-Mixtures of synthetic Al-substituted goethite (a-Feo.814AloA86OOH) and hematite (a-Fel.658Alo.34203) (75, 50, 25, 3~ hematite by weight) were studied by M6ssbauer spectroscopy to evaluate the use of that technique for quantitative analysis. M6ssbauer spectra for these mixtures, obtained in the temperature range 12-130 K, were better fitted by a distribution of magnetic fields than by two magne...

The magnitude and temperature-sensitivity of oxygen isotope fractionation in ferric oxide-water systems remain uncertain. In this study, three different synthetic methods are used to investigate the temperature dependence of the fractionation between water and hematite, akaganeite, and goethite at near-surface temperatures. Our results reveal two similarities among these ferric oxide-water syst...

A long-standing problem in aquatic geochemistry has been the incorporation of natural organic matter (NOM) into speciation models. The general effect of NOM on metal ion sorption by particles has been understood for some time, and significant progress has been made in elucidating some of the details of the role of NOM through the use of surrogate organic acids such as citric acid. However, a ga...

and the chemical weathering of primary minerals to secondary minerals (i.e., soil) on the surface. Physical properWe present a comprehensive study of the redox state of the lower atmosphere and surface of Venus. This study constrains ties such as the spectral reflectance, dielectric constant, the CO concentration and oxygen fugacity at the surface of electrical conductivity, magnetic susceptibi...

The visible light photochemical reactivity of a 50 nm thick α-Fe(2)O(3)(0001) (hematite) film on a SrTiO(3)(111) substrate is compared to the reactivities of bulk hematite and the same film supported by α-Al(2)O(3)(0001). The hematite film supported by SrTiO(3)(111) is far more reactive then the other two cases.

Our understanding of subsurface microbiology is hindered by the inaccessibility of this environment, particularly when the hydrogeologic medium is contaminated with toxic substances. In this study, surrogate geological media contained in a porous receptacle were incubated in a well within the saturated zone of a pristine region of an aquifer to capture populations from the extant communities. A...

The thermal decomposition of synthetic a-FeOOH in air has becn studied by X~ray powder diffraction (XRD), IR spectroscopy. transmission electron microscopy, and nitrogen adsorption. Three stages may be differentiated during the course ofthe reaction: (i) 200-250°C; slit-shaped micropores of nearly equal width, about 1.4 nm, are formed along the elongated direction of the lath-shaped acicular mí...