An experiment was conducted to examine the role of Mn in P fixation through comparing with Al and Fe. Hydroxides and oxides of Al, Fe and Mn were prepared in lab under opened and closed conditions to react with phosph...An experiment was conducted to examine the role of Mn in P fixation through comparing with Al and Fe. Hydroxides and oxides of Al, Fe and Mn were prepared in lab under opened and closed conditions to react with phosphate. The newly formed Mn hydroxide showed the strongest P-fixing abilityl even several times higher than Fe hydroxide, but became the lowest rapidly due to ageing when exposed to air. Mn oxide showed the lowest p-fixing ability. Therefore, a sound consideration on P fixation should be based on both quantities and p-fixing abilities of the compounds of Fe, Al and Mn. The importance of Mn on P availability should receive more attention especially under oxidation-reduction dynamic conditions.展开更多
Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise （EPR） near 13°N were analyzed using the scanning electron microscope （SEM） with an energy dispersive spectrometer （EDS）. These encrustations are ...Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise （EPR） near 13°N were analyzed using the scanning electron microscope （SEM） with an energy dispersive spectrometer （EDS）. These encrustations are mainly composed of amorphous Fe- Si-Mn-oxyhydroxides forming laminated, spherical, porous aggregates with some biodetritus, anhydrite, nontronite, and feldspar particles. Anhydrite particles and nontronite crystals in the Fe-Si-Mn-oxyhydroxide encrustations imply that the Fe-Si-Mn-oxyhy- droxide may have formed under relatively low- to high-temperature hydrothermal conditions. The Fe-Si-Mn-oxyhydroxide encrusta- tions on pillow basalts are 1-2mm thick. The growth rate of ferromanganese crusts in the survey area suggests that these encrusta- tions are an unlikely result of hydrogenic deposition alone having a hydrothermal and （Fe/Mn ratio up to 7.7 and Fe/（Fe＋Mn＋A1） ratio exceeding 0.78） hydrogenic origin （0.22 Fe/Mn ratio close to the mean value of 0.7 for open-ocean seamount crusts）. The varying Fe/Mn ratios indicate that the Fe-Si-Mn-oxyhydroxide encrustations have formed through several stages of seafloor hydrother- malism. It is suggested that, at the initial formation stage, dense Fe-Si-oxyhydroxides with low Mn content deposit from a relatively reducing hydrothermal fluid, and then the loose Fe-Si-Mn-oxyhydroxides deposit on the Fe-Si-oxyhydroxides. As the oxidation degree of hydrothermal fluid increases and Si-oxide is inhibited, Mn-oxide will precipitate with Fe-oxyhydroxides.展开更多
A series of selective extraction experiments were conducted on marine hydrogenic ferromanganese crusts from the seamount near the Line Island to investigate the distribution of rare earth elements （REEs） and the mec...A series of selective extraction experiments were conducted on marine hydrogenic ferromanganese crusts from the seamount near the Line Island to investigate the distribution of rare earth elements （REEs） and the mechanisms of combination between REEs and the hydrogenic ferromanganese crusts. The enrichment of REEs in hydrogenic ferromanganese crusts is attributed mainly to the mineral or oxide/hydroxide of the crust rather than the growth environment. The REEs are present mainly in amorphous ferric oxide/hydroxide rather than in 6-MnO2. Amorphous ferric oxide/hydroxide preferentially combines free REE3＋, while 6-MnO2 combines the REE-carbonate complexes in modern seawater. The REEs in seawater are combined more strongly with amorphous ferric oxide/hydroxides than with 6-MnO2. The positive Ce anomaly in hydrogenic ferromanganese crusts results from the oxidation of soluble Ce3＋ to insoluble Ce4＋ by the actively soluble oxygen of the bottom current rather than by the oxidation of δ-MnO2.展开更多
文摘An experiment was conducted to examine the role of Mn in P fixation through comparing with Al and Fe. Hydroxides and oxides of Al, Fe and Mn were prepared in lab under opened and closed conditions to react with phosphate. The newly formed Mn hydroxide showed the strongest P-fixing abilityl even several times higher than Fe hydroxide, but became the lowest rapidly due to ageing when exposed to air. Mn oxide showed the lowest p-fixing ability. Therefore, a sound consideration on P fixation should be based on both quantities and p-fixing abilities of the compounds of Fe, Al and Mn. The importance of Mn on P availability should receive more attention especially under oxidation-reduction dynamic conditions.
基金supported by the National Key Basic Research Program of China (2013CB429700)the Shandong Province Natural Science Foundation for Distinguished Young Scholars (JQ200913)+1 种基金the National Natural Science Foundation of China (40830849)the National Special Fund for the Eleventh Five-Year Plan of COMRA (DY125-12-R-02 and DY125-11-R-05)
文摘Fe-Si-Mn-oxyhydroxide encrustations at the East Pacific Rise （EPR） near 13°N were analyzed using the scanning electron microscope （SEM） with an energy dispersive spectrometer （EDS）. These encrustations are mainly composed of amorphous Fe- Si-Mn-oxyhydroxides forming laminated, spherical, porous aggregates with some biodetritus, anhydrite, nontronite, and feldspar particles. Anhydrite particles and nontronite crystals in the Fe-Si-Mn-oxyhydroxide encrustations imply that the Fe-Si-Mn-oxyhy- droxide may have formed under relatively low- to high-temperature hydrothermal conditions. The Fe-Si-Mn-oxyhydroxide encrusta- tions on pillow basalts are 1-2mm thick. The growth rate of ferromanganese crusts in the survey area suggests that these encrusta- tions are an unlikely result of hydrogenic deposition alone having a hydrothermal and （Fe/Mn ratio up to 7.7 and Fe/（Fe＋Mn＋A1） ratio exceeding 0.78） hydrogenic origin （0.22 Fe/Mn ratio close to the mean value of 0.7 for open-ocean seamount crusts）. The varying Fe/Mn ratios indicate that the Fe-Si-Mn-oxyhydroxide encrustations have formed through several stages of seafloor hydrother- malism. It is suggested that, at the initial formation stage, dense Fe-Si-oxyhydroxides with low Mn content deposit from a relatively reducing hydrothermal fluid, and then the loose Fe-Si-Mn-oxyhydroxides deposit on the Fe-Si-oxyhydroxides. As the oxidation degree of hydrothermal fluid increases and Si-oxide is inhibited, Mn-oxide will precipitate with Fe-oxyhydroxides.
基金supported by National Natural Science Foundation of China (Grant No. 40076015)China Ocean Mineral Resources R & D Association
文摘A series of selective extraction experiments were conducted on marine hydrogenic ferromanganese crusts from the seamount near the Line Island to investigate the distribution of rare earth elements （REEs） and the mechanisms of combination between REEs and the hydrogenic ferromanganese crusts. The enrichment of REEs in hydrogenic ferromanganese crusts is attributed mainly to the mineral or oxide/hydroxide of the crust rather than the growth environment. The REEs are present mainly in amorphous ferric oxide/hydroxide rather than in 6-MnO2. Amorphous ferric oxide/hydroxide preferentially combines free REE3＋, while 6-MnO2 combines the REE-carbonate complexes in modern seawater. The REEs in seawater are combined more strongly with amorphous ferric oxide/hydroxides than with 6-MnO2. The positive Ce anomaly in hydrogenic ferromanganese crusts results from the oxidation of soluble Ce3＋ to insoluble Ce4＋ by the actively soluble oxygen of the bottom current rather than by the oxidation of δ-MnO2.
