Micro-goethite in percolated water from Fushui Reservoir in Hubei Province,China

The sediments in the percolated water from Fushui Reservoir have been studied. The cause for formation of a special-shaped micro-goethite in the modern depositional environment (reservoir) as well as the action and the significance of microorganism in the biomineralization of iron are discussed in this paper. Tests show that the main cations in the percolated water include Ca²⁺, Mg²⁺, K⁺ and Na⁺, with minor Fe²⁺ and Fe³⁺, whereas the main anion is HCO₃⁻. The sediments from the percolated water are mainly oxidized products of iron. The mineral phase and the form of the particles from percolated water in Fushui Reservoir are studied by such means as powder X-ray diffraction (XRD), differential thermal analysis (DTA), infrared spectroscopic analysis (IR), Mössbauer spectrum, transmission electron microscope (TEM) and scanning electron microscope (SEM). The main mineral phases include goethite, quartz, illite, montmorillonite and small amounts of calcite, only slightly crystallized. The Mössbauer spectral characteristics and the special form of goethite imply that goethite originated from ferric bacteria. The following results can be reached: the sediments in Fushui Reservoir are mainly composed of amorphous ferric hydroxide colloid and weakly crystalline goethite; the genesis of goethite is related with ferric bacteria.