Long-term air pollution trend analysis in the South-eastern Baltic region, 1981-2017

European emissions data have been reported during the last 40 years under the Cooperative Programme for Monitoring and Evaluation of the Long-range Transmission of Air Pollutants in Europe (EMEP), launched by the UNECE Convention on Long-range Transboundary Air Pollution (CLRTAP). In this paper, long-term continuous data of gaseous and particulate air pollutants concentrations measured over a period of 36 years (1981-2017) from a coastal background EMEP air quality monitoring site in Preila, Lithuania, were analyzed. All the analyzed S- and N- species decreased during the 1981-2017 period except for nitrate concentration, which increased during the 1990s by 170%, and showed minor decreasing trend during the 2000-2017 period. The analysis has shown that despite the 95% and 79% decrease of sulfur dioxide and sulfate concentrations, respectively, sulfate comprised a considerable share of the ion balance. As the concentration of total sulfate decreased remarkably, the sea-related particles portion of the sulfate concentration increased up to 22%. The sulfur dioxide concentration at the Preila station has stabilized since 2015. Separation between the time series of sulfur dioxide and sulfate occurred in 2007-2008 with sulfate exceeding sulfur dioxide concentrations during the latest decade. This indicates the absence of local sulfur dioxide sources and relative increase in contributions by long-range transport of particulate forms of sulfur.

Automated summary

European emissions data over the past 4 decades have been analyzed through the EMEP program, showing a decrease in S- and N- species concentrations, except for nitrate. The study on a coastal background site in Lithuania revealed significant reductions in sulfur dioxide and sulfate concentrations, with an increase in sea-related sulfate particles. Additionally, the analysis indicated a stabilization of sulfur dioxide levels since 2015 and the dominance of sulfate over sulfur dioxide concentrations in recent years, suggesting a shift towards long-range transport of sulfur.