THE UNDERLYING PROCESSES OF PU AGING, DISTRIBUTION, AND MIGRATION IN ENVIRONMENTAL SYSTEMS WILL BE TESTED AT A NOVEL FIELD SITE AT THE DOE SAVANNAH RIVER SITE (SRS). THE SITE OF INTEREST IS POND B AT THE SRS WHICH RECEIVED REACTOR COOLANT WATER FOR A BRIEF TIME FROM 1961-1964 AND HAS RESIDUAL CONTAMINATION OF PU AMONG OTHER RADIONUCLIDES. PREVIOUS STUDIES IN THE LATE 1980’SDEMONSTRATED A SEASONAL CYCLE OF PU DISTRIBUTION BETWEEN SEDIMENTS AND THE AQUEOUS PHASE LINKED TO ANOXIC CONDITIONS. THESE PREVIOUS STUDIES RELATED PU RELEASE FROM BOTTOM SEDIMENTS DURING TIMES WHEN THE WATERS ARE OXIC FOLLOWED BY REDUCTION AND RETURN TO THE SEDIMENT ONCE THERMAL STRATIFICATION OCCURS. THEY WILL UTILIZE ADVANCED MASS SPECTROMETRY TECHNIQUES TO DETERMINE THE PRESENCE OF PU COMPLEXES WITH NATURAL ORGANIC MATTER WHICH APPEARS TO BE A MAJOR FACTOR CONTROLLING PU DISTRIBUTION IN NATURAL SYSTEMS. ONGOING STUDIES HAVE SHOWN THAT THE PU FRACTION FROM THE R-REACTOR IS BEING DILUTED BY ATMOSPHERIC FALLOUT. THE CO-ASSOCIATED REACTOR DERIVED PU WHICH IS BEING MIXED WITH ATMOSPHERIC FALLOUT PROVIDE AN OPPORTUNITY TO TEST TECHNIQUES CAPABLE OF DISTINGUISHING BETWEEN THESE TWO POOLS AND IDENTIFYING THE UNDERLYING MECHANISMS OF PU ENVIRONMENTAL MOBILITY. THIS PROJECT WILL EXAMINE THE SPATIAL VARIABILITY (LONG-TERM ASSOCIATION IN SEDIMENT) AND SEASONAL FLUX OF FE, PU, AND CARBON ACROSS THE SEASONAL REDOX GRADIENTS DEVELOPED IN THE SEDIMENT, THE PORE WATER, AND SURFACE WATER IN THE POND B SYSTEM. WHILE THE WORK IS FOCUSING ON A POND WATERSHED ENVIRONMENT, THEY PRESENT THIS AS A TEST CASE FOR THE DEPLOYMENT OF NOVEL GEOCHEMICAL AND BIOLOGICAL ANALYSIS TECHNIQUES WHICH CAN BE USED TO DETERMINE PU AND OTHER RADIONUCLIDE SPECIATION, CONCENTRATION, ISOTOPE RATIOS, AND ENVIRONMENTAL MOBILITY. THUS, THE KNOWLEDGE GAINED AND TECHNIQUES DEVELOPED IN THIS WORK ARE TRANSFERABLE TO OTHER SITES AND/OR ENVIRONMENTS.