Changes in mobility and solubility of the redox sensitive metals Fe, Mn and Co at the seawater-sediment interface following CO2 seepage
Other literature type
Ardelan, M. V.
(issn: 1726-4189, eissn: 1726-4189)
The impact of CO<sub>2</sub> 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 m<sup>3</sup>
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 CO<sub>2</sub> seepage study.
During the first phase of the experiment of CO<sub>2</sub> seepage (0–16 days), total
acid-leachable (pH 1) and "dissolved" (<0.2 μm) 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 CO<sub>2</sub> chamber to the
corresponding values in the control chamber (<i>R</i><sub>DFe</sub>, <i>R</i><sub>DMn</sub> and <i>R</i><sub>DCo</sub>) 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><sub>DFe</sub>, <i>R</i><sub>DMn</sub> and <i>R</i><sub>DCo</sub> were about 3 for all metals during
this part of the experiment.
DGT (diffusive gradients in thin film) labile fractions denoted Fe<sub>DGT</sub>, Mn<sub>DGT</sub>
and Co<sub>DGT</sub> were, respectively 50, 25 and 22 times higher in the CO<sub>2</sub> 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<sub>DGT</sub> in the CO<sub>2</sub> chamber to
that in the control (<i>R</i><sub>DGT</sub>-Fe) was still high, about 5, in the second phase
of the experiment, whereas the increase in Mn<sub>DGT</sub> and Co<sub>DGT</sub> slowed down. Our
results indicate that acidification following CO<sub>2</sub> seepage enhances the
mobility and solubility of Fe Mn and Co in sediment and overlying water with
contribution of changing in redox conditions and seepage related