The residence time of 210Po and 210Pb related to plankton in surface waters off Misaki, Japan

210Po and 210Pb are known for their preferential adsorption to fine organic and inorganic particles in the marine environment. As a consequence these nuclides are rapidly scavenged by fine particles in coastal waters. These radionuclides were analyzed in the bulk surface waters off the Misaki coast in Japan during 18 months to estimate the residence time of 210Po and 210Pb in surface waters. The surface water samples were collected monthly and immediately filtered through a plankton net. Using a simple box-model, the corresponding scavenging residence times of 210Po and 210Pb were estimated in the coastal waters to be >2.3 months and between 1.2 and 11 months, respectively. This suggests that 210Po is recycled in these surface waters while 210Pb is strongly scavenged. The recycling of 210Po is assumed to be caused by high primary production in these waters. (author)