Contents of metal trace elements (ETM) in some manganiferous soils derived from volcano-sedimentary materials in Côte d'Ivoire

Manganiferous soils have high contents of manganese, which, combined with trace elements could affect the physico-chemistry of the soil and lead to serious hazard on the environment and human. This study aims to assess the levels of trace elements on manganiferous soils of Côte d'Ivoire. A recognition site by manganiferous soil survey on three areas was applied. In these manganiferous soils abundance order of ETM, each site individually, is identical to the global abundance order : (Fe > Mn > Cu > Zn > Cr > Ni > Pb > Co > Cd). However, a difference is observed in Korhogo, at Ni > Cr. Among the ETM studied, Cu (172.8 mg.kg-1), Zn (110.73 mg.kg-1), Cd (1.06 mg.kg-1) and Mn (9228.96 mg.kg-1) are in the range of critical levels in soils, which can cause toxicity. A North-South gradient of increasing accumulation is for Cd. The opposite is observed for Zn. Mn is more abundant in Guitry but low in Bondoukou. Other ETM (Fe, Ni, Cu, Pb and Co) are more or less homogeneous in the different study areas. Dynamics and vertical distribution of ETM is very variable depending on the area and is mainly influenced by pedogenetic processes. The pH is frankly acids in these soils. A study on the speciation of trace metals in these soils should be conducted to better prevent potential contamination of environment.