REE and other trace and major elements in the topsoil layer of Santiago island, Cape Verde

摘要

Geochemistry of major, trace and rare earth elements (REEs) of soils of Santiago island (Cape Verde) has been done in order to characterize soils developed on volcanic rocks and Quaternary sediments, contributing to the establishment of a geochemical atlas of the island. Sampling was made according to the recommendations of the IGCP 259 ("International Geochemical Mapping"). REE clearly differentiate soils with contrasting parent materials, particularly carbonatites-related soils, where lower MREE/LREE and MREE/HREE ratios were found, associated with higher contents of Ba, Th and U. Total contents of Cs, As and Ga are associated with the finer soils. The percentage of Fe, Co, Mn and Sc extracted using aqua regia increased with increase of the clay size proportion. Concerning potentially pollutant elements, As contents increase with decreasing particle size, and very high concentrations of Cr were found in some soils. However, As is less available in the finer soils and the percentages of extraction of Cr are low, limiting eventual environmental and health effects in the Santiago island.