The atmospheric stability plays an important role in the accumulation of air pollutants and greatly influences their degradation, dispersion and deposition. These atmospheric qualities can be determined with various methods (Richardson number, Monin -Obukhov length, SRDT method) and the pollutant concentration increase demonstrates the atmospheric stability. In this study the cold periods were the most stable as well the PM 10 and CO pollutants had high concentrations. Between these two pollutants the correlation is high because their sources are the same: transport and biomass burning. The study of hourly averages highlighted the importance of traffic intensity since the concentration variation follows the traffic intensity. An increase in the wind speed in the basin results in the pollutants concentrations decrease, the negative correlation with the temperature indicating the importance of the photochemical processes.

As ozone is a secondary polluting substance, its oxides of nitrogen (NOx) play a significant role as precursors. Their existence is influenced by climatological and meteorological parameters, as well as other air pollutants (SOA, VOC). At present, alongside with various meteorological parameters (temperature, wind speed, relative humidity, sun intensity), other air pollutants (oxides of nitrogen, carbon monoxide, benzene) and other physical phenomena (dry deposition, meteoric stability) mostly the indirect effects of relative air humidity was examined in relation with the evolution of tropospheric ozone concentration. Our aim was, to examine the closed experiment of Jia and Xu (2014) (smog chamber), under atmospheric conditions, according to which in the case of high relative humidity the formation of ozone falls if benzene and ethylbenzene are added. According to the results, relative humidity has an increasing effect on water radical reactions and the hydration of glyoxal, while the concentration of the ozone changes as a result. At the same time, it can be observed that the higher the value of relative humidity is, the higher are also the values of ONO2, benzene and CO, whereas the concentration of O3 decreases. The reactions caused by the relative humidity of the air and VOC concentration in the experiment of Jia and Xu (2014) produced relatively adversary demonstrations in natural environment, because the experiment had been carried out at room temperature, whereas temperature and other parameters are subject to constant change in the natural environment.

ABSTRACT. In the present study, the changes of the concentration of air pollutants were examined, based on air pollution, meteorological and climatologic data gathered over an interval of two years (2012)(2013) by the regional measuring station located in the basin, as well as the sources of the air pollutants were studied with the help of factor analysis. Biomass burning, traffic and photochemistry were characteristic regarding the source of air pollutants. This was also confirmed by the correlations between pollutants. Furthermore, the increasingly busy car traffic in the cold season and the atmospheric stability characteristic for it are also important observations with regard to the sources of air pollutants.