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Abstract: Scientific findings from the last decades have clearly highlighted the need for a more comprehensive approach to atmospheric change processes. In fact, observation of atmospheric composition variables has been an important activity of atmospheric research that has developed instrumental tools (advanced analytical techniques) and platforms (instrumented passenger aircrafts, ground-based in situ and remote sensing stations, earth observation satellite instruments) providing essential information on the composition of the atmosphere. The variability of the atmospheric system and the extreme complexity of the atmospheric cycles for short-lived gaseous and aerosol species have led to the development of complex models to interpret observations, test our theoretical understanding of atmospheric chemistry and predict future atmospheric composition. The validation of numerical models requires accurate information concerning the variability of atmospheric composition for targeted species via comparison with observations and measurements. In this paper, we provide an overview of recent advances in instrumentation and methodologies for measuring atmospheric composition changes from space, aircraft and the surface as well as recent improvements in laboratory techniques that permitted scientific advance in the field of atmospheric chemistry. Emphasis is given to the most promising and innovative technologies that will become operational in the near future to improve knowledge of atmospheric composition. Our current observation capacity, however, is not satisfactory to understand and predict future atmospheric composition changes, in relation to predicted climate warming. Based on the limitation of the current European observing system, we address the major gaps in a second part of the paper to explain why further developments in current observation strategies are still needed to strengthen and optimise an observing system not only capable of responding to the requirements of atmospheric services but also to newly open scientific questions. [Copyright &y& Elsevier]

This work focuses on transport and properties of ash from the Icelandic volcano Grímsvötn that erupted in spring 2011. Atmospheric transport of volcanic ash from the eruption was simulated using the Danish Emergency Response Model of the Atmosphere (DERMA). The arrivals of volcanic particles were detected on-line at Mace Head at the West coast of Ireland during volcanic plume advection identified by high resolution time of flight aerosol mass spectrometry (HR-ToF AMS). Based on DERMA information aerosol particles were collected in Copenhagen, Denmark, before predicted arrival of the ash plume and during a period where ash was present in the air. Analysis of the meteorological conditions shows that the particles collected before arrival of the volcanic ash may serve as a good reference sample allowing identification of significant changes in ambient aerosol properties during the volcanic ash event over Copenhagen. Using single particle analysis in scanning electron microscopy (SEM), data on structure, chemical composition, size and morphology of individual volcanic ash particles from the Grímsvötn eruption after atmospheric transport to Scandinavia are provided. Particles were sliced with Focused Ion Beam (FIB). Element mappings from cross-sections through collected volcanic ash particles reveal inhomogeneous distributions of the elements K, Mg, Fe and Ti. [ABSTRACT FROM AUTHOR]

Abstract: We studied the evaporation of submicrometer-sized, aqueous solution aerosol particles containing different mixing ratios of succinic acid, sodium chloride, and water. A modified tandem differential mobility analyzer (TDMA) including a laminar flow-tube was deployed to measure the evaporation rates of the particles at ambient atmospheric pressure and temperature, and at different relative humidities. A phase equilibrium model (extended aerosol inorganic model, ) was applied to predict the concentration, activity coefficients, and partitioning of the evaporating species. We also investigated the particles evaporation by combining an evaporation model with the phase equilibrium model. The observed evaporation could be predicted with reasonable accuracy at large relative amounts of succinic acid. At low relative amounts, the overpredicted evaporation suggests that inorganic salts might enhance the particle phase partitioning of organic acids more than expected based on present aerosol thermodynamic models. [Copyright &y& Elsevier]

Abstract: Vapor pressures of five methyl-substituted dicarboxylic acids are inferred from measurements of evaporation rates of sub-micron particles using the TDMA technique at ambient temperatures. Vapor pressures obtained are: , , , , , , . These vapor pressures are compared with available literature data and with vapor pressures of the un-substituted acids. Our results demonstrate that molecular structure is important for solid state vapor pressures of secondary organic aerosol components at ambient conditions. [Copyright &y& Elsevier]