@article{fdi:010067770,
  title = {{O}rganic control of dioctahedral and trioctahedral clay formation in an alkaline soil system in the {P}antanal wetland of {N}hecolandia, {B}razil},
  author = {{B}arbi{\'e}ro, {L}aurent and {B}erger, {G}. and {F}ilho, {A}. {T}. {R}. and {M}eunier, {J}. {F}. and {M}artins-{S}ilva, {E}. {R}. and {F}urian, {S}.},
  editor = {},
  language = {{ENG}},
  abstract = {{R}ecent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the {N}hecolandia region, {P}antanal wetland. {T}he presence of trioctahedral {M}g-smectites (stevensite and saponite types), which requires low {A}l and {F}e contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral {F}e-mica (glauconite, and {F}e-illite), which instead requires solutions relatively enriched in {A}l and {F}e. {T}his study aims to understand the conditions of co-existence of both, {M}g-smectite and {F}e-mica a common clay association in former or modern alkaline soil systems and sediments. {T}he study was carried out along an alkaline soil catena representative of the region. {T}he soil organization revealed that {M}g-smectite occur in top soil close to the lake, whereas {F}e-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. {W}e propose here that this spatial distribution is controlled by the lateral transfer of {F}e and {A}l with organic ligands. {A}lkaline organic rich solutions ({DOC} up to 738 mg {L}-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 mu m, 0.2 mu m, 30 {KD}a, 10 {KD}a, 3 {KD}a) to separate colloidal and dissolved fractions. {F}e, {A}l, {S}i, {M}g and {K} were analysed for each fraction. {A}lthough the filtration had no influence on {S}i and {K} contents, almost 90% of {F}e (up to 2.3 mg {L}-1) and {A}l (up to 7 mg {L}-1) are retained at the first cutoff threshold of 0.45 mu m. {T}he treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of {F}e and {A}l were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing {M}g-smectite precipitation. {T}he fast mineralization of the organic matter a few meters apart from the lake favors the release of {F}e and {A}l necessary for {F}e-mica neoformation. {I}n comparison with chemical and mineralogical characteristics of alkaline environments described in the literature, the study suggests that the co-existence of trioctahedral {M}g-smectite and dioctahedral {F}e-mica should be regarded as a standard occurrence in alkaline soil systems with organic rich waters.},
  keywords = {{ZONE} {HUMIDE} ; {BRESIL} ; {MATO} {GROSSO} ; {PANTANAL} ; {NHECOLANDIA}},
  booktitle = {},
  journal = {{P}los {O}ne},
  volume = {11},
  numero = {7},
  pages = {e0159972 [23 p.]},
  ISSN = {1932-6203},
  year = {2016},
  DOI = {10.1371/journal.pone.0159972},
  URL = {https://www.documentation.ird.fr/hor/fdi:010067770},
}