Retention supports and geochemical interactions of Trace Elements in two soils irrigated by sewage (Meknes, Morocco)

The Ourzirha area located in the north-western of the Meknes City is an important agricultural region. This region is one of the principal suppliers of agricultural products to the Meknes citizens. However, the cultivated areas in the Ourzirha region are irrigated by a raw wastewater in major part. To explain and to predict the principal supports of the Trace Elements retention in these soils, two profiles subject to a sewage spreading are taken, a calcareous soil and a vertisol. Based on the vertical evolution of different studied parameters and the selective affinities of Trace Elements to the active soil fractions present in our profiles, we are tried to determine the various interactions between the considered Trace Elements and the clay, calcite and organic matter contents in studied profiles. The results of this study showed the importance of clay and organic matter as a dominant supports of these pollutants, especially in surface soil. In the calcareous soil, the calcite content influences strongly the distribution of Trace Elements along this profile. The mechanisms of the Trace Elements retention on studied profiles are considered as a selective adsorption on organic matter, clay and on calcite essentially. In fact, the possibility of a weak co-precipitation with calcite and organic matter in the calcareous soil isn't excluding. Also, in the vertisol probably, the Trace Elements contents are strongly influenced by the particular entering, favoured by a macro-porosity of this profile.