PRECIPITATIONS ET ACCUMULATIONS SALINES ESTIVALES DANS LES SOLS NUS SABLEUX EN ZONES ARIDES. CAS DE LA REGION DE OUARGLA.

Abstract

Ouargla oasis is located in southeastern Algeria at a distance of about 800 km from the capital, Algiers. Its soils are known for their sodicity and salinity, characters frequently encountered in the region. They have always had with the scientific community and public authorities a reputation for difficulty for any use, primarily agriculture. Our area of study, experienced in summer, concerned an excessively salty soil texture Sandy compounded by the non-functionality of the drainage system. To lead to physical, chemical and this soil, biological characterization on the one hand, and to identify the order of majority salt precipitation, to the geochemical approach, with a thermodynamic model, highlighted for three examined profiles neutral saline track considering ion stable as tracer chlorine best appropriate evaporites. It has been also shown until log concentration factor (log CF 0, 2), all calcite are supersaturated, hence their precipitation priority especially on surface horizons: P1H0, P2H0 and P3H0. This calcium precipitation is attested by > 8.5 pH values. It is basically calcite (CaCO3), magnesite (MgCO3) and dolomite (CaMg (CO3) 2). Concerning sulphated solutions, precipitation are recognized CF = 1.24 or chloride ion concentrations greater than 280 CT/l and sulphate more than 324 CT/l. For soluble minerals, halite (NaCl) seems the mineral the more porch of saturation.