The concentrations, size distributions, and elemental compositions of atmospheric aerosol particles over a small but representative (in terms of size, population, and geographical characteristics) insular coastal city in the North Aegean Sea were measured during winter and summer. Mean PM_2.0 and PM_1.0 concentrations at the city centre were respectively 26 and 21 μg m⁻³ during the cold period, and 21 and 15 μg m⁻³ during the warm period. Although these concentrations are considerably lower compared to corresponding values of PM_2.5 and PM_1.0 recorded in large cities in the region, they are still very close to the mean annual standards set by the EU for PM_2.5. Higher average mass concentrations (by ca. 26–36% for Total Suspended Particles, PM_2.0 and PM_1.0) were observed in the cold period compared to those in the warm period due to the additional emissions from domestic heating and the weaker atmospheric dilution. The elemental composition measurements showed that crustal and anthropogenic elements (i.e., K, Ca, Ti, Mg, Fe, As, S) in the collected particle samples were also enriched when polluted air masses were transported from Northeastern Turkey. These measurements also showed that natural sources contribute sea-salt and re-suspended soil to the particulate matter load in the city's atmosphere. Non-exhaust traffic emission sources were also found to be an important contributor, as indicated by the good correlations (R² = 0.40–0.91) between crustal and traffic-related elements (i.e., Zn, Cr, Cu, and Mn). Overall, PM measurements in the urban environment in the region are relatively high, being influenced by both local sources and long-transported air masses.

The unprecedented growth in aviation during the last years has resulted in a notable increase of local air pollution related to airports. The impacts of aviation on air quality can be extremely high particularly around airports serving remote insular regions with pristine atmospheric environments. Here we report measurements that show how the atmospheric aerosol is affected by the activity at a small airport in a remote region. More specifically, we provide measurements performed at the airport of Mytilene, Greece, a regional yet international airport that serves the entire island of Lesvos; the third largest island of the country. The measurements show that the activity during landing, taxiing and take-off of the aircrafts accounted for up to a 10-fold increase in particulate matter (PM) mass concentration in the vicinity of the airport. The number concentration of particles having diameters from 10 to 500 nm also increased from ca. 4 × 10² to 8 × 10⁵ particles cm^− 3, while the mean particle diameter decreased to 20 nm when aircrafts were present at the airport. Elemental analysis on particle samples collected simultaneously at the airport and at a remote site 3 km away, showed that the former were significantly influenced by combustion sources, and specifically from the engines of the aircrafts. Our results show that despite their small size, local airports serving remote insular regions should be considered as important air pollution hotspots, raising concerns for the exposure of the people working and leaving in their vicinities to hazardous pollutants.

Near real-time atmospheric particulate matter (PM) monitors are extensively used in air quality networks given their ability to provide continuous measurements with minimal attention by the operator. Their principle of operation is based on measurement of a physical parameter that is quantitatively linked to the PM mass concentration. Significant discrepancies between these measurements and those obtained by the reference gravimetric method, conducted in regions with diverse climatic conditions, have been reported in the literature. In this study we compare systematic PM_2.5 and PM₁₀ gravimetric (GM) and beta attenuation (BA) measurements performed at a suburban site in Athens, Greece, over a period of 4 years (2009-2012). In general, BA and GM datasets exhibited similar temporal variation for both PM size fractions. An overestimation of the ΒΑ measurements, which was ~30% for the PM_2.5 and ~10% for the PM₁₀ data, was observed. Good linear correlations between GM and BA data were observed, with estimated Pearson coefficients being 0.79 for the PM_2.5 and 0.85 for the PM₁₀ measurements. The respective fitted equations through the entire dataset were BA = 0.71 GM+6.2, and BA = 0.77 G M+4.1. Better correlation between GM and BA measurements was observed during the cold rather than the warm period. Discrepancies between BA and GM PM_2.5 measurements increased with increasing available water vapor, suggesting that the aerosol bound water has a strong effect on the measurements. The effect of filter material used for GM measurements (i.e., quartz, glass fiber, or Teflon) was also examined for the PM_2.5 dataset. Best correlation between BA and GM data was observed when glass fiber, which is incidentally the material of the BA filter tape, was used in the GM measurements. When the BA to GM relationship was examined by further categorizing the data by the season (i.e., cold and warm period) for different filter types, the relationships that were fitted to the data for the two seasons were similar when Teflon filters were used, but quite diverse when quartz and glass fiber filters were employed in the GM measurements. Finally, the variability of the ratio between the two measurement techniques was found to be potentially dependent on the availability of the volatility or stability in the aerosol phase of species such as ammonium nitrate.

Long-range transportation of air pollutants from industrial and urban environments can significantly affect the quality of the air in remote regions. In this study, we investigate episodes of particulate transport (PT) from Eurasia to the remote environment of Northeastern Mediterranean, i.e., the region of the North Aegean Sea (NAS), during the summer when the synoptic Etesian wind conditions prevail. A temporary monitoring station was set up at a remote region on the island of Lemnos, which is located at the center of the NAS at a distance of ca. 250 km from the continent. Measurements of the aerosol particle size distributions, the total number and mass concentrations, as well as the chemical composition of the particles were conducted from 27 August to 10 September 2011. During this period, the wind speeds were high (typically higher than 5.5 ms-1) with a direction that mostly ranged from north to northeast (68% frequency). Winds having direction ranging from northwest to south were less frequent (7% frequency), while the rest of the cases were characterized as calm (i.e., wind speeds less than 1 m s-1; 25% frequency). Seven PT episodes were observed during the sampling period. When the wind direction was northeastern we observed up to a six-fold increase in particle number concentration of nucleation mode, while the peak size of the particles decreased from 100 to 20 nm. Interestingly, the nucleation-mode particles grew from ca. 15 to 25 nm with rates of ca. 9.0 nm h-1, which are representative of polluted areas. Analysis of the chemical composition of particle samples collected on filters during the PT episodes shows that the concentration of sulfates and nitrates increased by ca. 60%, while the OC/EC ratio increased by ca. 22% compared to the rest of the sampling period. Back-trajectory analysis for the period during the episodes shows that the air masses arriving at the station passed over the greater Istanbul area and the Black Sea 9 to 12 h before reaching our station. These observations provide strong evidence that the air quality in the remote region of the NAS can be significantly affected by the transportation of particulate pollution during the summer period, having potentially important effects upon human health and climate in the region.