Applications of PB-210/RA-226 and PO-210/PB-210 Disequilibria in the Study of Marine Geochemical Processes

• Main Author: Bacon, M. P.
• Format: Report
• Language: English
• Published: Woods Hole Oceanographic Institution 1976
• Subjects: Atlantic Ocean; Aquatic Organisms; Fluids; Lead 210; Beta Decay Radioisotopes; Dispersions; Seawater; Polonium Isotopes; Ecological Concentration; Mixing; Beta-Minus Decay Radioisotopes; Surface Waters; Isotopes; Diffusion; Depth; Air; Fallout; Polonium 210; Even-Even Nuclei; Fallout Deposits; Plankton; Chemistry; Nuclei; Alpha Decay Radioisotopes; Lead Isotopes; Seas; Sampling; Aqueous Solutions; Surface Air; Solutions; Oxygen Compounds; Years Living Radioisotopes 520300* > Environment; Aquatic > Radioactive Materials Monitoring & Transport > (1989); Pacific Ocean; Dimensions; Days Living Radioisotopes; Radioecological Concentration; Gases; Radioisotopes; Hydrogen Compounds; Geochemistry; Particles; 520302 > Environment; Aquatic > Radioactive Materials Monitoring & Transport > Aquatic Ecosystems & Food Chains > (-1987); 54 Environmental Sciences; Mixtures; Water; Heavy Nuclei; Pacific; North Atlantic
• Online Access: https://doi.org/10.2172/7145091; https://digital.library.unt.edu/ark:/67531/metadc1418505/

The distribution of /sup 210/Pb and /sup 210/Po in dissolved (less than 0.4 micron) and particulate (greater than 0.4 micron) phases was measured at ten stations in the tropical and eastern North Atlantic and at two stations in the Pacific. Both radionuclides occur principally in the dissolved phase. Unsupported /sup 210/Pb activities, maintained by flux from the atmosphere, were present in the surface mixed layer and penetrated into the thermocline to depths of about 500 m. Dissolved /sup 210/Po was ordinarily present in the mixed layer at less than equilibrium concentrations, suggesting rapid biological removal of this nuclide. Particulate matter was enriched in /sup 210/Po, with /sup 210/Po//sup 210/Pb activity ratios greater than 1.0, similar to those reported for phytoplankton. Box-model calculations yield a 2-y residence time for /sup 210/Pb and a 0.6-y residence time for /sup 210/Po in the mixed layer. These residence times are considerably longer than the time calculated for turnover of particles in the mixed layer (about 0.1 y). At depths of 100 to 300 m, /sup 210/Po maxima occurred and unsupported /sup 210/Po was frequently present. Calculations indicate that at least 50 percent of the /sup 210/Po removed from the mixed layer is re-cycled within the thermocline. Similar calculations for /sup 210/Pb suggest much lower re-cycling efficiencies.