Nutrient inputs to sahelian soil by atmospheric dust deposition

Dust emission affects soil fertility through nutrient loss in source regions while dust deposition can represent a significant nutrient input for remote ecosystems. If the Sahel is a well-known dust source region, it is also a region where large amounts of dust from the Sahara desert are deposited.                                                         

To quantify the input of nutrients that mineral dust deposition represents for Sahelian soils and to identify the sources responsible for these deposits, a dedicated instrumental setup was deployed during two years in two Sahelian sites of the INDAAF Network : Bambey (Senegal) and Banizoumbou (Niger). The insoluble and the soluble fraction of the atmospheric deposits have been collected separately and analysed. In parallel,  the elemental composition and carbon content of PM₁₀ were determined. A special attention was given to the most important nutrients for the soil fertility in this region (P and N) and on the organic C. Other elements (Fe, Al, K, Ca, ...) were also analysed in order to identify the sources of the deposited particles.                                                

For most of the analysed elements, the elemental compositions of PM₁₀ and dust deposit are consistent and the dust samples composition reveals a seasonal change. During the dry season, the dust composition is similar in Niger and Senegal. During the wet season, mineral dust in Niger exhibits a typical signature of sahelian soils (i.e., enriched in Fe and depleted in Ca) while in Senegal dust composition suggests a regional source enriched in Ca. The analysis of the soluble and insoluble fraction of dust deposition allows to estimate the total annual amount of P, N and C deposited on Sahelian soil.