Interaction of sea ice sediments and surface sea water in the Arctic Ocean:: Evidence from excess 210Pb -: art. no. L12601

We measured the activities of Pb-210, Ra-226, U-238 and Cs-137 in a suite of ice-rafted sediments (IRS) from the Arctic Ocean in an attempt to assess the interaction of sea ice sediments and surface water. The concentrations of these nuclides were compared to those of the benthic sediments in the coastal and shelf regions of the Arctic Ocean, which are believed to be the major source region for the IRS. The concentration factors (CF = activity of a nuclide in IRS/average activity in benthic sediments) are similar to 1 and 4-92 for Cs-137 and Pb-210, respectively. The CF values for Cs-137 are comparable to the values that can be obtained from the previously published data while we report the first set of high CF values of Pb-210. A major portion of Pb-210 in some IRS samples is likely derived from surface waters and thus, the concentrations of Pb-210 combined with another particle-reactive radionuclide (such as Be-7, Th-234) in IRS might provide information on the residence time and transit time of sea ice-laden sediments.