@article{fdi:010062041,
  title = {{EXAFS} analysis of iron cycling in mangrove sediments downstream a lateritized ultramafic watershed ({V}avouto {B}ay, {N}ew {C}aledonia)},
  author = {{N}oel, {V}. and {M}archand, {C}yril and {J}uillot, {F}arid and {O}na-{N}guema, {G}. and {V}iollier, {E}. and {M}arakovic, {G}. and {O}livi, {L}. and {D}elbes, {L}. and {G}elebart, {F}. and {M}orin, {G}.},
  editor = {},
  language = {{ENG}},
  abstract = {{M}angrove forests are the dominant intertidal ecosystem of tropical coastlines. {I}n {N}ew {C}aledonia, mangroves act as a buffer zone between massive {F}e lateritic deposits and a lagoon partly registered by {UNESCO} as a {W}orld {H}eritage site. {T}he {N}ew {C}aledonian mangroves are characterized by a botanical gradient composed of three main vegetal stands (i.e., {R}hizophora spp., {A}vicennia marina and salt flat), which relies on the duration of tidal immersion that imposes gradients of pore-water salinity, oxygenation, and organic content in the sediment. {I}n the present study, we have determined the distribution and speciation of {F}e in mangrove sediments along this botanical gradient by using {X}-ray absorption spectroscopy ({XAS}) at the {F}e {K}-edge. {B}oth {XANES} and {EXAFS} results show that iron speciation strongly follows the redox boundaries marking the intertidal and depth zonations. {F}e-bearing minerals eroded from lateritic outcrops, mainly goethite (alpha-{F}e{OOH}) and phyllosilicates (serpentine and talc), are the major {F}e hosts in the upward horizons. {T}hese mineral species progressively disappear with increasing depth where pyrite ({F}e{S}2) forms, in the hydromorphic {R}hizophora and {A}vicennia zones. {S}ulfate reduction is not observed in the drier salt flat zone. {I}n addition to these reduction processes, intense re-oxidation of aqueous {F}e({II}) and pyrite leads to the formation of poorly ordered ferrihydrite, lepidocrocite (gamma-{F}e{OOH}) and likely goethite in the upper sediments beneath {A}vicennia and {R}hizophora stands. {T}he relative proportion of the newly formed poorly ordered ferrihydrite and lepidocrocite is found to be higher in the {R}hizophora mangrove stand, which is the closest to the shore. {T}idal fluctuations may thus be a major cause for continuous {F}e reduction-oxidation cycles in the vegetated mangrove stands, which could significantly affect the iron mass balance in mangrove systems.},
  keywords = {{NOUVELLE} {CALEDONIE}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {136},
  numero = {},
  pages = {211--228},
  ISSN = {0016-7037},
  year = {2014},
  DOI = {10.1016/j.gca.2014.03.019},
  URL = {https://www.documentation.ird.fr/hor/fdi:010062041},
}