Fractionation of Po-210 and Pb-210 in coastal waters of the NW Mediterranean continental margin

摘要

The natural radionuclides Po-210 and Pb-210 were analyzed in samples of surface sea water, rain and dry fallout, and river water collected along the NW Mediterranean coast as well as from a sediment trap moored 3 km south of Monaco. Using a box model calculation, the balances and fluxes of Po-210 and Pb-210 in the coastal waters of the NW Mediterranean were estimated. Atmospheric inputs of Po-210 and Pb-210 to Monaco coastal waters varied seasonally and were maximal in winter when storms and strong winds transfered continental Rn-222-rich air and aerosols of top soil particles to coastal surface waters, which in turn enhanced the Po-210 and Pb-210 input to these waters. The balance estimation using all fluxes in surface waters indicated that Pb-210 was removed from surface water with residence times of 2.1, 0.40, and 2.7 years for dissolved, particulate, and total Pb-210, respectively. In the bottom water and surface sediments, additional excess Pb-210 sinking and sedimentation fluxes were observed, suggesting a substantial down slope transport of sediment particles. Similarly, the residence times of Po-210 in surface water were 1.2, 0.38, and 0.77 years for dissolved, particulate, and total Po-210, respectively; however, a deficit in the Po-210 sinking flux in the bottom layer, compared to removal flux from the surface waters, suggested rapid degradation of Po-210-bearing biogenic particles during sinking following periods of low biological productivity. (C) 2003 Elsevier Science Ltd. All rights reserved. [References: 73]