Levels of nitrogen dioxide in the Zagreb air.

Surveillance of NO2 in Zagreb started in 1994 at five measuring sites. This paper presents the levels and trends of NO2 annual mean values for the period between 1994 and 1998. The obtained data are compared with the recommended and limit values according to the Law on Air Quality Protection in Croatia and the Ordinance on Recommended and Limit Air Quality Values. For the past five years, ever since the measurement commenced, the concentration levels of NO2 in Zagreb have kept between the national recommended and limit values at all measuring sites, indicating that the air has been moderately polluted. This paper also shows the variations of monthly mean values through 1998 at all sites. The levels of NO2 in the northern part of Zagreb were measured at two distances from traffic. Daily variations in the levels were measured near the road and presented as hourly averages for workdays and weekends in winter and in summer reflecting the activity pattern of emission sources.