Rapid changes of dust geochemistry in the Saharan Air Layer linked to sources and meteorology

Based at Izaña Observatory (∼2400 m a.s.l. in Tenerife), we performed 1-h resolution measurements of elemental composition of dust in the Saharan Air Layer (SAL) and studied the variability of the ratios of these elements to aluminium (elemental ratios). In a period (∼1 week) of continuous dust presence (50–200 μg/m3), we observed rapid variations of dust composition; some elemental ratios changed by a factor 2 in a few (5–8) hours. The lowest variability (Normalized Variability Range, %) was found for Si/Al (9%) and Fe/Al (9%), followed by the ratios of K, Ti, Mg, Mn, Ca and Sr to Al (20–80%), and the highest for S/Al, Na/Al and Cl/Al (110–160%) and a number of trace metals (Cr, Cu, Ni, Zn, Zr) and Br (>200%). This variability was induced by the alternating impacts of three of the large North African dust sources: NE Algeria (rich in evaporite minerals bearing Ca, S, Sr, K and Mg and in illite mineral), Western Sahara to Bechar region (containing Na, S and Cl rich Yermosol soils) and SW Sahara – Western Sahel (rich in illite and hematite). We traced the variability in large-scale meteorology using the so-called North African Dipole Intensity (NAFDI: strength of the subtropical Saharan high -Morocco-to the monsoon tropical low -Nigeria-). The mobilization of dust from the different sources was associated with westward propagating Harmattan pulses linked to the change of phase of NAFDI (- to +), the associated westward shifts of the Saharan Heat Low and convective monsoon inflow. We found a correlation between dust composition in the SAL and NAFDI: moderate NAFDI values (0 to +2.5) were associated with Ca, K, Na, Mg and S rich dust linked to dust sources in NE Algeria, whereas higher NAFDI values (+2.5 to +4) were linked to Fe rich dust (Ca, Na and S depleted) linked to dust sources in SW Sahara – Western Sahel. The results of this study also show that some trace elements (Br, Cr, Ni, Zn and Zr) are influenced by industrial emissions into North Africa.This study was performed within the project VARDUST-SAL (PGC 2018-099166-B-I00), funded by the Ministry of Science, Research and Innovation of Spain, the Research State Agency of Spain and the European Regional Development Fund (ERDF)

Impact of the 2021 La Palma volcanic eruption on air quality: Insights from a multidisciplinary approach

The La Palma 2021 volcanic eruption was the first subaerial eruption in a 50-year period in the Canary Islands (Spain), emitting ~1.8 Tg of sulphur dioxide (SO2) into the troposphere over nearly 3 months (19 September-13 December 2021), exceeding the total anthropogenic SO2 emitted from the 27 European Union countries in 2019. We conducted a comprehensive evaluation of the impact of the 2021 volcanic eruption on air quality (SO2, PM10 and PM2.5 concentrations) utilising a multidisciplinary approach, combining ground and satellite-based measurements with height-resolved aerosol and meteorological information. High concentrations of SO2, PM10 and PM2.5 were observed in La Palma (hourly mean SO2 up to ~2600 μg m−3 and also sporadically at ~140 km distance on the island of Tenerife (> 7700 μg m−3) in the free troposphere. PM10 and PM2.5 daily mean concentrations in La Palma peaked at ~380 and 60 μg m−3. Volcanic aerosols and desert dust both impacted the lower troposphere in a similar height range (~ 0–6 km) during the eruption, providing a unique opportunity to study the combined effect of both natural phenomena. The impact of the 2021 volcanic eruption on SO2 and PM concentrations was strongly influenced by the magnitude of the volcanic emissions, the injection height, the vertical stratification of the atmosphere and its seasonal dynamics. Mean daily SO2 concentrations increased during the eruption, from 38 μg m−3 (Phase I) to 92 μg m−3 (Phase II), showing an opposite temporal trend to mean daily SO2 emissions, which decreased from 34 kt (Phase I) to 7 kt (Phase II). The results of this study are relevant for emergency preparedness in all international areas at risk of volcanic eruptions; a multidisciplinary approach is key to understand the processes by which volcanic eruptions affect air quality and to mitigate and minimise impacts on the population.The authors also acknowledge the support from ACTRIS and ACTRIS-Spain, the Spanish Ministry of Science and Innovation and the support from the European Union H2020 program through the following projects (PID2019-104205GB-C21/AEI/10.13039/501100011033, EQC2018-004686-P, PID2019-103886RB-I00/AEI/10.13039/501100011033 and PID2020-521-118793GA-I00) and programs (GA No. 654109, 778349, 871115, 101008004 and 101086690). Research activities of the CSIC staff during the eruption were funded by CSIC through the CSIC-PIE project with ID numbers PIE20223PAL009 and PIE20223PAL013 (Real Decreto 1078/2021, de 7 de diciembre). Part of this study was performed within the framework of the project AERO-EXTREME (PID2021-125669NB-I00) funded by the Spanish State Research Agency (AEI) and ERDF funds

Transects and vertical profiles of PMx aerosols in Santo Antão and São Vicente, Cape Verde, in October 2019 - dataset

This file contains data of atmospheric aerosols particulate matter smaller than 10, 2.5 and 1 micron (PM10, PM2.5 and PM1) measured: -in vertical profiles, in sheets P1 to P3, -transects T1 to T3, -in ambient air at Porto Novo, Cova de Paul and Ribeira Grande each sheet contains the time, hour, latitude, longitude, temperature and humidity. Details on the methods used is described in: Sergio Rodríguez & Jessica López-Darias. Dust and tropical PMx aerosols in Cape Verde: sources, vertical distribution and stratified transport from North Africa. Atmospheric Research, 2021. DOI: xxxThis file contains data of aerosol PMx concentrations measured in Cape Verde (islands of Santo Antão and São Vicente) in October 2019 in the frame of the project VARDUSTSAL (PGC2018-099166-B-100; IP: Sergio Rodríguez) funded by the State Research Agency, the Ministry of Science, Innovation and Universities of Spain and the European Regional Development Fund. Data of vertical distributions and transfects of PMx near sources and in ambient air (including remote conditinos) are reported. Details are provided in Rodríguez & López-Darias (2021).Peer reviewe

Dust and tropical PMx aerosols in Cape Verde: Sources, vertical distributions and stratified transport from North Africa

We investigated the sources and processes affecting the vertical distribution of tropical PMx aerosols (particulate matter -PM- smaller than 10, 2.5 and 1 μm, PM10, PM2.5 and PM1, respectively) in the low troposphere of Santo Antão and São Vicente islands, in Cape Verde archipelago, a region where a better understanding of aerosols is needed due to their involvement in tropical meteorology and their impact on air quality, ocean and climate. We found that local sources had a low-scale impact. From transect measurements at ground level, we found that PMx levels were predominantly low, except near to PMx sources, where distinctive PM1 / PM2.5 ratios were measured, linked to vehicle exhaust (0.96), biomass burning (0.67) and Cape Verdean dust (0.36) emissions. The depth of the marine boundary layer (MBL) and the vertical distributions of PMx showed wide variability prompted by meteorological conditions. The trade winds prevailed in the MBL, whereas other airflows were situated above it: North-Atlantic, African easterly airflow and Saharan Air Layer. Under North-Atlantic airflow conditions, the MBL extended to 1400 m above sea level (m.a.s.l.). Above this altitude, PMx concentrations decreased quickly (< 3 μg/m3) due to the free troposphere conditions. Under Saharan dust conditions, the MBL was confined to just 70 m.a.s.l., whereas a complex dust stratification was observed above, characterized by alternating dry air layers with high dust loads (PM10 ~ 100 μg/m3) and more humid air layers with lower aerosol loads (PM10 ~ 40 μg/m3). Within the dry easterly African airflow occurring above the marine stratocumulus typical of the MBL top (placed at 500 m.a.s.l.), we detected layers enriched in hydrophilic aerosols (PM10: ~ 8 μg/m3). These were imbedded in relatively humid air (RH ~48%), probably linked to secondary aerosol formation by in-cloud processes in the marine stratocumulus situated below. We found that PMx transport from North Africa, both under dust and dust-free conditions, is associated with complex vertical stratifications, even within the dusty Saharan Air Layer.This study was performed within the framework of the project VARDUSTSAL (PGC2018-099166-B-I00), funded by the Agencia Estatal de Investigación / State Research Agency of Spain, the Ministry of Science, Innovation and Universities of Spain and the European Regional Development Fund (ERDF). JLD is awarded with an Agustín de Bethencourt postdoctoral contract funded by the Cabildo de Tenerife. The manuscript was revised by Guido Jones, currently funded by the Cabildo de Tenerife, under the TFinnova programme supported by MEDI and FDCAN funds.Peer reviewe

Estudio sobre la meteorología, niveles y composición de las partículas en suspensión durante la SuperCalima de febrero de 2020 en Canarias – base de datos de composición química

Sergio Rodríguez Jesús de la Rosa y Jessica López-Darias. Base de datos del Estudio sobre la meteorología, niveles y composición de las partículas en suspensión durante la SuperCalima de febrero de 2020 en Canarias. Informe del CSIC, la Universidad e Huelva y la Universidad de La Laguna para la Consejería de Transición Ecológica, Lucha contra el Cambio Climático y Planificación Territorial del Gobierno de Canarias.This dataset contains observations of chemical composition of PM10 airborne particles during February 2020 at El Rio site (Tenerife, Canary Islands, 28.145140oN, 16.523732oW, 500 meters above sea level), including the period 22-24 February, when the Canary Islands were impacted by a severe dust storm. Elemental composition was determined by IPC-OES and IPC-MS (after acid HNO3 : HF : HClO4 digestion), ions and cations by ion chromatography (after leaching in ultrasound bath) and elemental and organic carbon by Thermo-Optical Transmittance.Estudio financiado por el Gobierno de Canarias. Consejería de Transición Ecológica, Lucha contra el Cambio Climático y Planificación Territorial.Peer reviewe

African desert dust influences migrations and fisheries of the Atlantic skipjack-tuna

Atmospheric deposition of desert dust and other aerosols influence on the open ocean ecosystem and climate. These aerosols provide iron, phosphorus and bio-essential trace elements, which affect the composition and growth of phytoplankton, generating new organic matter that is distributed across the food web. Although this process has an impact on upper trophic levels and fisheries, direct evidence is lacking. Skipjack tropical tuna (Katsuwonus pelamis) is the most important commercial tuna in the Atlantic, main stocks occur in the tropical and subtropical North-East Atlantic. We found that the migrations and fisheries of skipjack are connected to Saharan dust variability. From boreal winter to summer, skipjack performs an Atlantic-Saharan migration, from equatorial (0-5°N) to subtropical waters of the North-East Atlantic (regularly reaching open waters off Mauritania ∼20°N and the Canary Islands ∼28°N), tracking the seasonal shift of dust deposition in the North-East Atlantic. The observed long-term associations of skipjack catch with the seasonal cycles, anomalies and meridional variability of dust over the North-East Atlantic, shows that along the year skipjack catches mainly occur in waters affected by massive dust deposition linked (i) to dust wet deposition in tropical waters and (ii) to dust dry deposition in the Saharan desert-dust outflow. Atmospheric deposition of dust in the open ocean and in upwelling waters contributes to support zooplankton-rich areas, which are optimal for feeding small fish, molluscs and cephalopods, and suitable for feeding large predators, as skipjacks, where they are caught in abundance. The most important fishing area of Atlantic skipjack tuna is located off North West Africa in the waters affected by massive dust deposition that underly the dusty airstream from the North Africa desert. The role of dust as fertilizing and supporter of phytoplankton and zooplankton rich areas also has implications for other species of fishing interest, including other tropical tuna (e.g. bigeye and yellowfin), which are often exploited simultaneously with skipjack by the same fisheries. As far as we know this is the first study showing the connexions between atmospheric inputs of desert dust to ocean and the migrations and fisheries of marine species. These results have important implications on our understanding on the influence of atmospheric dust on marine ecosystems and on the management of fisheries.This study is part of the project VARDUSTSAL (PGC2018-099166-B-I00), funded by the Agencia Estatal de Investigación/State Research Agency of Spain, the Ministry of Science, Innovation and Universities of Spain and the European Regional Development Fund (ERDF). JLD was awarded with an Agustín de Bethencourt postdoctoral contract funded by the Cabildo de Tenerife. The manuscript was revised by Guido Jones, currently funded by the Cabildo de Tenerife, under the TFinnova programme supported by MEDI and FDCAN funds. Skipjack catch data were provided by the Government of the Canary Islands and the International Commission for the Conservation of Atlantic Tunas. Data of MERRA-2 and NOBMS models and satellite MODIS observations were accessed by NASA - Giovanni platform.Peer reviewe

Tracking the changes of iron solubility and air pollutants traces as African dust transits the Atlantic in the Saharan dust outbreaks

We studied the solubility, in real sea water, of iron present in the African dust outbreaks that traverse the Atlantic. Based on measurements of soluble iron (sFe) and aerosol chemistry, we found iron solubilities within the range of 0.4–1.8% in Tenerife, 0.4–3.1% in Barbados and 1.6–12% in Miami. We apportioned the concentrations of sFe between the three sources and processes that we identified: (1) dust, (2) heavy fuel oil combustion emissions, associated with an excess of vanadium and nickel, and (3) atmospheric processing, which is influenced by acidic pollutants. We tracked the propagation of the dust-front of the African dust outbreaks across the Atlantic, which are associated with dust peak events at the impacting sites. During the westward transport across the Atlantic, the contribution to sFe from dust decreased (63%, 42% and 11% in Tenerife, Barbados and Miami, respectively), whereas the contribution due to atmospheric processing increased (26%, 44% and 80% in Tenerife, Barbados and Miami, respectively). In these Saharan-dust outbreaks, the concentrations of sFe due to heavy fuel oil combustion were significantly lower (mostly < 5 ng/m3) than those in the polluted marine atmosphere (10–200 ng/m3). The overall results are consistent with the idea that the mixing of dust with acid pollutants increases the solubility of iron during the African-dust outbreaks that traverse the Atlantic.The project AEROATLAN (CGL 2015-66299-P), is funded by the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund. M.I.G. was awarded with a grant provided by the Canarian Agency for Research, Innovation and Information Society, co-funded by the European Social Funds. JLD is awarded with a posdoc contract Agustín de Bethencourt, funded by the Program Fomento de Transferencia del Conocimiento of the Cabildo de Tenerife.Peer reviewe

Aerosol chemistry and soluble iron in Tenerife, Barbados and Miami in summer 2015 - dataset

This dataset contains data of aerosol chemistry and soluble iron collected in Tenerife, Barbados and Miami in summer 2015 within the frame of the project AEROATLAN (reference CGL2015-66299-P), funded by the Minister of Economy and Competitiveness of Spain and by the European Regional Development Fund.This dataset was obtained within the frame of the project AEROATLAN (reference CGL2015-66299-P), funded by the Minister of Economy and Competitiveness of Spain and by the European Regional Development Fund.N

High temporal resolution measurements of dust composition in the Saharan Air Layer - dataset

This dataset contains observations of elemental composition of atmospheric aerosols performed at Izaña Observatory, located (28◦18’N, 16◦29′W) at 2367 m.a.s.l. (meters above sea level), in Tenerife island. The measurements were performed with the objective of studying the variability of Saharan dust composition. The samples were analyzed with the technique PIXE (Particle Induced X ray Emission) at the Istituto Nazionale di Fisica Nucleare (INFN) at Florence (Italy). The variability of dust composition is compared with the variability of large-scale meteorology traced with the North African dipole Intensity (NAFDI), i.e. the differences of the anomaly of the geopotential heights at 700hPa between the subtropic (Morocco) and the tropic (Niger) in North Africa.This dataset was obtained within the frame of the projects POLLINDUST (reference CGL2011-26259) and AEROATLAN (reference CGL2015-66299-P), funded by the Minister of Economy and Competitiveness of Spain and by the European Regional Development Fund.Sheet , Sheet , Sheet .Peer reviewe

Impact of Saharan dust exposure on airway inflammation in patients with ischemic heart disease

Epidemiological studies found that increases in the concentrations of airborne particulate matter (PM) smaller than 10 microns diameter (PM10) in the ambient air due to desert dust outbreaks contribute to global burden of diseases, primarily as a result of increased risk of cardiovascular morbidity and mortality. No studies have investigated the possible association between desert dust inhalation and airway inflammation in patients with ischemic heart disease (IHD). Induced sputum was collected in 38 patients and analysed to determine markers of airway inflammation (Transforming Growth Factor-β1 [TGF-β1] and hydroxyproline) concentrations. For the purpose of the investigation, PM10 and reactive gases concentrations measured in the European Air Quality Network implemented in the Canary Islands were also used. We identified Saharan desert dust using meteorology and dust models. Patients affected by smoking, chronic obstructive pulmonary disease (COPD), asthma, pulmonary abnormalities, acute bronchial or pulmonary disease were excluded. The median of age of patients was 64.71 years (56.35–71.54) and 14 (38.84%) of them were women. TGF-β1 and hydroxyproline in sputum were highly associated to PM10 inhalation from the Saharan desert. According to a regression model, an increase of 1 µg/m3 of PM10 concentrations due to desert dust, results in an increase of 3.84 pg/gwt of TGF-β1 (R2 adjusted= 89.69%) and of 0.80 μg/gwt of hydroxyproline (R2 adjusted= 85.28%) in the sputum of patients. The results of this study indicate that the exposure to high PM10 concentrations due to Saharan dust events are associated with intense inflammatory reaction in the airway mucosae of IHD-patients.Peer reviewe