By studying, since the summer of 2003 until the winter of 2005 on various matrices (rocks, sediments, suspended matter, colloidal phase and dissolved phase), a geochemical statement (major and trace elements) was established on the Bouregreg river basin in Morocco. Geochemical study of waters and solid products or colloid transported on the whole of the basin can be particularly effective on the one hand to understand the transport and exchange processes of natural and anthropic constituents (in solution or adsorbed on suspended particles) and on the other hand to estimate anthropic contribution in the basin. The aim of this work was to develop a methodology allowing to establish a geochemical statement of this basin and to understand the behaviour of a natural system, by integrating the solid - liquid transfer phenomena The methodology combines so: (i) A biannual sampling, since the summer of 2003 until winter of 2005, of various matrices on the whole of the Bouregreg basin. (ii) A multi-element analytical protocol coupling the analysis by instrumental neutron activation analysis (INAA), the inductively coupled plasma-mass spectrometry (ICP-MS) and the inductively coupled plasma-atomic emission spectrometry (ICP-AES). (iii) Processing techniques of the data (comparison of average concentrations for each sample and variabilities for each site, normalized diagrams with regard to the average and upper continental crusts, comparison of elements ratios, choice of inert elements as references (example Ta or Yb), and finally a main component factor analysis ( CFA)). It can be inferred from rocks and sediments analyses: (i) The importance of the geochemical inheritance of the Bouregreg basin geologic environment (comparison between sediments and rocks, permanence of distributions along the river...). That results from the very compatible behaviour and from the inertia of certain elements during the deterioration (transition elements 3d (Co, Ni, Cr ...), internal transition elements f (rare earth element, Zr, Hf, Nb, Ta...). (ii) Geochemical homogeneity of the basin which translates also an inheritance during the crustal accretion (magmatism-metamorphism-sedimentation), (iii) The typology of this continental domain, rather of type upper continental crust. The water chemistry study in dissolved and particulate phases also allowed to confirm the behaviour difference between soluble elements which concentrations in water are bound to the basin lithology, and the other almost insoluble elements such as rare earth elements. The concentrations of these last ones in the dissolved phase are more bound to the internal chemistry of the river and to the existence of a colloidal phase. This is notably put in evidence during very low - waters where concentrations in organic suspended matters can be important. Besides, the influence of the human activities on metal pollution seemed very limited: the factors of enrichment did not show important value except for Cs, Li, Sb, Pb and As. This result confirms also the current weakness of the Bouregreg river chemical pollution.
