The Ebrié Lagoon is the most important lagoon system in Côte d'Ivoire. This ecosystem is today facing enormous risks of pollution. These are characterized by the water quality deterioration and a strong disturbance by metallic pollutants. In this study, the level of arsenic contamination of water and sediments in the western part of the Ebrié Lagoon was determined on a year. Water and sediment samples are taken monthly from February 2014 to January 2015 in continental and marine areas. Arsenic is analyzed by atomic absorption spectrometry at the wavelength 538 nm according to the EPA method, 2007. The seasonal variations in arsenic showed a significant difference between the continental and maritime areas. The results show that the water and sediments of the continental and maritime areas in the western part of the Ebrié Lagoon are contaminated by arsenic. The high values of water/sediment coefficients suggest that the sediments of these areas constitute an arsenic reservoir for the water column. The physico-chemical parameters studied have a strong correlation with arsenic. This arsenic pollution could disrupt the biological balance of the environment and adversely affect biological integrity and human health.

Pollution abatement techniques, inexpensive and environmentally friendly, are highly desirable and recommended. That is a reason when heterogeneous photocatalysis using TiO2 as a semiconductor is of considerable interest. In this study, the performance of 5 materials was evaluated in the photocatalytic degradation of diuron herbicide. The kinetic of disappearance is pseudo-order 1 whatever the material. This photodegradation is very little influenced by the initial pH of the solution; even if the best results are obtained for initial pH between 5 and 8. The presence of ions such as nitrate, sulfate and ammonium ions in the reaction medium causes a slight decrease in the initial rate of disappearance of the pollutant. This is explained by a competitive adsorption between the pollutant and the added ions and / or an oxidation reaction of these ions by the photogenerated oxidative species. A photocatalytic degradation order of the diuron according to the material used has been established. This order would be: TiO2 P25 > TiO2 PC500 > Our TiO2 > Quartzel > Média 1048.