engleski

Urban ozone in Croatia

Tropospheric ozone has been monitored at various locations in Croatia since 1975. These locations include sites as the TOR Network Station Puntijarka (located about 10 km north of the city of Zagreb on the ridge of mountain Medvednica ; 45.90º ; N ; 15.97º ; E, 980 m a.s.l.) and the urban centers of Zagreb (continental Croatia), Rovinj (a small Mediterranean town and important tourist centre in the northern Adriatic) and Osijek in eastern Slavonia (largest urban centre in Slavonija). Ozone data exist also for several seasons for the mountain sites Srđ (southern Adriatic, 42.65° N, 17.45° E, 412 m a.s.l., north of Dubrovnik) as well as for the island of Mali Lošinj (remote island, northern Adriatic). Ozone has been monitored with commercial Dasibi and Environment monitors, which have been regularly checked and calibrated against primary ozone standard instruments. The data were converted to hourly average volume fraction and analyzed in relation to meteorological data. The annual mean values and the least squares statistical analysis of the years 1990 - 2002 for the Puntijarka station are conform either with no increase of ozone volume fraction or a slight decrease of 3.1 ppb per decade. A possible reason for the observed trend is the depletion of ozone in the lower stratosphere resulting in a decreased input to the troposphere by diffusion and intrusion, but possibly also to the dramatic changes in Croatian industry and transportation. Simultaneous measurements at 180 m a.s.l. at the Ruđer Bošković Institute in the northern part of Zagreb, at 580 m a.s.l. on the mountain Medvednica and at Puntijarka station show that even at high photosmog conditions above Zagreb the Puntijarka station remains above the mixing layer and is largely unaffected by the city. The ozone volume fraction in Osijek twice exceeded the 80 ppb value. Thus not significant photochemical pollution problems are expected for the city. The data from the location Srđ above Dubrovnik show negligible average diurnal variation with a mean value of 38 ppb. The measurements in the southern Adriatic at Srđ show lower ozone levels than those found in the central and northern regions. Data for Mali Lošinj yield a summer mean value of 41 ppb and the polar plot of relative deviations from average and corresponding wind rose show that the average value is higher when the wind blows from the western sector than from the eastern. Long range transport was observed at Rovinj and Mali Lošinj as well as local photochemical production.

tropospheric ozone measurements

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