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 SO₄^2- 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).