@article{PAR00001599,
  title = {{E}vidence of {Z}n isotopic fractionation in a soil-plant system of a pristine tropical watershed ({N}simi, {C}ameroon)},
  author = {{V}iers, {J}. and {O}liva, {P}. and {N}onell, {A}. and {G}elabert, {A}. and {S}onke, {J}. {E}. and {F}reydier, {R}. and {G}ainville, {R}. and {D}upr{\'e}, {B}ernard},
  editor = {},
  language = {{ENG}},
  abstract = {{T}he objective of this study is to determine for the first time the zinc ({Z}n) isotopic composition of different soil horizons, parent rocks, litter, and plants from a single pristine watershed. {T}hree soil profiles from {N}simi-{Z}oetele site ({S}outh {C}ameroon, {A}frica) have been investigated. {T}he 666 {Z}n (666 {Z}n[(66 [({Z}n-66/{Z}n-64)(sample)/({Z}n-66/{Z}n-64)({JMC} 3-07490{L}))-1] * 10(3)) measured in the soils and rocks range from -0.05 to 0.64 parts per thousand. {I}n a typical hillslope soil profile developed in situ from a granitic parent rock, we observe two important and systematic trends: i) a weathering regime in the saprolite horizon that involves strong {Z}n depletion, with no or slight fractionation compared to the fresh igneous rock, and ii) a shallower weathering regime with significant depletion in heavy {Z}n isotopes in the most superficial soil horizons. {I}n contrast, the soil profile of the swamp zone does not exhibit isotopic fractionation between the soil and the parent rock. {S}ix plants and two litter samples were analyzed for their {Z}n isotopic compositions. delta {Z}n-66 varied from 0.75 to -0.91 parts per thousand among all samples. {P}lant roots and shoots are generally enriched in heavy isotopes (delta {Z}n-66 of +0.42 to +0.76 parts per thousand) relative to the litter layer (0.12 to 0.25 parts per thousand) and most superficial soils. {S}imilar to the controlled plant growth study of {W}eiss et al. [{W}eiss, {D}.{J}., {M}ason, {T}.{F}.{D}., {Z}hao, {F}.{J}., {K}irk, {G}.{J}.{D}., {C}oles, {B}.{J}. and {H}orstwood, {M}.{S}.{A}. (2005) {I}sotopic discrimination of zinc in higher plants. {N}ew {P}hytologist 165, 703710.], negative delta {Z}n-66 values were obtained for tree leaves (the most aerial part of the tree). {B}ased on biomass data for the tropical forest, vegetation is on average enriched in light isotopes compared to the litter and the superficial soil horizons which are the nutrients reservoirs. {D}ue to the age of these soils and the complexity of pedogenetic processes, it is difficult to explain the isotopic composition of the soils at present. {H}owever, the transformation of the saprolite horizon into a ferruginous horizon is associated with an enrichment in light {Z}n isotopes. {T}his observation may be due to the adsorption of {Z}n onto clays surfaces. {T}he uptake of {Z}n by roots in the soils leads to an enrichment in heavy isotopes. {O}nce the {Z}n is in the xylem, it will be transported within the plant. {D}uring this transport, both diffusion and active uptake of heavy isotopes by cells out of the xylem favour the mobility of light isotopes to the most aerial parts of the plants. {T}he difference in {Z}n isotopic composition between the deep horizons and the superficial horizons of soils suggests that {Z}n isotopes can be used to discriminate the source of {Z}n and other metals leaving the catchment by river water.},
  keywords = {zinc isotopes ; soil ; vegetation ; weathering ; cycle},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {239},
  numero = {1-2},
  pages = {124--137},
  ISSN = {0009-2541},
  year = {2007},
  DOI = {10.1016/j.chemgeo.2007.01.005},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00001599},
}