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Recent research has convincingly shown the advantages of combining environmental magnetism and geochemical analyses for the proxy estimation of anthropogenic pollution due to their atmospheric deposition in local environments. Few studies have also focused on anthropogenic particles deposited on snow. However, papers reporting on Sahara dust particles deposited on snow in central Europe and which involve magnetic methods are missing. To the best of our knowledge, this is the first study investigating the magnetic features of the SDE recorded in snowfall in this part of Europe (i.e. Poland). Our aim was to provide the magnetic characteristics and chemical elemental compositions of a snow horizon containing Saharan dust deposited near the Polish Jakuszyce meteorological station during a snowfall event that occurred from the 1st to the February 7, 2021. Samples of snow with and without Saharan dust were analysed with respect to iron oxide contents (magnetic susceptibility, hysteresis loop, magnetic remanence acquisition) and compared with chemical compositions. Our results revealed the presence of both ferrimagnetic magnetite and antiferromagnetic hematite in the dust-enriched horizon, and the diamagnetic behaviour of the reference layer consisting of 'pure' snow. The samples recorded the presence of geogenic elements such as Al, Fe, Mn, and Ti, anthropogenic elements such as As, Co, Cr, Cu, Ni, Pb, and Zn, and nutrients including Ca and K. The total concentrations of geogenic elements, nutrients, and anthropogenic elements in the snow samples with deposited Saharan dust were, respectively, >3700, >320, and >110 times greater than in the samples without Saharan dust. These findings may serve as reference data for a variety of environmental magnetic studies. [Display omitted] [ABSTRACT FROM AUTHOR]

We quantify the contributions of long-range and regionally transported aerosols to ambient primary PM 2.5 and PM 10 in a representative United States industrialized/urban atmosphere via detailed elemental analysis and chemical mass balance (CMB) modeling after identifying their presence using a variety of publicly available satellite data/information, software products, and synoptic-scale aerosol models. A year-long study in Houston, Texas identified North African dust as the principal long-range global source of primary particulate matter (PM). CMB estimated transatlantic dust from the Sahara-Sahel region to be dominant in the summer months contributing an average of 3.5 μg m−3 to PM 2.5 and 7.9 μg m−3 to PM 10 during May–August, i.e., the active Saharan dust season. Biomass burning was the chief source of regionally transported PM impacting air quality on different occasions throughout the year depending on the fire location. Four major biomass combustion events affecting air quality in Texas were calculated to contribute an average of 1.3 μg m−3 to PM 2.5 and 1.4 μg m−3 to PM 10 in corresponding samples whose origins were tracked to Canada, southeastern states of USA, and Central America using fire maps, HYSPLIT back trajectories, and the Navy Aerosol Analysis and Prediction System global aerosol model. Elemental concentrations and signature ratios revealed significant mixing of potassium, rare earth metals, and vanadium from proximal and distal crustal (natural) sources with anthropogenically emitted PM. This demonstrates the need to isolate the non-mineral components of these metals to employ them as tracers for primary PM emitted by biomass burning, petroleum refineries, and oil combustion. Transboundary contributions to primary PM 2.5 were 1.5 μg m−3 and 3.1 μg m−3 to PM 10 adding 16% to annual average mass concentration of both size fractions demonstrating that local sources were primarily responsible for ambient air quality with non-trivial contributions from international and interstate sources. Rigorously identifying and quantifying aerosol sources assists in improving air quality management policies designed to protect public health and comply with ever-decreasing federal PM standards that allow state agencies to exclude contributions that are not reasonably controllable or preventable from regulatory decisions and actions. [Display omitted] • Transboundary transport of primary aerosols into Houston, Texas quantified. • Saharan-Sahelian dust contributed ∼30% to PM 2.5 and PM 10 during May–August. • Central American smoke contributed almost half of transborder biomass burning PM. • On average, distal sources contributed 1.5 μg m−3 to PM 2.5 and 3.7 μg m−3 to PM 10 annually. • Non-mineral La, V, and K improve tracing of industrial and biomass burning aerosols. [ABSTRACT FROM AUTHOR]

An international team of scientists from government agencies and universities in the United States, U.S. Virgin Islands (USVI), Trinidad & Tobago, the Republic of Cape Verde, and the Republic of Mali (West Africa) is working together to elucidate the role Saharan dust may play in the degradation of Caribbean ecosystems. The first step has been to identify and quantify the persistent organic pollutants (POPs), trace metals, and viable microorganisms in the atmosphere in dust source areas of West Africa, and in dust episodes at downwind sites in the eastern Atlantic (Cape Verde) and the Caribbean (USVI and Trinidad & Tobago). Preliminary findings show that air samples from Mali contain a greater number of pesticides, polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) and in higher concentrations than the Caribbean sites. Overall, POP concentrations were similar in USVI and Trinidad samples. Trace metal concentrations were found to be similar to crustal composition with slight enrichment of lead in Mali. To date, hundreds of cultureable micro-organisms have been identified from Mali, Cape Verde, USVI, and Trinidad air samples. The sea fan pathogen, Aspergillus sydowii, has been identified in soil from Mali and in air samples from dust events in the Caribbean. We have shown that air samples from a dust-source region contain orders of magnitude more cultureable micro-organisms per volume than air samples from dust events in the Caribbean, which in turn contain 3-to 4-fold more cultureable microbes than during non-dust conditions. Rev. Biol. Trop. 54 (Suppl. 3): 9-21. Epub 2007 Jan. 15.Un grupo internacional de agencias gubernamentales y universidades de los Estados Unidos, las Islas Vírgenes (EUA), Trinidad y Tobago, la República de Cabo Verde y la República de Mali (África Oeste), está trabajando en conjunto para elucidar el papel que el polvo del Sahara puede estar jugando en el deterioro de los ecosistemas caribeños. El primer paso ha sido identificar y cuantificar los Contaminantes Orgánicos Persistentes (POPs, por sus siglas en inglés), los metales traza y los microorganismos viables presentes en la atmósfera de las áreas fuente de polvo de África occidental y en áreas ubicadas en la dirección del viento, como el Atlántico este (Cabo Verde) y el Caribe (IVEUA y Trinidad y Tobago), durante los episodios de transporte de polvo. Resultados preliminares indican que las muestras de aire de Mali contienen mayor número y mayores concentraciones de pesticidas, bifenilos policlorinados (PCBs) e hidrocarburos policíclicos aromáticos (PAHs) que las de los sitios del Caribe. Las concentraciones de POPs fueron similares en las muestras de USVI y de Trinidad. Se encontró que las concentraciones de metales traza fueron similares a las de la composición de la corteza, con un ligero enriquecimiento de plomo en Mali. Hasta la fecha, cientos de microorganismos cultivables han sido identificados en las muestras de Mali, Cabo Verde, IVEUA y Trinidad. Hallamos el patógeno de los abanicos de mar, Aspergillus sydowi, en las muestras de aire de Mali y en las muestras del Caribe durante polvaredas. Hemos demostrado que las muestras de aire provenientes de una región fuente de polvo, contienen más microorganismos cultivables por volumen -en órdenes de magnitud- que las muestras de aire tomadas en polvaredas en el Caribe, las cuales a su vez contienen tres a cuatro veces más microorganismos cultivables que aquellas tomadas cuando no hay polvaredas.

The long-term contemporary 210 Pb time series acquired during the period 2004–2011 at two distant sites of different altitude in the Mediterranean basin, El Arenosillo (40 m a.s.l. in southwestern Spain) and Mt. Cimone (2165 m a.s.l. in northern Italy), are analyzed and compared. Besides being considered a tracer of continental air masses, 210 Pb radionuclide is also a proxy of fine stable aerosol. For this reason, the measurements of PM 10 mass concentrations collected at the same time and the corresponding 210 Pb/PM 10 ratio at the two sites are considered to gain better insights into the origin and size of the particles. Three statistical trajectory methods are applied to identify and characterize the 210 Pb source regions at the two sites. The three methods yield similar outcomes in the source identification, which strengthens the robustness of our results. In addition to the importance of the transport from areas of continental Europe, this study highlights the relevant role of the Mediterranean Sea as a major 210 Pb reservoir layer associated to the aged air masses that accumulate in the western Mediterranean basin. The analysis of the sources points out the significant influence of northern Africa to 210 Pb increases at both sites as well, even though the most intensive episodes are not of Saharan origin. [ABSTRACT FROM AUTHOR]

The particle sizes of Saharan dust in marine sediment core records have been used frequently as a proxy for trade-wind speed. However, there are still large uncertainties with respect to the seasonality of the particle sizes of deposited Saharan dust off northwestern Africa and the factors influencing this seasonality. We investigated a three-year time-series of grain-size data from two sediment-trap moorings off Cape Blanc, Mauritania and compared them to observed wind-speed and precipitation as well as satellite images. Our results indicate a clear seasonality in the grain-size distributions: during summer the modal grain sizes were generally larger and the sorting was generally less pronounced compared to the winter season. Gravitational settling was the major deposition process during winter. We conclude that the following two mechanisms control the modal grain size of the collected dust during summer: (1) wet deposition causes increased deposition fluxes resulting in coarser modal grain sizes and (2) the development of cold fronts favors the emission and transport of coarse particles off Cape Blanc. Individual dust-storm events throughout the year could be recognized in the traps as anomalously coarse-grained samples. During winter and spring, intense cyclonic dust-storm events in the dust-source region explained the enhanced emission and transport of a larger component of coarse particles off Cape Blanc. The outcome of our study provides important implications for climate modellers and paleo-climatologists. [ABSTRACT FROM AUTHOR]

Several hundred tons of windblown dust material are lifted into the atmosphere and are transported every year from Saharan dust source areas towards Europe having an important climatic and other environmental effect also on distant areas. According to the systematic observations of modern Saharan dust events, it can be stated that dust deflated from North African source areas is a significant constituent of the atmosphere of the Carpathian Basin and Saharan dust deposition events are identifiable several times in a year. Dust episodes are connected to distinct meteorological situations, which are also the determining factors of the different kinds of depositional mechanisms. By using the adjusted values of dust deposition simulations of numerical models, the annual Saharan dust flux can be set into the range of 3.2–5.4 g/m 2 /y. Based on the results of past mass accumulation rates calculated from stratigraphic and sedimentary data of loess–paleosol sequences, the relative contribution of Saharan dust to interglacial paleosol material was quantified. According to these calculations, North African exotic dust material can represent 20–30% of clay and fine silt-sized soil components of interglacial paleosols in the Carpathian Basin. The syngenetic contribution of external aeolian dust material is capable to modify physicochemical properties of soils and hereby the paleoclimatic interpretation of these pedogene stratigraphic units. [ABSTRACT FROM AUTHOR]

Coarse (particulate matter (PM)) and fine (PM) fraction of PM samples were collected between December 2014 and February 2015 at an urban sampling site located at the Bolu plain, of the western Black Sea region of Turkey. The collected samples were analyzed in terms of metals (Al, As, Ba, Ca, Cu, Fe, K, Mg, Mn, Na, Pb, S, Si, Ti, V, and Zn); elemental carbon (EC); and organic carbon (OC). Elevated concentrations measured in this wintertime study were ∼7.8 μg/m in sum of PM and PM for SO and ∼59.9 μg/m in PM for OC. The contributions of primary and secondary OC (POC and SOC, respectively) to total OC mass were 60 and 40 %, respectively, while contribution of SOC to OC increased by up to 74 % in stable atmospheric conditions. The significantly high OC/EC ratio (∼10.1) found in this study relative to other wintertime studies was attributed to increased emissions from residential heating and lower mixing height observed during the study. Two and three factors were resolved by factor analysis for PM and PM, respectively. Two Saharan dust episodes were observed on 31 January and 1 February, during which crustal PM components such as Mg, Si, and Al increased as much as three times their background concentrations. [ABSTRACT FROM AUTHOR]

Vibrio is a ubiquitous genus of marine bacteria, typically comprising a small fraction of the total microbial community in surface waters, but capable of becoming a dominant taxon in response to poorly characterized factors. Iron (Fe), often restricted by limited bioavailability and low external supply, is an essential micronutrient that can limit Vibrio growth. Vibrio species have robust metabolic capabilities and an array of Fe-acquisition mechanisms, and are able to respond rapidly to nutrient influx, yet Vibrio response to environmental pulses of Fe remains uncharacterized. Here we examined the population growth of Vibrio after natural and simulated pulses of atmospherically transported Saharan dust, an important and episodic source of Fe to tropical marine waters. As a model for opportunistic bacterial heterotrophs, we demonstrated that Vibrio proliferate in response to a broad range of dust-Fe additions at rapid timescales. Within 24 h of exposure, strains of Vibrio cholerae and Vibrio alginolyticus were able to directly use Saharan dust-Fe to support rapid growth. These findings were also confirmed with in situ field studies; arrival of Saharan dust in the Caribbean and subtropical Atlantic coincided with high levels of dissolved Fe, followed by up to a 30-fold increase of culturable Vibrio over background levels within 24 h. The relative abundance of Vibrio increased from ∼1 to ∼20% of the total microbial community. This study, to our knowledge, is the first to describe Vibrio response to Saharan dust nutrients, having implications at the intersection of marine ecology, Fe biogeochemistry, and both human and environmental health. [ABSTRACT FROM AUTHOR]

A novel methodology was used to evaluate the contribution of Saharan dust to the atmospheric deposition of particulate material (PM), total phosphorus (TP), and total nitrogen (TN) in the southeastern Iberian Peninsula. Dry and wet aerosol depositions were measured weekly during two 1 year periods at one site and simultaneously during spring-summer of the same years at two other sites (intersite distance of ~ 40 km). Statistical relationships among depositions at the different sites permitted differentiation of Saharan dust inputs from locally derived dust. PM and TP depositions were synchronous among the three study sites; the synchrony was elevated during periods of Saharan intrusions (evaluated by air mass retrotrajectories analyses), but no temporal correlation was observed during periods without Saharan intrusions. According to analysis of variance results, PM and TP depositions were both significantly affected by Saharan intrusions. During weeks with Saharan intrusions, PM deposition increased around 85% above background levels, with no differences among the three sites, while TP deposition increased by 1.1 µmol TP m−2 d−1, i.e., 29% to 81% above background levels depending on the site. There were no correlations or differences in TN deposition among sites or as a function of Saharan intrusion periods. The annual contribution of PM and TP from Saharan dust was 75 kg ha−1 and 0.07 kg P ha−1, respectively, which can be considered a genuine input for the ecosystems in this area. This novel approach is likely to be valid in any area in the world under atmospheric deposition of long-range transported material. [ABSTRACT FROM AUTHOR]

Clay mineralogy of ODP Site 964 in the Ionian Sea was investigated in order to reconstruct variations in detrital sediment input to the central Mediterranean Sea and to reconstruct the corresponding climatic processes over the last 1500 kyr. The clay mineralogy of ODP Site 964 indicates a major shift in sedimentary sources from the Saharan Desert, which is characterized by a clay mineral assemblage of palygorskite–illite–kaolinite, to the Apennine Peninsula, characterized by an illite–smectite clay assemblage, at ~ 700 kyr. Prior to ~ 700 kyr, the low smectite content (10–20%) and the strong precessional cycles in the variations of kaolinite, illite and palygorskite indicate that terrigenous sediment to the central Mediterranean Sea mainly originated from Saharan dust and was strongly affected by the African monsoon, with a minor contribution of sediment deriving from the Apennine Peninsula. An increase in the illite/kaolinite ratio in the maxima of boreal summer insolation indicates a decreased dust input from the southern Sahara as a result of the northward displacement of the African Monsoon-ITCZ system. A gradual increase in smectite content has been identified between 1050 and 500 kyr, probably associated with environmental (vegetation) and/or hydrological changes in southern Europe linked to the occurrence of the MPT, and partly to tectonic uplift in the Apennine Peninsula. A marked increase in terrigenous flux is observed at around 350 kyr, coeval with a major phase of uplift in the Calabrian Arc. [ABSTRACT FROM AUTHOR]

In this study, the influence of an extraordinary Saharan dust episode over Turkey on 23–24 March 2016 and the atmospheric conditions that triggered this event were evaluated in detail. PM10 (particulate matter less than 10 μm) observations from 97 air quality stations, METAR (Meteorological Terminal Aviation Routine Weather Report) observations at 64 airports, atmospheric soundings, and satellite products were used for the analysis. To determine the surface and upper levels of atmospheric circulation, National Centers of Environmental Prediction (NCEP)/National Center for Atmospheric Research (NCAR) Reanalysis data were applied to the extreme dust episodes. On 23 March 2016, high southwesterly winds due to the interaction between surface low- and high-pressure centers over Italy and Levant basin brought thick dust particles from Libya to Turkey. The daily PM10 data from 43 stations exceeded their long-term spring means over Turkey (especially at the northern and western stations). As a consequence of the longitudinal movement of the surface low from Italy to the Balkan Peninsula, and the quasi-stationary conditions of the surface high-pressure center allowed for the penetration of strong south and southwesterly winds to inner parts of the country on the following day. As a consequence, 100%, 90%, 88%, and 87% of the monitoring stations in Marmara (NW Turkey), central Anatolia, western (Aegean) and northern (Black Sea) regions of Turkey, respectively, exhibited above-normal daily PM10 values. In addition, while strong subsidence at the low levels of the atmosphere plays a significant role in having excessive daily PM10 values in Black Sea, dry atmospheric conditions and thick inversion level near the ground surface of Marmara ensured this region to have peak PM10 values ~00 Local Time (LT).

134Cs was measured in soil samples collected in the Western Canary Islands during a survey carried out in 1990–1991. This was 4 to 5 years after the Chernobyl Nuclear Power plant accident (1986). Models of the radioactive plumes did not show that 134Cs released by the nuclear accident was transported directly from the accident site to these islands. In this work, we provide a possible explanation to how the 134Cs may have been transported and deposited in soils of these islands after the accident. Intermittent inputs of mineral dust from Africa, in the form of intense dust storms, arrive to these islands every year. We believe that the 134Cs from the accident may have been first deposited in Northern Africa, then resuspended and transported to the islands by various dust storms. Atmospheric records of African dust indicate that some strong events (high levels of particulate matter) took place in the 1986–1991 period. This hypothesis is supported by >20 years of aerosol data (2000−2022) collected at this site showing that 137Cs, another isotope of radiocaesium, is resuspended and transported to these islands in connection with these type of African dust storms. • 134Cs were recorded in soil samples of the Western Canary in the early 90s. • Previous models of the Chernobyl accident didn't show trajectories over this site. • 134Cs and 137Cs from could be resuspended and transported from the Sahara Desert to the Canary Island. • Aerosol data show that there is a continuous input of mineral dust from Africa. [ABSTRACT FROM AUTHOR]

The European AIRUSE LIFE+ project aims at testing existing and future mitigation measures and developing new strategies for the improvement of air quality in Southern European countries. The project involves public and private institutions of Spain, UK, Portugal, Italy and Greece. PM10 and PM2.5 daily samplings have been scheduled for one year (from January 2013) in four urban sites, Barcelona (Spain), Porto (Portugal), Athens (Greece), and Florence (Italy). The daily data set gives an overall representative picture of the PM composition in these urban sites. The project includes also samplings with hourly resolution for limited periods. Hourly samples give an easier identification of the different aerosol sources due to the capability of tracking rapid changes as the ones occurring in many particulate emissions as well as in atmospheric transport and dilution processes. The role of PIXE technique within the project has been described in this paper. The comparison of data obtained by different techniques (e.g. PIXE, IC and ICP) assured a quality assurance control on the huge quantity of data obtained in the project. PIXE data together with those obtained by other analytical techniques have been used to reconstruct the average aerosol chemical composition and in Positive Matrix Factorization (PMF) analysis to determine the aerosol sources and their impact on PM10 and PM2.5 mass. In particular the high sensitivity of PIXE for all the crustal elements (including Si which is not easily detected by ICP) allows the direct determination of the Saharan dust contribution. Finally, the 1-h resolution data, which can be obtained only by PIXE, confirmed and reinforced the identification of the aerosol sources obtained by the daily concentrations. [ABSTRACT FROM AUTHOR]

To better constrain Li dynamics in the tropics, we sampled critical zone compartments of a small forested andesitic catchment in Guadeloupe (soils, parent rock, atmospheric dust, plants, soil solutions, stream and rain waters). The aims of this study are to identify the origin of Li in the different compartments and to better characterize the behavior of Li and its isotopes during water–rock interaction in a highly cation-depleted soil. The Li isotope signature (δ 7 Li) of throughfall samples varies between + 11.2‰ and + 26.4‰. As this is lower than the seawater signature (31‰) and vegetation does not fractionate Li isotopes, our data indicate that Saharan dust (− 0.7‰) significantly contributes to the throughfall signature. Li isotope composition measured in a 12.5 m deep soil profile varies from + 3.9‰ near the surface to − 13.5‰ at 11 m depth. Compared to unweathered andesite (+ 5‰), the deep soil signature is in agreement with preferential incorporation of light Li into secondary minerals. In the top soil however, our results also emphasized that atmospheric deposition (wet and dry) is a main source of Li to the soil. The decreasing δ 7 Li with increasing depth is consistent with a vertical gradient of incorporation of heavy atmospheric Li, this input being maximal near the surface. At the catchment scale, throughfall and total atmospheric inputs (sea salts + Saharan dust) provide 12.1 and 23.9 g Li yr − 1 respectively to the Quiock Creek catchment. These fluxes represent 34% and 67%, respectively, of Li exported at the outlet indicating that atmospheric deposition is one of the main Li inputs to the critical zone. Li concentration and isotopic mass balance at the catchment scale indicate that in addition to atmospheric deposition, secondary mineral phase dissolution is a major solute source and that andesite no longer participates in significant production of Li. [ABSTRACT FROM AUTHOR]

The influence of direct dust-radiative forcing on the movement and track of Hurricane Helene (2006) is examined numerically using the Weather Research and Forecasting dust model. Numerical simulations show that the model-generated dust plume modifies the thermal field, causing a clockwise turning of the vertical shear surrounding the plume, which changes the deep layer steering flow. The change in the steering flow modifies Helene's moving speed and direction as it transits the plume. As Helene exits the plume, it has a different trajectory than it would have had in the absence of dust-radiative forcing. Consequently, the difference in the tracks with and without dust-radiative forcing continues to grow with distance from the plume. The dust-induced changes in temperature and wind together cause Helene's modeled storm track to be in closer agreement with the observed track; the dust-radiative forcing reduces the error in the model's 7-day track forecasts by an average of 27% (∼205 km). [ABSTRACT FROM AUTHOR]

Sr and Nd isotopes were applied to 5 soil profiles from the Muravera area, in south-eastern Sardinia. All the soils, which have developed during the Quaternary on the Lower Paleozoic metamorphic basement except for one on Eocene carbonates, are located far from major sources of pollution. Therefore, they are suitable for testing pedogenic processes and geochemical evolution to benefit for environmental studies. The Sr isotopic ratios range largely (δ 87 Sr = 1.7–65.9‰), even in each soil profile. In particular, the observed increase of δ 87 Sr with depth in the most of the metamorphic rock-based soils can be accounted for by the downward decrease of Sr contributions from organic matter and Saharan dust, both displaying lower isotopic ratios than the soil bedrocks. The carbonate rock-based soil exhibits δ 87 Sr higher (1.7–18.1‰) than the bedrock, indicating a significant contribution of radiogenic Sr from the siliciclastic fraction of the soil, and probably from dust input. The Nd isotopic ratios are slightly variable through the profiles ( ɛ Nd from −7.8 to −14.5), confirming little mobility of Nd and Sm during the pedogenesis. Among the minerals present in the soils, phosphates, albite, and calcite are those important in providing low radiogenic Sr and Nd to organic matter of the soils. Lastly, this isotopic study has in particular allowed for evaluating the potential proportion of contribution of Saharan dust to south-eastern Sardinia, thus corroborating the findings of other studies related to soils from the central-western Mediterranean. [ABSTRACT FROM AUTHOR]

The EU daily PM 10 limit-value of 50 μg m − 3 is frequently breached in the center of Athens, Greece. A total of 852 daily exceedances were recorded in the city-center during the 6-year period 2001–2006. These exceedances were more frequent in winter, followed by spring and autumn. For the needs of the study, the PM 10 episodes (i.e., concentrations 30% above the median value) were grouped in two categories: (a) the City-Center episodes and (b) the Wider Metropolitan Area episodes. It was assumed that City-Center episodes occurred when elevated PM 10 values were measured in the city-center exclusively, whereas Wider Metropolitan Area episodes occurred when high PM 10 concentrations were also measured in the suburbs. Then back-trajectory cluster analysis was performed in an attempt to associate high PM 10 levels with local dispersion or long-range transport. The City-Center episodes were associated according to the origin of air parcels with six types of air-masses (slow and fast moving from northern, northeasterly and southern directions, or stagnated around Athens) and were mainly due to traffic or other local sources, whereas the Wider Metropolitan Area episodes were mainly associated with air-masses coming from southern directions and were linked to long-range transport. On the whole, the analysis provided evidence of Sahara-dust events and sea-spray transportation. [ABSTRACT FROM AUTHOR]

The spatial and temporal distribution of particulate matter in the water column of the eastern tropical North Atlantic between 16.9–22.9°N and 16.6–29.3°W was investigated using optical measurements from transmissometers mounted on Argo floats. The corresponding profiles of beam attenuation coefficients measured from February 2008 to May 2009 were used to study particulate matter in different layers such as the surface nepheloid layer (SNL), subsurface nepheloid layer (SSNL), intermediate nepheloid layer (INL) and bottom nepheloid layer (BNL) as well as to investigate sinking particles (SP). The SNL were down to about 60 m water depth at thicknesses between 20 and 60 m. Our analyses verified high correlation between particulate matter and phytoplankton in the SNL. High offshore SNL extension of up to 750 km was found in the area of Cape Blanc filaments in January 2009. Their typical widths ranged from 11 to 72 km. Furthermore, float-borne observations even resolved atmospheric dust deposition into the surface water layer during a strong Saharan dust event in October 2008. The observed dust concentration in the mixed water layer was found to vary between 0.0021 and 0.0168 g m −3 depending on applied assumptions. An abrupt change from a SNL to a SSNL regime over distances of only 80 to 90 km was observed. The particulate matter in the SSNL showed lateral extensions from 420 to 1020 km offshore. A statistically significant correlation between the depth of subsurface particle maxima and the distance to shore was found. An averaged diameter of 30 km was determined for the sharply isolated patches of INL which was consistent with model simulations of other studies. The lateral transport of particulate matter in these INL features in the area of the giant Cape Blanc filaments was found to be more pronounced than reported in earlier studies. The distribution of particulate matter within the INL filaments reached up to 610 km off the shelf edge. The frequency of INL decreased with increasing distance to shore. The sinking velocity of particulate matter of one long-term observed INL was approximately 1.3 m day −1 . Highly concentrated BNLs with beam attenuation coefficients of up to 4.530 m −1 were observed in the continental slope region. INLs appeared more frequently than SP events which lead to the conclusion that the lateral transport of particulate matter in INL features in the study area was more important than their passive vertical sinking. [ABSTRACT FROM AUTHOR]

A severe PM 10 episode was observed at the high elevation observatory of Mt. Cimone (2165 m a.s.l.) in the period of 13th-15th March 2004; during the event PM 10 reached the maximum concentration (80 μg m −3 against an average of 8.8 ± 8.0 μg m −3 ) between 1998 and 2011. Meteo-synoptical analysis allowed to ascribe this event to a long lasting and highly coherent Saharan dust outbreak, starting at the beginning of March. The peculiar synoptic configuration causing this massive transport of dust was characterized by a steep gradient between an upper level trough extending to low latitudes with a minimum centred over the North-Western Algerian coast and a Saharan high extending all over the Mediterranean Sea with an elongated north-eastward tongue, whose synergic effect led to a peculiar funnel-shaped dust plume. During the period Mt. Cimone was located exactly along its main axis. The event was first analysed in association with simultaneous more or less conventional compositional parameters such as 7 Be, 210 Pb, and ozone. Subsequently, it was characterized in details both in terms of time and space evolution. The former aspect was investigated using number densities of fine and coarse particles obtained through an Optical Particle Counter which allowed to follow the event evolution at the sub-daily time scale while PM 10 membrane gravimetric analysis was limited by the 48-h sampling schedule suggesting the value of 80 μg m −3 recorded is even potentially smoothed down by sampling duration. Besides precise timing, optical counting enabled to detect the inception and development of the event through a steep and simultaneous increase of both coarse and fine particle number densities. Although the former increase was much more relevant, the latter occurrence is much less frequently documented for Saharan Dust events: a clear increase of particles in all the diameter ranges from 0.3 μm (lower limit of an OPC) up to 5.0 μm was observed during the event. The spatial extension of the event was also examined by means of the analysis of the AERONET ground-based sun photometer data from the Venice station for the event. Results confirmed a relevant increase of coarse particles over a distance of more than 150 km. Interestingly AERONET data indicates a more significant variation in the scattering properties of the aerosol rather than in the absorbing ones in connection with the arrival of the Saharan dust, an observation that within the intrinsic limitations of inverse methods to derive aerosol's optical properties is in agreement with some previous observations showing that dust in the Saharan desert region is much less absorbing than previously measured. [ABSTRACT FROM AUTHOR]

The present study analyses the peak 210 Pb activity concentrations observed all over the 1998–2011 period at the WMO-GAW high altitude site of Mt. Cimone (44.18N, 10.7E, 2165 m asl; Italy) in terms of meteorological conditions, links with other atmospheric species and population dose rate associated with this radiotracer. The highest 210 Pb events mainly occurred in the warm period and were associated with prolonged anticyclonic conditions, high temperatures, and low relative humidity values. A correlation with the seasonal pattern of the mixing height was also observed, suggesting the importance of thermal convection promoting uplift of warm air from the atmospheric boundary layer (ABL), transporting high concentrations of 222 Rn and thus 210 Pb. The main sources of high 210 Pb concentrations were identified by means of clusters of back-trajectories applied at three different heights. Sources located at east (central Europe), at west (Spain and France) and south (northern Africa) of Mt. Cimone were distinguished. The clusters obtained at the three heights were compared in order to study the extent between ABL and free troposphere during the highest 210 Pb events: a wide influence of the strong coupling among atmospheric vertical layers on 210 Pb activity concentrations increases was demonstrated. The annual effective dose from the potential inhalation of this radionuclide during the peak concentration episodes was also calculated. The average dose increase during the selected events represents only a small fraction of the total dose from all sources; these results are nevertheless useful for providing information on natural background dose contribution from inhalation which is required for the accurate assessment of dosimetric conditions in the case of nuclear emergencies. [ABSTRACT FROM AUTHOR]