@article{fdi:010070903,
  title = {{Z}inc and copper behaviour at the soil-river interface : new insights by {Z}n and {C}u isotopes in the organic-rich {R}io {N}egro basin},
  author = {{G}uinoiseau, {D}. and {G}elabert, {A}. and {A}llard, {T}. and {L}ouvat, {P}. and {M}oreira {T}urcq, {P}atricia and {B}enedetti, {M}. {F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he complex behaviour of {Z}n and {C}u at the soil-river interface was investigated in soil and riverine water samples from the {R}io {N}egro basin, a secondary tributary of the {R}io {A}mazonas, using their stable isotope compositions. {T}his acidic and organic river drains two types of intensely weathered terrains: podzols in its upstream part, and lateritic soils downstream. {B}ulk soil particles, suspended particulate matter ({SPM}) as well as colloidal fractions were sampled across the whole basin during low and high water stages. {I}n the basin, {Z}n and {C}u are mostly exported from lateritic soils and transported by organic colloids where significant losses are observed in the downstream part of the river. {T}he use of delta {Z}n-66 and delta {C}u-66 measurements reveals distinct stories for these two metals in suspended sediments and colloids. {I}n the colloids, the constant delta {Z}n-66(coll) across the basin is induced by the same weak association mode between {Z}n and organic ligands, regardless of the origin of the water. {B}y contrast, in {SPM}, the speciation of {Z}n and thus delta {Z}n-66({SPM}) differ according to the type of drained soils. {Z}n is associated with organic complexes in particles exported with water draining podzol whereas {Z}n2+ is incorporated in the structure of the remaining kaolinite clays in lateritic output. {T}he stronger reactivity of {C}u than {Z}n with organic ligands induces its complete complexation. {C}opper is controlled by refractory particulate organic matter ({POM}) and by reactive colloidal organic matter; the latter being enriched in delta {C}u-65 due to stronger binding interactions than in {POM}. {W}hile the {C}u content remains constant in the upstream part of the {R}io {N}egro, downstream, the decrease of {SPM} and colloidal {C}u fluxes is associated with a constant delta {C}u-65({SPM}) and with an increase of delta {C}u-65(coll) at the {R}io {N}egro outlet. {G}eochemical mass balance modelling, based on {SPM}, {C}u and {Z}n fluxes in {SPM} and their associated isotopic signatures, confirms distinct host phases for {Z}n and {C}u, and identifies the most probable places where losses of these two metals occur. {I}n colloids, the observed {C}u isotope fractionation (from 0.24 to 0.45%) superimposed on the significant {C}u-coll loss is assumed to result from a new isotopic equilibrium in a low velocity and high productivity zone: {C}u-rich colloids enriched in {C}u-63 aggregate and settle down, whereas the remaining heavy {C}u is partially complexed on strong organic ligands secreted by phytoplankton, forming new {C}u-colloids.},
  keywords = {{O}rganic-rich river ; {Z}inc and copper isotopes ; {R}io {N}egro ; {AMAZONIE} ; {BRESIL} ; {RIO} {NEGRO} {BASSIN}},
  booktitle = {},
  journal = {{G}eochimica et {C}osmochimica {A}cta},
  volume = {213},
  numero = {},
  pages = {178--197},
  ISSN = {0016-7037},
  year = {2017},
  DOI = {10.1016/j.gca.2017.06.030},
  URL = {https://www.documentation.ird.fr/hor/fdi:010070903},
}