Diurnal cycle of SO2 concentrations in Rijeka and its relation to maximum and average daily concentrations.

Continuous recording of SO2 concentrations at one site in Rijeka in the heating season has shown that in spite of geographic and climatic differences, the pattern of diurnal cycle of SO2 concentrations does not differ from that recorded in Zagreb and in other towns with a temperate climate. The pattern is characterized by two peaks: a higher one in the morning that represents daily maximum and a lower one in the afternoon that is a good approximation of daily mean. Accordingly, maximum and mean daily concentrations could be assessed by short-term samples collected over given periods (8-10 and 15-18 h). As the diurnal cycle of SO2 concentrations could be disturbed by changes in weather conditions, equations were developed and coefficients established for calculating correction factors for adjustment of the estimated daily maximum and mean concentrations from two samples of short duration. The equations developed in Zagreb proved to be also valid for Rijeka. Presumably, the procedure could be used in other towns in the temperate region after the pattern of diurnal cycle of SO2 concentrations has been verified and the coefficients necessary for calculating correction factors established.