The low end of the distributions are ultrafines - yet according to aerosol textbooks such particles are not considered dust but accumulation mode.
theoretically and possible both exist, however, i have not so far tested it,you could try ! in fact, in the interval (-∞,+1), it totally depend the accurate degree you required that you can fix maximum top value ,such as 10u...1mm,or 1cm,even1m on the “1”point, as well as also meet your the accurate degree you required, for example,The rate 3nm to 10u or 1mm,1cm, even 1m you would like to postulate the rate , may be “zero”, then next you could search the mean(the averaged value ) from 3nm to maximum top value(10u or 1mm,1cm, even 1m), continuously, may be , “possible perfect” distribution will be reached........of course, the lowest end of the distribution also near to pm scale ......if necessary....
06-oct-2017
In addition, you also may use alternative the interval(-1,+∞) , as well as use “right tail L distribution function” if you pay attention to and hope emphasize the “big dust” distribution,and mainly analyse big size dust, therefore, you should utilize “right tail L distribution function”! key is choice according to your problem......
As a mass size distribution yes we measured with low pressure cascade impactor from 60 nm till 10 micro-m and then some chemical analysis's were made for each size with atomic absorption and got some initial results for elemental size distribution but this work stopped because there is no financial support for analysis
At theBaltimore "Supersite" and elsewhere, we routinely measured particles with diameter between 9 nm and 20 um using a combination of two TSI aerosol spectrometers.
TSI sells a version that can sample/measure down to 3 nm. Chemical composition is achieved by analyzing size-segragated aerosol particle samples with micro-orifice impactors (MSP company; See papers by Khulmey and Marple) .
Thanks John, I'm aware of your system. My concern is how to explain the formation ("aerosolization") of 9-20 nm (or even less) particles, when in aerosol textbooks it says inertial entrainment is impossible (due to relatively strong van der Waals forces/inertial ones ratio). Is it rapid nucleation of even smaller (molecular size) aerosols?
Robert, 9 to 20 nm particles are produced by uncontrolled combustion sources and result from nucleation and subsequent growth of new particles via gas phase reactions. I agree that aerosolization would be negligible in the this size range.
You are right, however,, in addition, there is another mechanism of becoming "airborne", discovered by geology prospectors and confirmed by, for instance, Beauford, Barber, Barringer, proving that plants exude, via leaves, Zn65 and Pb210 in a form that penetrates through high efficiency filters. They published it in Nature and Science (mid 70s), cited over 150 x. I can send them to you, if you are interested. Clearly there was no combustion involved.
Robert, I'm not surprized, but I don't know that I would call that dust. I suspect that penetration through High Efficiency filters was via leaks or small tares. Or simply very small but measurable due to the high sensitivity of radioactivity measurements. Regarding dust in the 9 to 20 nm range, I doubt we have any good measurements of dust in that range. There is so little total mass in that range, most of it is ammonium sulfate, nitrate, and soot, and it would easily be masked by silica particles emitted from coal combustion and other such sources. I imagine there might be some dust produced in the 9 to 22 nm range, but short of a high energy (e.g., nuclear) explosion, it would be very small. I'm sure you know that observation of mineral or other "dust" particles on impactor stages collecting such small particles are typically the result of particle "bounce" - which puts large particles on backup filters and stages collecting much smaller particles. However, it might be interesting to inspect single-particle Mass Spectrometry data. But, it could also well be inconclusive.
Definitely, let's stick to the definitions that's in textbooks (Hinds etc.): nucleation mode (/Aitken), accumulation, coarse (dust). Also I agree there is not a good measurement of "dust" in the 9-20 nm range. What forces at room temperatures could make solids airborne?
What we (and others) measured as getting past the high efficiency filters was not leaks. In our measurements, what was past the filter, was up to 100 x more than on the high efficiency filters. All these data were published in peer-reviewed journals, and most comprehensively in the "Data(set)", with Phil Hopke as the second author, in our ppt presentation, available on RG
Clearly, what others and we discovered is a major anomaly. Whether it'll be accepted - and tested - by the mainstream science remains to be seen.
I remember J T Dickinson from WSU, who thought the work of our group at the former US Bureau of Mines was good, told me "go and do your experiments better".
And I agree, to inspect single-particle by Mass Spectrometry would be interesting - past the high efficiency filters ...
Yes, size distribution of dusts can be measured across a wide range, typically from 3 nanometers to greater than 10 micrometers.
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