own colloid and travel relatively unimpeded in the subsurface. Some data suggest that Pu sorption to colloids is a very fast process while desorption is very slow or simply does not occur. Slow desorption of Pu from colloids could allow Pu sorbed to a colloid to travel much farther than if sorption were an equilibrium process. However, PU sorption (and particularly desorption) data in the literature are scant and sometimes contradictory. In some cases, Pu desorption is rather fast, with rates dependent on colloid mineralogy.