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Chemical Composition of the Saharan Dust and of the Fine Fraction of Saharan Soils Along With Data From Literature a
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1] Two types of samples were used to chemically characterize the Saharan end-member: fine fractions of surface soil samples collected in Northern Africa and particulate phases of typical Saharan rains. Since the concentrations measured in the particulate phase of the Saharan rains were corrected from the dissolution losses in rainwater, these parti...
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Context 1
... The concentrations of Al, Fe, Pb, and P are reported in Table 2. For the particulate phase of the Saharan rains the concentrations were recalculated, taking into account the loss of the particulate mass due to the dissolution of CaCO 3 . ...
Context 2
... phosphate was not measured in the rainwater, the amount of phosphorus that had dissolved from the partic- ulate phase was estimated from the total particle load collected for each rain. Using the relationships [% PO 4 3À dissolved = F (particles load)] established experimentally by Ridame and Guieu [2002], the total particulate phosphorus was recalculated (Table 2): up to 13% of the particulate phosphorus (including all the particulate forms of phospho- rus) had been dissolved in the rainwater. This type of correction was not applied for Al and Fe since the dis- solution of these metals remains very low in Saharan rain- water [Guieu and Thomas, 1996] and does not affect the total concentration. ...
Context 3
... this uncertainty, the lead concentrations in soils may be the most representative of the concentration in the Saharan end-member. Thus we assume that an average Table 2): Saharan soils, coarse fraction [Guieu and Thomas, 1996;Herut et al., 1999;Tomadin et al., 1984]; particulate phase of Saharan rains [Avila et al., 1998a;Coudé-Gaussen, 1982;Ganor and Foner, 1996;Bücher and Lucas, 1975;Bücher et al., 1983;Bücher, 1989;Guieu, 1991]; crust composition [Mason, 1982;Martin and Withfield, 1983;Taylor and McLennan, 1985;Wedepohl, 1995]. Table 3. Mean Concentrations (± 1 sigma) of Al, Fe, P, and Pb in the Saharan Dust and in the Saharan Soils, Along With Ratios Elt/(Fe or Al) a ...
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... Recent decades have seen an increase in atmospheric dust emissions due to the expansion of arid areas, the emergence of playas from shrinking lakes, land abandonment, changes in land use, soil disturbance, and wildfires (Dong et al., 2020;Moulin and Chiapello, 2006;Zhou et al., 2023). Dust deposition contributes essential trace elements as well as organic and inorganic nutrients to terrestrial and aquatic ecosystems (Guieu et al., 2002;Jickells et al., 2016). Specifically, dust deposition can enrich oligotrophic ecosystems by providing minerals rich in elements such as phosphorus (P) and iron (Fe) (Brahney et al., 2014;Mahowald et al., 2005). ...
... Consequently, primary production is low, particularly in the eastern part of the basin. Dust transport to the EMS mainly occurs in springearly summer and is a major source of new nitrogen and phosphate for the EMS (Guerzoni et al., 1999;Herut et al., 1999;Guieu, 2002), contributing~60% and~30% of the total nitrogen and phosphate supply, respectively (Krom et al., 2004). Several micro-and mesocosm experiments in the Mediterranean Sea have shown that Chla concentrations and primary production rates increase after dust addition (Herut et al., 2005;Ridame et al., 2014;Herut et al., 2016;Gazeau et al., 2021b), suggesting that dust input may indeed have a fertilizing effect. ...
To assess the effects of dust deposition on the strength of the biological pump in the Mediterranean Sea by acting as fertilizer and/or ballasting agent, we analyzed fluxes of mineral dust, particulate organic carbon (POC) and inorganic carbon (PIC), and source-specific lipid biomarkers (i.e., higher plant-derived long-chain fatty acids and phytoplankton-derived alkenones, C30 1,15 diols, and sterols) in sinking particles. Sinking particles were collected at ten-day intervals by a sediment-trap mooring deployed in the Ionian Basin from April 2017 to May 2018 at 2340 m water depth. High POC fluxes occur during summer, when surface ocean primary production is lowest due to thermal stratification. Notably, these high POC fluxes coincide with pulses of substantial dust deposition, suggesting that POC export is primarily driven by dust deposition and subsequent ballasting. However, the lipid composition, and thereby that of the phytoplankton community, differs between dust events. (Seasonal) variations in the properties of the deposited dust, presumably associated with its provenance, likely control the effect of dust deposition on phytoplankton response and export in the Ionian Basin. Although POC export is associated with dust deposition, the net effect of dust deposition on the biological pump is more ambiguous as not all dust events are associated with an increase in POC export, and most dust events are also associated with PIC export that has a counteracting effect on the biological pump. Multi-year time series of dust deposition and biogenic export are required to validate the seasonal variations in dust-driven export of biogenic material observed here, and to account for effects of interannual variations in dust fluxes and phytoplankton production on the strength of the biological pump.
... Thus, the nature of Fe in the dust can profoundly impact its dissolution rate in seawater, thereby influencing phytoplankton growth, productivity, and the overall functioning of the biological carbon pump in the SO (Deppeler and Davidson, 2017). Patagonian dust exhibits a distinct chemical composition, dominated by quartz, and crystallinity (grain size<5 mm) (Qu, 2016) compared to other desertic dusts like those from Sahara, characterized by a relatively high presence of illite and a central size class typically ranging between 10-20 mm (Molinaroli, 1996;Guieu et al., 2002;Laity, 2008). Moreover, the SO, where these particles settle, also features specific physical (cold temperature, mixed layer depth of 50-90 m) and biogeochemical (HNLC area, dominance of diatoms south of the Polar Front) characteristics compared to other oceans (De Broyer et al., 2014). ...
... Consequently, the discrepancy between our dissolution rate and other studies could primarily be attributed to the nature of the dust (whether it contains Fe in aluminosilicate, Fe-oxide, and amorphous Fe) and the variation in size class distribution. Saharan soils typically are composed of larger grain sizes, averaging around 10-20 μm (Guieu et al., 2002), which could potentially impede the dissolution process. However, the absence of a detailed mineralogical analysis of the dust used for the Saharan aerosol dissolution hampers a comprehensive understanding of the difference dissolution rate of Fe-dust. ...
Although the input of desert dust as a key source of trace metals in the Southern Ocean (SO) has been previously studied, the dissolution process of metals in surface waters, particularly iron (Fe), remain poorly understood. Given the crucial role of Fe in primary production and the biological carbon pump in the SO, we focused on experimental estimations of Fe dissolution from Patagonian dust, the primary natural dust source in the SO. Our study considered both current and projected future conditions, encompassing sea-surface warming, acidification, increased photosynthetically active radiation, and doubled dust inputs. Through controlled laboratory experiments using filtered SO seawater, conducted over 7 days, we assessed changes in particulate Fe (pFe) concentrations, Fe redox speciation (Fe(II)/Fe(III)), and in the mineralogy of Fe-bearing dust in abiotic condition. The predominant minerals in the dust included quartz and aluminosilicates, with silicon (Si), aluminum (Al), and Fe as the major elements. No significant alterations in the mineralogy and the elemental composition of the dust were recorded during the dissolution experiments, neither under present nor under projected future conditions. The particulate Fe(II)/Fe(III) ratio remained consistently at 0.25 during the experiments, unaffected by changed conditions. Consequently, changes in environmental conditions in the SO would therefore not significantly alter the mineralogy and redox speciation of pFe in the Patagonian dust. On the contrary, pFe exhibited a dissolution rate of 3.8% and 1.6% per day under present and future conditions, respectively. The environmental changes anticipated for 2100 in the SO will likely to result in a decrease in the dissolution rate of pFe. Thus, even though a doubling of dust input by 2100 is anticipated, it will unlikely provide significantly more dissolved Fe (dFe) in seawater in the SO. Consequently, the future intensification of Patagonian dust inputs may not alleviate the Fe limitation in the SO.
... In addition, the cross-border dust mass contains different types of aerosols (sea salt, sulfate, and organic carbons) from neighboring countries, and their deposition affects water sources. If the dust mass contains iron and aluminum, it increases the primary production of phytoplankton and stimulates growth [44,[71][72][73]. The positive cor- The AOTA value is 0.13, 0.12, 0.11, and 0.09 in Mahabad, Urmia, Tabriz, and Sarab, respectively (Figure 6a). ...
... In addition, the cross-border dust mass contains different types of aerosols (sea salt, sulfate, and organic carbons) from neighboring countries, and their deposition affects water sources. If the dust mass contains iron and aluminum, it increases the primary production of phytoplankton and stimulates growth [44,[71][72][73]. The positive correlation between dust and chlorophyll in Lake Urmia indicates the effect of dust-containing effective particles on increased chlorophyll in the lake [45]. ...
The living conditions in the Urmia Basin (northwestern Iran) face significant challenges due to dust events. This study investigates the spatial and temporal characteristics of dust phenomena in the Urmia Basin using MERRA-2 data and observational data from Tabriz, Urmia, Sarab, and Mahabad over a 30-year period (1990–2019). The findings reveal that despite several fluctuations, the annual number of dusty days increased from the 1990s to the 2010s in the Urmia Basin. The maximum number of dusty days was found to predominantly occur in May (spring) and October (autumn), driven by two distinct mechanisms. In early autumn, developing synoptic systems associated with increased wind speeds can cause dust emission from dry land sources. Consequently, an increase in dust wet deposition, precipitation, dust surface concentration, and the number of dusty days occurs in October. In contrast, a sharp decrease in precipitation from April to May leads to drying soil and dust emission in May. Among the studied cities, Tabriz experienced the highest number of dusty days (728) due to the combined effects of cross-border and local dust sources. The highest dust column density and dust dry deposition in the south and east of Urmia Lake indicate the impact of declining water levels, which resulted in a dry lakebed as the primary local dust source. The MERRA-2 spatial distribution reveals that dust surface concentration, and the number of dusty days decrease similarly from the southwest to the northeast of the Urmia Basin as the distance from cross-border dust sources increases. A positive correlation is observed between the number of dusty days and MEERA-2 data, including dust surface concentration, dust dry deposition, column mass dust, and total aerosol extinction, with coefficients of 0.74, 0.71, 0.69, and 0.68, respectively.
... In many mountain settings, dust size distributions straddle the informal boundaries commonly used to distinguish fine ('small') far-traveled dust from coarse ('large') dust more likely to be regionally sourced (Stuut et al 2009). Far-traveled material would be expected to geochemically homogenous due to mixing during transport, whereas more regionally derived dust should reflect the geology of specific source areas (Guieu et al 2002, Fitzgerald et al 2015. A central question in studies of mountain dust, therefore, is the relative importance of regionally sourced material with spatially varying properties, and fartraveled material that could be well-mixed and uniform over large regions. ...
Mountain environments are profoundly impacted by the deposition of mineral dust, yet the degree to which this material is far-traveled or intra-regional is typically unclear. This distinction is fundamental to model future changes in mountain geoecosystems resulting from climatic or anthropogenic forcing in dust source regions. We address this question with a network of 17 passive dust samplers installed in primarily mountain locations in Utah, Nevada, and Idaho between October, 2020 and October 2021. For each collector, the dust deposition rate was calculated, and the physical and chemical properties of the dust were constrained. Results were combined with backward trajectory modeling to identify the geologic characteristics of the area over which air passed most frequently in route to each collector (the “hot spot”). Dust properties differ significantly between collectors, hot spots for many collectors are spatially discrete, and the dominant geologies in the hot spots corresponding to each collector vary considerably. These results support the hypothesis that the majority of the dust deposited in the areas we studied is sourced from arid lowlands in the surrounding region.
... Observation, SYNOP) and empirical equations that relate these data to PM dust concentrations (e.g., Camino et al., 2015). Climatologies based on human-observer reports of dust storms in SYNOPs are discussed in several studies (e.g., Mahowald et al., 2010;Cowie et al., 2014;Klose et al., 2010;O'Loingsigh et al., 2010), along with several issues related to the recording and archiving of SYNOP dust codes Measurements of dust deposition fluxes have been obtained directly by weighting the deposited mass on filters or indirectly from aluminum deposition measurements (e.g., Guieu et al., 2002;Anderson et al., 2016;Laurent et al., 2015;Stuut et al., 2022) or by measuring atmospheric aerosol concentrations and assuming the dust dry deposition velocity and scavenging ratio (e.g., Le Bolloch et al., 1996). Although there have been many studies that characterize the physical and chemical composition of deposited dust, only a few of them have dealt with synthesizing these observations (e.g., Lawrence and Neff, 2009). ...
Mineral dust produced by wind erosion of arid and semi-arid surfaces is a major component of atmospheric aerosol that affects climate, weather, ecosystems, and socio-economic 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 forecasts 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 non-scientific stakeholders.
... This work is also mentioned that the historical main peaks of PM 2.5 in the state of Texas, attributed to Sahara dust, appear in the month of July, these peaks were identified by multiangle imaging spectroradiometer (MIRS) and total ozone spectrometer (TOMS) (Husar 2004;Wang 2015). In another report, he is proposed a new technique to quantify the composition of Saharan dust in the western Mediterranean Sea based on its Al or Fe composition (Guieu et al. 2002). In other work, it is reported that the chemical signature of the Sahara dust can change depending on wet or dry atmospheric conditions, identifying the main existence of sulfates and nitrates under wet conditions and Ca 2+ under dry conditions (Morales-Baquero et al. 2013). ...
... However, a clear difference in composition is identified in comparison with the samples obtained during the free day of S.D. In comparison with free days S.D., the particles influenced by the Saharan dust show a huge increase in Al 2 O 3 as well as SO 3 . According to the previous literature, the Saharan dust which have been transported for long distance shown appreciable content of Al 2 O 3 as it is observed in Fig. 6d and e (Husar 2004;Guieu et al. 2002). The significative increase in SO 3 in these samples is attributed to the sulfate covering previously reported in the literature which is attributed to the interactions between SO 3 and the PM 2.5 (Husar 2004;Vasilatou et al. 2017). ...
... According to the previous literature, it is reported that Fe is found to be the element with the more significant seasonal variability, displaying much higher concentrations during cold period with values of 15.93 ng m −3 but only 4.43 ng m −3 on warm periods during a sampling campaign carried out on a suburban station in Athens, Greece (Vasilatou et al. 2017). Considering this report, the behavior of the Fe concentration in Monterrey Mexico can be different from than previous reports (Guieu et al. 2002;Morales-Baquero et al. 2013). It is worth mentioning that the sampling campaign of our work was carried out in the month of July (warm period) during which, according to the literature, a decrease in the Fe content is observed. ...
In this work, the influence of Saharan dust (S.D.) on the physicochemical properties of the PM2.5 in the Monterrey Metropolitan Area in Mexico is studied. PM2.5 sampling was carried out in a strategic sampling point during the alert peak of Saharan dust in July 2021. Additional samples were taken during the same weather season for comparison purposes. The characterization of the elemental composition in PM2.5 was carried out by FRX and EDS. The crystalline phases and the morphology were investigated by XRD and SEM, respectively. Organic matter was analyzed by TGA. Results revealed that S.D. contributes to the increase of > 22% of PM2.5 of the MMA. This increase in PM2.5concentration comes together with the increase of the elemental concentration of S and Al in 13 and 35 wt% (FRX) respectively, as calcium sulfates and aluminum oxides. A decrease in the Fe content of S.D. is attributed to the warm season and/or the long distance from the original source. In addition, the arrival of the Saharan dust decreases approximately 10% the amount of organic matter in PM2.5 samples as well as the particle size distribution from 0.660 to 0.469 μm with significant changes in the particle morphology and in the crystalline compounds. During the free days of Saharan dust in the MMA, the chemical composition of PM2.5 is associated with crustal suspended particles as well as burning fuels and industrial activities emissions located near the sampling point. Zn could require more attention due to its possible inhalation risk.
... Fe/Al, TiO 2 /Al 2 O 3 , Na/K and Ti/Zr were similar in the different soil and parent material samples; for example, the Fe/Al ratio in the studied soil horizons was between 0.25 and 0.45 with the highest values in cluster 3 (samples clustered with PL and SD); the ratio in SD collected above the Tyrrhenian Sea had a Fe/Al ratio between 0.39 and 0.8 (Guieu et al., 2002;Moreno et al., 2006;Nava et al., 2012;Ridame et al., 1999). R 2 O 3 /TiO 2 was highest in DolSi, followed by Rendzic Leptosols and Phaeozems; all other samples could not be separated into recognizable groups. ...
Very different soil types occur across a few tens of meters on dolostone, in a never glaciated karst landscape in the Lombard Pre-Alps (Selvino, Italy). This substrate is locally enriched in well-crystallized sand-grained quartz. The quartz content is responsible for the localized genesis of Podzols. Other soil types observed in the area include strongly rubified (Terra Rossa) horizons (paleosols), preserved in the most protected dolostone cracks. Non-rubified Luvisols and Cambisols were observed in karst dry valleys and dolines while Rendzic Leptosols/ Phaeozems were common on the steepest slopes. Such a variety of soils was explained assuming different parent materials (dolostone, silica-rich dolostone, with different amounts of aeolian inputs, ascertained using textural properties, mineralogy, micromorphology, total element composition, mass balance calculations, rare earth elements , and stable elements. Many soils were highly polycyclic, with different layers associated to different parent materials and characterized by different pedogenic processes evidencing different ages. We were thus able to distinguish the horizons mainly developed from the dissolution of the dolostone from those formed in Pleistocene loess. The geochemistry of all surface soil horizons, including Podzols and Rendzic Leptosols/ Phaeozems, apparently formed from pure or quartz-rich dolostone dissolution, has been influenced by recent aeolian additions (likely Saharan dust), with deeply modified effects according to different pedogenetic processes acting locally. Saharan dust, in fact, significantly increased metal and rare earth elements contents compared to the substrate, also in the youngest and least weathered soil types.
... Planktonic food webs are structured by phytoplanktonic communities and carbon fluxes are controlled by a large microbial loop (Uitz et al., 2006;Hunt et al., 2017;Mayot et al., 2017;Leblanc et al., 2018;Salhi et al., 2018;Ramírez-Romero et al., 2020). However, the Mediterranean Sea is under both natural and anthropogenic pressure, because its waters are enriched by the deposition of atmospheric particles from large plumes of Saharan dust (Guieu et al., 2002) and by the increasingly intensive anthropogenic activities of its 22 bordering countries (Grousset et al., 1995;Radakovich et al., 2008;Heimbürger et al., 2010;Chifflet et al., 2019;Migon et al., 2020). In this context, plankton could be a key agent in the transfer of metals and metalloids in marine food webs (Cossa and Coquery, 2005;Chouvelon et al., 2019). ...
Particle-size classes (7 fractions from 0.8 to 2000 μm) were collected in the deep chlorophyll maximum along a Mediterranean transect including the northern coastal zone (bays of Toulon and Marseilles, France), the offshore zone (near the North Balearic Thermal Front), and the southern coastal zone (Gulf of Gabès, Tunisia). Concentrations of biotic metals and metalloids (As, Cd, Cr, Cu, Fe, Mn, Ni, Sb, V, Zn) bound to living or dead organisms and faecal pellets were assessed by phosphorus normalisation. Biotic metals and metalloids concentrations (except Cr, Mn, and V) were higher in the offshore zone than in the coastal zones. In addition, biotic Sb and V concentrations appeared to be affected by atmospheric deposition, and biotic Cr concentrations appeared to be affected by local anthropogenic inputs. Essential elements (Cd, Cu, Fe, Mn, Ni, V, Zn) were very likely controlled both by the metabolic activity of certain organisms (nanoeukaryotes, copepods) and trophic structure. In the northern coastal zone, biomagnification of essential elements was controlled by copepods activities. In the offshore zone, metals and metalloids were not biomagnified probably due to homeostasis regulatory processes in organisms. In the southern coastal zone, biomagnification of As, Cu, Cr, Sb could probably induce specific effects within the planktonic network.
... The Mediterranean Sea is a semi-enclosed sea that covers ~0.7 % of the total ocean surface area (~0.25 % by volume), contains 4 to 18 % of the world's marine diversity (Bianchi and Morri, 2000;UNEP/MAP-RAC-SPA, 2008) and is characterized by oligotrophic conditions due to its low content in nutrient (The MerMex Group, 2011;Marañón et al., 2021). The Mediterranean Sea is subject to natural and anthropogenic exogenous chemical substances coming from rivers, effluents and atmospheric deposition (Guieu et al., 2002;Heimbürger et al., 2010Heimbürger et al., , 2011Pey et al., 2010;Llamas-Dios et al., 2021;Desboeufs et al., 2022). Important changes have been observed in recent decades in small pelagic fish populations of the northwestern Mediterranean Sea related to various environmental factors (Coll et al., 2019). ...
This study uses Cu and Zn isotopic compositions as proxies of sources and metal transfers in the planktonic food webs from the Mediterranean Sea. Plankton was collected in spring 2019 in the deep chlorophyll maximum (DCM) along a North-South transect including coastal and offshore zones (MERITE-HIPPOCAMPE campaign). δ⁶⁵Cu and δ⁶⁶Zn were determined on four planktonic size fractions from 60 to 2000 μm. Combined δ⁶⁵Cu and δ⁶⁶Zn with geochemical tracers (Ti, particulate organic phosphorus) showed that geogenic particles were ubiquitous with plankton assemblages. The δ¹⁵N ecological tracer showed that planktonic food web was enriched in heavy isotopes of Cu and Zn in the higher trophic levels. δ⁶⁵Cu were correlated with picoplankton in the offshore zone, and with zooplankton in the southern coastal zone. Firmicutes bacteria were found correlated with δ⁶⁶Zn in northern and southern coastal zones suggesting decomposition of particulate matter at the DCM. These findings suggest that biogeochemical process may impact Cu and Zn isotopy in the planktonic community.
