Preservation of particulate non-lithogenic uranium in marine sediments |
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| Authors: | Yan Zheng Robert F Anderson Alexander van GeenMartin Q Fleisher |
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| Institution: | 1 Lamont-Doherty Earth Observatory of Columbia University, New York, NY 10964, USA
2 Department of Earth and Environmental Sciences, Columbia University, New York, NY 10962, USA |
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| Abstract: | Particulate non-lithogenic uranium (PNU), excess U above detrital background levels found in marine particulate matter, is formed in surface waters throughout the ocean. Previous studies have shown that PNU is regenerated completely prior to burial of particles in sediments within well-oxygenated open-ocean regions. However, the fate of PNU has never been examined in ocean margin regions or in anoxic basins. Here we evaluate the preservation of PNU in ocean margin sediments and within semi-enclosed basins using samples from sediment traps deployed at multiple depths and surface sediments. Organic carbon fluxes at the sediment trap locations ranged from 0.1 to 4.3 g/cm2 kyr, while the dissolved oxygen concentration in the water column ranged from <3 μM to ∼ 270 μM. Preservation of PNU increases with decreasing dissolved oxygen concentration, approaching 100% preservation at oxygen concentration < 25 μM. PNU contributes as much as 40 to 70% of the total authigenic U in sediments in the Santa Barbara Basin and seasonally anoxic Saanich Inlet, and some 10% to 50% of the total authigenic U in sediments off the central California Margin. |
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