Abstract.We discuss the capability of current state-of-theart chemistry and transport models to reproduce air quality trends and interannual variability. Documenting these strengths and weaknesses on the basis of historical simulations is essential before the models are used to investigate future air quality projections. To achieve this, a coordinated modelling exercise was performed in the framework of the CityZEN European Project. It involved six regional and global chemistry-transport models (BOLCHEM, CHIMERE, EMEP, EURAD, OSLOCTM2 and MOZART) simulating air quality over the past decade in the Western European anthropogenic emissions hotspots.Comparisons between models and observations allow assessing the skills of the models to capture the trends in basic atmospheric constituents (NO 2 , O 3 , and PM 10 ). We find that the trends of primary constituents are well reproduced (except in some countries -owing to their sensitivity to the emission inventory) although capturing the more moderate trends of secondary species such as O 3 is more challenging. Apart from the long term trend, the modelled monthly variCorrespondence to: A. Colette (augustin.colette@ineris.fr) ability is consistent with the observations but the year-to-year variability is generally underestimated.A comparison of simulations where anthropogenic emissions are kept constant is also investigated. We find that the magnitude of the emission-driven trend exceeds the natural variability for primary compounds. We can thus conclude that emission management strategies have had a significant impact over the past 10 yr, hence supporting further emission reductions.

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Abstract. In order to explore future air quality in Europe at the 2030 horizon, two emission scenarios developed in the framework of the Global Energy Assessment including varying assumptions on climate and energy access policies are investigated with an ensemble of six regional and global atmospheric chemistry transport models.A specific focus is given in the paper to the assessment of uncertainties and robustness of the projected changes in air quality. The present work relies on an ensemble of chemistry transport models giving insight into the model spread. Both regional and global scale models were involved, so that the ensemble benefits from medium-resolution approaches as well as global models that capture long-range transport. For each scenario a whole decade is modelled in order to gain statistical confidence in the results. A statistical downscaling approach is used to correct the distribution of the modelled projection. Last, the modelling experiment is related to a hind-cast study published earlier, where the performances of all participating models were extensively documented.The analysis is presented in an exposure-based framework in order to discuss policy relevant changes. According to the emission projections, ozone precursors such as NO x will drop down to 30 % to 50 % of their current levels, depending on the scenario. As a result, annual mean O 3 will slightly increase in NO x saturated areas but the overall O 3 burden will decrease substantially. Exposure to detrimental O 3 levels for health (SOMO35) will be reduced down to 45 % to 70 % of their current levels. And the fraction of stations where present-day exceedences of daily maximum O 3 is higher than 120 µg m −3 more than 25 days per year will drop from 43 % down to 2 to 8 %.We conclude that air pollution mitigation measures (present in both scenarios) are the main factors leading to the improvement, but an additional cobenefit of at least 40 % Published by Copernicus Publications on behalf of the European Geosciences Union.

Atmospheric pressure plasma jets generate reactive oxygen and nitrogen species (RONS) in liquids and biological media, which find application in the new area of plasma medicine. These plasma-treated liquids demonstrated recently to possess selective properties on killing cancer cells and attract attention towards new plasma-based cancer therapies. These allow for local delivery by injection in the tumor but can be quickly washed away by body fluids. By confining these RONS in a suitable biocompatible delivery system, great perspectives can be opened in the design of novel biomaterials aimed for cancer therapies. Gelatin solutions are evaluated here to store RONS generated by atmospheric pressure plasma jets, and their release properties are evaluated. The concentration of RONS was studied in 2% gelatin as a function of different plasma parameters (treatment time, nozzle distance and gas flow) with two different plasma jets. Much higher production of reactive species (H 2 O 2 and NO 2-) was revealed in the polymer solution than in water after plasma treatment. The amount of RONS generated in gelatin is greatly improved with respect to water, with concentrations of H 2 O 2 and NO 2between 2 and 12 times higher for the longest plasma treatments. Plasma-treated gelatin exhibited the release of these RONS to a liquid media, which induced an effective killing of bone cancer cells. Indeed, in vitro studies on Sarcoma Osteogenic (SaOS-2) cell line exposed to plasma-treated gelatin lead to timedependent increasing cytotoxicity with the longer plasma treatment time of gelatin. While SaOS-2 cell viability decreased down to 12%-23% after 72 hours for cells exposed to 3-min treated gelatin, viability of healthy cells (hMSC) was preserved (around 90%), establishing the selectivity of the plasma-treated gelatin on cancer cells. This sets the basis for designing improved hydrogels with high capacity to deliver RONS locally to tumors.