The effects of volcanic eruptions on the frequency of particulate matter suspension events in Iceland

Large quantities of natural particulate matter are generated in Iceland every year. Glaciers, rivers, and explosive volcanic eruptions contribute to the production of suspended material in the air. With frequent high winds and sparse vegetation cover, fine and coarse particles are suspended and transported over land and out to sea. Observations of particulate matter during the period of 1966–2016 were used to determine the impact of explosive volcanic eruptions on the number of observed particulate matter events. These observations were made by weather observers at synoptic weather stations distributed around Iceland. Deposits from some explosive volcanic eruptions that produce new source material were found to increase the number of observations of particulate matter at stations relatively close to the volcano (within 125 km) for at least several months after the end of the eruption. This signal is only observed for eruptions that produced enough material to be classified into Volcano Explosive Index (VEI) of 3, or greater, and did not end during the winter, and is only rarely seen at the national scale. Eruptions starting shortly before or during the winter season and ending before the spring melt did not have an impact on the observations of suspended particulate matter due to snow covering the fresh material, reducing the potential for resuspension. The data set is insufficient to explain why only some eruptions fulfilling the criteria produce local effects persisting over multiple months. Seasonality, weather, and wind conditions are much stronger factors for increasing the number of particulate matter (PM) events than the creation of new material provided by explosive volcanic eruptions. A PM event is defined to occur when any type of PM is observed in the atmosphere.