The change in O3, SO2 and NO2 concentrations in Lithuania

Due to the dynamic nature of the atmosphere, substantial amounts of gaseous and particulate pollutants are transported to the areas distant from their sources. In order to determine the regional concentration levels of atmospheric pollutants in Lithuania, concentrations of gaseous O-3, SO2, NO2 and other pollutants have been measured at the Preila background station (55 degrees 20' N and 21 degrees 00' E, 5 m a.s.l.) since 1981. The long-term concentration data set enabled us to get temporal trends, both on a seasonal and longer time scale, to identify source areas of pollutants and to relate them to the emission data. Based on the data obtained, the different tendencies in the pollutant concentration changes were revealed. Positive trends for ozone (of 2.9% per year during 1983-2000) and a distinct negative trend for both sulphur dioxide (of 3.8% per year during 1981-2000) and nitrogen dioxide (of 3.8% per year during 1983-2000) were found. The air mass back-trajectory analysis was used to assess the source region of air pollutants transported to Lithuania. The pollutant concentration levels were compared with their emission changes in Europe and Lithuania. The general trends in SO2 as well as in NO2 concentrations observed are consistent with changes in SO2 and NO2 emissions in Europe and Lithuania.