A sink-to-source reverse approach to identify dust source regions within the Sahara based on PM₁₀ levels measured on the West African coast

West Africa is a key region for the transport and deposition of Saharan mineral dust, with major impacts on air quality, climate, and ecosystems. Dust sources are numerous within the Sahara and their spatial extent remains poorly constrained, as do their granulometric, mineralogical, and chemical characteristics, which however control their impacts. Moreover, emission maps available in the literature do not allow the relative contribution of different source regions to a given impacted area to be assessed.This study proposes a sink-to-source reverse approach aimed at improving the characterization of dust emission areas affecting the coastal West Africa. It is based on a three-year time series of PM₁₀ concentrations measured in Casamance, southern Senegal, a region under the influence of easterly winds (Harmattan) responsible for the transport of Saharan dust in the lower troposphere during the dry season. The measurements were conducted at a rural site (Pointe Saint Georges), minimally influenced by local and anthropogenic emissions.PM₁₀ concentrations were coupled with air mass back-trajectories calculated using the HYSPLIT model and analyzed with the ZeFir software in order to identify potential source regions. Preliminary results suggest that, during high PM₁₀ concentration events observed along the West African coast, dust derived from two dominant sectors : one to the north-east including areas in Mauritania and across the Algerian-Mali border, and one to the east across the Sahelian region, confirming earlier findings (Le Quilleuc et al., 2021, JGR, doi.org/10.1029/2021JD035030). These results will be discussed in the light of emission areas provided by the satellite-based IDDI (Infrared Difference Dust Index) product as well as data on dust sources from the literature.The results that will be presented highlight the potential of this sink-to-source approach for identifying mineral dust source areas based on airborne concentrations. This methodology, relying on low-cost sensors, is reproducible and applicable to any site located downwind of desert regions.Keywords : PM₁₀, Saharan dust, Casamance, Senegal, air mass back-trajectories, HYSPLIT, ZeFir software, IDDI, sources