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

Abstract

Concentration profiles of Pb-210 and Po-210 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 Pb-210 over the area were low ( < 5 dpm kg(-1)) due to the efficient removal of Pb-210 from the water column over the shelf. Evidence for release of Po-210 is seen in a sub-surface layer, close to the sediment-water interface, where Po-210 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 Pb-210 and Po-210 activities. The atmospheric input of Pb-210 is the major source of Pb-210 in the region with minor contribution from the Pb-210 rich Kuroshio Water. The K-d values of Po-210 varied by a factor of 50 while the corresponding values of Pb-210 varied only by a factor of 4. It appears that in waters where particle concentrations are high ( > 10 mg l(-1)), the K-d appears to be independent of particle concentration. (C) 1999 Elsevier Science Ltd. All rights reserved.