@incollection{PAR00007500,
  title = {{N}atural arsenic in groundwater and alkaline lakes at the upper {P}araguay basin, {P}antanal, {B}razil},
  author = {{B}arbi{\'e}ro, {L}aurent and {F}urquim, {S}.{A}.{C}. and {V}all{\`e}s, {V}. and {F}urian, {S}. and {S}akamoto, {A}. and {R}ezende {F}ilho, {A}. and {F}ort, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A} distinctive feature of {N}hecolândia, a sub-region of the {P}antanal wetland in {B}razil, is the presence of both saline (alkaline) and freshwater lakes. {S}aline lakes were attributed to a past arid phase during the {P}leistocene, but recent studies have shown that the geochemistry of the saline lakes arises from the current concentration process of fresh waters that is supplied to the {P}antanal every year. {T}he region is mainly used for cattle farming, more recently eco-tourism is becoming widespread and water conservation agencies worry about arsenic contents in surface and shallow ground water. {T}he study was carried out along a 600 m-long transect that linked a freshwater lake to a saline lake. {T}he spatial distribution of arsenic is studied, based on soil morphology, according to p{H}, redox conditions ({E}h) and dissolved organic carbon ({DOC}), and also compared to distribution of major elements. {T}hree main processes, responsible for the chemical variability, were identified: (1) the concentration of the solution under the influence of evaporation and the associated precipitations ({M}g-calcite, illite, sodium carbonate); (2) oxidation of sulphides included in clay layers and subsequent development of acid conditions; (3) buffering of acid conditions by clay dissolution. {A}rsenic contents are not affected by the last two processes (2 and 3) but evolve in proportion to the concentration. {A}rsenic concentrations in water ranged from 0.11 mg/l to 3.68 mg/l, i.e. 368 times higher than the {W}orld {H}ealth {O}rganization ({WHO}) guidelines for drinking water. {T}he arsenic speciation [index word 1] as calculated from field conditions indicated that the {A}s({V}) redox state dominated in the groundwater and in the lakes, whereas some proportion of {A}s({III}) could occur on the shore and in the sediments of the saline lake. {A}s({III}) from the sediment can be remobilised and dispersed into the water following the disturbance of the sediments by cattle that come to drink water. {A}rsenic contents increased with most of the other dissolved species; hence competitive adsorption [index word 16] prevent dissolved arsenic regulation by solid phase reaction. {M}oreover, the p{H}-values increased above 8 with increasing arsenic, favouring {A}s({V}) desorption. {A}s a consequence, the good correlation established between arsenic contents and electrical conductivity (r2 = 0.97) should help to indirectly evaluate the arsenic contents in shallow groundwater and lakes of the region.},
  keywords = {{A}lkaline lake ; {U}pper {P}araguay {B}asin ; {W}etland ; {P}antanal ; {B}razil ; {BRESIL}},
  booktitle = {{A}rsenic in soil and groundwater environment : biogeochemical interactions, health effects and remediation},
  numero = {},
  pages = {101--126},
  address = {{A}msterdam},
  publisher = {{E}lsevier},
  series = {},
  year = {2007},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00007500},
}