Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 7 2 2010 10.5194/bg-7-569-2010 http://www.biogeosciences.net/7/569/2010/ http://www.biogeosciences.net/7/569/2010/bg-7-569-2010.html http://www.biogeosciences.net/7/569/2010/bg-7-569-2010.pdf 569 583 2010-02-11 Changes in mobility and solubility of the redox sensitive metals Fe, Mn and Co at the seawater-sediment interface following CO₂ seepage M. V. Ardelan murato@nt.ntnu.no E. Steinnes Norwegian University of Science and Technology, Department of Chemistry, 7491 Trondheim, Norway The impact of CO₂ seepage on the solubility and distribution of the redox-sensitive metals iron, manganese, and cobalt in seawater and sediment pore water has been studied in experiments in laboratory-scale 0.6 m³ chambers. The mobility and solubility of Fe, Mn and Co were investigated in seawater, membrane filtered seawater, and DGT samplers deployed in water and sediment during a 26 day CO₂ seepage study. <br><br> During the first phase of the experiment of CO₂ seepage (0–16 days), total acid-leachable (pH 1) and "dissolved" (&lt;0.2 &mu;m) concentrations of Fe, Mn and Co (DFe, DMn and DCo) in the seawater increased significantly; the ratios of concentrations of DFe, DMn and DCo in the CO₂ chamber to the corresponding values in the control chamber (<i>R</i>_DFe, <i>R</i>_DMn and <i>R</i>_DCo) were as high as 6, 65 and 58, respectively. The second phase of experiment consisted of an additional 10 days of incubation, where the concentrations of all the metals studied still increased but at reduced rates for DMn and DCo. The highest values of <i>R</i>_DFe, <i>R</i>_DMn and <i>R</i>_DCo were about 3 for all metals during this part of the experiment. <br><br> DGT (diffusive gradients in thin film) labile fractions denoted Fe_DGT, Mn_DGT and Co_DGT were, respectively 50, 25 and 22 times higher in the CO₂ seepage chamber than in the control chamber in the first phase of the experiment. During the second phase, all DGT labile metal concentrations still increased considerably, most notably for Fe. The ratio of Fe_DGT in the CO₂ chamber to that in the control (<i>R</i>_DGT-Fe) was still high, about 5, in the second phase of the experiment, whereas the increase in Mn_DGT and Co_DGT slowed down. 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