Lead-210 and polonium-210 in the winter well-mixed turbid waters in the mouth of the Yellow Sea

Concentration profiles of 210Pb and 210Po were measured along a traverse of the mouth of the Yellow Sea in February 1993. Winter time suspended particulate matter concentration was more than 10–100 mg l-1 in the coastal domain and less than 10 mg l-1 in the central domain. Concentrations of dissolved 210Pb over the area were low (<5 dpm kg-1) due to the efficient removal of 210Pb from the water column over the shelf. Evidence for release of 210Po is seen in a sub-surface layer, close to the sediment–water interface, where 210Po is enriched in the dissolved form and depleted in the particles. The high concentration of SPM in the mouth of the Yellow Sea appears to determine dissolved and particulate 210Pb and 210Po activities. The atmospheric input of 210Pb is the major source of 210Pb in the region with minor contribution from the 210Pb rich Kuroshio Water. The Kd values of 210Po varied by a factor of 50 while the corresponding values of 210Pb varied only by a factor of 4. It appears that in waters where particle concentrations are high (>10 mg l-1), the Kd appears to be independent of particle concentration.