Radionuclides released into the Susquehanna-Chesapeake System from the Three Mile Island, Peach Bottom, and Calvert Cliffs nuclear power plants are partitioned among dissolved, particulate, and biological phases and may thus exist in a number c c physical and chemical forms. In this project, we have measured the dissolved and 137 137 particulate distributions of fallout Cs; reactor-released Cs, Cs, Zn, Co, and Co; and naturally occurring Be and Pb in the lower Susquehanna River and Upper Chesapeake Bay. In addition, we chemically leached suspended particles and bottom sediments in the laboratory to determine radionuclide partitioning among different particulate-sorbing phases to complement the site-specific field data. This information has been used to document the important geochemical processes that affect the transport, sorption, distribution, and fate of reactor-released radionuclides (and by analogy, other trace contaminants) in this river-estuarine system. Knowledge of the mechanisms, kinetic factors, and processes that affect radionuclide distributions is crucial for predicting their biological availability, toxicity, chemical behavior, physical transport, and accumulation in aquatic systems. The results from this project provide the information necessary for developing accurate radionuc11 de-transport and biological-uptake models. V/ / v11 EXECUTIVE SUMHARY Radioactivity is introduced into the Susquehanna River-Chesapeake Bay System from three sources: nature, atmospheric tests of nuclear weapons, and controlled low-level releases from thr Three Mile Island. Peach Bottom, and Calvert Cliffs nuclear power plants. Samples of water, suspended matter, and sediments were collected over a three-year time period at four sites: Conowingo Pond, Susquehanna Flats, Annapolis, and Calvert Cliffs. These sites were chosen because they cover a significant range in estuarine salinity, span the major zones of fine-particle deposition, and arc within the influence of reactor releases. Dissolved and particulate distributions of naturally occurring Be and Pb, fallout Cs, and reactor-released Cs, Cs, Zn, Co, and Co were quantified at each of these four sites. The distribution data have been used to (1) describe sorption kinetics and estimate radionuclide removal rates from the water column, (2) determine radionuclide partitioning among different particulate sorbing phases (clay surfaces, organics, Fe-Mn coatings, and mineral lattices), and (3) document the important geochemical processes that affect the fate of radionuclides (and by analogy, other trace contaminants) in the Susquehanna-Chesapeake Bay System. The concentration, transport, and fate of reactor-released radionuclides in freshwater areas is primarily governed by variations in radionuclide Input and fine-particle dynamics. Because variations in input and particle dynamics are short term; chemical equilibrium is continually adjusting and is therefore rarely attained at the time of sample collection. As a result, measured radionuclide concentrations and their particl...
