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This study examines the regional impact of the COVID-19 lockdown restrictions on pollution in Ireland by comparing the 2020 measurements of ozone (O3), nitrogen dioxide (NO2), and particulate matter (PM) from monitoring stations around the country to the previous 3-year average. Results indicate that O3 was 5.6% lower and 13.7% higher than previous years during the lockdown at rural and suburban sites, respectively. NO2 decreased by 50.7% in urban areas, but increased slightly in agricultural regions, consistent with satellite observations. PM concentrations did not change significantly compared to previous years; however, a reduction in the signal variability in the smaller size particle measurements may be the result of different emission sources. The reduction in NO2 likely increased the ratio of volatile organic compounds (VOCs) to NOx (nitrogen oxides), creating a NOx limited environment, which resulted in an initial increase in O3 in suburban areas, and the lower than usual levels observed at rural sites. Meteorology showed higher than average wind speeds prior to lockdown, which likely acted to disperse PM and NO2.

A near real-time assimilation and forecast system of aerosols has been developed by integration in the ECMWF IFS code within the GEMS project. The GEMS aerosol modeling system is novel as it is the first aerosol model fully coupled to a NWP model with data assimilation. Aerosol optical depth (AOD) data of the MODIS instrument on Terra and Aqua satellites was assimilated. The performance of the aerosol model was evaluated by the means of case studies. The assimilation of MODIS AOD improved the subsequent aerosol predictions when compared with observations, in particular concerning correlations and AOD peak values. The assimilation is less effective in correcting a positive or a negative bias.

C.D. O’Dowd and P.E. Wagner (eds.), Nucleation and Atmospheric Aerosols, 1064–1069. © Springer 2007 Abstract An alternative method for the estimation of chemical aerosol fluxes, based on a vertical concentration gradient measurement, has been developed and executed at the coastal research station in Mace Head, Ireland. Total gravimetric PM1.0 mass, sea salt and water insoluble organic carbon (WINSOC) concentration profiles showed a net production, while nssSO 4 and water soluble organic carbon (WSOC) concentration profiles showed a net removal at the surface. It was concluded that WSOC was predominantly of secondary origin, while WINSOC was predominantly of primary origin. Potential influence of the surf zone emissions was limited to 5–20% and the measured fluxes were characteristic of the coastal zone of up to 5 km. Sea salt concentration and mass flux relationships with the wind speed were established and fitted with power function (C = a*U b). A comparison with the mass flux, derived from eddy correlation measurements yielded good agreement.

Coastal nucleation events and behavior of cluster ions were characterized through the measurements of air ion mobility distributions at the Mace Head research station on the west coast of Ireland in 2006. We measured concentrations of cluster ions and charged aerosol particles in the size range of 0.4–40 nm. These measurements allow us to characterize freshly nucleated charged particles with diameter below 3 nm. The analysis shows that bursts of intermediate ions (1.6–7 nm) are a frequent phenomenon in marine coastal environment. Nucleation evens occurred during most of the measurement days. We classified the nucleation burst events. Particle formation and growth events mostly coincided with the presence of low tide. Small ions concentrations appear to be strongly dependent on the variations of meteorological parameters including wind speed and direction.

During the summer of 2006 a measurement campaign was conducted on a ship in the North Atlantic. We measured the concentration, size distribution and hygroscopicity of the atmospheric aerosol particles. The size distribution consisted of two separate modes, one peaking at 50 nm and the other at 200 nm. Based on the hygroscopicity measurements, the first mode was internally mixed and had a hygro- scopic growth factor of 1.6-1.7. In the afternoon of 13 June we observed a mode of small particles, which grew during the evening to 30-40 nm. These particles are believed to be secondary particles, which would make this a very rare observation. Further analysis will be made once more supporting data becomes available.

Organic marine aerosol (of both primary and secondary origin) represents a potentially important component of the marine biota and climate feedback system involving aerosols and clouds (O’Dowd et al., 2004; Cavalli et al., 2004). In order to assess the potential influence of costal environment on marine aerosol chemical composition, both organic and inorganic, two parallel aerosol data sets, collected in two campaigns in the framework of the EC project MAP, are compared in this work. The field experiments have been carried out from June 5 and July 5 2006, during the period of high oceanic biological activity at Mace Head Atmospheric Research Station (costal site) and on board of the oceanographic vessel “Celtic Explorer” (open ocean site). At both the sites the sampling has been fixed approximately at 10 m height above the sea level. Aerosol samples were collected, under clean conditions (Cavalli et al., 2004) by means of 8stages Berner impactors equipped with tedlar foils, collecting particles in eight size fractions between 0.060 and 16 μm diameter. In order to obtain a detailed chemical characterization of organic fraction, aerosol samples were also collected by high volume virtual impactors, segregating fine (a. d. less than 1 μm diameter ) and coarse particles (a. d. between 1 and 10 μm diameter ) on quartz filters. Three parallel aerosol samples were collected during the campaigns as a result of sampling time of the order of 50 hours each. WSOC (Water Soluble Organic Carbon) and main inorganic ions analyses were performed on tedlar foils, while high volume samples were used for Total Carbon (TC) analyses and for organics chemical characterization (HPLC fractionation, HNMR functional group analyses and tensioactive properties analysis). Non-sea-salt (nss) sulphate is the dominant species in submicron fraction in both samples sets, showing a similar trend both in coastal and in open ocean samples. For each stage of the fine fraction coastal site samples show an average nssSO4 concentration higher than the open ocean samples. On the contrary, average WSOC concentration in the fine fraction is very similar for samples collected at Mace Head Station and at the open ocean site. The ratio between WSOC and WIOC (Water Insoluble Organic Carbon) is slightly lower in samples collected at the coastal site, being WSOC the dominant fraction of organics in both samples sets. Coarse fraction is dominated by sea salt in all the size intervals; however, in terms of absolute mass the coastal samples result enriched in sea salt as compared to open ocean samples. Concerning WSOC chemical characterization, HNMR analyses show that functional groups distribution in samples collected during the cruise is consistent with the one of samples collected at Mace Head Station, suggesting the same chemical composition and the same origin. Moreover, the investigation of tensioactive properties of fine fraction isolated WSOC highlights the same behaviour for both samples collected in middle ocean and at the coastal site. In conclusion, our results show strong similarity between aerosol physico-chemical properties at coastal station and open ocean site , especially for the main organic components thus excluding potential effects of the shore line environment on marine organic aerosol.

Aerosol dynamical simulations of coastal new particle formation have been performed in order to investigate the nucleation and growth mechanisms in this environment. In the simulations, it is assumed that the nucleating vapour is iodine dioxide. Both Eulerian and Lagrangian type simulations have been performed and compared to observations. We have found it difficult to achieve the observed, enormous growth rates, and simulations agree with the experiments only when OIO concentration is very high and growth time has been prolonged

The present work reviews the state of knowledge on organic marine aerosol, starting with an historic overview of the topic from the early 1970s to the most recent years. New results from the MAP-EU project are then reported, showing the main features of the organic fraction, and illustrating how primary and secondary components of marine aerosols can be distinguished by means of chemical analysis. The findings also have potential implications for the atmospheric chemis- try of aerosol particles and clouds.

Chemical composition of TSP matter has been studied during long-term measurement campaign at Mace Head during 2001–2004. Aerosol particles in clean marine air masses were sampled in parallel with continuous samples to reveal relative contribution of natural sources. Inorganic composition changes revealed strong seasonal patterns, with dominant contribution of sea salt (40–95%) and anthropogenic nitrate. Natural biogenic sources contributed significantly to total aerosol budget. Wind speed and sea salt mass relationship has been examined and used to predict nssSO4 concentration in marine environment. Predicted nssSO4 was overestimated by 34%, but correlation between predicted and measured values was 0.61 at P << 0.01.

International audience; It was performed sensitivity tests of dual-polarization polar nephelometer (D2PN) data to optical and microphysical parameters of population of spherical aerosol particles. Measurement errors were modeled as Gaussian random variables with zero mean and a standard deviation of 10%. It is shown that data of the D2PN enable to retrieve microphysical parameters along with the assessment of the refractive index.