| Summary: | Two clear episodes were detected when the main source of aerosols was the volcano, with well-defined size distribution spectra of PM1 chemical components in the accumulation mode. The ammonium to sulfate molar ratio (ASR) during Episodes 1 and 2 is 0.81, suggesting that sulfate particles were partially neutralized by ammonium and determined by volcanic eruptions. However, during Episodes 3 and 4 the ASR was higher (1.0) and determined by both volcanic and non-volcanic origin components. This study shows that the sulfate emissions from the volcano at Grimsvötn in Iceland reached distances farther than 3000 km, and they can have an influence on the local concentration and size distribution spectra of PM1 chemical components. Over the period of the volcanic eruption (Episode 1) the sulfate concentrations increased by a factor of 3 and reached 90% of PM1, while the nitrate and organic levels remained low and unchanged. The volcanic sulfate contribution made up about 250% of the average concentration of anthropogenic sulfate in Vilnius.
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