engleski

Sulphur and nitrogen in PM10 from the Rijeka Bay area, Croatia

Airborne ammonium, nitrate and sulphates in PM10 fraction are the result of the complex chemical reactions of their precursor pollutants. During a 1-year period samples of PM10 were collected at two sites: in the very city center (Site 1) and in the proximity of shipyard located 6 km eastwards from the city (Site 2). Except the minimum in August, the airborne concentrations of sulphates are almost constant and approx 5.5 µg/m3 at both sites. The contributions of sea-salt sulphates are approx 10% at both sites. The concentrations of ammonium and nitrates show a seasonal behaviour with minimal values in warm period (April-October) and increase during winter. Such a behaviour is the result of photochemical and chemical reaction in the summer time. Thus the ratio W/S is maximal for nitrates (W/S=3), while lower for ammonium (W/S=1.5). Unlike nitrogen species, the concentrations of sulphates are somewhat higher (approx 10%) in summer than in winter time due to photochemical transformation of SO2 to SO42- in the warm period. From the µeq/m3 concentrations of airborne sulphates, nitrates and ammonium it is evident that the ammonium sulphate is the dominant species, approx six time more abundant that ammonium nitrate in summer time. In the winter time the ratio (NH4)2SO4/NH4NO3 is 1.4 ( Site 1) to 1.6 (Site 2). In relation to wind direction, no particular direction is found for airborne sulphates at Site 1, while nitrates and ammonium indicate the common E-ESE (industrial zone) and N (busy street) direction.

PM10 ; sulphates ; nitrates ; ammonium

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