Organic compounds in the air of the Mediterranean Sea: the 2013 cruise of Urania

The ability of the organic pollutants such as polycyclic aromatic hydrocarbons ( PAHs) to migrate from polluted areas through the movement of air masses up to remote regions is well known. Many studies have been made on PAHs in the different compartments of the environment, due to their carcinogenic and mutagenic activity displayed on living beings and humans (Romagnoli et al 2014). The marine atmospheric environment is a receptor for PAHs, which are overall generated by the incomplete combustion of carbon containing fuels (biomass burning, road transport, domestic heating). Long range transport from urban and industrial sources is ascertained as predominant sources of PAHs in the Mediterranean (Tsapakis and Stephanou, 2005a, Mulder at all 2014); meanwhile, shipping-related sources (engine exhausts) may be important near transport routes and affect the chemical composition of the atmosphere. In the framework of MEDOCEANOR measurement program (founded by the Italian National Research Council - CNR) and as support to the GMOS objectives, the RV Urania ship of CNR was used to carry out a research cruise in the Mediterranean Basin during JulyAugust 2013. The oceanographic campaign started from the harbor of Palermo (Sicily) and finished in Messina (Sicily). It explored the Eastern Mediterranean Sea basin following the route showed in Figure 1. Figure 1. Route run by the RV Urania during the 2013 oceanographic campaign and sampling sites selected. Both airborne particulates and gaseous pollutants were collected along the route (with ship in movement) and also during stops made to investigate the environment features in various sites (see the map). Our main goal was to determine the PAH loads in atmosphere, in order to estimate the air quality with regard to them and identify their major sources across the Mediterranean sea, in the summer season. For this purpose, besides neat concentrations, attention was paid to two topics, namely: - the percent profile of PAHs investigated; - some selected diagnostic concentration ratios PAHs were monitored as particulate through collecting PM10 at medium volume conditions and applying a consolidated procedure. In addition, some measurements were made of VOCs and carbonyls. The former were collected on carbon cartridges, thermally desorbed and analyzed by GC-MSD; the latter were collected on silica/DNPH cartridges, solvent extracted and analyzed by HPLC-UVA. Results Table 1 shows the total PAH average (?15 PAH) for the three environmental contour types, i.e. harbors, movements (cruising) and stops. Compared to results of the summer 2010 cruise (Mulder at all, 2014), our data suggest that the PAH levels remained fairly unchanged. ( g/m3 ) Harbours Stops Cruising PAHs 1.67 ± 0.23 0.22 ± 0.06 0.26 ± 0.27 Benzene 0.03 ± 0.03 0.11 ± 0.13 0.05 ± 0.03 Toluene 0.46 ± 0.38 0.25 ± 0.25 0.20 ± 0.11 HCHO 3.4 ± 2.0 0.86 ± 0.67 0.82 ± 0.66 CH3CHO 2.7 ± 0.4 1.30 ± 0.89 1.22 ± 0.97 Table 1. Mean concentrations of airborne toxicants measured in the summer 2013 cruise A wide PAH variability was observed, with maximums in harbours; two samplings during shipping were very different from the other ones (1.03 vs. 0.12 ng/m3 ). Anyway, benzo[a]pyrene never exceeded 0.1 ng/m3 . These differences originated from the distinct impact of sources other than ship emission plumes (e.g., industrial and harbour plants along coasts, transport from land) as well as from atmospheric reactivity, as confirmed by the different concentration ratios of selected PAHs. For instance, distinct rates were found for the BaA/CH (0.44 in harbours, 0.55 in stops and 0.22 in movement), the CH/BaP (2.00, 1.73 and 0.79, respectively), and the BaP/BeP ratios (0.38, 0.64 and 0.75, respectively). As for gaseous compounds, harbors were affec