HR: 0800h
AN: C11B-0449    [Abstracts]
TI: Constraining the Time-Scale of Interaction of Sea Ice Sediments and Surface Sea Water in the Arctic Ocean Using Short-Lived Radionuclide Tracers
AU: * Baskaran, M
EM: Baskaran@wayne.edu
AU: Andersson, P S
EM: Per.Andersson@nrm.se
AF: Swedish Museum of Natural History, Laboratory for Isotope Geology, Stockholm, 104 05, Sweden
AU: Jweda, J
EM: jweda@comcast.net
AF: Wayne State University, Department of Geology, Detroit, MI 48202, United States
AU: Dahlqvist, R
EM: Ralf.Dahlqvist@earth.ox.ac.uk
AF: Swedish Museum of Natural History, Laboratory for Isotope Geology, Stockholm, 104 05, Sweden
AU: Ketterer, M E
EM: Michael.Ketterer@NAU.EDU
AF: Northern Arizona University, Department of Chemistry and Biochemistry, Flagstaff, AZ 86011, United States
AB: We measured the activities of short-lived radionuclides (Th-234, Be-7, Po-210, Pb-210, Cs-137, Th-234, Ra-226 and Ra-228) and concentrations of several elements (Be, Pb, Fe, Al, Co, Ni, Cu and Zn) on a suite of ice-rafted sediments (IRS) collected during BERINGIA-2005 in the Western Arctic Ocean. A suite of water samples were also collected and analyzed for particulate and dissolved Be-7, Po-210, Pb-210, Th-234, Ra-226 and Ra-228. The activities of Be-7 and Pb-210 in the IRS are 1-2 orders of magnitude higher than those reported in the source sediments. Presence of excess Th-234 in the IRS indicates that the removal of Th-234 from surface seawater took place on time scales comparable to the mean-life of Th-234. While the Po-210/Pb-210 activity ratios in the source sediments (1.0) and the atmospheric depositional input (~0.1) are known, varying ratios of 0.78 to 1.0 were found in the IRS. This ratio can be utilized to obtain the residence time of the IRS in sea ice. The activity of Ra-226 and Ra-228 in all the IRS is nearly constant (within a factor of 1.6) and are comparable to the benthic sediments in the source region. The activities of atmospherically-delivered radionuclides, Be-7 and Pb-210, in IRS varied by factors of ~4.5 and 9, respectively, and this variation is attributed to differences in the extent of interaction of surface water with IRS and differences in the mean-lives of these nuclides. While significant enrichment of Be-7 and Pb-210 has been found, there is no enrichment of stable Pb or Be. The Al-normalized enrichment factor for elements measured (Co, Ni, Cu, Zn, Pb and Be) indicate that there is no significant enrichment of these elements, with Al-normalized enrichment factors less than 1.3.
DE: 0700 CRYOSPHERE (4540)
DE: 0750 Sea ice (4540)
DE: 4558 Sediment transport (1862)
DE: 4860 Radioactivity and radioisotopes
DE: 4875 Trace elements (0489)
SC: Cryosphere [C]
MN: 2007 Fall Meeting