Physical properties of suspended dust during moist and low wind conditions in Iceland

We measured a dust event which occurred during wet and low wind/windless conditions as the result of surface heating in August 2013. Maximum particle number concentration (PM~0.3-10 μm) reached 149,954 particles cm -3 min -1 while mass concentration (PM<10 μm) was 1757 μg m -3 min -1 . The suspended dust was very fine with the highest number of particles in the size range 0.3-0.337 μm, followed by particles 1.5-5 μm in diameter. Close-to-ultrafine particle size distributions showed a significant increase in number with the severity of the measured dust event (during dust peaks). Number concentrations were well correlated with mass concentrations. The mineralogy and geochemical compositions showed that glaciogenic dust contains sharp-tipped shards with bubbles and 80 % of the particulate matter is volcanic glass rich in heavy metals. Wet dust particles were mobilized within < 4 hours. This is the first scientific study of particle size distributions in an Icelandic dust event including findings on initiation of dust suspension.