BUSCADOR RECOLECTA

We focused this research on the composition of the organic aerosols transported in the two main airflows of the subtropical North Atlantic free troposphere: (i) the Saharan Air Layer - the warm, dry and dusty airstream that expands from North Africa to the Americas at subtropical and tropical latitudes - and (ii) the westerlies, which flow from North America over the North Atlantic at mid- and subtropical latitudes. We determined the inorganic compounds (secondary inorganic species and elemental composition), elemental carbon and the organic fraction (bulk organic carbon and organic speciation) present in the aerosol collected at Izaña Observatory, ∼2400m.a.s.l. on the island of Tenerife. The concentrations of all inorganic and almost all organic compounds were higher in the Saharan Air Layer than in the westerlies, with bulk organic matter concentrations within the range 0.02-4.0μ-3. In the Saharan Air Layer, the total aerosol population was by far dominated by dust (93% of bulk mass), which was mixed with secondary inorganic pollutants ( < 5%) and organic matter (∼1.5%). The chemical speciation of the organic aerosols (levoglucosan, dicarboxylic acids, saccharides, n-alkanes, hopanes, polycyclic aromatic hydrocarbons and those formed after oxidation of α-pinene and isoprene, determined by gas chromatography coupled with mass spectrometry) accounted for 15% of the bulk organic matter (determined by the thermo-optical transmission technique); the most abundant organic compounds were saccharides (associated with surface soils), secondary organic aerosols linked to oxidation of biogenic isoprene (SOA ISO) and dicarboxylic acids (linked to several primary sources and SOA). When the Saharan Air Layer shifted southward, Izaña was within the westerlies stream and organic matter accounted for 28% of the bulk mass of aerosols. In the westerlies, the organic aerosol species determined accounted for 64% of the bulk organic matter, with SOA ISO and dicarboxylic acids being the most abundant; the highest concentration of organic matter (3.6μ-3) and of some organic species (e.g. levoglucosan and some dicarboxylic acids) were associated with biomass burning linked to a fire in North America. In the Saharan Air Layer, the correlation found between SOA ISO and nitrate suggests a large-scale impact of enhancement of the formation rate of secondary organic aerosols due to interaction with anthropogenic NO emissions. © 2017 Author(s)., This study was performed within the
context of the projects AEROATLAN (CGL2015-66299-P;
MINECO/FEDER) and TEAPARTICLE (CGL2011-29621),
supported by the Ministry of Economy and Competitiveness of
Spain and the European Regional Development Fund (ERDF).
The authors acknowledge the NOAA Air Resources Laboratory
(ARL) for the provision of the HYSPLIT back-trajectories used
in this publication. The excellent work performed by the staff of
the Atmospheric Research Centre (Concepción Bayo, Cándida
Hernández, Fernando de Ory, Virgilio Carreño, Rubén del Campo
and SIELTEC Canarias) and of the Institute of Environmental
Assessment and Water Research (Roser Chaler, Dori Fanjul, and
Bibiano Hortelano) is appreciated. M. Isabel García acknowledges
the grant of the Canarian Agency for Research, Innovation and
Information Society (ACIISI), co-funded by the European Social
Funds. Measurements at Izaña Observatory are performed within
the context Global Atmospheric Watch networks with the financial
support of the State Meteorological Agency of Spain (AEMET)., Peer reviewed

In the AEROATLAN project we study the composition of aerosols collected over ∼ 5 years at Izaña Observatory (located at ∼ 2400ma.s.l. in Tenerife, the Canary Islands) under the prevailing westerly airflows typical of the North Atlantic free troposphere at subtropical latitudes and midlatitudes. Mass concentrations of sub-10μm aerosols (PM10) carried by westerly winds to Izaña, after transatlantic transport, are typically within the range 1.2 and 4.2μgmĝ'3 (20th and 80th percentiles). The main contributors to background levels of aerosols (PM10 within the 1st-50th percentiles Combining double low line 0.15-2.54μgmĝ'3) are North American dust (53%), non-sea-salt sulfate (14%) and organic matter (18%). High PM10 events (75th-95th percentiles ≈ 4.0-9.0μgmĝ'3) are prompted by dust (56%), organic matter (24%) and non-sea-salt sulfate (9%). These aerosol components experience a seasonal evolution explained by (i) their spatial distribution in North America and (ii) the seasonal shift of the North American outflow, which migrates from low latitudes in winter (∼ 32°N, January-March) to high latitudes in summer (∼ 52°N, August-September). The westerlies carry maximum loads of non-sea-salt sulfate, ammonium and organic matter in spring (March-May), of North American dust from midwinter to mid-spring (February-May) and of elemental carbon in summer (August-September). Our results suggest that a significant fraction of organic aerosols may be linked to sources other than combustion (e.g. biogenic); further studies are necessary for this topic. The present study suggests that long-term evolution of the aerosol composition in the North Atlantic free troposphere will be influenced by air quality policies and the use of soils (potential dust emitter) in North America. © The Author(s) 2017., This study is part of the project AEROATLAN (CGL2015-66299-P), funded by the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund (ERDF). The long-term records of the GAW
aerosol programme are also funded by AEMET. M. Isabel García
acknowledges the grant of the Canarian Agency for Research,
Innovation and Information Society (ACIISI) co-funded by the
European Social Funds. The authors gratefully acknowledge the
NOAA/ESRL Physical Sciences Division for the provision of the
NCAR/NCEP reanalysis; NILU for providing FLEXTRA backtrajectories based on meteorological data provided from ECMWF
(European Centre for Medium Range Weather Forecast); the BSC
(Barcelona Supercomputing Centre) for providing DREAM8b
model; the Oak Ridge National Laboratory (ORNL) Distributed
Active Archive Centre (DAAC), part of the NASA Earth Observing
System Data and Information System (EOSDIS), for providing
the Global Fire Emissions Database; the GES-DISC Interactive
Online Visualization ANd aNalysis Infrastructure (Giovanni), part
of the NASA’s Goddard Earth Science (GES) Data and Information
Service Centre (DISC), for the OMI AI data set; and the Storm
Prediction Centre, part of the NOAA National Weather service, for
providing the Severe Weather Database Files for US tornadoes.
We also thank to Juan José Bustos for the calculation of the
back-trajectories, Javier López-Solano for his assistance with the
Aerosol Index data processing and Yvonne Boose for providing the
picture of the Saharan Air Layer conditions. The excellent work
performed by the staff of Izaña Observatory (Concepción Bayo,
Cándida Hernández, Fernando de Ory, Virgilio Carreño, Rubén del
Campo and SIELTEC Canarias) is appreciated., Peer reviewed

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 <01-aerosols 2010, Sheet <02-NAFDI 2010>, Sheet <03-aerosols 2013>, Sheet <04-NAFDI 2013>., Peer reviewed

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., No

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 reviewed