Eyjafjallajökull 2010 - Grain size distribution

Grain size of the ash from Eyjafjallajökull eruption - samples from April 28 - Björn Oddsson

Particle size of the ash from Eyjafjallajökull eruption - Þröstur Þorsteinsson (throsturt@raunvis.hi.is, ThrosturTh@gmail.com)

Measurements show, as was to be expected, that the particle size is greater closer to the eruption site. However, one (sample collected on 18. April) of the two samples taken 20 km away (also sample on 17. April), is very similar to the one taken nearly 60 km away (15. April).


               

The figure below shows description of the data from 15. April (but same applies to the other dates):

1) Fraction of mass of particles smaller than a give size (the size given on the x-axis). Therefore for the largest particles, around 300 micro-m the fraction is 100%, since all particles smaller, and then about 25% of the total mass is particles smaller than 10 micro-m (PM10, which is familiar to many from Particulate Matter pollution measurements).

2) Shows the mass fraction within each size range.

3) Shows the number of particles within each size range, given that there is 1 particle in the largest size class. We can see that there are then 1 particle of size ~300 micro-m, but 10 thousand of the size 10 micro-m and about a million of the size smaller than 2.5 micro-m.



The sample collected on 15. April by Sigurður Reynir Gíslason and on the 17 and 18. Aoruk by Guðrún Larsen and Ármann Höskuldsson.

Particle size in the ash from Eyjafjallajökull eruption, sample from 15 April 2010 - Þröstur Þorsteinsson (throsturt@raunvis.hi.is, ThrosturTh@gmail.com)


By making small assumptions, such as same spherical shape and density for all particle sizes (1 to 300 micro-m), we can calculate the number of particles of a given size range from the data about mass fraction below a certain grain size.

The figure below shows (labels in Icelandic):

1) Fraction of mass of particles smaller than a give size (the size given on the x-axis). Therefore for the largest particles, around 300 micro-m the fraction is 100%, since all particles smaller, and then about 25% of the total mass is particles smaller than 10 micro-m (PM10, which is familiar to many from Particulate Matter pollution measurements).

2) Shows the mass fraction within each size range.

3) Shows the number of particles within each size range, given that there is 1 particle in the largest size class. We can see that there are then 1 particle of size ~300 micro-m, but 10 thousand of the size 10 micro-m and about a million of the size smaller than 2.5 micro-m.

Samples were measured at Innovation Center Iceland (the first graph above) at the request of The Environment Agency of Iceland.
The samples were collected by Sigurður Reynir Gíslason and Helgi Arnar Alfreðsson from the Institute of Earth Sciences, University of Iceland.