High levels of particulate matter in Iceland due to direct ash emissions by the Eyjafjallajokull eruption and resuspension of deposited ash

The dangers to people living near a volcano due to lava and pyroclastic flows, and, on glacier-or snow-covered volcanoes, jokulhlaups, are well known. The level of risk to human health due to high concentrations of ash from direct emission and resuspension from the ground is, however, not as well known. The eruption at Eyjafjallajokull, 14 April to 20 May 2010, produced abundant particulate matter due to its explosive eruption style. Even after the volcanic activity ceased, high particulate matter (PM) concentrations were still measured on several occasions, due to resuspended ash. The 24 hour mean concentration of PM10 in the small town of Vik, 38 km SE of the volcano, reached 1230 mu g m(-3), which is about 25 times the health limit, on 7 May 2010, with 10 min average values over 13,000 mu g m(-3). Even after the eruption ceased, values as high as 8000 mu g m(-3) (10 min), and 900 mu g m(-3) (24 h), were measured because of resuspension of freshly deposited fine ash. In Reykjavik, 125 km WNW of the volcano, the PM10 concentration reached over 2000 mu g m(-3) (10 min) during an ash storm on 4 June 2010, which should have warranted airport closure. Summarizing, our study reveals the importance of ash resuspension compared to direct volcanic ash emissions. This likely has implications for air quality but could also have detrimental effects on the quality of ash dispersion model predictions, which so far generally do not include this secondary source of volcanic ash.