The authors presented the results of synchronous observations of ozone and gaseous impurity concentrations, chemical composition of aerosol and meteorological parameters with the high time resolution (minutes) at the background site Mondy located in the highland area of East Siberia. They also analyzed seasonal dynamics of ozone, gaseous impurities of sulfur and nitrogen, ionic composition of aerosol for the log-term period of observations (1998-2016). Ozone variability in the boundary layer depended on complicated relief and dynamic processes occurring in the atmosphere. The concentration of ions in aerosol decreased in 2 times for the period of 2010-2015 compared to that at the beginning of the new millennium. The composition of dominant ions in aerosol also changed: currently the dominant anions and cations are sulfate, nitrate, chloride, potassium and sodium. Taking into account the remote location of the site, absence of anthropogenic pollution sources and a large series of data of different parameters obtained within on-line monitoring, this site may be regarded as a representative background global site for the vast region of Central Asia.