ROBERT SZEP, REKA KERESZTES, SZENDE TONK, ATTILA KORODI, MIHAELA EMANUELA CRACIUN THE EXAMINATION OF THE EFFECTS OF RELATIVE HUMIDITY ON THE CHANGES OF TROPOSPHERIC OZONE CONCENTRATIONS IN THE CIUC BASIN, ROMANIA 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.