Particle size distribution factor as an indicator for the impact of the Eyjafjallajokull ash plume at ground level in Augsburg, Germany

During the time period of the Eyjafjallajokull volcano eruption in 2010 increased mass concentration of PM(10) (particulate matter, diameter < 10 mu m) were observed at ground level in Augsburg, Germany. In particular on 19 and 20 April 2010 the daily PM10 limit value of 50 mu g m(-3) was exceeded. Because ambient particles are in general a complex mixture originating from different sources, a source apportionment method (positive matrix factorization (PMF)) was applied to particle size distribution data in the size range from 3 nm to 10 mu m to identify and estimate the volcanic ash contribution to the overall PM10 load in the ambient air in Augsburg. A PMF factor with relevant particle mass concentration in the size range between 1 and 4 mu m (maximum at 2 mu m) was associated with long range transported dust. This factor increased from background concentration to high levels simultaneously with the arrival of the volcanic ash plume in the planetary boundary layer. Hence, we assume that this factor could be used as an indicator for the impact of the Eyjafjallajokull ash plume on ground level in Augsburg. From 17 to 22 April 2010 long range transported dust factor contributed on average 30% (12 mu g m(-3)) to PM10. On 19 April 2010 at 20:00 UTC+1 the maximum percentage of the long range transported dust factor accounted for around 65% (35 mu g m(-3)) to PM10 and three hours later the maximum absolute value with around 48 mu g m(-3) (61 %) was observed. Additional PMF analyses for a Saharan dust event occurred in May and June 2008 suggest, that the long range transported dust factor could also be used as an indicator for Saharan dust events.