Do bromine and surface-active substances influence the coastal atmospheric particle growth?

New particle formation (NPF) is considered a major source of aerosol particles and cloud condensation nuclei (CCN); however, our understanding of NPF and the subsequent particle growth mechanisms in coastal areas remains limited. This study provides evidence of frequent NPF events followed by particle growth in the middle Adriatic Sea during the summer months at the coastal station of Rogoznica in Croatia. To our knowledge, this is the first study to report such events in this region. Our research aims to improve the understanding of NPF by investigating particle growth through detailed physicochemical characterization and event classification. We used a combination of online measurements and offline particle collection, followed by a thorough chemical analysis. Our results suggest the role of bromine in the particle growth process and provide evidence for its involvement in combination with organic compounds. In addition, we demonstrated the significant influence of surface-active substances (SAS) on particle growth. NPF and particle growth events have been observed in air masses originating from the Adriatic Sea, which can serve as an important source of volatile organic compounds (VOC). Our study shows an intricate interplay between bromine, organic carbon (OC), and SAS in atmospheric particle growth, contributing to a better understanding of coastal NPF processes. In this context, we also introduced a new approach using the semi-empirical 1st derivative method to determine the growth rate for each time point that is not sensitive to the nonlinear behavior of the particle growth over time. We observed that during NPF and particle growth event days, the OC concentration measured in the ultrafine mode particle fraction was higher compared to non-event days. Moreover, in contrast to non-event days, bromine compounds were detected in the ultrafine mode atmospheric particle fraction on nearly all NPF and particle growth event days. Regarding sulfuric acid, the measured sulfate concentration in the ultrafine mode atmospheric particle fraction on both NPF event and non-event days showed no significant differences. This suggests that sulfuric acid may not be the primary factor influencing the appearance of NPF and the particle growth process in the coastal region of Rogoznica.

Airborne desert dust in the Northern Adriatic area (Croatia): Different sources.

During the implementation of the INTERREG IT-HR project ECOMOBILITY, whose one of the goals was to estimate the impact of ship emissions on air quality in the port city of Rijeka (Croatia) and Venice (Italy), two particular weekly samples were collected in Rijeka, during the first and the thirteen weeks of sampling, i.e. S01 (16.10.-23.10.2018) and S13 (24.04.-30.04.2019.), respectively. Both samples have similarities regarding species characteristic for desert dust contribution, but HYSPLIT analyses excluded Saharan desert to be the source of the S01 sample. Unlike Saharan dust, this sample had a high contribution of fine and ultrafine particles (>50 % and 9.8 %, respectively), as well as secondary inorganic (sulfates, ammonium) and organic (water soluble organic compounds - WSOC) aerosols. Detailed synoptic situation and HYSPLIT backward trajectories pointed out the Syrian Desert as the source of this collected sample. The same source was proved by MERRA-2 reanalysis of the desert dust emission. Although the Saharan dust episodes, mostly in precipitation, are well known in the Northern Adriatic area, this is the first time to indicate Syrian Desert as a source of airborne particulates. This assumption was confirmed with chemical species characteristic for the Syrian Desert, i.e. higher content of potassium from K- feldspar and phosphates.

Sources of airborne particulates (PM10) in the port city of Rijeka, Croatia.

The air quality monitoring in Rijeka started in the early 1970s and has been oriented to air pollution caused by the big industrial sources (new petroleum refinery, oil burning power plant, coke plant), while maritime traffic was neglected. First emission inventory comprising port emission was done only in 2008 indicating similar level of emissions as road traffic. Further analyses on maritime impact were done within MED project POSEIDON. This was the good opportunity to perform positive matrix factorization (PMF) analysis on airborne particulate data and identify principal sources of pollution within the Rijeka urban area. PMF analyses of PM10 collected from the urban background site in the period 2008-2010 identified 5 factors: biomass burning, secondary sulphates, sea spray, road/soil dust and metal industry/traffic. Condition probability functions (CPF) obtained from PMF factors of dust and secondary sulphates indicate that Ca, Fe, Zn and Cu originate from harbour area due to reloading of fertilizers and metal waste, as well as SO42- and NH4+ pointing to maritime corridor leading to the Rijeka harbour. These data could not quantify the maritime impact on the air quality, but gave the first estimation of contribution of various sources to air pollution within the Rijeka Bay area. The maritime contribution to air quality was estimated in other part of the same project, as primary PM2.5 emission obtained from vanadium. Both primary PM2.5 emission and polynuclear aromatic hydrocarbon profiles indicated reduced economic activity, including maritime traffic, during economic crisis in the period 2008-2012.

Characterization of airborne particulate fractions from the port city of Rijeka, Croatia.

The aim of this work was characterization of airborne particulates in the port city of Rijeka in order to evaluate impact of ship emissions on air quality. Samples of airborne particulates were collected with a ten stages cascade impactor during two campaigns: autumn and spring. A total of 16 weekly samples were analyzed on mass concentration, ions, metals and carbonaceous species (EC, OC, WSOC). Distribution of airborne fractions showed a bimodal distribution, with two maxima: one in coarse, and other in fine fraction. Source apportionment using PMF receptor model identified six sources of airborne particulates in Rijeka: crustal, biomass burning, sea salt, traffic/metal industry, combustion/SIA and HFO burning, i.e., ship emission (contribution 3%). The contribution of ship traffic to primary emission of particulate matter, using vanadium as tracer, indicated a twofold increase for PM10 and PM2.5 relative to 2012-14. An unusual desert dust event was registered in autumn campaign.

Secondary Sulfur and Nitrogen Species in PM10 from the Rijeka Bay Area (Croatia).

Samples of PM10 were collected over a 12 month period at two sites approximately 5 km apart. Site 1 was an urban site in the center of the city of Rijeka, Croatia, and Site 2 was an industrial site in the proximity of a shipyard, located in the southeastwards direction from the city. No significant differences in airborne concentrations of PM10 or secondary inorganic ions were found between the two sites. Therefore, the sampling continued only at Site 1. The dominant airborne compound was ammonium sulfate, being approximately six times more abundant in the summer (S) months than ammonium nitrate. This ratio was lower in the winter (W) months, being approximately 1.5 at both sites. Seasonal distribution of secondary inorganic aerosols (SIA), particularly SO42- is emphasized in 2008-2009 with W/S <1, most likely caused by local emissions, meteorology and long-range transport. In spite of closing down the petroleum refinery facilities in mid-2008, no significant decline in airborne concentrations of sulfates, nitrates or ammonium were observed during the period from 2007 to 2009 at the site nearest to the refinery (Site 1).