Forms and distribution of Ce in a ferromanganese nodule

Abstract

We studied the distribution and speciation of Ce in a previously-characterized ferromanganese nodule from the South Pacific Gyre using X-ray microspectroscopy.We find Ce in three types of environmentdiffusely in all parts of the nodule except the Fe-rich, Mn-poor "matrix", fluorapatite grains with a negative Ce anomaly suggestive of an authigenic origin, and localized spots whose composition is consistent with a pseudobinary mixture of sorbed Ce 4+ and a mix of sorbed Ce 3+ and CeO 2. In contrast with some other elements such as Ti, there is no clear correlation of the Ce concentration in the diffuse areas with either that of Mn, Fe or any linear combination of the two.We argue that the CeO 2 came from oxidation of Ce 3+ in the water column, while the Ce in the Mn-rich regions may have been initially deposited as Ce 4+ and then partially reduced.

Quantification of anthropogenic and geogenic Ce in sewage sludge based on Ce oxidation state and rare earth element patterns

“…Cerium (Ce) is the most abundant element among the rare earth elements (REE) ( Henderson, 2013 ). In the environment, most REE are exclusively present in the trivalent state, but Ce may also occur in the tetravalent state ( Marcus et al., 2018 ; Takahashi et al., 2000 , Takahashi et al., 2002 , Takahashi et al., 2005 ). Cerium (III), resulting from weathering of rocks, can precipitate as Ce(IV) under oxidizing conditions, resulting in a distinct transport, fractionation and enrichment behaviour of Ce compared to other REE, which is referred to as the Ce-anomaly ( Henderson, 2013 ).…”

Synchrotron hard X-ray chemical imaging of trace element speciation in heterogeneous samples: development of criteria for uncertainty analysis

“…In this approach, XRF maps of the same area are recorded at multiple energies around an absorption edge to obtain spatially resolved speciation information at the micrometre scale. 12,13 In micro-focused X-ray experiments for chemical imaging (sometimes also called 'Chemicalstate maps', e.g. 13 ), a large fraction of the beam is focused onto a micrometre sized spot on the sample using slits and/or Kirkpatrick-Baez (KB) mirrors.…”

“…12,13 In micro-focused X-ray experiments for chemical imaging (sometimes also called 'Chemicalstate maps', e.g. 13 ), a large fraction of the beam is focused onto a micrometre sized spot on the sample using slits and/or Kirkpatrick-Baez (KB) mirrors. 5,10 High photon ux densities allow users to obtain chemical images of absorbers at low concentrations in complex matrices such as environmental samples within a few hours.…”

“…16 The new possibilities offered by the chemical imaging attracted increased attention in environmental sciences 12,13,[17][18][19][20][21] where elements of interest oen occur at low concentrations (e.g., Cu in digested sewage sludge 480-700 mg kg À1 ) and unevenly distributed in the sample matrix. 12 Because of the potential beam damage induced by high photon ux densities, only a limited number (typically ranging from 3-10) 13,17 of XRF maps around an X-ray absorption edge of a specic element of interest may be recorded to derive the chemical speciation of the absorber atom at the micrometre scale. 22 Nevertheless, caused by the short dwell times (few milliseconds) and low element concentrations, data acquired with even the most advanced detector systems 23 contains increased amounts of noise compared to spectra recorded on bulk samples using longer dwell times (up to seconds).…”

Spectroscopic Insights Into Ferromanganese Crust Formation and Diagenesis

“…Fe‐Mn crusts are passive recorders of changes in seawater chemistry that, in concert with calibrated age models, allow access to a wide range of paleo‐environmental records (Banakar & Hein, 2000; Christensen et al., 1997; Dausmann et al., 2015; Frank et al., 2006; Frank & O'Nions, 1998; Horner et al., 2015; Klemm et al., 2005; Marcus et al., 2018; Nielsen et al., 2009). Analytical targets for paleo‐records include proxies of Earth's crust and mantle processes, marine productivity, and other geochemical processes that produce variations in seawater chemistry.…”