Understanding the solubility dynamics of elements during wet deposition is crucial for assessing their environmental impacts. In this study, we investigated the solubility behaviour of various elements originating from natural and anthropogenic sources using a dataset of 106 samples describing the sequential collections of 8 rainfall events. Our results reveal distinct solubility patterns depending on the type of event, with mineral-dust events exhibiting lower solubility and anthropogenic events displaying higher solubility, in relation with dust content and pH. The study of intra-event solubility reveals variations over short periods during a rain event, which evolve differently according to the chemical elements and depend mainly on the origin of the aerosols scavenged by the rain. In the case where the aerosol origin is the same during a rain event, the precipitation characteristics and in-cloud scavenging mechanisms play a role on the elemental solubility as the rainfall progresses.

This paper presents the first investigation of the solubility of iron in mineral dust aerosols collected at the Henties Bay Aerosol Observatory (HBAO), in Namibia, from April to December 2017. During the study period, 10 intense dust events occurred. Elemental iron reached peak concentrations as high as 1.5 µg m−3, significantly higher than background levels. These events are attributed to wind erosion of natural soils from the surrounding gravel plains of the Namib desert. The composition of the sampled dust is found to be overall similar to that of aerosols from northern Africa but is characterized by persistent and high concentrations of fluorine which are attributed to local fugitive dust. The fractional solubility of Fe (%SFe) for both the identified dust episodes and background conditions ranged between 1.3 % and 20 % and averaged at 7.9 % (±4.1 %) and 6.8 (±3.3 %), respectively. Even under background conditions, the %SFe was correlated with that of Al and Si. The solubility was lower between June and August and increased from September onwards during the austral spring. The relation to measured concentrations of particulate MSA (methane sulfonic acid), solar irradiance, and wind speed suggests a possible two-way interaction whereby marine biogenic emissions from the coastal Benguela upwelling to the atmosphere would increase the solubility of iron-bearing dust according to the photo-reduction processes. This first investigation points to the western coast of southern Africa as a complex environment with multiple processes and active exchanges between the atmosphere and the Atlantic Ocean, requiring further research.

Soil texture and soil surface aggregate size distribution (ASD) are key factors to study soil erodibility by wind and sediment size distribution (SSD) in arid and semi-arid areas. However, less research has studied the effect of soil fractions on soil erodibility and wind-blown sediment size of calcareous soils. In the present study, we focused on the size fractionation and particle size distribution (PSD) of 60 calcareous soil samples collected from 20 semi-arid and arid areas in Fars province, southern Iran. Extensive in-situ wind tunnel experiments were conducted under controlled high wind speed to measure wind erosion rate (WER) and SSD. The results showed that the calcareous soils had different erodibility based on their PSD. Generally, the most erodible soils to the wind force were those with less than 10 % of clay and higher frequency of the 0.1–0.2 mm size class. However, when the soil clay content exceeds 20 %, ASD got dominated with the fraction of 0.4–0.8 mm and WER of the calcareous soils got limited. Besides, size range of 0.063–0.2 mm was suggested as the most wind erodible fraction of the calcareous soils. Furthermore, the mean weight diameter (MWD) of sediment particles averagely reduced 1.3 times as compared to that of the soil samples and WER got inhibited for regions in which the difference of soil and sediment MWD exceeded 0.05 mm. The SSD was significantly controlled by soil PSD and suspension-size sediments < 0.1 mm (SSS) were negatively proportional to soil clay, MWD, geometric mean diameter of soil particles (GMD), dry stable aggregates > 0.25 mm (DSA), and organic carbon as logarithmic equations. Moreover, the presence of the size fractions > 0.2 mm restricted the potential of calcareous soils to generate SSS, which would be quite beneficial for wind erosion combat and dust control of calcareous soils.

Abstract. Mineral dust is the largest contributor to elemental iron in the atmosphere, and, by deposition, to the oceans, where elemental iron is the main limiting nutrient. Southern Africa is an important source at the regional scale, and for the Southern Ocean, however limited knowledge is currently available about the fractional solubility of iron from those sources, as well as on the atmospheric processes conditioning its dissolution during deposition. This paper presents the first investigation of the solubility of iron in mineral dust aerosols from 176 filter samples collected at the Henties Bay Aerosol Observatory (HBAO), in Namibia, from April to December 2017. During the study period, 10 intense dust events occurred. Elemental iron reached peak concentrations as high as 1.5 µg m-3, significantly higher than background levels. These events are attributed to wind erosion of natural soils from the surrounding gravel plains of the Namib desert. The composition of the sampled dust is found to be overall similar to that of aerosols from northern Africa, but characterised by persistent and high concentrations of fluorine, which are attributed to fugi-tive dust from mining activities and soil labouring for construction. The fractional solubility of Fe (%SFe) for both the identified dust episodes and background conditions ranged between 1.3 to 20 %, in the range of values previously observed in the remote Southern Ocean. Even in background conditions, the iron fractional solubility was correlated to aluminium and silicon solubility. The solubility was lower between June and August, and increased from September onwards, during the austral spring months. The relation with measured concentrations of particulate MSA (methanesulfonic acid), solar irradiance and wind speed suggests a possible two-way interac-tion whereby marine biogenic emissions from the coastal Benguela upwelling to the atmosphere would increase the solubility of iron-bearing dust, according to the photo-reduction processes pro-posed by Johansen and Key (2006). The subsequent deposition of soluble iron could act to further enhance marine biogenic emissions. This first investigation points to the west coast of southern Africa as a complex and dynamic environment with multiple processes and active exchanges between the atmosphere and the Atlantic Ocean, requiring further research.

A measurement campaign was conducted in the Paris region, focusing on the evolution of chemical composition of wet deposition during rainfall events from sequential sampling. A total of eight rain events were documented and characterized by varying meteorological conditions, atmospheric dynamics, and aerosol particle concentrations representative of urban conditions and influenced by long-range mineral dust transport. The intra-event evolution of the chemical composition of wet deposition revealed the predominant role of meteorological parameters and local sources in the observed mass concentration variability. From selected case studies, the washout ratios (WRs) and scavenging coefficients were quantified by conducting simultaneous measurements of aerosol particle composition and wet deposition. The results highlighted a variability of the WR and scavenging coefficients depending on the rainfall rate and on the chemical species. Scavenging coefficients estimated from WR ranged from 5.4×10-8 to 1.1×10-5 s−1 for chemical elements, and they are within the range of values reported in the literature for 0.2–2 µm particle diameters. Our results pointed out that the scavenging coefficient increases with rainfall rate according to a power law, as previously shown in the literature, indicating a stronger removal of particles from the atmosphere with greater precipitation intensity. Quantitative analysis of the data allowed us to estimate the relative contributions of in-cloud scavenging (ICS) for selected rain events. The ICS relative contributions ranged on average from 23 % to 62 % depending on the rain events, and they varied according to the chemical species within the same rain event. This highlights the variability and complexity of the wet deposition process and the influence of specific factors on the contribution of ICS, such as aerosol particle size and hygroscopicity. Overall, this study highlights the variability of wet deposition and its chemical composition and the need to consider the specificities of each event to fully understand the underlying mechanisms.

Mineral dust produced by wind erosion of arid and semiarid surfaces is a major component of atmospheric aerosol that affects climate, weather, ecosystems, and socioeconomic sectors such as human health, transportation, solar energy, and air quality. Understanding these effects and ultimately improving the resilience of affected countries requires a reliable, dense, and diverse set of dust observations, fundamental for the development and the provision of skillful dust-forecast-tailored products. The last decade has seen a notable improvement of dust observational capabilities in terms of considered parameters, geographical coverage, and delivery times, as well as of tailored products of interest to both the scientific community and the various end-users. Given this progress, here we review the current state of observational capabilities, including in situ, ground-based, and satellite remote sensing observations in northern Africa, the Middle East, and Europe for the provision of dust information considering the needs of various users. We also critically discuss observational gaps and related unresolved questions while providing suggestions for overcoming the current limitations. Our review aims to be a milestone for discussing dust observational gaps at a global level to address the needs of users, from research communities to nonscientific stakeholders.

The objective of this study is to confirm the possibility of tracing sources of airborne mineral dust using elemental ratios. The region of study is the north-eastern part of the Sahara where dust compositional data were lacking; 272 mineral dust samples collected at 3 experimental stations of Egypt were analyzed by X-ray fluorescence. Based on the mineral dust concentration, 65% of the samples correspond to moderate (3–10 μg m −3 ), 22% to medium (10–25 μg m −3 ), and 13% to intense (> 25 μg m −3 ) dust events. The Ca/Al and (Mg + Ca)/Fe ratios were found to be strongly correlated and their ranges of variation to cover are more than one order of magnitude, which confirms their interest for the tracing of the dust sources. Using a combination of MODIS satellite observations, HYSPLIT back-trajectory analysis, and simulations with dust emission models, the large (> 6) and intermediate (2–6) Ca/Al ratios were shown to correspond to dust originating from saline playas (chotts) and calcareous surfaces, respectively. Conversely, the lowest (< 2) ratios correspond to dust emitted by siliceous sand seas (ergs). Therefore, a classification of the dust in 3 categories (erg-like, calcareous, and chott-like) based on Ca/Al is proposed. The events of moderate to medium intensity are dominated by chott-like and calcareous dust, which suggests that these sources are activated during erosion events of limited (local) extension. Conversely, the fact that the dust composition is more likely to be of the erg-like type during intense events underlines the dominant role played by sand dune fields during major erosion events.

Wet deposition is a key mechanism influencing lifetime of particles in the atmosphere. It allows the deposition of particles via two distinct processes, washout and rainout. Wet deposition of particles is highly variable in space and time depending both on atmospheric aerosol loads and precipitation. This variability can be observed from an event to another as well as within an event. Studying the chemical composition of wet deposition can help us to understand the origin of the aerosols as well as the way they are deposited. Indeed, depending on their intrinsic properties, aerosols have specific chemical signatures. Sequential rain sampling provides a means to monitor the chemical composition of wet deposition throughout a rain event, trace its origin, and discuss the relative contribution of rainout and washout during a single event. In order to address these issues, an automatic sequential rain sampler was specifically developed to collect the rain in consecutive fractions. The sampler has a large sampling area (1 m(2)) and an automatic distribution system allowing the sampling of wet deposition with high temporal resolution to document intra-event deposition variability and a sufficient volume to analyze the dissolved and particulate phases of the rain. Two rain events collected in July 2021 and February 2022 in an urban site in the surroundings of the Paris agglomeration were studied. Our results allowed us to quantify how the total mass concentration decreases with the precipitation amount during a rain event until reaching a constant level. By combining elemental and ionic analysis, the evolution of particulate and dissolved major and trace element concentrations is documented for these two rainfall events. The particulate phase shows a higher decreasing trend than the dissolved one. Major elements such as Fe, Si and Al are predominantly in the particulate phase while trace metals (TMs), like Mn and Zn, are shared in both dissolved and particulate phases. However, each element shows an increasing ratio of its dissolved to total (dissolved + particulate) fraction as rainfall progresses, especially for TM. The study of dissolved compounds (SO42-, NH4+ and NO3-) confirms that concentrations are decreasing with rainfall depth but that the variations are influenced by changes in rainfall intensity. The rainout and washout relative contributions to wet deposition are discussed regarding the studied chemical species and the rain events.

The size distribution of the vertical flux of dust freshly emitted from a wind‐eroded surface was recently shown to depend on the thermal stratification of the surface boundary layer (SBL). These new results question the way dust emission is currently represented in the dust models and emphasize the need to identify the factors controlling the intensity and size‐resolved dust flux at emission. In this study, we re‐analyze the data of two major campaigns (JADE and WIND‐O‐V) performed on unvegetated plots and during which the characteristics of the (a) surface of the eroding fields, (b) aerodynamic conditions (wind speed, stability of the SBL), (c) saltation flux (intensity and size distribution), and (d) vertical dust flux (intensity and size distribution) determined by the gradient method were carefully documented. The magnitude and size distribution of the vertical dust flux are found to be deeply intertwined and to be controlled in the first place by the kinetic energy of the saltating sand grains, and to a lesser extent by the size‐dependent uplift of the sandblasted particles. In unstable conditions coarser sand grains are mobilized, which increases the kinetic energy of the saltation flux and leads to the production of finer particles by sandblasting. Conversely, the uplift of supermicron particles is facilitated by the increase of the wind friction velocity, which results in an enrichment of the vertical dust flux in the coarsest particles at large wind speeds. The implications of these new findings are particularly important for the modeling of the dust emission/transport/deposition cycle.

Based on a large number of in‐situ measurements performed over a 9‐years period in two Sahelian stations, we investigate the drivers of the dust wet deposition in relation to the meteorological situations and the PM10 (Particulate Matter with diameter lower than 10 μm) surface concentrations. Precipitation associated with cold pools (CP) contribute to more than 90% of the precipitation amount associated with the collected wet deposition samples. The wet deposition events associated with these CP control by far the wet deposition, that is, 66% and 81%, depending on the station. The dust washout ratios (WR) corresponding to the most convective events under high level of dust concentrations were found to be in the range of 319–766 while WR of other kind of events are depending on the dilution effect. This range of value are in the lower range of WR previously estimated and used in dust modeling studies (200–2000).

In the semi-arid Sahel region, wet deposition can represent more than half of the total annual deposition and are associated to different rainfall types, from stratiform precipitation to convective systems. Surface parameters such as temperature, wind speed, wind direction as well as rainfall rate can be used to distinguish these situations. We investigate the behaviour of dust wet deposition at the event-scale based on a multiannual (2007 to 2016) monitoring of wet deposition fluxes, PM10 concentration, precipitation and meteorological parameters in two Sahelian stations Banizoumbou (Niger, 13.54°N, 2.66 E) and Cinzana (Mali, 13.28°N, 5.93°W) of the INDAAF network. Rainfall events have been classified into three types: (i) stratiform, convective associated with (ii) weak precipitation or (iii) intense precipitation. This classification is based on selected criteria regarding evolutions of surface temperature, of wind speed and direction before and after the rainfall onset as well as on the event rainfall rate. Based on an interpretation of hundreds of single events, almost 25% of wet deposition events are associated with non-convective situation, more than 40% with atmospheric convective situation and weak precipitation, and more than 35% events with atmospheric convective situation combined with intense precipitation. This exhaustive work over a long-time period of measurements illustrates the predominance of convective situations regarding wet deposition in the two Sahelian stations. Washout ratios (WR) have been computed from PM10 concentrations, precipitation and deposition fluxes for each kind of events when data were concomitant. The dependency of WR to precipitation amount is shown to differ depending on the rain types. For instance, the decreasing dependency of WR with the precipitation amount of non-convective events has been quantified and could be explained by a dilution effect of the deposition. On the contrary, no clear dependency of WR with the precipitation has been observed for atmospheric convective conditions associated with intense rainfall rate.

Air pollution in Chinese megacities has reached extremely hazardous levels, and human activities are responsible for the emission or production of large amounts of particulate matter (PM). In addition to PM from anthropogenic sources, natural phenomena, such as dust storms over Asian deserts, may also emit large amounts of PM, which lead episodically to poor air quality over Chinese megacities. In this paper, we quantify the degradation of air quality by dust over Beijing, Chengdu and Shanghai megacities using the three dimensions (3D) chemistry transport model CHIMERE, which simulates dust emission and transport online. In the first part of our work, we evaluate dust emissions using Moderate Resolution Imaging Spectroradiometer (MODIS) and Infrared Atmospheric Sounding Interferometer (IASI) satellite observations of aerosol optical depth, respectively, in the visible and the thermal infrared over source areas. PM simulations were also evaluated compared to surface monitoring stations. Then, mineral dust emissions and their impacts on particle composition of several Chinese megacities were analyzed. Dust emissions and transport over China were simulated during three years (2011, 2013 and 2015). Annual dust contributions to the PM 10 budget over Beijing, Chengdu and Shanghai were evaluated respectively as 6.6%, 9.5% and 9.3%. Dust outbreaks largely contribute to poor air quality events during springtime. Indeed it was found that dust significantly contribute for 22%, 52% and 43% of spring PM 10 events (for Beijing, Chengdu and Shanghai respectively).

An advanced dust reanalysis with high spatial (at 10km x 10km) and temporal resolution is produced in the framework of DustClim project (Dust Storms Assessment for the development of user-oriented Climate Services in Northern Africa, Middle East and Europe) [1], aiming to provide reliable information on dust storms current conditions and predictions, focusing on the dust impacts on various socio-economic sectors. This regional reanalysis is based on the assimilation of dust-related satellite observations from MODIS instrument [2], in the Multiscale Online Nonhydrostatic Atmosphere Chemistry model (NMMB-MONARCH) [3], over the region of Northern Africa, Middle East and Europe. The reanalysis is now available for a seven-year period (2011-2016) providing the following dust products: Columnar and surface concentration, distributed in 8 dust particle size bins, with effective radius ranging from 0,15μm to 7,1μm, dust load, dry and wet dust deposition, dust optical depth (DOD) and coarse dust optical depth (radius>1μm) at 550nm and profiles of dust extinction coefficient at 550nm. A thorough evaluation of the reanalysis is in progress to assess the quality and uncertainty of the dust simulations, using dust-filtered products, retrieved from different measurement techniques, both from in-situ and remote sensing observations. The datasets considered for the DustClim reanalysis evaluation, provide observations of variables that are included in the model simulations. The DOD is provided by AERONET network [4] and by IASI [5], POLDER [6], MISR [7] and MODIS space-borne sensors; Dust extinction profiles are provided by ACTRIS/EARLINET network [8] and CALIPSO/LIVAS dataset [9]; Dust PM10 surface concentrations derived from INDAAF/SDT [10] network and estimated from PM10 measurements [11] performed within EEA/EIONET [12] network; Dust deposition measurements collected by the INDAAF/SDT and the CARAGA/DEMO [13] networks; Dust size distribution from in situ observations (ground-based and airborne); And column-averaged dust size distribution at selected stations from the AERONET network. In this work, we present the results of the model evaluation for the year 2012. The first evaluation results will focus on dust extinction coefficient profiles from EARLINET and LIVAS, on DOD using AERONET, MISR and MODIS datasets, and on dust PM10 concentration from INDAAF/SDT network. Moreover, a DOD climatology covering the whole reanalysis period (2011-2016) will be compared with the results obtained from AERONET network. References [1] https://sds-was.aemet.es/projects-research/dustclim [2] https://modis.gsfc.nasa.gov/ [3] Di Tomaso et al., Geosci. Model Dev., 10, 1107-1129, doi:10.5194/gmd-10-1107-2017., 2017. [4] https://aeronet.gsfc.nasa.gov/ [5] Cuesta et al., J. Geophys. Res., 120, 7099-7127, 2015. [6] http://www.icare.univ-lille1.fr/parasol/overview/ [7] https://misr.jpl.nasa.gov/ [8] https://www.earlinet.org/ [9] Marinou et al., Atmos. Chem. Phys., 17, 5893–5919, https://doi.org/10.5194/acp-17-5893-2017, 2017. [10] https://indaaf.obs-mip.fr/ [11] Barnaba et al., Atmospheric environment, 161, 288-305, 2017. [12] https://www.eionet.europa.eu/ [13] Laurent et al., Atmos. Meas. Tech., 8, 2801–2811, 2015. Acknowledgement DustClim project is part of ERA4CS, an ERA-NET initiated by JPI Climate, and funded by FORMAS (SE), DLR (DE), BMWFW (AT), IFD (DK), MINECO (ES), ANR (FR) with co-funding by the European Union (Grant 690462).

Soil erosion controlled by the wind effect on the surface, has been largely studied by field in-situ measurements as well as laboratory or numerical simulations. Nevertheless, more in-situ measurements and observations are needed to document this phenomenon for various desert areas. In the present study, we focus on the documentation of different properties of a wide range of semi-arid and arid soils of the Fars province, and how they control the soil erosion by wind. By improving our knowledge on soil properties which lead to the limitation of soil erosion by wind, it will be possible to better prevent wind erosion in the Fars province. Extensive wind tunnel experiments were conducted in 20 different arid and semi-arid regions. For each region, three wind tunnel experiments were done to encounter local soil variability. We determined threshold wind speeds for which soil erosion was observed. Other experiments were conducted at the same high wind speed, and duration conditions, allowing discussing soil erosion rates by wind regarding soil properties. As already documented in the literature, our results pointed out a significant negative power relationship between wind erosion rate and different soil physical properties, including soil surface gravel cover, the mean weight diameter (MWD) of soil particles, and soil clay and moisture contents. Moreover, a nonlinear relationship as a power function was found between the increase of soil organic carbon and the decrease of soil losses by wind in the studied semi-arid and arid soils. We determined critical values of these soil properties for which wind erosion in Fars province is limited under high wind speed conditions. Additionally, the effects of the electrical conductivity (EC), sodium adsorption ratio (SAR), and calcium carbonate equivalent (CCE) on wind erodibility were discussed at low and high concentrations and for different soil textures.

The Sahara is a major source of mineral particles for the Mediterranean Sea. The air-suspended particles alter the radiative transfer of solar and terrestrial radiation and the input of nutrients resulting from the deposition of mineral dust into the surface waters is thought to be essential for the development of marine ecosystems. In order to document the spatial and temporal variabilities of the dust atmospheric content and deposition flux close to the North-African coast where the impacts are expected to be the largest but where experimental stations are cruelly lacking, we use the MERRA-2 monthly reanalysis data of the 1980-2018 period. We have extracted the dust optical depth (AOD(dust)), surface concentrations (C-dust), precipitations (Prcp), and deposition fluxes (F-dry, F-wet, and F-tot) of 14 areas (7 coastal and 7 offshore) regularly spaced from the Straights of Gibraltar in the west to Egypt and Cyprus in the east. The principal Component Analysis (PCA) shows that 86% of the variability of AOD(dust) can be explained by two factors only: F1 whose influence is dominant in the Central Mediterranean and peaks in spring, and F2 whose importance decreases from Morocco to Egypt and peaks in summer. The variability of the surface concentration is more complex than that of the optical depth. AOD(dust) and C-dust are maximal downwind of the main Algerian and Libyan dust sources, which is to say on and off the coast of the Central Mediterranean (south-Tunisia, Libya, Malta...). In spite of the climate change already underway, no long-term trend of C-dust or AOD(dust) can yet be evidenced for any of the 14 areas between 1980 and 2018. Along the coast of the eastern basin, the low precipitations (from 6.1 to 10.5 mm month(-1) on average) explain that dry deposition accounts for a significant (45-53%) proportion of the total deposition. Everywhere else, wet deposition dominates and particularly in the marine areas where it represents about 90% of the total. From 1980 to 2018, the monthly averaged F-tot did not increase significantly. It varies from 0.24 (eastern Egypt) to 0.63 gm(-2) month(-1) (south-Tunisia) along the North-African coast, and from 0.26 (Baleares) to 0.48 gm(-2) month(-1) (Malta) in the marine areas. Because of the spatial variability of the precipitations, the largest deposition fluxes do not necessarily coincide with the regions of largest atmospheric dust content.

Mineral dust aerosols, produced by wind erosion in arid regions and semi-arid surfaces, are important components of the atmosphere that affect the Earth radiative budget, atmospheric chemistry and biogeochemical cycles. Dust aerosol particles are composed of a complex mixture of various minerals, mainly clays, calcite, quartz, feldspars and iron oxides. The nature and the relative abundance of the minerals are key parameters to evaluate mineral dust environmental impacts. Strong limitations remain to quantify the mineralogical composition of dust particles, mainly due to the low mass of in-situ collected dust particle samples. In this study, an analytical method and X-Ray Diffraction (XRD) measurements are presented to quantify the mineralogical composition of low mass aerosol particle samples. The method is applied on reference minerals (illite, kaolinite and palygorskite) commonly present in desert dust aerosols, as well as on lab-generated dust aerosols from desert soils. XRD measurements of theses samples in rotation in a glass capillary are combined with the Rietveld refinement method. The results obtained are repeatable and confronted to theoretical values given in the literature for the reference minerals. This method allows us to quantify the mineralogical composition of low mass dust mineral samples with an unprecedented accuracy.

The first aim of this study is to document the variability of the elemental composition of the mineral dust collected along the Mediterranean coast in Central Tunisia. The second aim is to correlate this composition with the different source-areas from which the mineral dust (MD) originates. In all, 190 daily aerosol samples are analyzed by X-Ray Fluorescence (XRF), and the elemental composition of the mineral dust is obtained by subtracting the non-crustal share from the bulk composition. On the basis of the MD concentration, 149 samples are classified as corresponding to “moderate” (3 < MD < 25 μg m−3) dust-events, and 17 to “intense” (MD > 25 μg m−3) ones. By using a combination of MODIS satellite observations, HYSPLIT back-trajectory analysis, and dust emission simulations with the CHIMERE model, three geographical areas are identified as being at the origin of the intense events. From east to west, Area #1 corresponds to the south-east of Tunisia/west of Lybia region, Area #2 corresponds to the Algerian/Tunisian Border and contains the Chott El Jerid depression. Finally, Area #3 is in Central Algeria. Elemental ratios are commonly used to discuss the nature and origin of airborne particles. In good agreement with previous observations, the Ca/Al ratio is significantly larger in Area #1 than in Area #3 (2.4 ± 0.4 as compared to 1.3 ± 0.3). With values of 4.1 ± 0.8 and 2.8 ± 0.3 for Areas #1 and 3, respectively, a similar contrast is observed for the (Mg + Ca)/Fe ratio. In Area #2 that is at the origin of 5 of the 9 intense events and thus appears as being the most influential source-region for Central Tunisia, the Ca/Al ratio (2.8 ± 0.9) compares to that of Area #1 but (Mg + Ca)/Fe (7.3 ± 0.7) is significantly larger than in Areas #1 and 3. These differences of dust composition for the three source areas are confirmed by laboratory experiments in which mineral aerosols are generated using natural soils collected in the source regions and subsequently analyzed by XRF. These results do not only emphasize the strength of the link existing between the composition of the source soil and that of the aerosol generated from it, they also document the variability of the dust composition in the Central Mediterranean region and confirm the interest of using the Ca/Al and (Mg + Ca)/Fe ratios as tracers of the source areas.