CHARACTERISTICS OF LACUSTRINE DIAGENETIC IRON OXYHYDROXIDES

Citation
D. Fortin et al., CHARACTERISTICS OF LACUSTRINE DIAGENETIC IRON OXYHYDROXIDES, Geochimica et cosmochimica acta, 57(18), 1993, pp. 4391-4404
Citations number
84
Categorie Soggetti
Geosciences, Interdisciplinary
ISSN journal
00167037
Volume
57
Issue
18
Year of publication
1993
Pages
4391 - 4404
Database
ISI
SICI code
0016-7037(1993)57:18<4391:COLDIO>2.0.ZU;2-7
Abstract
Diagenetic iron oxyhydroxides formed by the oxidation of iron(II) were allowed to deposit onto inert collectors vertically inserted into the sediments of eight lakes chosen to represent a range of lake pH value s. Particles comprising the iron-rich deposits have been characterized at macroscopic (composition; X-ray diffraction) and microscopic (tran smission electron microscopy; energy dispersive spectroscopy; electron diffraction) levels. The only crystalline forms of Fe(III) oxyhydroxi des identified were poorly ordered ferrihydrite and lepidocrocite. Mor phologies of lepidocrocite (lath-type) and presumably of ferrihydrite (spherical and ellipsoidal particles) are similar to those reported pr eviously as being formed in the water column of seasonally anoxic lake s. Deposition of iron oxyhydroxides in the lake sediments also appears to occur on bacterial cells and on their exopolymers. Silicon, sulfat e. chloride, phosphate, manganese, calcium, and aluminum represented m inor components of the diagenetic Fe(III) oxyhydroxides, whereas organ ic carbon was a more abundant component. Calculations with a diffuse l ayer version of the surface complexation model using the ambient disso lved concentrations, and comparison of the predicted and measured comp ositions of the iron-rich particles suggest that sulfate, phosphate, a nd probably calcium were sorbed on the iron oxyhydroxides, whereas sil icon was probably more firmly bound at the surface.