F. Cavalli

Biogenically driven organic contribution to marine aerosol.

Marine aerosol contributes significantly to the global aerosol load and consequently has an important impact on both the Earths albedo and climate. So far, much of the focus on marine aerosol has centred on the production of aerosol from sea-salt and non-sea-salt sulphates. Recent field experiments, however, have shown that known aerosol production processes for inorganic species cannot account for the entire aerosol mass that occurs in submicrometre sizes. Several experimental studies have pointed to the presence of significant concentrations of organic matter in marine aerosol. There is some information available about the composition of organic matter, but the contribution of organic matter to marine aerosol, as a function of aerosol size, as well as its characterization as hydrophilic or hydrophobic, has been lacking. Here we measure the physical and chemical characteristics of submicrometre marine aerosol over the North Atlantic Ocean during plankton blooms progressing from spring through to autumn. We find that during bloom periods, the organic fraction dominates and contributes 63% to the submicrometre aerosol mass (about 45% is water-insoluble and about 18% water-soluble). In winter, when biological activity is at its lowest, the organic fraction decreases to 15%. Our model simulations indicate that organic matter can enhance the cloud droplet concentration by 15% to more than 100% and is therefore an important component of the aerosol–cloud–climate feedback system involving marine biota.

Advances in characterization of size‐resolved organic matter in marine aerosol over the North Atlantic

0.80 m gm � 3 , the remainder being non-sea-salt (nss) sulphate, 0.03 ± 0.01 m gm � 3 , and nitrate, 0.13 ± 0.04 m gm � 3 . By comparison, the mass of sea salt, nss sulphate, and nitrate in the submicron mode is found to be 0.39 ± 0.08 m gm � 3 , 0.26 ± 0.04 m gm � 3 , and 0.02 ± 0.01 m gm � 3 , respectively. Water-soluble organic carbon (WSOC) is observed in the submicron mode with a mass concentration of 0.25 ± 0.04 m gm � 3 , comparable to that of nss sulphate, and in the supermicron mode with a mass concentration of 0.17 ± 0.04 m gm � 3 . The WSOC to total carbon (TC) ratio is found to be 0.20 ± 0.12 for the submicron fraction and 0.29 ± 0.08 for the supermicron fraction, while the black carbon (BC) to TC ratio is, on average, 0.032 ± 0.001 for both aerosol modes. The remaining carbon, water-insoluble organic carbon, contributes 0.66 ± 0.11 m gm � 3 and 0.26 ± 0.06 m gm � 3 to the submicron and supermicron modes, respectively and, thus, represents the dominant submicron aerosol species. Furthermore, the WSOC chemical composition comprises mainly aliphatic and only partially oxidized species and humiclike substances, resulting in appreciable surface-active properties. The observed organic matter chemical features (size-dependent concentration, hydrophobic nature of a substantial fraction of the organic matter, and low oxidized and surface-active WSOC species) are consistent with the hypothesis of a primary marine source; bubble-bursting processes, occurring at the surface of the North Atlantic Ocean during phytoplankton blooms, effectively transfer organic matter into marine aerosol particles, particularly enriching the fine-aerosol fraction. INDEX TERMS: 0305 Atmospheric Composition and Structure: Aerosols and particles (0345, 4801); 0315 Atmospheric Composition and Structure: Biosphere/atmosphere interactions; 0365 Atmospheric Composition and Structure: Troposphere—composition and chemistry;

Seasonal Characteristics of the Physicochemical Properties of North Atlantic Marine Atmospheric Aerosols

The aerosol size distribution modal diameters show seasonal variations, 0.031 mm in winter and 0.049 mm in summer for the Aitken mode and 0.103 mm in winter and 0.177 mm in summer for the accumulation mode. The accumulation mode mass also showed a seasonal variation, minimum in winter and maximum in summer. A supermicron sized particle mode was found at 2 mm for all seasons showing 30% higher mass concentration during winter than summer resulting from higher wind speed conditions. Chemical analysis showed that the concentration of sea salt has a seasonal pattern, minimum in summer and maximum in winter because of a dependency of sea-salt load on wind speeds. By contrast, the non-sea-salt (nss) sulphate concentration in fine mode particles exhibited lower values during winter and higher values during midsummer. The water soluble organic carbon (WSOC) and total carbon (TC) analysis also showed a distinctive seasonal pattern. The WSOC concentration during the high biological activity period peaked at 0.2 mgC m A3 , while it was lower than 0.05 mgC m A3 during the low biological activity period. The aerosol light scattering coefficient showed a minimum value of 5.5 Mm A1 in August and a maximum of 21 Mm A1 in February. This seasonal variation was due to the higher contribution of sea salt in the MBL during North Atlantic winter. By contrast, aerosols during late spring and summer exhibited larger angstrom parameters than winter, indicating a large contribution of the biogenically driven fine or accumulation modes. Seasonal characteristics of North Atlantic marine aerosols suggest an important link between marine aerosols and biological activity through primary production of marine aerosols.

Solubility properties of surfactants in atmospheric aerosol and cloud/fog water samples

[1]xa0Organic films on deliquesced aerosols and cloud droplets lower the surface tension of water and may inhibit the exchange of water vapor and gases between the gas and the liquid phase, with important implications for aerosol and cloud microphysics and heterogeneous chemistry. This study provides an estimate of the solubility properties of surfactants in aerosol and fog/cloud water samples on the basis of the dilatational rheological properties of the surface films. The variations of surface tension induced by the fast expansion/compression of the films were measured by means of a drop shape tensiometer and were linked to the capacity of surfactants to exchange between the surface layer and bulk solution, and ultimately to their water-solubility. The results are in agreement with the properties of standards of soluble surfactants and can be interpreted by the theory of formation of hydrophilic adsorption layers. These findings suggest that the water-soluble organic compounds (WSOC) are the main contributors to the formation of films on cloud/fog droplets. It follows that the surface coverage of film-forming compounds is mainly controlled by the bulk concentration of WSOC, regardless of the available surface area. This also supports that the surface tension decreases observed under laboratory conditions actually occur in the atmosphere.

JRC Ispra EMEP - GAW Regional Station for Atmospheric Research: 2010 Report

The aim of the JRC-Ispra station for atmospheric research (45°49’N, 8°38’E) is to monitor atmospheric parameters (pollutant concentrations and fluxes, atmospheric particle chemical composition, number size distribution and optical properties) to contribute in assessing the impact of European policies on air pollution and climate change. The station has been operated continuously since November 1985, with a gap in gas phase data due to a severe breakdown of the data acquisition system in 2003 though. The measurements performed in 2007 led to annual averages of ca. 32 μg m O3, 0.8 μg m SO2, 21 μg m NO2 and 30 μg m PM10. Carbonaceous species (organic matter plus elemental carbon) are the main constituents of PM2.5 (> 55 %) followed by NH4NO3 (20-30 %) and (NH4)2SO4 (10-20 %). The measurements confirmed the seasonal variations observed over the previous years, mainly driven by meteorology rather than by changes in emissions. Aerosol physical and optical properties were also measured in 2007. The average particle number (from 10 nm to 10 μm) was about 9200 cm in 2007. The mean (close to dry) aerosol single scattering albedo (0.79) was low compared to the values generally observed in Europe, which means that the cooling effect of aerosols is reduced in our region compared to others. Long-term trends (over 20 years) show consistent decreases in sulfur concentrations and deposition, PM mass concentration (-0.9 μg m yr) and in extreme ozone value occurrence frequency. The decreasing trends in oxidised and reduced nitrogen species are much less pronounced. However, historical minimum in NO3, NH4, (and SO4) wet deposition, as well as in O3 pollution indicators (AOT40 and SOMO35) were observed in 2007. How to obtain EU publications Our priced publications are available from EU Bookshop (http://bookshop.europa.eu), where you can place an order with the sales agent of your choice. The Publications Office has a worldwide network of sales agents. You can obtain their contact details by sending a fax to (352) 29 29-42758.

Nucleation Events in Melpitz, Germany, and Po Valley, Italy: Similarities and Differences

This study has been designed to investigate the factors that influence the occurrence of new particle formation events (particles >3 nm) in two anthropo- genically influenced boundary layer regimes in Central Europe (Melpitz, Eastern Germany) and Southern Europe (San Pietro Capofiume SPC in the Po Valley, Italy). In particular, we study the similarities and differences of factors driving nucleation events at these two locations. The analysis encompasses three years of data at each observation site, between July 2003 and June 2006. Particle size distribution measurements were carried out using twin DMPS systems (Differential Mobility Particle Sizers) at each site, with particle size ranges of 3-800 nm, and 3-600 nm at Melpitz and SPC, respectively. In addition to particle size measurements, several gas and meteorological parameters are being measured for stations, including SO 2 , NO, NO 2 , NO x , O 3 , temperature, relative humidity, wind direction, wind speed, global radiation, precipitation, and atmospheric pressure. We utilized these parameters in our analysis of particle formation and growth processes. Our preliminarily results show that for Melpitz station, it is possible to separate between nucleation days and nonnucleation days by using just two variables (a product of radiation and sulphuric dioxide - its increase indicates increase of sulphuric acid concentration - and condensation sinkCS). This result for Melpitz indicates that low enough CS value is needed together with high enough sulphuric acid production to drive nucleation and vice verse for nonnucleation days. For SPC station the same criterion could not separate nucleation days and nonnucleation days as efficiently as for Melpitz, and an overlap region between nucleation and nonnucleation days remained. Interestingly, however, the nonnucleation days in Po Valley are bound by the same criterion as in Melpitz, and it is the nucleation days that cause the Po Valley overlap.