Abstract. This study aims to determine the mineral contribution to PM 10 in the central Mediterranean Sea, based on 7 yr of daily PM 10 samplings made on the island of Lampedusa (35.5 • N, 12.6 • E).The chemical composition of the PM 10 samples was determined by ion chromatography for the main ions, and, on selected samples, by particle-induced X-ray emission (PIXE) for the total content of crustal markers. Aerosol optical depth measurements were carried out in parallel to the PM 10 sampling.The average PM 10 concentration at Lampedusa over the period June 2004-December 2010 is 31.5 µg m −3 , with low interannual variability. The annual means are below the EU annual standard for PM 10 , but 9.9 % of the total number of daily data exceeds the daily threshold value established by the European Commission for PM (50 µg m −3 , European Community, EC/30/1999).The Saharan dust contribution to PM 10 was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases in which crustal content exceeded the 75th percentile of the crustal oxide content distribution were identified as elevated dust events. Using this threshold, we obtained 175 events. Fifty-five elevated dust events (31.6 %) displayed PM 10 higher than 50 µg m −3 , with dust contributing by 33 % on average.The crustal contribution to PM 10 has an annual average value of 5.42 µg m −3 , and reaches a value as high as 67.9 µg m −3 (corresponding to 49 % of PM 10 ) during an intense Saharan dust event.The crustal content estimated from a single tracer, such as Al or Ca, is in good agreement with the one calculated as the sum of the metal oxides. Conversely, larger crustal contents are derived by applying the EU guidelines for demonstration and subtraction of exceedances in PM 10 levels due to high background of natural aerosol. The crustal aerosol amount and contribution to PM 10 showed a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 500 nm up to 0.28 in June-August). We found that 71.3 % of the dust events identified from optical properties over the atmospheric column display a high dust content at the ground level. Conversely, the remaining 28.7 % of cases present a negligible or small impact on the surface aerosol composition due to the transport processes over the Mediterranean Sea, where dust frequently travels above the marine boundary layer, especially in summer.Published by Copernicus Publications on behalf of the European Geosciences Union. M. Marconi et al.: Saharan dust aerosol over the central Mediterranean SeaBased on backward trajectories, two regions, one in Algeria-Tunisia, and one in Libya, are identified as main source areas for intense dust episodes occurring mainly in autumn and winter. Data on the bulk composition of mineral aerosol arising from these two source areas are scarce; results on characteristic ratios between ele...

Abstract. The Mediterranean Basin atmosphere is influenced by both strong natural and anthropogenic aerosol emissions and is also subject to important climatic forcings. Several programs have addressed the study of the Mediterranean basin; nevertheless important pieces of information are still missing. In this framework, PM10 samples were collected on a daily basis on the island of Lampedusa (35.5° N, 12.6° E; 45 m a.s.l.), which is far from continental pollution sources (the nearest coast, in Tunisia, is more than 100 km away). After mass gravimetric measurements, different portions of the samples were analyzed to determine the ionic content by ion chromatography (IC), the soluble metals by inductively coupled plasma atomic emission spectrometry (ICP-AES), and the total (soluble + insoluble) elemental composition by particle-induced x-ray emission (PIXE). Data from 2007 and 2008 are used in this study. The Positive Matrix Factorization (PMF) model was applied to the 2-year long data set of PM10 mass concentration and chemical composition to assess the aerosol sources affecting the central Mediterranean basin. Seven sources were resolved: sea salt, mineral dust, biogenic emissions, primary particulate ship emissions, secondary sulfate, secondary nitrate, and combustion emissions. Source contributions to the total PM10 mass were estimated to be about 40 % for sea salt, around 25 % for mineral dust, 10 % each for secondary nitrate and secondary sulfate, and 5 % each for primary particulate ship emissions, biogenic emissions, and combustion emissions. Large variations in absolute and relative contributions are found and appear to depend on the season and on transport episodes. In addition, the secondary sulfate due to ship emissions was estimated and found to contribute by about one-third to the total sulfate mass. Results for the sea-salt and mineral dust sources were compared with estimates of the same contributions obtained from independent approaches, leading to an estimate of the water content bound to the sea salt in the marine source.

Abstract. Particulate matter with aerodynamic diameters lower than 10 µm, (PM 10 ) aerosol samples were collected during summer 2013 within the framework of the Chemistry and Aerosol Mediterranean Experiment (ChArMEx) at two sites located north (Capo Granitola) and south (Lampedusa Island), respectively, of the main Mediterranean shipping route in the Straight of Sicily.The PM 10 samples were collected with 12 h time resolutions at both sites. Selected metals, main anions, cations and elemental and organic carbon were determined.The evolution of soluble V and Ni concentrations (typical markers of heavy fuel oil combustion) was related to meteorology and ship traffic intensity in the Straight of Sicily, using a high-resolution regional model for calculation of back trajectories. Elevated concentration of V and Ni at Capo Granitola and Lampedusa are found to correspond with air masses from the Straight of Sicily and coincidences between trajectories and positions of large ships; the vertical structure of the planetary boundary layer also appears to play a role, with high V values associated with strong inversions and a stable boundary layer. The V concentration was generally lower at Lampedusa than at Capo Granitola V, where it reached a peak value of 40 ng m −3 .Concentrations of rare earth elements (REEs), La and Ce in particular, were used to identify possible contributions from refineries, whose emissions are also characterized by elevated V and Ni amounts; refinery emissions are expected to display high La / Ce and La / V ratios due to the use of La in the fluid catalytic converter systems. In general, low La / Ce and La / V ratios were observed in the PM samples. The combination of the analyses based on chemical markers, air mass trajectories and ship routes allows us to unambiguously identify the large role of the ship source in the Straight of Sicily.Based on the sampled aerosols, ratios of the main aerosol species arising from ship emission with respect to V were estimated with the aim of deriving a lower limit for the total ship contribution to PM 10 . The estimated minimum ship emission contributions to PM 10 were 2.0 µg m −3 at Lampedusa and 3.0 µg m −3 at Capo Granitola, corresponding with 11 and 8.6 % of PM 10 , respectively.

Ice cores are widely used to reconstruct past changes of the climate system. For instance, the ice core record of numerous water-soluble and insoluble chemical species that are trapped in snow and ice offer the possibility to investigate past changes of various key compounds present in the atmosphere (i.e., aerosol, reactive gases). We developed a new method for the quantitative determination of fluoride in ice cores at sub-μg L(-1) levels by coupling a flow injection analysis technique with a fast ion chromatography separation based on the "heart cut" column switching technology. Sensitivity, linear range (up to 60 μg L(-1)), reproducibility, and detection limit (0.02 μg L(-1)) were evaluated for the new method. This method was successfully applied to the analysis of fluoride at trace levels in more than 450 recent snow samples collected during the 1998-1999 International Trans-Antarctica Scientific Expedition traverse in East Antarctica at sites located between 170 and 850 km from the coastline.

This study aims at the determination of the mineral contribution to PM₁₀ in the central Mediterranean Sea on the basis of 7 yr of PM₁₀ chemical composition daily measurements made on the island of Lampedusa (35.5° N, 12.6° E). Aerosol optical depth measurements are carried out in parallel while sampling with a multi-stage impactor, and observations with an optical particle counter were performed in selected periods. Based on daily samples, the total content and soluble fraction of selected metals are used to identify and characterize the dust events. The total contribution is determined by PIXE (particle-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 pH 1.5.

The average PM₁₀ concentration at Lampedusa calculated over the period June 2004–December 2010 is 31.5 μg m⁻³, with low interannual variability. The annual means are below the EU annual standard for PM₁₀, but 9.9% of the total number of daily data exceed the daily threshold value established by the European Commission for PM (50 μg m⁻³, European Community, EC/30/1999).

The Saharan dust contribution to PM₁₀ was derived by calculating the contribution of Al, Si, Fe, Ti, non-sea-salt (nss) Ca, nssNa, and nssK oxides in samples in which PIXE data were available. Cases with crustal content exceeding the 75th percentile of the crustal oxide content distribution were identified as dust events. Using this threshold we identify 175 events; 31.6% of them (55 events) present PM₁₀ higher than 50 μg m⁻³, with dust contributing by 33% on average.

The annual average crustal contribution to PM₁₀ is 5.42 μg m⁻³, reaching a value as high as 67.9 μg m⁻³, 49% of PM₁₀, during an intense Saharan dust event. The crustal aerosol amount and contribution to PM₁₀ shows a very small seasonal dependence; conversely, the dust columnar burden displays an evident annual cycle, with a strong summer maximum (monthly average aerosol optical depth at 495.7 nm up to 0.28 in June–August). We found that 71.3% of the events identified from optical properties over the air column display a high dust content at the ground level. Conversely, the remaining 28.7% of cases present a negligible or small impact of dust on the surface aerosol composition due to the Saharan dust transport processes over the Mediterranean that frequently occur above the marine boundary layer especially in spring, summer and early autumn.

The solubility of different elements presents a large variability. In general, the solubility is lower in Saharan dust samples than for non-Saharan dust events. The solubility also displays a marked dependency on size for Saharan dust samples. Crustal markers show two relative maxima ...