Residence times of surface water and particle-reactive 210Pb and 210Po in the East China and Yellow seas

228Ra, 226Ra, 210Pb, and 210Po were measured in the surface waters of the East China and Yellow seas. Using mass balance equations for the Ra isotopes, we estimated the total flux of diffusion from sediments and desorption from suspended particles to be 0.1 dpm 226Ra cm−2 a−1 and 1 dpm 228Ra cm−2 a−1, and residence times to be 2–3 years for the waters on the East China Sea Shelf and 5–6 years for Yellow Sea waters. Box-model calculations yielded generally congruent scavenging residence times for 210Pb and 210Po in the waters of ~2 months on the shelf and ~7 months in the Kuroshio Current. These suggest that reactive heavy metals and pollutants discharged through rivers from the continent to the East Asian continental shelf are largely deposited on the bottom sediments prior to transport to the pelagic ocean by lateral mixing.