The behavior of Al,Mn, Ba,Sr, REE and Th isotopes during in vitro degradation of large marine particles |
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| Affiliation: | 1. Physics and Astronomy, Curtin University, Perth, Western Australia, Australia;2. Antarctic Climate and Ecosystems CRC, University of Tasmania, Hobart, Tasmania, Australia;3. Institute for Marine and Antarctic Studies, University of Tasmania, Hobart, Australia;4. CSIRO Oceans and Atmosphere Flagship, Aspendale, Victoria, Australia;5. Central Science Laboratory, University of Tasmania, Hobart, Tasmania, Australia;6. Environmental Research Institute of the Supervising Scientist, Department of the Environment, Darwin, Northern Territory, Australia |
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| Abstract: | The extent and the time constant of dissolution of a set of inorganic tracers during the decomposition of large marine particles are estimated through in vitro experiments. Large marine particles were collected with in situ pumps at 30 m and 200 m in the Ligurian Sea at the end of summer. They were subsequently incubated under laboratory conditions with their own bacterial assemblage for 20 days in batches under oxic conditions in the dark. Some samples were initially sterilized in order to observe possible differences between biotic and abiotic samples. Particulate (>0.2 μm) and dissolved (<0.2 μm) concentrations of Al, Sr, Ba, Mn, Rare Earth Elements (REE) and Th isotopes were determined over time. We obtain percentages of dissolution in agreement with the general knowledge about the solubility of these tracers: Th≈Al2 respiration. Speciation calculations suggest that this pH shift leads to a decrease of the complexation of dissolved REE by carbonate ions. Th isotope data are consistent with an irreversible dissolution of Th and they do not support a rapid particle–solution chemical equilibrium. |
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