Saharan dust

Levels of total suspended particles, PM10, PM2.5 and PM1 were continuously monitored at an urban kerbside in the Metropolitan area of Barcelona from June 1999 to June 2000. The results show that hourly levels of PM2.5 and PM1 are consistent with the daily cycle of gaseous pollutants emitted by traffic, whereas TSP and PM10 do not follow the same trend, at least in the diurnal period. The PM2.5/PM10 ratio is dependent on the traffic emissions, whereas additional contribution sources for the >10 mm fraction must be taken into account in the diurnal period. Different PM10 and PM2.5 source apportionment techniques were compared. A methodology based on the chemical determination of 83% of both PM10 and PM2.5 masses allowed us to quantify the marine (4% in PM10 and o1% in PM2.5), crustal (26% in PM10 and 8% in PM2.5) and anthropogenic (54% in PM10 and 73% in PM2.5) loads. Peaks of crustal contribution to PM10 (up to 44% of the PM10 mass) were recorded under Saharan air mass intrusions. A different seasonal trend was observed for levels of sulphate and nitrate, probably as a consequence of the different thermodynamic behaviour of these PM species and the higher summer oxidation rate of SO 2 . r

Simultaneous measurements of airborne radionuclides 7Be and 210Pb, together with aerosol mass load PM10, have been routinely carried out at the Global WMO-GAW station of Mt. Cimone (Italy, 2165m a.s.l., 44° 12' N, 10° 42' E) from 1998 to 2011. The experimental activity was started with the purpose of gaining a better understanding of the vertical and horizontal transports taking place at this site affecting the atmospheric chemical composition. The time series of the collected data is presented and discussed in this paper. The 7Be concentrations in this period are in the range 0.05-15.8mBqm-3 with the presence of two distinct relative maxima during winter/spring and summer, suggesting an origin from different physical processes. The 210Pb concentrations collected during the period are in the range 0.05-2.30mBqm-3 and are characterized by a single maximum during the warm period. The 7Be/210Pb ratio was in the range 0.5-127.8 and is characterized by a maximum during the cold period. The frequency distributions of the three parameters and the seasonal/interannual variabilities are investigated and presented.

In this report, winter mass balances of eight glaciers in the Lombardy region (Central Italian Alps) are presented for the season 2017/2018. Data were provided by the Glaciological Service of Lombardy (Servizio Glaciologico Lombardo, SGL) network. The 2017/18 point winter balances in the Lombardy region are the most negative since 2007 in terms of snow depth, and since 2012 in terms of SWE. We also evaluate the possible effect of Saharan dust deposition in decreasing snow albedo and hence in increasing snow melting. In fact, despite an average precipitation sum from October to May, the very high air temperature of the late spring and the concurrent Saharan dust deposition promoted an early start of the snowmelt that lowered both snow depth and SWE values at the typical time of accumulation measurements.

In total 562 daily PM 10 and PM 2:5 samples were collected from April 2001 to April 2002 at a rural site (Erdemli) located on the coast of the Eastern Mediterranean. The annual mean PM 10 and PM 2:5 levels were 36:4 AE 27:8 and 9:7 AE 5:9 mg m À3 , respectively. PM 10 and PM 2:5 concentrations indicated orders of magnitude change from day to day (PM 10 ¼ 22326 mg m À3 ; PM 2:5 ¼ 0:5228 mg m À3 ). The highest levels of PM 10 were observed during the transition period (March, April and May) due to mineral dust transported from North Africa and during winter due to sea spray generation. However, PM 2:5 levels exhibited higher concentrations during summer resulting from an enhanced production of secondary aerosols. The PM 2:5 =PM 10 ratio (0.25) and categorization of air mass back trajectories indicated that PM 10 at the study area is dominated by primary aerosol emissions (mineral dust particles from the Saharan Desert and sea salt particles from the Mediterranean Sea itself). During the whole sampling period 28 and 51 events exceeded the recommended maximum values of 50 and 15 mg m À3 for PM 10 and PM 2:5 , respectively. Source apportionment analysis indicated that PM 10 exceedances originated as a consequence of natural events (mineral dust $40%; sea salt $50%) whereas PM 2:5 exceedances were accounted primarily by pollution events (in 90% of the cases). r

The Basic Environmental Observatory (BEO) at Moussala peak is the main site for permanent uninterrupted in-situ observations of atmospheric aerosol properties in southeastern Europe. It is a region, which suffers a very severe impact of Sahara dust storms due to a long-range air mass transport. Despite the large distance away from the southernmost part of the region, direct Sahara dust events (SDEs) are common for the BEO site, mainly during late winter and spring. Moreover, in many cases particles of Saharan origin have been detected over Moussala, mainly after a SDE occurring over central and southeastern Europe. This paper reports seven events registered at Moussala BEO by a 3563 TSI Nephelometer during the period between April 1 and June 30, 2013. The impact is also estimated quantitatively of the mineral dust particles on the overall optical depth for the period reported.

In order to analyze the troposphere dynamics under particular conditions in NorthEast region of Romania, various types of aerosols chemical compositions have been studied using complementary techniques. Thus, the seasonal trends of aerosols and its external influences have been studied using aerosol optical properties retrieved from Aerosol Robotic Network (AERONET). Complementary studies were taken into account by using several meteorological factors, computational models and meteorological data. Moreover, this paper presents optical properties analysis of different types of aerosols and the seasonal variability of them in one year of measurements. The major categories of aerosol types are evidenced, such as urban/industrial aerosol, biomass burning and mineral dust.

The significance of Saharan dust deposits for ecosystems has been demonstrated in several studies, showing its influence on pedogenesis and soil chemical and physical parameters by the addition of nutrient elements. This contribution is especially important for volcanic soils poor in plant-available phosphorous as those of the island of La Palma (Canary Islands, Spain). Thus, this study investigates the spatial distribution of Saharan dust on the island, and determines its influence on soil properties and thus on the ecosystem of the island. Since silt-sized quartz is not autochthonously formed on the island, it served as a reliable indicator for Saharan dust. Quartz was identified and quantified using X-ray diffractometry. The influence of Saharan dust additions on soil properties was assessed by texture analyses and analyses of plant-available phosphorous, an element strongly limiting plant-growth on the island due to its fixation in the structure of amorphous volcanic clay. A luff-lee-effect revealed significant influence on dust distribution, whereas small geomorphologic structures as hollows and mounds hardly influenced the dust distribution pattern. A positive correlation of quartz content with the proportion of the grain size fraction 0.5-10 µm demonstrates an influence on soil physical properties, apparently influencing available water capacity. Furthermore, our data suggest an increasing content of plant-available phosphorous with a rising amount of Saharan dust in the soils. Thus, the input of Saharan dust influences soil fertility of La Palma and is an important factor regarding the fragility of the La Palma ecosystems.

Effects of atmospheric deposition and other environmental factors on phytoplankton dynamics were evaluated from an open (having offshore characteristics) and a coastal station in the northeastern Mediterranean between December 2000 and December 2001. Data on phytoplankton, chlorophyll a, nutrients, temperature and salinity were obtained at biweekly or more intense intervals during 1 yr, whilst transport of Saharan dust towards the sampling region was monitored daily by SeaWiFS (sea-viewing wide field-of-view sensor) images. Diatoms were the group of highest average biomass during the entire investigation period. Although coccolithophores (mainly Emiliania huxleyi) numerically dominated at the open station during the study period, their maximum abundance was as low as 50 × 10 3 cells l-1. The intensity of dust transport was observed to be highest in spring. Less intense transports were observed in summer and autumn. Several intense episodic dry and wet dust deposition events during the spring season observed by SeaWiFS images caused little or no increase in phytoplankton abundance and biomass in the following days and weeks. Nevertheless, it appears that less intense dust transport events increased phytoplankton abundance and biomass in August, September and October 2001, when water column stratification was at its peak. However, these increases were much weaker than the major winter-early spring bloom (in February and March), which was caused by upwelling, mixing the water column. We suggest that the impact of atmospheric nutrient input on phytoplankton in the Mediterranean is rather low on a yearly basis.

AERONET sun photometer measurements performed at five different sites of the Central Mediterranean during strong Saharan dust outbreaks are used to characterize optical and physical properties of dust particles. Sun photometer retrievals are combined at two of the five sites with lidar observations. It is shown that at low aerosol optical depths (AODs) the dust particle properties are quite dependent on dust load and monitoring site location. Differences on retrieved particle properties reduce with increasing dust load. AERONET retrievals at AOD (440 nm) z 0.6 are then used in this paper to characterize dust particles over the central Mediterranean basin leading to columnar averaged values of the real refractive index bnN = 1.5 F 0.1, the imaginary refractive index bkN = 0.004 F 0.002, the single scattering albedo bSSAN= 0.89 F 0.03, and the Angstrom exponent bÅ N = 0.2 F 0.1. It is shown that Å represents the best marker to trace the temporal evolution of dust events. Volume size distributions show a dominant coarse mode peaking at 1.7-3 Am. In particular, the average coarse mode that is centred at i 2.2 Am at Lampedusa, which is~200 km away from the northwest Africa coast, gets peaked at i 1.7 Am at Lecce, which is~800 km away. Lidar retrievals are used to characterize the vertical distribution of dust particles by the vertical profiles of the backscatter and extinction coefficients, the lidar ratio, and the depolarization ratio. Lidar retrievals show that over the Mediterranean basin, dust layers generally extend from 1 up to 6 km and that their vertical distribution can significantly change within a few hours. It is also shown that at high values of the AODs dust particles are characterized by lidar ratios spanning the 50-70 sr range and depolarization ratios larger than 30%. D

Airborne particulate matter plays an important role in the Earth's energy balance. One of the main reasons is that the real size of a significant number of the particles, mainly those of anthropogenic origin, is similar to the wavelength of visible light. Knowledge of the composition of such particles, as well as their dynamics and trajectories in the atmosphere is therefore very important. In the period from 23 February to 22 March 2000, a movement of airborne particulate matter going over Europe and towards Azores was identified based on satellite observation. This work presents a preliminary study based on PIXE and nuclear micro-probe analysis of samples collected during that period both in Portugal mainland and in Terceira Island in the Azores. Time-shifted correlation of sample composition and individual particle composition are presented and discussed. Results point to the possibility of inferring long-range transport of aerosol particles from the samples multi-element analysis, and to the existence of fractions of the North Atlantic aerosol identical at both Portugal mainland and Terceira Island. Keywords  Aerosol;  Azores;  Long-range transport;  Multi-element analysis;  PIXE

Two desert loess–paleosol sequences in sediment traps were investigated using (pedo-) stratigraphy, sedimentology, soil mineralogy and IRSL dating. So far we cannot recognise significant IRSL age-underestimates from the polymineral fine-grain fraction of our samples. We establish a first palaeoclimatic sequence spanning the past ca 200 ka which can be compared to data from other Canary Islands and surrounding areas, including terrestrial and deep sea records. More humid phases on Lanzarote are apparently triggered by Milankovich forcing, but the climate remained semi-arid to arid all over the past 200 ka. The onset of human occupation of the island during a slightly moister period is bracketed between 5 and 10 ka, based on the occurrence of archaeosediments containing bones of ovicaprid. This is the first proof of much earlier occupation than witnessed so far from archaeological records. The early subsidiary economy had a strong impact on soil stability and landscape shaping of the island.

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 ...

This paper describes 3-hourly radiosonde observations of the Saharan air layer (SAL) acquired from the NOAA Ship Ronald H. Brown during the 2004 Aerosol and Ocean Science Expedition (AEROSE). The sampling frequency allows for unique vertical cross-sectional analyses of SAL phenomena, including dust events detected by shipboard Sun photometers, observed during March 2004. The observational analyses provide, for the first time, a coherent, 2-dimensional space-time depiction of the SAL as an expansive warm, dry, stable column located above the marine boundary layer. Midlevel easterly wind maxima are also observed to occur near the leading edge of the dry layers. The AEROSE sounding data will be useful for studies of the SAL, as well as for validation of environmental satellite sensors, especially the Aqua Atmospheric Infrared Sounder (AIRS). Citation: Nalli,

Aeolian sediments trapped in volcanically dammed valleys on Lanzarote, Canary Islands, were investigated in order to reveal environmental changes over the last 180 ka. Clay content and frequency dependent magnetic susceptibility were used as proxies for pedogenesis and palaeo-soil moisture. During the last 180 ka, these proxies showed a general pattern of enhanced soil moisture during glacials and stadials and more arid conditions during interglacials and interstadials. Comparisons of these results with proxies from regional palaeoclimate studies identified a positive correlation with proxies of trade wind strength off northwest Africa and inverse correlations with both sea surface temperatures in the northeast Atlantic and the extent of Mediterranean vegetation. Possible causes for the observed pattern include a glacial enhancement of precipitation from westerly cyclones, a change in relative humidity due to fluctuating air temperatures and an occasional influence of the African summer monsoon. Although it is not yet possible to clearly differentiate among these factors, it is clear that the first two factors must have been primarily dominant. These results represent the first quasicontinuous terrestrial data testifying to environmental changes in the northwest African coastal area for the last 180 ka and complement the abundant data derived from marine cores of the region. High latitude dynamics had a major influence in this area and were intermediated by North Atlantic sea surface temperatures. A possible negative correlation can also be observed with the orbital obliquity cycle with a 10 ka time lag, which is similar to the lag recorded from North Atlantic sea surface temperatures.

Levels of total suspended particles, PM10, PM2.5 and PM1 were continuously monitored at an urban kerbside in the Metropolitan area of Barcelona from June 1999 to June 2000. The results show that hourly levels of PM2.5 and PM1 are consistent with the daily cycle of gaseous pollutants emitted by traffic, whereas TSP and PM10 do not follow the same trend, at least in the diurnal period. The PM2.5/PM10 ratio is dependent on the traffic emissions, whereas additional contribution sources for the >10 mm fraction must be taken into account in the diurnal period. Different PM10 and PM2.5 source apportionment techniques were compared. A methodology based on the chemical determination of 83% of both PM10 and PM2.5 masses allowed us to quantify the marine (4% in PM10 and o1% in PM2.5), crustal (26% in PM10 and 8% in PM2.5) and anthropogenic (54% in PM10 and 73% in PM2.5) loads. Peaks of crustal contribution to PM10 (up to 44% of the PM10 mass) were recorded under Saharan air mass intrusions. A different seasonal trend was observed for levels of sulphate and nitrate, probably as a consequence of the different thermodynamic behaviour of these PM species and the higher summer oxidation rate of SO 2 . r

Se describe la composición mineralógica y elemental del contenido particulado de las lluvias de barro recogidas en el Montseny (nordeste península Ibérica) desde 1983 a 1998. Se han identificado 3 áreas-fuente en el norte de África: el Sahara occidental, el Atlas marroquí y el Sahara central. Entre zonas, se han hallado diferencias significativas en la mineralogía y contenido elemental del material particulado. Se ha analizado la frecuencia de las lluvias de barro, que presentan alta variabilidad interanual. De hecho, dos episodios aportaron el 60% del total depositado en 15 años. Estacionalmente, las lluvias de barro predominaron en primavera y otoño. Las aportaciones de cationes básicos y P de las lluvias de barro constituyen porcentajes de entre 60-100% en las entradas totales atmosféricas. Referido a la circulación de nutrientes en el ecosistema forestal, la deposición de K + , Ca +2 y Mg +2 por las lluvias de barro aporta el 27%, 45% y 84% respectivamente de las necesidades nutritivas de este encinar.

Vertically resolved observations of dust optical properties were carried out at the EARLINET station of Naples (southern Italy, 40.838°N, 14.183°E, 118 m above sea level) from May 2000 to August 2003. 45 outbreaks with a mean temporal length of about 4 days were observed, 40% of which were characterized by dust plume intrusion into the Planetary Boundary Layer. The mean values of the altitude of base, top and of the thickness of the dust plume were derived. Dust optical properties were studied along the vertical profile in terms of statistical and climatological analysis of aerosol backscatter, extinction and lidar ratio measured inside the dust layer. Mean values of backscattering and extinction coefficients of (1.2 ± 0.1) 10 −6 m −1 sr −1 and (0.61 ± 0.06) 10 −4 m −1 , respectively, were obtained in the whole observation period, while the mean value of LR at 351 nm resulted to be 47 ± 3 sr. Mean values of dust concentration and dust fluxes were also estimated. The highest values of concentration have been observed on spring and summer months resulting of (150 ± 60) μg·m −3 and (80 ± 30) μg·m -3 , and mean dust fluxes were (0.8 ± 0.4)·10 −3 g m −2 s −1 and (1.6 ± 0.7)·10 −3 g m −2 s −1 , respectively. Finally, aerosol optical properties retrieved from lidar vertical profiles and sun-photometer measurement, in-situ sampling and models outcomes were used to fully examine the most intense dust outbreak observed during the whole study period.

The present study analyses the peak 210Pb activity concentrations observed all over the 1998-2011 period at the WMO-GAW high altitude site of Mt. Cimone (44.18N, 10.7E, 2165masl; Italy) in terms of meteorological conditions, links with other atmospheric species and population dose rate associated with this radiotracer. The highest 210Pb 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 222Rn and thus 210Pb. The main sources of high 210Pb 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 210Pb events: a wide influence of the strong coupling among atmospheric vertical layers on 210Pb 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.

Neste artigo apresentam-se os resultados da quantificação do berílio 7 e chumbo 210 associados a aerossol atmosférico originário do Deserto do Saara e que cruza o Atlântico Norte até aos Açores. O conhecimento da actividade destes isótopos poderá permitir o estudo de intrusões estratosféricas bem como prever algumas características físicas deste tipo de transporte atmosférico. Por outro lado, será possível, com base nos rácios destes dois isótopos, distinguir aerossol de origem marinha e insular de aerossol de origem continental.

Concentrations of airborne particulates undergo a seasonal evolution characterised by a summer maximum in rural areas in Eastern Spain. In the summer months the daily mean concentrations of PM10 and TSP (PM) experience wide variations. In 3-day periods, increases in the PM ...

The Raman lidar system BASIL was operational in Achern (Black Forest) between 25 May and 30 August 2007 in the framework of the Convective and Orographically-induced Precipitation Study (COPS). The system performed continuous measurements over a period of approx. 36 h from 06:22 UTC on 1 August to 18:28 UTC on 2 August 2007, capturing the signature of a severe Saharan dust outbreak episode. The data clearly reveal the presence of two almost separate aerosol layers: a lower layer located between 1.5 and 3.5 km above ground level (a.g.l.) and an upper layer extending between 3.0 and 6.0 km a.g.l. The time evolution of the dust cloud is illustrated and discussed in the paper in terms of several optical parameters (particle backscatter ratio at 532 and 1064 nm, the colour ratio and the backscatter Angström parameter). An inversion algorithm was used to retrieve particle size and microphysical parameters, i.e., mean and effective radius, number, surface area, volume concentration, and complex refractive index, as well as the parameters of a bimodal particle size distribution (PSD), from the multi-wavelength lidar data of particle backscattering, extinction and depolarization. The retrieval scheme employs Tikhonov's inversion with regularization and makes use of kernel functions for randomly oriented spheroids. Size and microphysical parameters of dust particles are estimated as a function of altitude at different times during the dust outbreak event. Retrieval results reveal the presence of a fine mode with radii of 0.1 e0.2 mm and a coarse mode with radii of 3e5 mm both in the lower and upper dust layers, and the dominance in the upper dust layer of a coarse mode with radii of 4e5 mm. Effective radius varies with altitude in the range 0.1e1.5 mm, while volume concentration is found to not exceed 92 mm 3 cm À3. The real and imaginary part of the complex refractive index vary in the range 1.4e1.6 and 0.004e0.008, respectively.

This paper presents samples of Saharan dust outbreak affecting the Mediterranean Tunisian coasts and its impact on PM10 (Particles with an aerodynamic diameter below 10 µm) surface concentrations measured at seven monitoring stations during summer 2006. During the events, the daily PM10 levels at all stations exceeded EU and Tunisian air quality standard limits which are equal to 50 µg/m3. The maximum values ranged from 200 µg/m3 to 300 µg/m3 depending on the monitoring station. The impact is even more dramatic on PM10 hourly concentrations leading to maximum hourly peaks ranging from 400 µg/m3 to 850 µg/m3 again depending on the monitoring station (industrial or residential, traffic and commercial). Comparison between backward air masses trajectories reaching Tunisian coasts and satellite imageries vis-à-vis the PM10 hourly concentrations measured at the monitoring stations during 2006 evidenced the influence of the Saharan dust outbreaks on surface concentrations. The origin of th...

Annual volume-weighted mean (VWM) concentrations in rainwater collected at La Castanya (LC, Montseny Mountains, NE Spain) were analysed from 1983 to 2000 to study the temporal trends in precipitation chemistry, and the causes behind the changes. A significant positive correlation was found between annual rainwater SO 4 2À concentrations at LC and Spanish SO 2 emissions (r ¼ 0:73; P ¼ 0:0008) both decreasing remarkably during this period. Rainwater alkalinity increased during the period, shifting from negative values at the beginning (VWM in the 5 initial years=À2.7 meq l À1) to alkaline values in recent years (VWM in the 5 final years=18.0 meq l À1). Stepwise regression analysis indicated that 88% of the variation of alkalinity could be accounted for by the variability of non-marine Ca 2+ and non-marine SO 4 2À , with a more prominent dependence on Ca 2+. Rains of African provenance were highly enriched in alkalinity and Ca 2+ , but no significant increases in their occurrence were found for the study period. Because of the reported higher dust updraft in northern Africa during years of high North Atlantic Oscillation (NAO) index, we also explored the relationship between rainwater variables associated with an African provenance and NAO. Annual precipitation was inversely related to NAO (r ¼ À0:61; P ¼ 0:007). The annual wet deposition of African dust-related elements showed no correlation with NAO, probably because wet deposition of these elements depends on two factors (precipitation and dust updraft) which have opposite behaviour with respect to NAO. We hypothesise that dry deposition of African dust during dry spells (not sampled in this study) might be higher during high NAO-index years.

Southern European countries are often affected in summer by transboundary air pollution from Saharan dust. However, very few studies deal with Saharan dust pollution at high altitudes in winter. In Italy, the exceptional event occurred on February 19, 2014, colored in red the entire mountain range (Alps and Apennines) and allowed to characterize the particulate matter deposited on snow from a morphological and chemical point of view. Snow samples were collected after this event in four areas in the Alps and one in the Apennines. The particulate matter of the melted snow samples was analyzed by scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS) and by inductively coupled plasma mass spectrometry (ICP-MS). These analyses confirmed the presence of Saharan dust particle components in all areas with similar percentages, supported also by the positive correlations between Mg-Ca, Al-Ca, Al-Mg, and Al-K in all samples.

An overall Holocene increase of Saharan dust input to the Canary Islands and to the North Canary Basin is accompanied by a strong coarsening of Saharan dust in loess-like sediments deposited on Lanzarote from ~7-8 ka. No similar coarsening events are indicated in investigations of the sedimentological record for the last 180 ka, a period showing several dramatic climate changes. Therefore a mobilisation of Holocene dust by anthropogenic activity in the northwest Sahara east of the Canary Islands is assumed. Although scarce archaeological data from the coastal area of that region does not point to strong anthropogenic activity during the early Holocene, a high density of unexplored archaeological remains is reported from the coastal hinterlands in the Western Sahara. Thus, the hypothesis of early anthropogenic activity cannot be excluded.

Mineral dust is an important aerosol species in the Earth's atmosphere and has a major source within North Africa, of which the Sahara forms the major part. Aerosol Time of Flight Mass Spectrometry (ATOFMS) is first used to determine the mixing state of dust particles collected from the land surface in the Saharan region, showing low abundance of species such as nitrate and sulphate internally mixed with the dust mineral matrix. These data are then compared with the ATOFMS single particle mass spectra of Saharan dust particles detected in the marine atmosphere in the vicinity of the Cape Verde islands, which are further compared with those from particles with longer atmospheric residence sampled at a coastal station at Mace Head, Ireland. Saharan dust particles collected near the Cape Verde Islands showed increased internally mixed nitrate but no sulphate, whilst Saharan dust particles collected on the coast of Ireland showed a very high degree of internally mixed secondary species including nitrate, sulphate and methanesulphonate. This uptake of secondary species will change the pH and hygroscopic properties of the aerosol dust and thus can influence the budgets of other reactive gases, as well as influencing the radiative properties of the particles and the availability of metals for dissolution.

El transporte intercontinental de material mineral desde África hacia el Caribe, Norteamérica y Suramérica es un fenómeno de interés investigativo internacional. Varios estudios han llamado la atención sobre los efectos meteorológicos y las implicaciones climáticas derivadas de la presencia de este aerosol en la atmósfera, como también de los potenciales efectos sobre la salud humana. La región Caribe colombiana no es ajena a esta problemática, pero son escasos los estudios realizados. Por lo anterior, el objetivo de este artículo es identificar eventos de intrusión de polvo de origen africano en la región Caribe de Colombia.Metodológicamente se analizaron mapas de concentración de polvo generados por los modelos GEOS- 5, SKIRON, NAAPS y CALIPSO, entre el 01 de enero y el 31 de diciembre de 2012.También se utilizaron imágenes generadas por el sensor satelital MODIS e información de redes de calidad del aire de la región. Según los resultados obtenidos, existen evidencias para afirmar que al norte de Colombia, en la región Caribe, se detectan eventos de intrusión de polvo de origen africano. El periodo del año en que se presentan mayores niveles de concentración es entre marzo y septiembre, sobresaliendo los meses de marzo, junio, julio y agosto.

An overall Holocene increase of Saharan dust input to the Canary Islands and to the North Canary Basin is accompanied by a strong coarsening of Saharan dust in loess-like sediments deposited on Lanzarote from ~7-8 ka. No similar coarsening events are indicated in investigations of the sedimentological record for the last 180 ka, a period showing several dramatic climate changes. Therefore a mobilisation of Holocene dust by anthropogenic activity in the northwest Sahara east of the Canary Islands is assumed. Although scarce archaeological data from the coastal area of that region does not point to strong anthropogenic activity during the early Holocene, a high density of unexplored archaeological remains is reported from the coastal hinterlands in the Western Sahara. Thus, the hypothesis of early anthropogenic activity cannot be excluded.

This study analyses the Saharan dust (SD) events over Athens during 2000–2005 using daily Moderate Resolution Imaging Spectroradiometer (MODIS) and Total Ozone Mapping Spectrometer (TOMS) satellite data. The dust events were identified using the MODIS daily observations over Greece and the dates with detectable dust plumes were collected. The aerosol optical depth (AOD550) and fine-mode (FM) values from Terra-MODIS and

Schon erfahrenen Seemännern waren die Staubstürme bekannt, die zwischen den Kontinenten westwärts von Afrika über den Atlantik zogen. 2 Doch war es Charles Darwin, der diese Phänomene erstmals in seinen wissenschaftlichen Aufzeichnungen belegte. So heißt es in seinen Notizen, die während einer Forschungsreise auf der Beagle zu Papier gebracht wurden: »Am 16. Januar 1832 warfen wir in Porto Praya auf St. Jago, der Hauptinsel des Cap Verd'schen Archipels, Anker.« 3 »Meist ist die Atmosphäre dunstig, und zwar in Folge eines unfühlbar feinen Staubes, welcher, wie wir fanden, die astronomischen Instrumente unbedeutend beschädigt hatte. Am Morgen, ehe wir in Porto Praya vor Anker gingen, sammelte ich ein kleines Päckchen dieses braun gefärbten feinen Staubes, welcher offenbar durch die Gaze der Windfahne an der Mastspitze vom Winde filtrirt worden zu sein scheint. Mr. Lyell hat mir noch vier Päckchen von Staub gegeben, welcher auf ein Schiff einige hundert Meilen nördlich von diesen Inseln gefallen war.« 4

In this study a set of 340 PM10 and PM2.5 samples collected throughout 16 months at rural, an urban kerbside and an industrial background site (affected by the emissions from the ceramic manufacture and other activities) were interpreted. On the regional scale, the main PM10 sources were mineral dust (mainly Al O , Fe, Ti, Sr, CaCO , Mg, 2 3 3 Mn and K), emissions derived from power generation (SO , V, Zn and Ni), vehicle exhausts (organic and elemental _ 4 carbon, NO and trace elements) and marine aerosol (Na, Cl and Mg). The latter was not identified in PM2.5. At y 3 the industrial site, additional PM10 sources were identified (tile covering in the ceramic production, petrochemical emissions and bio-mass burning from a large orange tree cultivation area). The contribution of each PM source to PM10 and PM2.5 levels experiences significant variations depending on the type of PM episode (Local-urban mainly in autumn-winter, regional mainly in summer, African or Atlantic episode), which are discussed in this study. The results show that it would be very difficult to meet the EU limit values for PM10 established for 2010. The annual mean PM levels are 22.0 mg PM10ym at the rural and 49.5 mg PM10ym and 33.9 mg PM2.5ym at the urban site. 3 3 3 The natural contribution in this region, estimated at 6 mgym of natural mineral dust (resulting from the African 3 events and natural resuspension) and 2 mgym of marine aerosol, accounts for 40% of the 2010 EU annual limit 3 value (20 mg PM10ym). Mineral dust concentrations at the urban and industrial sites are higher than those at the 3 rural site because of the urban road dust and the ceramic-production contributions, respectively. At the urban site, the vehicle exhaust contribution (17 mgym) alone is very close to the 2010 EU PM10 limit value. At the rural site, the 3 African dust is the main contributor to PM10 levels during the highest daily mean PM10 events (100th-97th percentile range). At the urban site, the vehicle exhaust product is the main contributor to PM10 and PM2.5 levels during the highest daily mean PM events (100th-85th percentile range). Mineral dust concentrations during African

Concentrations of airborne particulates undergo a seasonal evolution characterised by a summer maximum in rural areas in Eastern Spain. In the summer months the daily mean concentrations of PM10 and TSP (PM) experience wide variations. In 3-day periods, increases in the PM concentrations from 15 to 30-40 mg/m 3 are frequently reported, and increases from 15 to 40-60 mg/m 3 occur several times throughout the summer. These variations are simultaneously reported at rural stations throughout the flat Ebro basin (600 m a.s.l.) and at mountain sites located at high altitude (>1000 m a.s.l.). The origin of high and low PM episodes was investigated by correlating PM levels with the concentrations of gaseous pollutants, and making use of meteorological analysis and satellite observations. The highest PM events (daily concentrations in the range 40-60 mg/m 3) were documented during outbreaks of African dust. The second highest PM events (daily concentrations in the range 20-45 mg/m 3) were recorded during regional episodes associated with ozone events. These summer regional PM episodes were induced by the abrupt orography surrounding the Western Mediterranean and by the regional meteorology, which favour the ageing of polluted air masses into the basin. These regional events occur in a synoptic meteorological context characterised by a weak pressure horizontal gradient over the Western Mediterranean often associated with the development of the Iberian thermal low, when advection of air masses is not significant. In this meteorological context, the transport of particulate pollutants from urban/industrial to rural sites is brought about by the breeze circulation at the coastal (sea breeze) and mountain (mountain breeze) sites. The persistence of this breeze circulation for several days (periods of up to 2 weeks were reported) results in a low renovation of air masses leading to an accumulation of airborne particulates in the regional atmosphere. The lowest PM events (daily concentrations o20 mg/m 3) were reported during abrupt entries of Atlantic air into the Mediterranean.

Using an integrated dust-storm modeling system, we simulate the severe Saharan dust episode between 1 and 10 March 2004. The simulations are compared with surface synoptic data and satellite images and are found to agree well with the observations. The synoptic systems that generated the dust storms and the evolution of the dust patterns are analyzed. It is revealed that a cyclogenesis over central Sahara, accompanied by an anticyclone over the Atlantic and a monsoon trough in the tropics, was responsible for the widespread continental-scale dust storms in North Africa. Dust first appeared in west Sahara, then in east Sahara and much of the dust emitted from east Sahara was transported to the monsoon trough, resulting in high concentrations of suspended dust over the Sahel (column dust load up to 10 g m −2). The main dust source regions were (1) Mauritania, (2) Chad and Niger, and (3) Libya, Egypt, and Sudan. The region between 10°N and 17°N was one of net dust deposition. We estimate that 715.8 megatons (Mt) of dust was emitted from North Africa during the episode, 608.2 Mt of which was deposited to the continent, and the net dust emission was 107.6 Mt. Of the 107.6 Mt, with respect to the model domain, 7.3 Mt was deposited to the ocean, 79.8 Mt was transported across the domain boundaries, and 20.5 Mt was suspended in the atmosphere.

ABSTRACT Cloud- and rain-water samples collected between 1984 and 2007 in the Luquillo Experimental Forest, Puerto Rico, were analyzed in order to understand the main processes and sources that control their chemistry. Three sites were used: El Verde Field Station (380 m asl), Bisley (361 m asl), and East Peak (1051 m asl). Bulk rainwater samples were collected from all sites, and cloud water was also collected on East Peak. All samples were analyzed for pH, conductivity, and concentrations of Cl−, SO42−, NO3−, NH4+, Na+, K+, Ca2+ and Mg2+. Similar patterns in overall chemistry were observed for both cloud- and rain-water samples. The majority of samples had low acidity (average pH of 4.4–5.0), similar to other remote sites. Sea salt (Na+ and Cl−) had a large influence on rain and cloud chemistry and accounted for approximately 70% of the total mass of solutes, followed by SO4=, which controls the acidity of the clouds and rainwater. Calcium accounted for 6–8% of the total cations and dominated neutralization processes. The highest concentrations of Ca2+ and NO3− in both cloud- and rain-water were observed in the summertime when large amounts of dust from the African continent reached the sites. Enrichment Factor and Principal Component Analyses showed that Na+, Cl−, and Mg2+ in the cloud- and rain-water were primarily of marine origin, while most of the Ca2+ was from crustal sources; and NO3− was predominantly anthropogenic, presumably from both local and long-range sources. In general, the results of this study suggested that cloud- and rain-water chemistry in northeastern Puerto Rico is strongly influenced by natural and marine sources rather than local anthropogenic sources. The pollutant species in the samples were mainly derived from long distance transport.

ABSTRACT Cloud- and rain-water samples collected between 1984 and 2007 in the Luquillo Experimental Forest, Puerto Rico, were analyzed in order to understand the main processes and sources that control their chemistry. Three sites were used: El Verde Field Station (380 m asl), Bisley (361 m asl), and East Peak (1051 m asl). Bulk rainwater samples were collected from all sites, and cloud water was also collected on East Peak. All samples were analyzed for pH, conductivity, and concentrations of Cl−, SO42−, NO3−, NH4+, Na+, K+, Ca2+ and Mg2+. Similar patterns in overall chemistry were observed for both cloud- and rain-water samples. The majority of samples had low acidity (average pH of 4.4–5.0), similar to other remote sites. Sea salt (Na+ and Cl−) had a large influence on rain and cloud chemistry and accounted for approximately 70% of the total mass of solutes, followed by SO4=, which controls the acidity of the clouds and rainwater. Calcium accounted for 6–8% of the total cations and dominated neutralization processes. The highest concentrations of Ca2+ and NO3− in both cloud- and rain-water were observed in the summertime when large amounts of dust from the African continent reached the sites. Enrichment Factor and Principal Component Analyses showed that Na+, Cl−, and Mg2+ in the cloud- and rain-water were primarily of marine origin, while most of the Ca2+ was from crustal sources; and NO3− was predominantly anthropogenic, presumably from both local and long-range sources. In general, the results of this study suggested that cloud- and rain-water chemistry in northeastern Puerto Rico is strongly influenced by natural and marine sources rather than local anthropogenic sources. The pollutant species in the samples were mainly derived from long distance transport.