Shaked,Y.(2008): Iron redox dynamics in the surface waters of the Gulf of Aqaba, Red Sea. Geochimica et Cosmochimica Acta, 72, 1540-1554.

『紅海のアカバ湾表面水における鉄の酸化還元の動力学』


Abstract
 Redox transformations of iron in the surface waters of the Gulf of Aqaba, Red Sea, were studied on recurrent cruises from September 2006 to May 2007. Fe (II) concentrations and oxidation kinetics were measured in situ using luminol chemiluminescence. High Fe (II) concentrations of 200-400 pM were recorded in the autumn, followed by low concentrations of 20-130 pM in the winter-spring. A distinct diurnal pattern in Fe (II) concentrations was observed in the autumn with maximum values coinciding with maximum solar irradiance. In situ and in vitro Fe(II) oxidation rates showed temporal and spatial variability that was accounted for by changes in water temperature and pH. Dissolved oxygen was found to be the dominant oxidant in all but one cruise. In situ photoreduction rates (deduced from oxidation rates) were linearly correlated with solar irradiance during the autumn, suggesting that the reducible iron pool was not exhausted even at the strongest irradiances and that it was kept constant throughout the season. Phytoplankton had no discernible influence on Fe (II) production, consumption, or oxidation kinetics. Given the fast oxidation and photoreduction rates of up to 180 pM min-1, the turn-over rates of iron were estimated at 10-30 per day. Such a dynamic Fe redox cycle probably influences the chemical reactivity and bioavailability of iron and may enhance the solubility of the abundant aerosol dust.』

1. Introduction
2. Study area
3. Methods
 3.1. Water sampling and trace metal clean protocols
 3.2. Fe (II) determination
 3.3. Total and filtered Fe determination
 3.4.l Reagents
 3.5. Other methods
4. Results and discussion
 4.1. Seasonal and diurnal variations in surface Fe (II) concentrations
 4.2. The role of photoreduction in Fe (II) formation
 4.3. Fe (II) oxidation rates
 4.4. The role of oxidation in determining autumn steady state Fe (II) concentrations
 4.5. The lack of biological influence on the iron redox cycle in the Gulf of Aqaba
 4.6. Implications for iron recycling and bioavailability
5. Conclusions
Acknowledgments
References


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