Portal de Periódicos da CAPES

Comportement isotopique au cours de l'evaporation de deux bassins sahariens

1967; Elsevier BV; Volume: 3; Linguagem: Inglês

10.1016/0012-821x(67)90046-5

1385-013X

Jean‐Charles Fontes, Roberto Gonfiantini,

Water management and technologies

The evolution of the water isotopic composition of two basins having no outlet in the North-Western Sahara (Gara Diba Guelta and el Melah Sebkha) has been studied. A regular sampling taken during the whole drying process of these basins (4 months for the Guelta and 6 months for the Sebkha) showed a considerable isotopic enrichment (more than 30% for oxygen-18 and more than 100% for deuterium) due to the low relative humidity. The last samples collected in the Sebkha show an inversion in the isotopic enrichment, due to a decrease of the solvent activity. The piot of δ D against δ 18O gives a straight line with a 4.6 slope and whose intersection with the meteoritic waters straight line gives the isotopic composition of the rainfalls which fed the basins. A theoretical model giving an account of the experimental values was developed for the Guelta evaporating water. It provided us with an estimate of the amount of water evaporated between the rainfall and the sampling and of the amount of salts dissolved by ground leaching.