i PLUTONIUM-HUMIC ACID STABILITY CONSTANT DETERMINATION AND

ii Plutonium has been released to the environment through a variety of intentional and unintentional mechanisms, including atmospheric testing, disposition from weapons manufacturing processes, and subsurface disposal. Therefore, a thorough understanding of the chemical, physical, and biological processes affecting plutonium transport is imperative. It has been shown that humic acid (HA) (a refractory component of natural organic matter (NOM)) can effectively solubilize plutonium (Santschi et al., 2002). Increased solubility may result in enhanced subsurface transport, due to the higher concentration of Pu in the aqueous phase. In contrast, the formation of ternary surface complexes may hinder actinide transport. Solution pH is likely to affect the dominance of one species over another. For these reasons, a better understanding of binary Pu-HA and Pu-mineral and ternary Pu-HA-mineral systems is essential for accurately predicting plutonium fate and transport. The primary objective of this research was to determine the conditional stabilit