Short communicationChemical speciation of chromium in sea water: Part 2. Effects of Manganese Oxides and Reducible Organic Materials on the Redox Processes of Chromium
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Cited by (103)
Marine microbial Mn(II) oxidation mediates Cr(III) oxidation and isotope fractionation
2021, Geochimica et Cosmochimica ActaCitation Excerpt :The rates of Cr(III) oxidation were more rapid for the Chesapeake Bay water samples than for ASW, even though the Mn oxidation rates were similar (Table 2). Cr(III) complexation by natural organic ligands would result in slower precipitation of Cr(III) (oxyhydr)oxide and allow more time for soluble Cr(III) to react with MnOx (Nakayama et al., 1981; Pettine et al., 2008), whereas the reaction of precipitated Cr(III) (oxyhydr)oxide and insoluble MnOx would be very slow. This result is consistent with the proposition that natural organic ligands likely stabilize Cr(III) in seawater (Elderfield, 1970), because previous measurements of high dissolved Cr(III) were found in seawater with low MnOx concentrations (Elderfield, 1970).
Biogeochemical cycle of chromium isotopes at the modern Earth's surface and its applications as a paleo-environment proxy
2020, Chemical GeologyCitation Excerpt :In this step, the sample dissolved in 6 M HCl is passed through a column charged with Dowex AG 1 × 8 anion resin (100–200 mesh) to remove Fe, since Fe has high affinity for the anion resin in 6 M HCl (Frei and Rosing, 2005; Schoenberg and von Blanckenburg, 2005). This step is extremely crucial because (1) Fe is a common element in most natural rocks, (2) a Fe (II) co-precipitation technique (Cranston and Murray, 1978; Nakayama et al., 1981a, 1981b, 1981c) is occasionally utilized to reduce Cr (VI) in sample solutions and simultaneously scavenge Cr (III) for purification procedures (Scheiderich et al., 2015; Holmden et al., 2016), (3) a small proportion of Fe (~0.0008%) could also be eluted from the cation exchange column in 0.5 M HCl together with Cr (Bonnand et al., 2011); and (4) 54Fe will cause isotopic interference on 54Cr during analysis on a mass spectrometer. Earlier stable Cr isotope values were typically measured by thermal ionization mass spectrometer (TIMS; e.g. Ball and Bassett, 2000; Ellis et al., 2002; Fujii et al., 2006; Frei et al., 2009).
Chromium isotopes in marine hydrothermal sediments
2019, Chemical GeologyChromium isotope cycling in the water column and sediments of the Peruvian continental margin
2019, Geochimica et Cosmochimica ActaChromium isotope systematics in the Connecticut River
2017, Chemical GeologyCitation Excerpt :Normalizing Cr to Al concentrations changed the direction of the Cr concentration trend between our two sampling sessions (April and October (Fig. 4B–D)), confirming that higher Cr concentrations found in April samples are indeed because of increased suspended silicate component represented by high Al concentration. Fe and Mn are closely linked with Cr cycling because of adsorption of Cr to iron oxides and oxidation of Cr(III) by Mn oxides (Ellis et al., 2002; Ellis et al., 2004; Wang et al., 2010; Nakayama et al., 1981). Higher Fe (and potentially higher Mn) in April samples suggest higher oxide load.