Note: Front Cover -- U-Th Series Nuclides in Aquatic Systems -- Copyright page -- Dedication to Karl K. Turekian -- Contents -- Contributors -- Chapter 1. Introduction -- 1. Overview -- 2. Organization of the Volume -- Acknowledgements -- References -- Chapter 2. U- and Th-Series Nuclides in the Atmosphere: Supply, Exchange, Scavenging, and Applications to Aquatic Processes -- 1. Introduction -- 2. Sources of U- and Th-Series Nuclides to the Atmosphere -- 3. Atmospheric Distributions -- 4. Aerosol Scavenging Residence Times Using 222Rn and its Daughters -- 5. Applications of Rn Daughters of Atmospheric Origin to Study Aquatic Processes -- 6. Processes across Aquatic Interfaces -- 7. Perspectives and Future Directions -- Acknowledgements -- References -- Chapter 3. U-Series Geochemistry in Weathering Profiles, River Waters and Lakes -- 1. Introduction -- 2. Radionuclide Fractionation in Surface Environments -- 3. Radioactive Disequilibria in Weathering Profiles and Soils -- 4. U Series in Rivers -- 5. Review of Models for U-Series Fractionation in Surficial Environments -- 6. U-Series Disequilibria in Lakes -- 7. Future Perspectives -- Acknowledgments -- References -- Chapter 4. Investigating Groundwater Processes Using U- and Th-Series Nuclides -- 1. Introduction -- 2. General Element Behavior in Groundwaters -- 3. Modeling Nuclide Transport in Aquifers -- 4. Obtaining Solutions to the Model Equations -- 5. Radon and Recoil Rates -- 6. Ra Isotopes -- 7. Th Isotopes -- 8. U Isotopes -- 9. 210Pb -- 10. Summary and Future Studies -- Acknowledgments -- References -- Chapter 5. Uranium- and Thorium-Series Nuclides as Tracers of Submarine Groundwater Discharge -- 1. Introduction -- 2. How U-Th Isotopes are Used to Quantify Submarine Groundwater Discharge (SGD) -- 3. Radium -- 4. Radon -- 5. Uranium -- 6. Synthesis of Existing Studies. , 7. Towards a Global Estimate of SGD -- 8. Perspectives and Future Directions -- Acknowledgments -- References -- Chapter 6. U- and Th-Series Nuclides in Estuarine Environments -- 1. Introduction: Estuarine Processes -- 2. Uranium -- 3. Thorium -- 4. Radium -- 5. Radon -- 6. Lead-210 and Polonium-210 -- 7. Future Studies -- References -- Chapter 7. U- and Th-Series Nuclides as Tracers of Particle Dynamics, Scavenging and Biogeochemical Cycles in the Oceans -- 1. Abundance and Distribution of U-Th Nuclides in the Sea -- 2. Introduction to Particle Cycling and Scavenging in the Ocean -- 3. The Scavenging Process as Understood from Thorium Isotopes -- 4. Scavenging and Th Speciation -- 5. 226Ra-210Pb-210Po -- 6. The Role of Particle Composition -- 7. Boundary Scavenging -- 8. Calibration of Vertical Particle Fluxes -- 9. Summary and Outlook -- References -- Chapter 8. The Bioaccumulation of U- and Th-Series Radionuclides in Marine Organisms -- 1. Introduction -- 2. Radionuclides of Interest and their Bioavailability -- 3. Models of Uptake and Trophic Transfer -- 4. Biodetritus and Vertical Transport -- 5. Potential Impacts of Natural Radioactivity -- 6. Synthesis and Conclusions -- 7. Future Outlook and Perspectives -- References -- Chapter 9. Ocean Circulation/Mixing Studies with Decay-Series Isotopes -- 1. Introduction -- 2. General Transport Equations -- 3. Basic Ocean Mixing/Circulation Models -- 4. Radium Isotopes for Tracing Oceanic Mixing/Circulation -- 5. Radon-222 as a Vertical Mixing Tracer in the Deep Sea -- 6. Actinium-227 as a Diapycnal Mixing Tracer in the Deep Sea -- 7. Tracing Ocean Circulation Using Particle-Reactive Radionuclides -- 8. Closing Remarks and Future Prospects -- Acknowledgments -- References -- Chapter 10. Uranium- and Thorium-Series Radionuclides in Marine Groundwaters -- 1. Introduction. , 2. U- and Th-Series Radionuclides in High-Temperature Marine Groundwaters: Hydrothermal Fluids -- 3. U- and Th-Series Radionuclides in Low-Temperature Marine Groundwaters: Sediment Pore Water -- 4. Future Directions -- Acknowledgments -- References -- Chapter 11. Sediment Signatures of U- and Th-Series Nuclides and their Application as Paleoceanographic Tracers -- 1. Introduction -- 2. Long-Lived U-Series Nuclides in Sediments -- 3. Short-Lived U-Series Nuclides in Sediments: Application to Sediment Mixing and Accumulation -- 4. Authigenic Uranium as a Tracer of Sediment Redox State -- 5. Use of 230Th as a Constant Flux Proxy -- 6. 231Pa/230Th: Proxy for Particle Flux and Productivity -- 7. 231Pa/230Th: Proxy of Ocean Circulation -- 8. Modeling Studies -- 9. Manganese Crusts and Nodules -- 10. Summary and Outlook -- Acknowledgments -- References -- Appendix A. Charts of the 238U, 235U, 232Th, and 241Am Decay Series with Principal Modes of Decay, their Intensities and Energies -- 1. Introduction -- 2. Sources of Data -- References -- Appendix B. Systematics of Radioactive Decay -- 1. Overview of Decay Equations -- 2. Examples of Applications -- References -- Author Index -- Subject Index.