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We investigated an unusual elevated-ozone episode that took place at a high altitude measuring site Zavižan (44.817°N, 14.983°E, 1594 m a.s.l.). The episode was characterized by three consecutive peaks. The first one was the highest (over 120 ppbv), and it occurred at the late night on 17 July. Following two (both about 110 ppbv) appeared approximately 18 and 36 hours after the first peak, respectively. The night-time maximum and the departure from the usual diurnal variation of ozone concentration during investigated episode point to the non-local pollution sources, rather than to local photochemical production. Thus, recorded ozone peaks might arise due to the long-range transport of photo-oxidants ; 2) stratospheric ozone intrusion ; or 3) they might be result of both (1) and (2). In order to inspect which of above processes is responsible for the increased ozone concentrations we applied the unified EMEP model, which among others, simulates atmospheric transport and deposition of photo-oxidants, and, a mesoscale numerical weather prediction model WRF-ARW V2.2. Additionally, the larger scale atmospheric conditions were examined based on the ECMWF ERA-40 reanalysis fields. Results suggest that the stratospheric ozone intrusion played an important role in the occurrence of investigated episode.

This study investigates the influence of weather types found over the continental part of Croatia on daily PM10 concentrations and concentrations of metallic compounds in PM10 (namely manganese, lead and cadmium) in air during 2000-2002 period. Pollutant concentrations were measured at the northern, residential part of Zagreb, far from the major pollution sources. Weather types were determined from synoptic charts. In the employed categorization six different patterns were recognized: radiation weather type, high pressure ridge, precipitation weather type, southeastern advection, northeastern advection and wind weather type. The most frequently, elevated concentrations were related to radiation weather type and southeastern advection, while the lowest concentrations were recorded during the wind weather type. Obtained results generally suggest a major role of the local pollution sources, and particularly of the Zagreb industrial zone, in suspended particles/metallic compounds pollution. Since cadmium exhibits somewhat different behavior, the role of the long-range transport in cadmium pollution needs to be further investigated. Synoptic conditions favorable for elevated concentrations occurred in about 37 % of investigated days. Typically, these conditions are characterized by 1) the weak winds and turbulence, and consequently, inefficient pollutant concentration dilution (the nighttime and wintertime radiative conditions) ; or 2) southeastern airflow (southeastern advection and daytime radiative conditions), which transports pollutants from industrial zone of Zagreb towards the measuring site. Due to the latter, particulate pollutants emitted in the industrial zone pass rather frequently above the eastern part of Zagreb.

A Lagrangian receptor-oriented long-range transport model has been applied in order to estimate the relative contribution of domestic, Austrian, Hungarian, Italian and Slovenian emissions to the long-term deposition of airborne sulphur in Croatia. During the November 1, 1991 to April 30, 1992 period 163.31 thousands of tonnes of sulphur were deposited over Croatia, where 90.9% originated from transboundary emission sources. Relative contribution of domestic sources was the biggest (9.1%), while Austrian contribution was the smallest (0.4%).