@article{fdi:010053724,
  title = {{D}issolved organic matter dynamic in the {A}mazon basin : sorption by mineral surfaces},
  author = {{P}erez, {M}. {A}. {P}. and {M}oreira {T}urcq, {P}atricia and {G}allard, {H}. and {A}llard, {T}. and {B}enedetti, {M}.{F}.},
  editor = {},
  language = {{ENG}},
  abstract = {{I}n aquatic systems, soprtion of organic matter ({OM}) on environmental surfaces or its preference to remain dissolved is highly important for determining its potential transport and/or susceptibility to degradation. {I}n the {A}mazon and other major rivers of the world, transported {OM} is either adsorbed to fine minerals or remains dissolved. {T}he fate of autochthonous {OM} in {A}mazon floodplains and allochthonous {OM} from the river can be addressed by characterizing the nature of {OM} interactions with the sediment material. {T}his goal was pursued in this study using {R}io {N}egro and {A}mazon {R}iver samples as well as those collected from floodplain lakes during phytoplanktonic blooms, small black rivers, soil solution issued from podzolic areas in the {R}io {N}egro watershed and "terra firme" stream flowing into the floodplain. {T}he amount of carbon surface loading expressed as the adsorbed organic carbon per unit of surface area of the substrate was obtained by batch experiments with mineral phases representative of soils, suspended matter found in the {A}mazon basin and extracted {OM} fractions (the hydrophobic, {HPO} and the transphilic, {TPH} fractions of {OM}). {T}he bulk dissolved organic matter samples were characterized by carbon and nitrogen isotopic measurements as well as elementary composition, specific {UV} absorbance ({SUVA}), molecular weight ({M}w) and {FTIR} spectroscopy. {T}o our knowledge, these are the first {C} and {N} isotopic composition data reported for extracted {OM} fractions in the {A}mazon basin. {T}he {R}io {N}egro basin water samples had high [{DOC}] correlated with conductivity. {T}he {SUVA} values ranged from 4.0 to 7.3 m(-1)l mg(-1){C} and were within the range of measurements reported for the {A}mazon {R}iver. {T}he delta {C}-13 values of all {HPO} fractions varied from -27.7 to -30.2%.. {T}he delta {C}-13 values for the {TPH} fractions were systematically 1%. higher than their respective {HPO} fraction. {A}n increasing trend between the weight average {M}w of the {DOC} as function of the {C}/{N} ratio (the higher {C}/{N} the higher {M}w) is reported. {T}his trend is inferred to result from both mixing between 2 end-members and {OM} fractionation. {C}arbon surface loadings calculated for {HPO} and {TPH} fractions ranged between 23 to 309 mu g{C} m(-2) and 38 to 145 mu g{C} m(-2), respectively. {C}arbon surface loadings with goethite and the {R}io {N}egro organic matter fractions cluster around the average value of 24.5 +/- 4 mu g{C} m(-2). {W}ith the help of the p{H} dependant dissociation measurements and {NICA}-{D}onnan model parameters, it was possible to estimate the amount of deprotonated sites on the {OM} interacting with the sediment material. {T}he amount of carbon surface loading was correlated with the calculated residual negative charge of the {OM} fractions (i.e. {HPO} or {TPH}). {T}hese analyses showed that higher residual negative charges were associated with lower carbon surface loadings on the treated sediment. {T}he decrease of the negative charge was suggested to reduce the net electrostatic repulsion between the {OM} fractions and the clay surfaces and promote ligand exchange reactions governing sorption to clays. {T}he preferential uptake of the high molecular weight fraction demonstrates that the chemical nature of the organic matter remaining in solution differs from that of the adsorbed fraction.},
  keywords = {{R}ivers ; {O}rganic matter ; {R}eactivity ; {A}dsorption ; {DOC} ; {S}ediment},
  booktitle = {},
  journal = {{C}hemical {G}eology},
  volume = {286},
  numero = {3-4},
  pages = {158--168},
  ISSN = {0009-2541},
  year = {2011},
  DOI = {10.1016/j.chemgeo.2011.05.004},
  URL = {https://www.documentation.ird.fr/hor/fdi:010053724},
}