## 4 Summary and Conclusions  
This paper combines measurements and modelling approaches to investigate the air quality and the impact of ship emissions on NO\({}_{\chi}\), O\({}_{3}\), and PM in a Mediterranean port city (Brindisi, Apulia Region, Southern Italy). As for measurements, 100 daily samples of fine PM were collected on the roof of the ASI building during a field experimental campaign. The PM\({}_{2.5}\) samples were chemically characterized in terms of ionic fraction, carbonaceous components and metals. A statistical analysis was conducted integrating complementary tools, LDA and PCA. PCA was useful to examine data structure in terms of the main sources which in this case were crustal and ship emissions (29% of the total variance), sea spray (17% of the total variance), combustion (7% of the total variance), vehicular traffic (8%), industrial (5%), and secondary aerosol (10%). By PCA no statistical differentiation of samples for the two prevailing wind directions was obtained. Probably, more useful information could be obtained using wind selective samplers. The application of LDA was successful in separating the contribution between prevalent wind directions associated to the main contributing sources: the method assigned samples to the category 'Urban-Industrial' with good percentage of correct predictions (61%), and samples to the category 'Port' with a high percentage of correct predictions (83%), respectively. Then, the air quality and the direct impact of ship emissions contribution during the experimental period were quantified by employing a numerical modelling system (coupling offline the mesoscale chemistry model BOLCHEM and the local scale dispersion model ADMS-Urban). BOLCHEM simulations were performed to reproduce ground pollutants concentrations and the impact of ship-related PM emissions on PM\({}_{2.5}\) and PM\({}_{10}\) concentrations, as well as of NO\({}_{\chi}\) and NMVOC emissions on NO\({}_{\chi}\) and O\({}_{3}\) concentration, at a regional scale. The spatial distribution of concentration levels at local scale has been then assessed using ADMS-Urban. BOLCHEM results showed that the impact of ship emissions covered an area of a few dozen kilometers and was, on average for the field experimental campaign period, 37.6% for NO\({}_{\chi}\), \(-11.7\%\) for O\({}_{3}\), 4.3% for PM\({}_{10}\), and 6.1% for PM\({}_{2.5}\), the last one distributed between primary (2.7%) and secondary fraction (3.4%). At a local scale, the analysis of high-resolution modelling results obtained from ADMS-Urban highlighted that, at ASI position, the impact of ship emissions on PM\({}_{2.5}\) was 6.8% when the sampling site was positioned downwind to the port area and reduced to lower than 3.0% at about 2 km far from the sources. This study is an example of integrated methodologies which could be further tested in other port cities which could have even larger complexity than in our case in terms of sources, topographic features, and in turns of meteorological processes. Conceptualization, R.C., A.G., R.B., S.D.S., P.I. ; Data curation, M.S., T.S. ; Formal analysis, M.S., T.S., A.D., P.I. ; Investigation, R.C., A.G., M.S., T.S., A.M.; Methodology, R.C., A.G., R.B., S.D.S., A.D., P.I. ; Resources, A.G., S.D.S. ; Software, R.C., R.B., A.M.; Supervision, P.I. ; Visualization, R.C., R.B., A.M., P.I. ; Writing--original draft, R.C., A.G., R.B., P.I. ; Writing--review & editing, S.D.S., A.D. All authors have read and agreed to the published version of the manuscript. This work has been done with the financial support of CESAPO project (Contribution of Emission Sources on the Air quality of the Port cities in Greece and Italy), European Territorial Cooperation Programme Italy 2007-2013 and of POSEIDON Project (Pollution monitoring of ship emissions: an integrated approach for harbours of the Adriatic basin), MED program 2007-2013. This research was also supported by the PON 254/Ric. Potenziamento del \"CENTRO RICERCHE PER LA SALUTE DELLUOMO E DELL'AMBIENTE\" Cod. PONa3_00334 Project.