Nanogoethite is the dominant reactive oxyhydroxide phase in lake and marine sediments

Abstract

Iron oxides affect many elemental cycles in aquatic sediments via numerous redox reactions and their large sorption capacities for phosphate and trace elements. The reactive ferric oxides and oxyhydroxides are usually quantified by operationally defined selective chemical extractions that are not mineral specific. We have used cryogenic 57 Fe Mössbauer spectroscopy to show that the reactive iron oxyhydroxide phase in a large variety of lacustrine and marine environments is nanophase goethite (␣-FeOOH), rather than the assumed surface-complex-stabilized, two-line ferrihydrite and accompanying mixture of clay and oxyhydroxide Fe-bearing phases. This result implies that the kinetic and stability parameters of the type of nanogoethite that we observe to be present in sediments should be first determined and then used in models of early diagenesis. The identity and characteristics of the reactive phase will also set constraints on the mechanisms of its authigenesis.

Products of abiotic U(VI) reduction by biogenic magnetite and vivianite

“…Molecular U(IV) produced by biogenic vivianite and phosphate treated biogenic magnetite Corr et al, 2004) and/or phases with low crystallinity. Similar results have been reported by Van der Zee et al (2003) and Thompson et al (2006) and for soil and sediment samples, and have been attributed to nano-goethite phases. This could also include some transition state between HFO and magnetite.…”

“…T, again consistent with nanoparticulate phases. The magnetite phase could be confirmed at 77 K. The iron(II) phase in the 77 K spectrum could be interpreted as siderite, consistent with the analysis at 245 K. The spectra at 77 K spectra also showed broader peaks compared to those of highly crystalline samples, typical for small particle sizes that have previously been referred to as 'collapsed sextet' (Van der Zee et al, 2003;Thompson et al, 2006). At 5 K, the H field of the nanoparticulate Fe(III) phase increases to values in the range of magnetite (36-52 T) and cannot be resolved due to overlapping features.…”

“…Similar results have been reported by Goya et al (2003) and Corr et al (2004) for synthetic, nanoparticulate (<10 nm) magnetite. However, the small H is not unique to nano-magnetite and could also correspond to other small particle sizes and/or phases with low crystallinity, consistent with nano-goethite phases as reported by Van der Zee et al (2003) and Thompson et al (2006) and. Siderite was detected as the third mineral phase in the sample (ca.…”

Iron oxide minerals in dust-source sediments from the Bodélé Depression, Chad: Implications for radiative properties and Fe bioavailability of dust plumes from the Sahara

“…The fact that the sextet associated with goethite in CH02 and CH39 was found at 4.2 K but not at 300 K indicated complete magnetic order for goethite only at very low temperatures and superparamagnetism at 300 K. This type of behavior occurs in nanogoethite when particle sizes are less than ~20 nm (Vandenberghe et al, 1990;van der Zee et al, 2003). Unlike the RT spectra for CH02, the doublet subspectral area was diminished to account for 39% of the total Fe in the sample, whereas hematite and goethite accounted for 24% and 37%, respectively.…”

Environmental Risks of Nanotechnology: National Nanotechnology Initiative Funding, 2000−2004

“…Perceived environmental risks can prove to be nanotechnology's Achilles' heel. Whereas natural nanoparticles are a key component in our ecosystem, as "nanofossils" (8), products of chemical weathering (9), products of microbial and microbial-related processes (10)(11)(12)(13), and components of aquatic sediments (14,15), the behavior of manufactured nanoparticles and new nanoproducts in the environment is largely unknown. Incidental nanoparticles, i.e., nanoparticles produced as byproducts of processes such as combustion and pollution, already are inadvertently released in the environment, where they have been linked with negative health effects and changes in cloud properties (16).…”