@article{fdi:010082535,
  title = {{S}ynchrotron-based speciation of chromium in an oxisol from {N}ew {C}aledonia : importance of secondary {F}e-oxyhydroxides},
  author = {{F}andeur, {D}. and {J}uillot, {F}. and {M}orin, {G}. and {O}livi, {L}. and {C}ognigni, {A}. and {A}mbrosi, {J}.{P}. and {G}uyot, {F}. and {F}ritsch, {E}mmanuel},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n {N}ew {C}aledonia, the weathering of ultamafic rocks under a tropical climate has led to the residual accumulation of trace elements in lateritic soils widely dominated by {F}e-oxyhydroxides. {T}he speciation of trace elements, {S}uch as {C}r. {N}i, and {C}o, in these {O}xisols remains a major subject of interest regarding mining and environmental issues. {W}e have assessed the speciation of chromium in the upper part of all {O}xisol, by combining bulk and spatially resolved chemical analyses ({EPMA} and {SEM}-{EDS}) with synchrotron-based spectroscopic data ({EXAFS} and {XANES}). {EPMA} indicates that the main hosts for chromium in the bedrock sample are the silicates forsterite, enstatite, and lizardite. {H}osting of chromium in these easily weatherable mineral species {C}ould lead to a significant loss of this element upon weathering. {H}owever. total analyses of major elements indicate only a slight depiction of {C}r, together with an immobility of {F}e and {A}l and drastic losses of {S}i and {M}g, after the weathering of the bedrock. {S}uch a low mobility of chromium is likely related to its significant incorporation in goethite and hematite formed after the weathering of {F}e2+-bearing primary silicates. {T}his efficiency of secondary {F}e-oxyhydrox ides at immobilizing chromium is demonstrated by quantitative analysis of {EXAFS} data that indicates that these mineral species host between 67 and 75 wt% of total {C}r (compared to the 18 to 22 wt% of total {C}r hosted by chromite). {I}n addition, {SEM} observation and {SEM}-{EDS} analyses performed on the {O}xisol samples also show some evidence for chemical weathering of chromite. {C}hromite could then represent a past and/or present source of chromium upon extended tropical weathering of the studied {O}xisol, rather than a stable host. {T}hese results emphasize the importance of secondary {F}e-oxyhydroxides. compared to {C}r-spinels, on chromium hosting in {O}xisols developed upon tropical weathering of ultramafic rocks. {A}lthough the trapping mechanism of chromium mainly corresponds to incorporation within the structural network of goethite and hematite, sorption reactions at the {S}urface of these mineral {S}pecies {C}ould also he involved ill {S}uch a process. {I}n addition, considering their potential oxidative reactivity that call generate {C}r6+ or enhance the chemical weathering of chromite, the occurrence of {M}n oxides could significantly modify the behavior of chromium upon weathering. {T}hese considerations indicate that further studies are needed to assess the actual potential of chromium release front {O}xisols developed upon weathering of ultramafic rocks under a tropical climate.},
  keywords = {{C}hromium ; speciation ; {O}xisol ; {N}ew {C}aledonia},
  booktitle = {},
  journal = {{A}merican {M}ineralogist},
  volume = {94},
  numero = {5-6},
  pages = {710--719},
  ISSN = {0003-004{X}},
  year = {2009},
  DOI = {10.2138/am.2009.3073},
  URL = {https://www.documentation.ird.fr/hor/fdi:010082535},
}