SO2 oxidation in supercooled droplets in the presence of O2

Sulphur dioxide oxidation in supercooled monodisperse droplets at T4213 7C was studied in the presence of oxygen. The SO2 concentration was found to range from 0.08 to 7.1 ppmv and the contact time between gases and droplets was 210 s. The experimental results showed that sulphate concentration due to SO2 oxidation is independent of temperature, i.e. the increase of SO2 solubility in the liquid phase balances the rate constant decrease of the oxidation reaction. Following McKay’s kinetics (Atmos. Environ., 5 (1971) 7), we calculated the rate constant at T4213 7C and the activation energy. A comparison was made between experimental S(VI) oxidation concentrations due to oxygen and theoretical oxidation values due to O3, H2O2 and oxygen in the presence of catalyzers (Fe31, Mn21)

In situ atomic force microscopy in the study of electrogeneration of polybithiophene on Pt electrode

Electrochemical AFM technique has been used for the in situ study of the electrogeneration-deposition process of polybithiophene at varying the polymerisation conditions, such as supporting electrolyte, i.e., LiClO4 or tetrabutylammonium hexafluorophosphate, and polymerisation procedure, i.e., either potentiostatic or potentiodynamic method. In order to better follow the evolution of the morphology of the deposit, particularly during the early stages of the polymer film growth, a suitable home-made electrochemical cell has been used

Holocene volcanic history as recorded in the sulfate stratigraphy of the European Project for Ice Coring in Antarctica Dome C (EDC96) ice core

A detailed history of Holocene volcanism was reconstructed using the sulfate record of the European Project for Ice Coring in Antarctica Dome C (EDC96) ice core. This first complete Holocene volcanic record from an Antarctic core provides a reliable database to compare with long records from Antarctic and Greenland ice cores. A threshold method based on statistical treatment of the lognormal sulfate flux distribution was used to differentiate volcanic sulfate spikes from sulfate background concentrations. Ninety-six eruptions were identified in the EDC96 ice core during the Holocene, with a mean of 7.9 events per millennium. The frequency distribution (events per millennium) showed that the last 2000 years were a period of enhanced volcanic activity. EDC96 volcanic signatures for the last millennium are in good agreement with those recorded in other Antarctic ice cores. For older periods, comparison is in some cases less reliable, mainly because of dating uncertainties. Sulfate depositional fluxes of individual volcanic events vary greatly among the different cores. A volcanic flux normalization (volcanic flux/Tambora flux ratio) was used to evaluate the relative intensity of the same event recorded at different sites in the last millennium. Normalized flux variability for the same event showed the highest value in the 1100–1500 AD period. This pattern could mirror changes in regional transport linked to climatic variations such as slight warming stages in the Southern Hemisphere (Southern Hemisphere Medieval Warming–like period?)

Volcanic synchronisation of the EPICA-DC and TALDICE ice cores for the last 42 kyr BP

The age scale synchronisation between the Talos Dome and the EPICA Dome C ice cores was carried on through the identification of several common volcanic signatures. This paper describes the rigorous method, using the signature of volcanic sulphate, which was employed for the last 42 kyr of the record. Using this tight stratigraphic link, we transferred the EDC age scale to the Talos Dome ice core, producing a new age scale for the last 12 kyr. We estimated the discrepancies between the modelled TALDICE-1 age scale and the new scale during the studied period, by evaluating the ratio R of the apparent duration of temporal intervals between pairs of isochrones. Except for a very few cases, R ranges between 0.8 and 1.2, corresponding to an uncertainty of up to 20% in the estimate of the time duration in at least one of the two ice cores. At this stage our approach does not allow us to unequivocally identify which of the models is affected by errors, but, taking into account only the historically known volcanic events, we found that discrepancies up to 200 yr appear in the last two millennia in the TALDICE-1 model, while our new age scale shows a much better agreement with the volcanic absolute horizons. Thus, we propose for the Talos Dome ice core a new age scale (covering the whole Holocene) obtained by a direct transfer, via our stratigraphic link, from the EDC modelled age scale by Lemieux-Dudon et al. (2010)

Source apportionment of PM10 in the Western Mediterranean based on observations from a cruise ship

Abstract Two intensive PM10 sampling campaigns were performed in the summers of 2009 and 2010 on the ship Costa Pacifica during cruises in the Western Mediterranean. Samples, mainly collected on an hourly basis, were analysed with different techniques (Particle Induced X-Ray Emission, PIXE; Energy Dispersive - X Ray Fluorescence, ED-XRF; Ion Chromatography, IC; Thermo-optical analysis) to retrieve the PM10 composition and its time pattern. The data were used for obtaining information about the sources of aerosol, with a focus on ship emissions, through apportionment using chemical marker compounds, correlation analysis and Positive Matrix Factorization (PMF) receptor modelling. For the campaign in 2010, 66% of the aerosol sulphate was found to be anthropogenic, only minor contributions of dust and sea salt sulphate were observed while the biogenic contribution, estimated based on the measurements of MSA, was found to be more important (26%), but influenced by large uncertainties. V and Ni were found to be suitable tracers of ship emissions during the campaigns. Four sources of aerosol were resolved by the PMF analysis; the source having the largest impact on PM10, BC and sulphate was identified as a mixed source, comprising emissions from ships. The correlations between sulphate and V and Ni showed the influence of ship emissions on sulphate in marine air masses. For the leg Palma–Tunis crossing a main ship route, the correlations between aerosol sulphate and V and Ni were particularly strong (r2 = 0.9 for both elements)