engleski

Carbon content in PM2.5 at a coastal measuring site in Croatia

Rijeka is the principal seaport and third largest city in Croatia. It is located in the Primorje-Gorski Kotar County on Kvarner Bay, an inlet of the Adriatic Sea and has a population of about 130000 inhabitants. The city's economy largely depends on shipbuilding and maritime transport. The terrain configuration, with mountains rising steeply just a few kilometres inland from the shores of the Adriatic, provides for some striking climatic and landscape contrasts within a small geographic area. Rijeka has a humid subtropical climate with warm summers and relatively mild winters with frequent rainfall and cold (bura) winds. This study is the first research on particulate matter with an equivalent aerodynamic diameter of less than 2.5 µm (PM2.5) and the carbon content in it at a coastal urban background station located in Rijeka. Mass concentrations of elemental (EC), organic (OC) and total carbon (TC) in) were investigated from January 1st 2017 to April 30th 2019. Sampling was conducted during 24-hour periods from approximately 55 m3 of ambient air on quartz fibre filters (Pall Tissuequartz 2600QAT-UP, 47 mm) pre-fired at 850°C for 3 hours. Mass concentrations of 850 PM2.5 samples were determined gravimetrically according to the standard EN 12341:2014. Carbon content was measured by the thermal-optical transmittance method (TOT) using a carbon aerosol analyser with a flame ionization detector and EUSAAR_2 temperature program operating according to the standard EN 16909:2017. The average PM2.5 mass concentration (11.1 µg m-3) did not exceed the limit value of 25 µg m-3 and the maximum was observed in winter (51.3 µg m-3). Carbon mass concentrations revealed strong seasonality having its low in summer and high in winter. The average OC/EC mass ratio values of around 6 pointed to the influence of secondary organic aerosols. Average TC mass contribution to the total PM2.5 mass was 34 %, of which 21 % SOC (secondary OC), 8 % POC (primary OC) and 5 % EC. High mass contribution of SOC to the total OC mass (as much as 73 %), can be explained by the warm climate suitable for photochemical reactions and the formation of SOC from sea spray.

EC, OC, OC/EC ratio, POC and SOC

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