## 1 Introduction  
Air pollution is among the most critical environment issue and it is strictly linked to climate change through emissions, processes, chemistry, and dynamic of the atmosphere [1; 2]. Atmospheric particles, for example, play crucial roles in deteriorating air quality and affecting human health, in the pollution transfer to ecosystems, in the direct and indirect effects on atmospheric radiative balance, and in the climate system [3; 4; 5]. The identification and quantification of air pollution sources are then important tasks for abatement strategies and mitigation actions. Ship emissions represent a large and growing contribution to the total emissions from the transportation sector. In contrast to the progress in reducing anthropogenic emissions on land since the 1990s due to regulation in Europe, emissions from marine transportation have continued to increase [6]. Nowadays, their effects on atmospheric pollution and climate are not negligible. Key emitted compounds are carbon dioxide (CO\({}_{2}\)), nitrogen oxides (NO\({}_{\text{X}}\)), carbon monoxide (CO), volatile organic compounds (VOC), sulphur dioxide (SO\({}_{2}\)), black carbon (BC), and organic aerosol (OA) [7]. Nearly 70% of ship emissions occur within 400 km of coastlines and they contributed to increase the air pollutants concentration level in coastal areas and harbour cities [8; 9]. The effect on PM\({}_{2.5}\) concentration and sulphur and nitrogen deposition in European coastal regions are greater when emissions occur near the coast rather than offshore, while for ozone (O\({}_{3}\)) larger contributions are from open sea shipping [10; 11]. Several authors have estimated the impact of ship emissions in the Mediterranean area, where, especially during summer months, meteorological and chemical conditions favour the formation of secondary gases and aerosols. [PERSON] and [PERSON] [12] employed a regional atmospheric-chemistry model to determine the origin, the seasonal variability of secondary gases and aerosol and their effects on climate. [PERSON] et al. [13] found that shipping emissions played an important role on O\({}_{3}\) levels compared to road transport sector near the coastal zone. The effect of international shipping on air pollution have been studied in several papers [14; 15]. [PERSON] et al. [14] quantified the global impact of shipping on atmospheric chemistry and radiative forcing, as well as the associated uncertainties. Different ship emission scenarios, including ship emissions increase up to 2030, were investigated. It was found that under pessimistic anthropogenic sources emissions scenario, increasing emissions from shipping would significantly counteract the benefits derived from reducing SO\({}_{2}\) emissions from all other anthropogenic sources. [PERSON] et al. [15] evaluated the impact of low-sulphur marine fuels in global shipping on public health and on climate, the last in terms of net aerosol forcing, for the year 2020. Considering that the International Maritime Organization (IMO) proposed the change in the standards of sulphur in fuel oil from 3.5% (by mass) to 0.5% after 1 January 2020, they found that lower sulphur fuels reduced ship-related premature mortality and morbidity by 34% and 54%, respectively, and radiative cooling from ship aerosols by about 80%, equating to a 3% increase in current estimates of total anthropogenic forcing. Urban area with ports, often in combination with petrochemical and energy intensive industries, are thus particularly exposed to ship emissions. Several studies have demonstrated advancements in the assessment of shipping emission impact on air quality and human health and in the implementation of control techniques, technology improvements in ship engines, and mitigation measures in port areas [16; 17]. Recently, [PERSON] et al. [18] reviewed the status of the air quality measured in harbour areas and found that emissions from the maritime transport sector should be considered as a significant source of NO\({}_{2}\), PM\({}_{10}\), and PM\({}_{2.5}\).