Trace element variation in size-fractionated African desert dusts

摘要: Abstract Desert particulate samples from locations in the Sahara–Sahel dust corridor (Western Sahara, Algeria, Chad and Niger) were segregated into size fractions ranging 20 μm analysed using inductively coupled plasma atomic emission spectrometry (ICP-AES) mass (ICP-MS). The size-fractionated contain higher concentrations of Al, Na, Mg, Fe most trace elements finer, phyllosilicate-rich materials. A notable exception is provided by Zr Hf, which concentrate coarser due to a abundance coarse detrital zircon. Equally explicable natural processes are enrichments (relative average upper continental crust) incompatible with ionic potential (Nb, Ce, La), these being more resistant chemical weathering. In contrast, show relative loss large ion lithophile (Rb, Cs Ba), calcareous enrichment Sr depletion Nb. However, not all geochemical variations exhibited easily invoking “natural” processes: anomalous several transition metals (Zn, Pb, Cd) can be attributed anthropogenic pollution, Cr, Ni Mo abrasive interaction between siliceous sample fractionation equipment.