Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European... more Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5–10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. D...
The sea area between Norway and Svalbard Islands (Norwegian and Greenland Seas) is a critical sit... more The sea area between Norway and Svalbard Islands (Norwegian and Greenland Seas) is a critical site to study the effects of the climate change on the high-latitude Northern-Hemisphere regions. In particular, changes in extension and/or in the persistence of annual sea-ice, availability of nutrients and trace-elements in the biological-active marine layers and sea surface temperatures could affect the marine primary productivity and the emission into the atmosphere of dimethylsulphide (DMS), produced by phytoplankton metabolic processes. This volatile compound is oxidised in the atmosphere mainly to sulphuric acid and Methanesulphonic acid (MSA), which undergo gas-to-particle processes and form secondary sub-micrometric aerosol particles. In this way, they play a relevant role as cloud concentration nuclei (CCN), therefore controlling the climate through scattering/absorption of solar irradiation and changes in cloud coverage (and so affecting albedo). Here, we report the spatial dist...
Atmospheric aerosols are estimated to play a relevant role in climate change, also in relation to... more Atmospheric aerosols are estimated to play a relevant role in climate change, also in relation to global warming and to the hydrological cycle; information on aerosol sources and impact are among the data needed to constrain uncertainties in climate change models. This is particularly important in the Mediterranean basin, whose atmosphere is heavily polluted and characterized by strong influences from both natural and anthropogenic emissions. An investigation aimed at assessing the aerosol sources affecting the Central Mediterranean basin has been carried out by applying the Positive Matrix Factorization (PMF) model to a 2-year long data set of PM10 mass concentration and chemical composition of samples collected on the island of Lampedusa (35.5° N, 12.6° E, 45 m a.s.l.). Lampedusa is an ideal site for this kind of studies, as it is far from continental pollution sources (the nearest coast, in Tunisia, is more than 100 km away). Samples were collected on a daily basis; after mass gr...
Firn core methanesulphonic acid (MSA) stratigraphy from Talos Dome (East Antarctica) was compared... more Firn core methanesulphonic acid (MSA) stratigraphy from Talos Dome (East Antarctica) was compared with anomalies of the satellite-measured sea ice extent in the Ross Sea and Wilkes Land oceanic sector. In spite of the sparseness of sea ice data, the MSA maxima fit with many positive sea ice anomalies in the Ross Sea. This evidence suggests that marine biogenic activity enhanced by large sea ice cover is an important, but not exclusive, factor in controlling MSA concentration in snow precipitation at Talos Dome. Other than source intensity, differences in regional atmospheric transport mechanisms affect the arrival of MSA-rich aerosol at Talos Dome. To clarify the role of transport processes in bringing biogenic aerosol to Talos Dome, a spectral analysis was applied to the MSA, SOI (South Oscillation Index), and SAM (Southern Annular Mode) record. Synchronicity or phase shift between the chemical signature and atmospheric circulation modes were tested. The variations in the MSA profile have a periodicity of 6.9, 4.9, 3.5, and 2.9 years. The 6.9 and 2.9 year periodicities show a strong positive correlation and are synchronous with corresponding SOI periodicity. This variability could be related to an increase in MSA source intensity (by dimethylsulphide from phytoplanktonic activity) linked to the sea ice extent in the Ross Sea area, but also to an increased strength in transport processes. Both of these factors are correlated with La Niñ a events (SOI positive values). Furthermore, SAM positive values are related to an increased sea ice extent in the Ross Sea sector and show two main periodicities 3.3 and 3.8 years. These periodicities determine the MSA variability at 3.5 years. However, the effect of intensification of the polar vortex and the consequent reduction in transport process intensity, which reduce the delivery of air masses enriched in MSA from oceanic areas to Talos Dome, make the effect of the SAM on the MSA concentration at Talos Dome less active than the SOI. In this way, snow deposition at the Talos Dome records larger MSA concentration by the combined effects of increased source emissions and more efficient transport processes. The MSA record from Talos Dome can therefore be considered a reliable proxy of sea ice extent when the effect of changes in transport processes in this region of Antarctica is considered. Over the previous 140 years, these conditions occur with a periodicity of 6.9 years.
ABSTRACT Saharan dust largely affects air pollution and climate. This study aims at determining t... more ABSTRACT Saharan dust largely affects air pollution and climate. This study aims at determining the mineral contribution to PM10 in the Central Mediterranean Sea based on 7 years of PM10 chemical composition measurements at the island of Lampedusa (35.5°N, 12.6° E). Total content and soluble fractions of selected elements and metals are used to characterize the dust events. The soluble + insoluble contribution is determined by PIXE, (Particles Induced X-ray Emission), while the composition of the soluble fraction by ICP-AES, (Inductively coupled plasma - atomic emission spectroscopy) after extraction with HNO3 at pH1.5. The solubility of each element and its size distribution are analyzed with the aim of obtaining information on their sources, mixing processes, and availability for the environment. The Saharan dust contribution to the total PM was estimated by considering Al, Si, Ca, non-sea-salt Na, K and Fe oxides. During strong Saharan dust events PM10 is often higher than 50μg m-3, and the dust contribution is about 50%. The crustal aerosol amount and contribution to PM10 shows a very small seasonal dependence; conversely, the dust optical depth displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm as large as 0.28 in June-August). We found that only 49% of the events identified from optical properties over the air column display a high dust content at the ground level, demonstrating that Saharan dust transport frequently occurs above the marine boundary layer, with negligible or small impact on the surface aerosol properties. The average size distribution obtained by Optical Particle Counter during the days with high mineral content comprises three modes, whose median radii are at about 0.29 um, 2.2 um, and 7.2 um, respectively. Solubility of each elements present a large variability in the condition of extraction, but usually in Saharan dust events the solubility is lower than in non-Saharan dust events. Markers of crust present two relative maxima in the size range 2.1-3.3 um and 5.8-9 um, generally characterized by low solubility. Conversely, elements having also anthropic source present a maxima in the finest fraction, characterized by highly soluble components. For instance Fe, K and Co present a very low solubility in the coarse fraction (8 % in the size range 2.1-3.3 um for Fe), on the contrary the finest fraction is characterized by high solubility (69 % in the size range 0.4-0.7 um for Fe).
Biomass burning (BB) is a significant source of particulate matter (PM) in many parts of the worl... more Biomass burning (BB) is a significant source of particulate matter (PM) in many parts of the world. Whereas numerous studies demonstrate the relevance of BB emissions in central and northern Europe, the quantification of this source has been assessed only in few cities in southern European countries. In this work, the application of Positive Matrix Factorisation (PMF) allowed a clear identification and quantification of an unexpected very high biomass burning contribution in Tuscany (central Italy), in the most polluted site of the PATOS project. In this urban background site, BB accounted for 37% of the mass of PM10 (particulate matter with aerodynamic diameter<10 μm) as annual average, and more than 50% during winter, being the main cause of all the PM10 limit exceedances. Due to the chemical complexity of BB emissions, an accurate assessment of this source contribution is not always easily achievable using just a single tracer. The present work takes advantage of the combination of a long-term daily data-set, characterized by an extended chemical speciation, with a short-term high time resolution (1-hour) and size-segregated data-set, obtained by PIXE analyses of streaker samples. The hourly time pattern of the BB source, characterised by a periodic behaviour with peaks starting at about 6 p.m. and lasting all the evening-night, and its strong seasonality, with higher values in the winter period, clearly confirmed the hypothesis of a domestic heating source (also excluding important contributions from wildfires and agricultural wastes burning).
Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as th... more Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as they cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at the ground level. To estimate the Saharan dust contribution to PM 10 , a significant dust intrusion event that occurred in June 2006 is investigated, joining numerical simulations and specific measurements. As a first step, a synoptic analysis of this episode is performed. Such analysis, based only on meteorological and aerosol optical thickness observations, does not allow the assessment of exhaustive informations. In fact, it is not possible to distinguish dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition. The approach proposed in this work applies an ad hoc model chain to describe emission, transport and deposition dynamics. Furthermore, physical and chemical analyses (PIXE analysis and ion chromatography) were used to measure the concentration of all soil-related elements to quantify the contribution of dust particles to PM 10 . The comparison between simulation results and in-situ measurements show a satisfying agreement, and supports the effectiveness of the model chain to estimate the Saharan dust contribution at ground level.
ABSTRACT Using high resolution chemical impurity and dielectric profiling data annual layers have... more ABSTRACT Using high resolution chemical impurity and dielectric profiling data annual layers have been counted on the EPICA ice core from Dronning Maud Land (EDML), Antarctica spanning the past 16700 years. The methodology used for counting Greenland ice cores and creating the Greenland Ice Core Chronology 2005 (GICC05) [Rasmussen et al., 2006] has also been implemented for the EDML counting. The estimated maximum counting error for the EDML counting is approx. 5%, but a preliminary volcanic matching with Greenland ice core records suggest differences of 1% or less during the Holocene between the EDML counting and GICC05. A comparison of cosmogenic isotope records from EDML and Greenland also suggests differences of less than 1% between the two annual layer counted chronologies. Reference: Rasmussen, S.O., Andersen, K.K., Svensson, A., Steffensen, J.P., Vinther, B.M., Clausen, H.B., Andersen, M.L.S., Johnsen, S.J., Larsen, L.B., Dahl-Jensen, D., Bigler, M., Röthlisberger R., Fischer H., Goto-Azuma K., Hansson M.E., Ruth U, A new Greenland ice core chronology for the last glacial termination, Journal of Geophysical Research Vol. 111, D06102, doi:10.1029/2005JD006079. 2006.
In Milan (MI), the largest city in Northern Italy, the annually average PM2.5 concentration is ab... more In Milan (MI), the largest city in Northern Italy, the annually average PM2.5 concentration is above 25 μg m − 3 , the value that the EU established as a target for 2010, and the upper limit from 2015 onwards (2008/30/CE). Over a three-year period (2006-2009) PM concentrations and chemical compositions were measured in an urban site (MI), a rural site (OB) and a remote site (ASC) in Northern Italy. Chemical characterization (EC/ OC, inorganic ions, elements, C20-C32 n-alkanes, C2-C5 mono and dicarboxylic acids, levoglucosan and PAHs) was carried out on PM2.5 samples from the three sites, and PM10 from MI. Molecular markers were used in Chemical Mass Balance (CMB) modelling to estimate the contributions of primary sources to OC, and then PM mass from each source was reconstructed in MI, OB and ASC for different seasons. Estimates of the traffic (TR) source contribution to PM2.5 mass ranged from 4.1 (± 2.0) μg m − 3 during the summer, to 13.3 (±6.7) μg m − 3 during the winter in MI. TR was the main primary source for PM2.5 concentrations in MI (17-24%). Its contribution was lower at the OB site (7-9%) and at the remote ASC site (3-4%). TR is a local source, while biomass burning (BB) is a diffuse regional source in Northern Italy: during fall and winter, BB was 25-30% and 27-31% of PM2.5 at MI and OB respectively. Other primary sources accounted for a small amount of the PM2.5, i.e. natural gas combustion (0-1%), plant debris (0-4%), road dust (RD = 0-4%; but 15% at ASC during winter and 10% of PM10 at MI during summer) and sea salt (0-1%). Secondary inorganic + organic aerosol constituted the major part of the PM2.5 mass during spring and summer (50-65%) at the three sites.
Sea-salt aerosol (SSA) is the dominant contributor to cloud condensation nuclei over ocean areas,... more Sea-salt aerosol (SSA) is the dominant contributor to cloud condensation nuclei over ocean areas, where wind speed is significant. Thereby, SSA could affect cloud formation and play an important role in the Earth weather and climate. Rainfall could produce large impact on SSA concentration due to wet removal processes. An analysis of changes in sea-salt aerosol concentration after rainfall is essential for a deeper understanding of the process of SSA loading in the boundary layer. The current experimental study focused on analyzing time variations of SSA mass concentration after rainfall, on the basis of long-term daily SSA measurements during the three-year period 2006-2008, at the tiny Mediterranean island of Lampedusa (Central Mediterranean). To study the effect of rainfall on SSA time variations, we used the superposed epoch method. We applied this approach to differing rainfall events related to different months and atmospheric/sea conditions. Integrated processing was applied to SSA concentration anomalies, in order to filter out random variability. Observational evidence of SSA mass concentration oscillations after rainfall with a maximum on the 2nd day and a minimum on the 4th day was obtained. The knowledge of SSA variations after rainfall is important for validating rainout parameterization in existing sea-salt aerosol and climate models.
Atmospheric Chemistry and Physics Discussions, 2011
Measurements of aerosol chemical composition made on the island of Lampedusa, south of the Sicily... more Measurements of aerosol chemical composition made on the island of Lampedusa, south of the Sicily channel, during years 2004-2008, are used to identify the influence of ship emissions on aerosol particles in the Central Mediterranean. Evidence of ship emissions influence is found in 17 % of the daily samples. Aerosol samples influenced 20 bustion (V, Ni, Al, Fe) are distributed in the sub-micrometric fraction of the aerosol, and the metals are present as free metals, carbonates, oxides hydrates or labile complex with organic ligands, so that they are dissolved in mild condition (HNO 3 , pH1.5).
From January to December 2010, surface snow samples were collected with monthly resolution at the... more From January to December 2010, surface snow samples were collected with monthly resolution at the Concordia station (75°06'S, 123°20'E), on the Antarctic plateau, and analysed for major and trace elements in both dissolved and particulate (i.e. insoluble particles, >0.45μm) phase. Additional surface snow samples were collected with daily resolution, for the determination of sea-salt sodium and not-sea-salt calcium, in order to support the discussion on the seasonal variations of trace elements. Concentrations of alkaline and alkaline-earth elements were higher in winter (April-October) than in summer (November-March) by a factor of 1.2-3.3, in agreement with the higher concentration of sea-salt atmospheric particles reaching the Antarctic plateau during the winter. Similarly, trace elements were generally higher in winter by a factor of 1.2-1.5, whereas Al and Fe did not show any significant seasonal trend. Partitioning between dissolved and particulate phases did not change with the sampling period, but it depended only on the element: alkaline and alkaline-earth elements, as well as Co, Cu, Mn, Pb and Zn were for the most part (>80%) in the dissolved phase, whereas Al and Fe were mainly associated with the particulate phase (>80%) and Cd, Cr, V were nearly equally distributed between the phases. Finally, the estimated marine and crustal enrichment factors indicated that Cd, Cr, Cu, Pb and Zn have a dominant anthropogenic origin, with a possible contribution from the Concordia station activities.
... 168 spots), requires about 9 h. The interest for a detailed, size-resolved and high ... varia... more ... 168 spots), requires about 9 h. The interest for a detailed, size-resolved and high ... variations with climatic changes, dust stratigraphies have been obtained by the chemical and physical ... are reported; in accordance with recent literature,[17] the ice dust composition during the cold ...
An example of an integrated approach to assess air pollution threats to cultural heritage in a se... more An example of an integrated approach to assess air pollution threats to cultural heritage in a semi-confined environment is presented in this work, where the monitoring campaign carried out at the Michelozzo's Courtyard (in Palazzo Vecchio, Florence, Italy) is used as a case study. A wide research project was carried out, with the main aim of obtaining the first quantitative data on air quality and microclimate conditions inside the Courtyard, and, if possible, identifying the main causes of degradation and suggesting appropriate conservation strategies. The investigation adopted a holistic approach involving thermographic measurements on the wall paintings, microclimatic analysis, gaseous pollutant monitoring, atmospheric particles characterisation and dry deposition compositional analysis. Attention was focused on the wall painting depicting the city of Hall because of its anomalous and critical conservation conditions, which are visible at a glance, due to the contrast between a wide darker zone around the central subject of the painting and external lighter areas.
The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and seq... more The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and sequential ice. Numerous chemical species have been measured along the length of the cores. Here we concentrate on interpreting the main low-resolution patterns of major ions. We extend the published record for non-sea-salt calcium, sea-salt sodium and non-sea-salt sulfate flux to 800 ka. The non-sea-salt calcium record confirms that terrestrial dust originating from South America closely mirrored Antarctic climate, both at orbital and millennial timescales. A major cause of the main trends is most likely climate in southern South America, which could be sensitive to subtle changes in atmospheric circulation. Seasalt sodium also follows temperature, but with a threshold at low temperature. We re-examine the use of sodium as a sea ice proxy, concluding that it is probably reflecting extent, with high salt concentrations reflecting larger ice extents. With this interpretation, the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials. Non-sea-salt sulfate flux is almost constant along the core, confirming the lack of change in marine productivity (for sulfur-producing organisms) in the areas of the Southern Ocean contributing to the flux at Dome C. For the first time we also present long records of reversible species such as nitrate and chloride, and show that the pattern of post-depositional losses described for shallower ice is maintained in older ice. It appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site, and the results suggest a possible correction to accumulation rates in one early interglacial. Taken together the chemistry records offer a number of constraints on the way the Earth system combined to give the major climate fluctuations of the late Quaternary period.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008
An analytical procedure has been implemented in this work for an accurate geochemical characteriz... more An analytical procedure has been implemented in this work for an accurate geochemical characterization and quantitative analysis of the fine dust (particles diameter<5μm) trapped in Antarctic ice cores and the fine fraction of potential source areas (PSA) sediments by size selection, filtering and PIXE–PIGE combined measurements. The underestimation of concentrations of the lighter elements, like Na, Mg, Al and Si,
Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European... more Continuous sea salt and mineral dust aerosol records have been studied on the two EPICA (European Project for Ice Coring in Antarctica) deep ice cores. The joint use of these records from opposite sides of the East Antarctic plateau allows for an estimate of changes in dust transport and emission intensity as well as for the identification of regional differences in the sea salt aerosol source. The mineral dust flux records at both sites show a strong coherency over the last 150 kyr related to dust emission changes in the glacial Patagonian dust source with three times higher dust fluxes in the Atlantic compared to the Indian Ocean sector of the Southern Ocean (SO). Using a simple conceptual transport model this indicates that transport can explain only 40% of the atmospheric dust concentration changes in Antarctica, while factor 5–10 changes occurred. Accordingly, the main cause for the strong glacial dust flux changes in Antarctica must lie in environmental changes in Patagonia. D...
The sea area between Norway and Svalbard Islands (Norwegian and Greenland Seas) is a critical sit... more The sea area between Norway and Svalbard Islands (Norwegian and Greenland Seas) is a critical site to study the effects of the climate change on the high-latitude Northern-Hemisphere regions. In particular, changes in extension and/or in the persistence of annual sea-ice, availability of nutrients and trace-elements in the biological-active marine layers and sea surface temperatures could affect the marine primary productivity and the emission into the atmosphere of dimethylsulphide (DMS), produced by phytoplankton metabolic processes. This volatile compound is oxidised in the atmosphere mainly to sulphuric acid and Methanesulphonic acid (MSA), which undergo gas-to-particle processes and form secondary sub-micrometric aerosol particles. In this way, they play a relevant role as cloud concentration nuclei (CCN), therefore controlling the climate through scattering/absorption of solar irradiation and changes in cloud coverage (and so affecting albedo). Here, we report the spatial dist...
Atmospheric aerosols are estimated to play a relevant role in climate change, also in relation to... more Atmospheric aerosols are estimated to play a relevant role in climate change, also in relation to global warming and to the hydrological cycle; information on aerosol sources and impact are among the data needed to constrain uncertainties in climate change models. This is particularly important in the Mediterranean basin, whose atmosphere is heavily polluted and characterized by strong influences from both natural and anthropogenic emissions. An investigation aimed at assessing the aerosol sources affecting the Central Mediterranean basin has been carried out by applying the Positive Matrix Factorization (PMF) model to a 2-year long data set of PM10 mass concentration and chemical composition of samples collected on the island of Lampedusa (35.5° N, 12.6° E, 45 m a.s.l.). Lampedusa is an ideal site for this kind of studies, as it is far from continental pollution sources (the nearest coast, in Tunisia, is more than 100 km away). Samples were collected on a daily basis; after mass gr...
Firn core methanesulphonic acid (MSA) stratigraphy from Talos Dome (East Antarctica) was compared... more Firn core methanesulphonic acid (MSA) stratigraphy from Talos Dome (East Antarctica) was compared with anomalies of the satellite-measured sea ice extent in the Ross Sea and Wilkes Land oceanic sector. In spite of the sparseness of sea ice data, the MSA maxima fit with many positive sea ice anomalies in the Ross Sea. This evidence suggests that marine biogenic activity enhanced by large sea ice cover is an important, but not exclusive, factor in controlling MSA concentration in snow precipitation at Talos Dome. Other than source intensity, differences in regional atmospheric transport mechanisms affect the arrival of MSA-rich aerosol at Talos Dome. To clarify the role of transport processes in bringing biogenic aerosol to Talos Dome, a spectral analysis was applied to the MSA, SOI (South Oscillation Index), and SAM (Southern Annular Mode) record. Synchronicity or phase shift between the chemical signature and atmospheric circulation modes were tested. The variations in the MSA profile have a periodicity of 6.9, 4.9, 3.5, and 2.9 years. The 6.9 and 2.9 year periodicities show a strong positive correlation and are synchronous with corresponding SOI periodicity. This variability could be related to an increase in MSA source intensity (by dimethylsulphide from phytoplanktonic activity) linked to the sea ice extent in the Ross Sea area, but also to an increased strength in transport processes. Both of these factors are correlated with La Niñ a events (SOI positive values). Furthermore, SAM positive values are related to an increased sea ice extent in the Ross Sea sector and show two main periodicities 3.3 and 3.8 years. These periodicities determine the MSA variability at 3.5 years. However, the effect of intensification of the polar vortex and the consequent reduction in transport process intensity, which reduce the delivery of air masses enriched in MSA from oceanic areas to Talos Dome, make the effect of the SAM on the MSA concentration at Talos Dome less active than the SOI. In this way, snow deposition at the Talos Dome records larger MSA concentration by the combined effects of increased source emissions and more efficient transport processes. The MSA record from Talos Dome can therefore be considered a reliable proxy of sea ice extent when the effect of changes in transport processes in this region of Antarctica is considered. Over the previous 140 years, these conditions occur with a periodicity of 6.9 years.
ABSTRACT Saharan dust largely affects air pollution and climate. This study aims at determining t... more ABSTRACT Saharan dust largely affects air pollution and climate. This study aims at determining the mineral contribution to PM10 in the Central Mediterranean Sea based on 7 years of PM10 chemical composition measurements at the island of Lampedusa (35.5°N, 12.6° E). Total content and soluble fractions of selected elements and metals are used to characterize the dust events. The soluble + insoluble contribution is determined by PIXE, (Particles Induced X-ray Emission), while the composition of the soluble fraction by ICP-AES, (Inductively coupled plasma - atomic emission spectroscopy) after extraction with HNO3 at pH1.5. The solubility of each element and its size distribution are analyzed with the aim of obtaining information on their sources, mixing processes, and availability for the environment. The Saharan dust contribution to the total PM was estimated by considering Al, Si, Ca, non-sea-salt Na, K and Fe oxides. During strong Saharan dust events PM10 is often higher than 50μg m-3, and the dust contribution is about 50%. The crustal aerosol amount and contribution to PM10 shows a very small seasonal dependence; conversely, the dust optical depth displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm as large as 0.28 in June-August). We found that only 49% of the events identified from optical properties over the air column display a high dust content at the ground level, demonstrating that Saharan dust transport frequently occurs above the marine boundary layer, with negligible or small impact on the surface aerosol properties. The average size distribution obtained by Optical Particle Counter during the days with high mineral content comprises three modes, whose median radii are at about 0.29 um, 2.2 um, and 7.2 um, respectively. Solubility of each elements present a large variability in the condition of extraction, but usually in Saharan dust events the solubility is lower than in non-Saharan dust events. Markers of crust present two relative maxima in the size range 2.1-3.3 um and 5.8-9 um, generally characterized by low solubility. Conversely, elements having also anthropic source present a maxima in the finest fraction, characterized by highly soluble components. For instance Fe, K and Co present a very low solubility in the coarse fraction (8 % in the size range 2.1-3.3 um for Fe), on the contrary the finest fraction is characterized by high solubility (69 % in the size range 0.4-0.7 um for Fe).
Biomass burning (BB) is a significant source of particulate matter (PM) in many parts of the worl... more Biomass burning (BB) is a significant source of particulate matter (PM) in many parts of the world. Whereas numerous studies demonstrate the relevance of BB emissions in central and northern Europe, the quantification of this source has been assessed only in few cities in southern European countries. In this work, the application of Positive Matrix Factorisation (PMF) allowed a clear identification and quantification of an unexpected very high biomass burning contribution in Tuscany (central Italy), in the most polluted site of the PATOS project. In this urban background site, BB accounted for 37% of the mass of PM10 (particulate matter with aerodynamic diameter<10 μm) as annual average, and more than 50% during winter, being the main cause of all the PM10 limit exceedances. Due to the chemical complexity of BB emissions, an accurate assessment of this source contribution is not always easily achievable using just a single tracer. The present work takes advantage of the combination of a long-term daily data-set, characterized by an extended chemical speciation, with a short-term high time resolution (1-hour) and size-segregated data-set, obtained by PIXE analyses of streaker samples. The hourly time pattern of the BB source, characterised by a periodic behaviour with peaks starting at about 6 p.m. and lasting all the evening-night, and its strong seasonality, with higher values in the winter period, clearly confirmed the hypothesis of a domestic heating source (also excluding important contributions from wildfires and agricultural wastes burning).
Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as th... more Dust intrusions from African desert regions have an impact on the Mediterranean Basin (MB), as they cause an anomalous increase of aerosol concentrations in the tropospheric column and often an increase of particulate matter at the ground level. To estimate the Saharan dust contribution to PM 10 , a significant dust intrusion event that occurred in June 2006 is investigated, joining numerical simulations and specific measurements. As a first step, a synoptic analysis of this episode is performed. Such analysis, based only on meteorological and aerosol optical thickness observations, does not allow the assessment of exhaustive informations. In fact, it is not possible to distinguish dust outbreaks transported above the boundary layer without any impact at the ground level from those causing deposition. The approach proposed in this work applies an ad hoc model chain to describe emission, transport and deposition dynamics. Furthermore, physical and chemical analyses (PIXE analysis and ion chromatography) were used to measure the concentration of all soil-related elements to quantify the contribution of dust particles to PM 10 . The comparison between simulation results and in-situ measurements show a satisfying agreement, and supports the effectiveness of the model chain to estimate the Saharan dust contribution at ground level.
ABSTRACT Using high resolution chemical impurity and dielectric profiling data annual layers have... more ABSTRACT Using high resolution chemical impurity and dielectric profiling data annual layers have been counted on the EPICA ice core from Dronning Maud Land (EDML), Antarctica spanning the past 16700 years. The methodology used for counting Greenland ice cores and creating the Greenland Ice Core Chronology 2005 (GICC05) [Rasmussen et al., 2006] has also been implemented for the EDML counting. The estimated maximum counting error for the EDML counting is approx. 5%, but a preliminary volcanic matching with Greenland ice core records suggest differences of 1% or less during the Holocene between the EDML counting and GICC05. A comparison of cosmogenic isotope records from EDML and Greenland also suggests differences of less than 1% between the two annual layer counted chronologies. Reference: Rasmussen, S.O., Andersen, K.K., Svensson, A., Steffensen, J.P., Vinther, B.M., Clausen, H.B., Andersen, M.L.S., Johnsen, S.J., Larsen, L.B., Dahl-Jensen, D., Bigler, M., Röthlisberger R., Fischer H., Goto-Azuma K., Hansson M.E., Ruth U, A new Greenland ice core chronology for the last glacial termination, Journal of Geophysical Research Vol. 111, D06102, doi:10.1029/2005JD006079. 2006.
In Milan (MI), the largest city in Northern Italy, the annually average PM2.5 concentration is ab... more In Milan (MI), the largest city in Northern Italy, the annually average PM2.5 concentration is above 25 μg m − 3 , the value that the EU established as a target for 2010, and the upper limit from 2015 onwards (2008/30/CE). Over a three-year period (2006-2009) PM concentrations and chemical compositions were measured in an urban site (MI), a rural site (OB) and a remote site (ASC) in Northern Italy. Chemical characterization (EC/ OC, inorganic ions, elements, C20-C32 n-alkanes, C2-C5 mono and dicarboxylic acids, levoglucosan and PAHs) was carried out on PM2.5 samples from the three sites, and PM10 from MI. Molecular markers were used in Chemical Mass Balance (CMB) modelling to estimate the contributions of primary sources to OC, and then PM mass from each source was reconstructed in MI, OB and ASC for different seasons. Estimates of the traffic (TR) source contribution to PM2.5 mass ranged from 4.1 (± 2.0) μg m − 3 during the summer, to 13.3 (±6.7) μg m − 3 during the winter in MI. TR was the main primary source for PM2.5 concentrations in MI (17-24%). Its contribution was lower at the OB site (7-9%) and at the remote ASC site (3-4%). TR is a local source, while biomass burning (BB) is a diffuse regional source in Northern Italy: during fall and winter, BB was 25-30% and 27-31% of PM2.5 at MI and OB respectively. Other primary sources accounted for a small amount of the PM2.5, i.e. natural gas combustion (0-1%), plant debris (0-4%), road dust (RD = 0-4%; but 15% at ASC during winter and 10% of PM10 at MI during summer) and sea salt (0-1%). Secondary inorganic + organic aerosol constituted the major part of the PM2.5 mass during spring and summer (50-65%) at the three sites.
Sea-salt aerosol (SSA) is the dominant contributor to cloud condensation nuclei over ocean areas,... more Sea-salt aerosol (SSA) is the dominant contributor to cloud condensation nuclei over ocean areas, where wind speed is significant. Thereby, SSA could affect cloud formation and play an important role in the Earth weather and climate. Rainfall could produce large impact on SSA concentration due to wet removal processes. An analysis of changes in sea-salt aerosol concentration after rainfall is essential for a deeper understanding of the process of SSA loading in the boundary layer. The current experimental study focused on analyzing time variations of SSA mass concentration after rainfall, on the basis of long-term daily SSA measurements during the three-year period 2006-2008, at the tiny Mediterranean island of Lampedusa (Central Mediterranean). To study the effect of rainfall on SSA time variations, we used the superposed epoch method. We applied this approach to differing rainfall events related to different months and atmospheric/sea conditions. Integrated processing was applied to SSA concentration anomalies, in order to filter out random variability. Observational evidence of SSA mass concentration oscillations after rainfall with a maximum on the 2nd day and a minimum on the 4th day was obtained. The knowledge of SSA variations after rainfall is important for validating rainout parameterization in existing sea-salt aerosol and climate models.
Atmospheric Chemistry and Physics Discussions, 2011
Measurements of aerosol chemical composition made on the island of Lampedusa, south of the Sicily... more Measurements of aerosol chemical composition made on the island of Lampedusa, south of the Sicily channel, during years 2004-2008, are used to identify the influence of ship emissions on aerosol particles in the Central Mediterranean. Evidence of ship emissions influence is found in 17 % of the daily samples. Aerosol samples influenced 20 bustion (V, Ni, Al, Fe) are distributed in the sub-micrometric fraction of the aerosol, and the metals are present as free metals, carbonates, oxides hydrates or labile complex with organic ligands, so that they are dissolved in mild condition (HNO 3 , pH1.5).
From January to December 2010, surface snow samples were collected with monthly resolution at the... more From January to December 2010, surface snow samples were collected with monthly resolution at the Concordia station (75°06'S, 123°20'E), on the Antarctic plateau, and analysed for major and trace elements in both dissolved and particulate (i.e. insoluble particles, >0.45μm) phase. Additional surface snow samples were collected with daily resolution, for the determination of sea-salt sodium and not-sea-salt calcium, in order to support the discussion on the seasonal variations of trace elements. Concentrations of alkaline and alkaline-earth elements were higher in winter (April-October) than in summer (November-March) by a factor of 1.2-3.3, in agreement with the higher concentration of sea-salt atmospheric particles reaching the Antarctic plateau during the winter. Similarly, trace elements were generally higher in winter by a factor of 1.2-1.5, whereas Al and Fe did not show any significant seasonal trend. Partitioning between dissolved and particulate phases did not change with the sampling period, but it depended only on the element: alkaline and alkaline-earth elements, as well as Co, Cu, Mn, Pb and Zn were for the most part (>80%) in the dissolved phase, whereas Al and Fe were mainly associated with the particulate phase (>80%) and Cd, Cr, V were nearly equally distributed between the phases. Finally, the estimated marine and crustal enrichment factors indicated that Cd, Cr, Cu, Pb and Zn have a dominant anthropogenic origin, with a possible contribution from the Concordia station activities.
... 168 spots), requires about 9 h. The interest for a detailed, size-resolved and high ... varia... more ... 168 spots), requires about 9 h. The interest for a detailed, size-resolved and high ... variations with climatic changes, dust stratigraphies have been obtained by the chemical and physical ... are reported; in accordance with recent literature,[17] the ice dust composition during the cold ...
An example of an integrated approach to assess air pollution threats to cultural heritage in a se... more An example of an integrated approach to assess air pollution threats to cultural heritage in a semi-confined environment is presented in this work, where the monitoring campaign carried out at the Michelozzo's Courtyard (in Palazzo Vecchio, Florence, Italy) is used as a case study. A wide research project was carried out, with the main aim of obtaining the first quantitative data on air quality and microclimate conditions inside the Courtyard, and, if possible, identifying the main causes of degradation and suggesting appropriate conservation strategies. The investigation adopted a holistic approach involving thermographic measurements on the wall paintings, microclimatic analysis, gaseous pollutant monitoring, atmospheric particles characterisation and dry deposition compositional analysis. Attention was focused on the wall painting depicting the city of Hall because of its anomalous and critical conservation conditions, which are visible at a glance, due to the contrast between a wide darker zone around the central subject of the painting and external lighter areas.
The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and seq... more The EPICA ice core from Dome C extends 3259 m in depth, and encompasses 800 ka of datable and sequential ice. Numerous chemical species have been measured along the length of the cores. Here we concentrate on interpreting the main low-resolution patterns of major ions. We extend the published record for non-sea-salt calcium, sea-salt sodium and non-sea-salt sulfate flux to 800 ka. The non-sea-salt calcium record confirms that terrestrial dust originating from South America closely mirrored Antarctic climate, both at orbital and millennial timescales. A major cause of the main trends is most likely climate in southern South America, which could be sensitive to subtle changes in atmospheric circulation. Seasalt sodium also follows temperature, but with a threshold at low temperature. We re-examine the use of sodium as a sea ice proxy, concluding that it is probably reflecting extent, with high salt concentrations reflecting larger ice extents. With this interpretation, the sodium flux record indicates low ice extent operating as an amplifier in warm interglacials. Non-sea-salt sulfate flux is almost constant along the core, confirming the lack of change in marine productivity (for sulfur-producing organisms) in the areas of the Southern Ocean contributing to the flux at Dome C. For the first time we also present long records of reversible species such as nitrate and chloride, and show that the pattern of post-depositional losses described for shallower ice is maintained in older ice. It appears possible to use these concentrations to constrain snow accumulation rates in interglacial ice at this site, and the results suggest a possible correction to accumulation rates in one early interglacial. Taken together the chemistry records offer a number of constraints on the way the Earth system combined to give the major climate fluctuations of the late Quaternary period.
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 2008
An analytical procedure has been implemented in this work for an accurate geochemical characteriz... more An analytical procedure has been implemented in this work for an accurate geochemical characterization and quantitative analysis of the fine dust (particles diameter<5μm) trapped in Antarctic ice cores and the fine fraction of potential source areas (PSA) sediments by size selection, filtering and PIXE–PIGE combined measurements. The underestimation of concentrations of the lighter elements, like Na, Mg, Al and Si,
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Papers by Roberto Udisti