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 (sorry for the labels which are 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 Nýsköpunarmiðstöð Íslands (the first graph above) at the request of Umhverfisstofnunar.
The samples were collected by Sigurður Reynir Gíslason and other good people from the Institute of Earth Sciences, University of Iceland.
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