Mining soils are generally characterized by soils having a coarse texture and low fertility, which makes revegetation a very difficult and delicate operation, especially in arid and semi-arid zones. The main objective of this work is to evaluate different substrates that can both contribute to the successful reclamation of phosphate mining soils and the valorization of phosphate by-product and sewage sludge. The study was carried out in pots under a greenhouse on Italian ryegrass (Lolium multiflorum). The experimental design is a randomized complete block with ten treatments, four repetitions from five substrates: phosphogypsum (PG), phosphate sludge (PS), sewage sludge (SS), topsoil from mining (TS) and phosphate waste rocks (PWR); this corresponds to soil after rock phosphate extraction. Nitrogen fertilization was applied to treatments after soil depletion in treatments not receiving sludge. An aerial biomass measurement and nutrient analysis were carried out for the three cuts. The results showed that a proportion of 65% of PG enriched the substrate in phosphorus by improving the crop yield. The addition of 5% of SS contributed to a significant improvement of ryegrass aerial biomass. In the absence of SS application, the addition of nitrogen is required to maintain crop growth. For large-scale application, TS can be mixed with PS, SS and PG for mine site reclamation.

The objective of this study was to evaluate the effect of mixtures of the phosphate industry’s by-products and sewage sludge on some heavy metals (Pb, Zn and Cd) in the soil–plant system and the microbial load (bacteria, fungi and actinobacteria) in the soil. The experimental layout was a completely randomized design with ten treatments and four replications. The treatments consist of a combination of five substrates: phosphogypsum (PG), phosphate sludge (PS), sewage sludge (SS), phosphate waste rocks (PWR) and original mine topsoil (TS). Heavy metals analysis, phytoextraction efficiency (PEE) and bioconcentration factor (BCF) were carried out for three Ryegrass cuts. The microbial load of each treatment was determined at the end of the experiment. The results showed that the Pb, Zn and Cd contents of the treatments were well below the permissible limits given in the literature. The highest BCF and PEE were with treatment T4. Furthermore, bacteria, fungi and actinobacteria were significantly influenced by the different proportions of by-products used in the treatments, with the highest richness observed for the T4 treatment. For a successful reclamation of mine sites, it would be useful to determine the speciation of metals in the soil solution and the microbial genetic diversity.

*Impacts dangereux des décharges municipales à ciel ouvert sur le sol : Cas de la décharge du Parc de M'Ploussoue de Bonoua, Côte Ivoire ABSTRACT: In Ivory Coast, most of the uncontrolled dumpsites are open-air and is one of the most common methods adopted. To study the impact of the solid waste on soil, soil samples were collected from the dumpsite of M'Ploussoue Park in Bonoua. The physical and chemical parameters such as size particle, pH, Exchangeable cations, CEC and the contents in heavy metals, were studied using various analytical techniques. It has been found that most of all the heavy metals analyzed contents exceeds the permissible limits in accordance with CCME soil quality standards. It's conclude that M'Ploussoue Park dumpsite is characterized as polluted site whose the contamination is due to the solid waste materials that are dumped in the area.

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