Variability, origin and physical characteristics of dust aerosol in Iceland

Emissions of particulate matter from the natural sources account for a significant part of the total particulate air pollution. Less industrialized and inhibited regions, such as deserts, can contribute remarkably to air pollution. Iceland is a good example of such areas. The trends in long-term dust activity in Iceland and results from the pioneer field experiments on dust atmospheric and snow measurements are presented in this thesis. Long-term dust frequency in Iceland is based on the meteorological data from 30 weather stations in period 1949-2011. Dust day frequency in Iceland is similar to the major desert areas of the world (Mongolia, Iran, USA, China). Frequent volcanic eruptions with the re-suspension of volcanic materials and dust haze increase the number of dust events fourfold, resulting in 135 dust days annually. The Sea Level Pressure oscillation controlled whether dust events occurred in NE or in southern part of Iceland. The Arctic dust events (NE Iceland) were typically warm and during summer/autumn (May-September) while the Sub-Arctic dust events (S Iceland) were mainly cold and during winter/spring (March-May). A total of 32 severe dust storms (visibility < 500 m) was observed. Dust deposition of 31 – 40 million tons influences areas of > 500,000 km2, while some dust plumes are spanning > 1000 km at times. These results confirm that Icelandic dust sources are the most active in the Arctic/sub-Arctic region. Dust is also distributed over glaciers (about 4.5 million t annually) and oceans (6 – 14 million t annually). Our measurements show that Icelandic dust deposited on snow lowers the snow albedo and reduces the snow density as much as Black Carbon, the most powerful absorbing aerosol. The dust has a marked influence on Icelandic ecosystems. The oceanic deposition of the iron-rich dust can potentially affect the primary productivity in oceans around Iceland, especially in spring and late summer. The investigations of physical properties of volcanic dust reveal major differences in mineralogy, geochemical compositions, shapes, sizes and colour, compared to the crustal mineral dust. Icelandic dust is of volcanic origin, dark in colour with sharp-tipped shards and large bubbles. About 80 % of the particulate matter is volcanic glass rich in heavy metals, such iron and titanium. Suspended dust measured at the glacial dust source consists of extreme numbers of close-to-ultrafine particles with a similar numbers as reported during the active eruptions. However, giant Icelandic particles (50 – 100 µm), can travel long distances. Suspended grains > 2 mm were captured during the severe dust storm after the Eyjafjallajokull eruption in 2010, when the aeolian transport exceeded 11 t of materials over one meter wide transect. This places Icelandic dust storms among the most extreme wind erosion events recorded on Earth. First experiments on optical properties of volcanic dust in the laboratory show that Icelandic dust has same or lower spectral reflectance than Black Carbon. This indicates that climate forcing of Icelandic volcanic dust is different to that concluded for mineral dust in climate change predictions. Icelandic volcanic dust tends to act as a positive climate forcing agent, both directly and indirectly. The high frequency, severity and year-round activity of volcanic dust emissions suggest that Icelandic dust contributes to Arctic warming. Iceland is not only a substantial source for local air pollution; it has likely long-term effects on the Arctic and European air pollution.

Author dc:creator

• Dagsson-Waldhauserová, Pavla, 1980-

Contributors dc:contributor

• Landbúnaðarháskóli Íslands
• Háskóli Íslands

• Doktorsritgerðir
• Rykmengun

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/1946/19910

OAI identifier oai:identifier

oai:skemman.is:1946/19910