Bulldust micron rating

[slick1]

Hi,

Anyone out there know what the micron rating is for Bulldust?

That's the very fine and light dust that collects in depressions in the Australian outback.

I don't have any to analyse... so no way of figuring it out by myself.

Maybe next time I'm in the outback I'll take a sample.

 

[crinkles]

I would say it is probably some form of dry silt-sized particles which are classified as between 20 and 75 micron.

take a sample, next time. I may be able to arrange for a test to AS however it will be a few hundred $.

 

[crinkles]

http://www2b.abc.net.au/science/k2/stn/newposts/3193/topic3193089.shtm

the above link has mentions of between 2 and 100 micron

personally i don't think it would be less than 20 micron. below that, things become very cohesive when dry and you have like hard clay pad conditions. therefore i think it must be a silt! even if the bulldust is made up of more than 1 smaller particles held together.

 

[crinkles]

http://www.nt.gov.au/nreta/natres/soil/management/pdf/TransportCorridors.pdf

tghe above link mentions siltstone derived soils are also prone to making bulldust, therefore silt seems to be the go. 20 -75 micron.

 

[XS650]

Originally Posted By: slick1
Hi,

Anyone out there know what the micron rating is for Bulldust?



I've been looking far an old source that made a rough estimate of dust micron size by how long it stayed up in still air but can't find it. IIRC, the "technical" term used by the air cleaner engineer that used the method for guesstimates was "hang time".

 

[crinkles]

XS650, this stuff actually settles

you can do an estimate of PSD int he fraction less than 75 micron with particles in suspension and a hydrometer.

 

[slick1]

I think the guy who said 40 nm (nano metres) might be correct.

I'm pretty sure that it's at the lower end of the scale... just a bit unsure how fine.

I'm pretty sure I could do my own testing if I had a sample. The problem is you've got to go quite far out of the way to get some... or get someone to bring some back.

Mobile phones don't work so well in the outback!

If XS650 finds his "old" source I'd really like to take a look at it.

It's not really related to erosion... so the erosion document doesn't really tackle it.

Imagine it as finely ground flour... but even lighter... and that might do it justice.

Thanks for all the suggestions.

 

[crinkles]

i don't think it would be in the nanometer range. do you mean micrometer?

 

[slick1]

1 micrometer = 1,000 nanometers

Thus if the particle is in the nanometer range if it's under 1 micron... and if you take a look at the air filtration tests in the air filter section you'll see that the stuff air filters are filtering goes down in the sub micron range... which takes it into the nanometer range (what goes in the air filter ends up in the oil).

The best answer I can find at the moment seems to suggest particles can be down to 40nm... but the response refers to iron oxide (which is probably common in some types of bulldust ie. the red type)... not actual bulldust... so I consider the question still not definitively answered.

http://www2b.abc.net.au/science/k2/stn/newposts/3193/topic3193089.shtm

Originally Posted By: crinkles
i don't think it would be in the nanometer range. do you mean micrometer?