An inter-comparison of size segregated carbonaceous aerosol collected by low-volume impactor in the port-cities of Venice (Italy) and Rijeka (Croatia)

Abstract

Size-segregated analysis of organic and elemental carbon (EC, OC) in aerosol is essential in understanding sources and effects on the environment. However, these studies are scarce, especially in coastal areas stressed by anthropogenic emissions and with interactions between anthropogenic and natural emissions. To partially fill this lack of information, aerosol size segregated samples were taken between August 2018 and May 2019, using a MOUDI impactor. Measurements were performed in two port-cities of Northern Adriatic Sea, Venice (Italy) and Rijeka (Croatia). A thermal-optical analysis (EUSAAR2) allowed EC and OC determination in different size ranges. For Rijeka site, the water soluble organic carbon content (WSOC) was analysed. OC and EC average concentrations in Venice were 3.16 (±0.97) and 0.40 (±0.13) μg/m3; in Rijeka: 2.48 (±0.65) and 0.37 (±0.08) μg/m3. The OC size distributions were bimodal at both sites, with an accumulation mode in the size range 0.56–0.32 μm, a coarse mode in the range 5.6–3.2 μm. EC showed a bimodal distribution in Rijeka, a single fine mode in Venice. The EC/TC ratio was large in the fine mode at both sites, however, in Rijeka non-negligible values were found in the coarse fraction suggesting contributions from resuspension of carbon-loaded dust and mixing of anthropogenic particles with sea spray. The WSOC/OC analysis as function of particle size in Rijeka showed a total value of 0.51 (±0.12) with an increase in the coarse fraction likely due to contributions of water soluble carbon from sea spray and biogenic emissions.