Plutonium, like other actinides, readily forms a plutonium dioxide (plutonyl) core (PuO). In the environment, this plutonyl core readily complexes with carbonate as well as other oxygen moieties (OH, NO, NO, and SO) to form charged complexes which can be readily mobile with low affinities to soil.
*PuOCO
*PuO(CO)
*PuO(CO)
PuO formed from neutralizing highly acidic nitric acid solutions tends to form polymeric PuO which is resistant to complexation. Plutonium also readily shifts valences between the +3, +4, +5 and +6 states. It is common for some fraction of plutonium in solution to exist in all of these states in equilibrium.
Plutonium is known to bind to soil particles very strongly; see above for an X-ray spectroscopic study of plutonium in soil and concrete. While caesium has very different chemistry to the actinides, it is well known that both caesium and many actinides bind strongly to the minerals in soil. it has been possible to use Cs-labeled soil to study the migration of Pu and Cs is soils. It has been shown that colloidal transport processes control the migration of Cs (and will control the migration of Pu) in the soil at the Waste Isolation Pilot Plant.