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(mailto:[log in to unmask]) writes:
What would be interesting to know is how far afield the dust drifts
relative to other sprays.
Its mainly a matter of particle size and weight. I've done a lot of
work on fall-out from emission sources. Dispersion of dust particles versus
an aerosols are very different. Plus, particulates often tend to
agglomerate or clump, making them even heavier and more likely to drop out quickly.
As an example, when I was studying fall-out from a smelter, the
concentration of lead particles which were associated with the dust blowing off the
slag piles (surface source of dust near ground level) fell off very rapidly
with distance. Across the street, the dust on window sills was 50% lead.
1/8 mile away, the concentrations were considerably lower. By 1/4 mile,
barely detectable.
Now, arsenic has a very small particle size, acts more like a gas.
Everything from the smelter went through a baghouse, yet arsenic from the stack
was dispersed over miles from the smelter (tall source height + small
particle size). In our work near Tacoma, WA - we found arsenic from the smelter
traveling as far as north Whidbey Island, and the Canadian Air
Pollution monitors picked it up on Vancouver Island.
In one alleged case of corn drill dust kill, I sampled the dust on front
of hives and in the beeyard which was about 1/4 mile from nearest field.
NADA, no clothianidin. However, as one would expect, the soils in the newly
planted field had detectable levels.
Hot, dry conditions, with good wind blowing over beeyard, I'd expect some
exposure to a yard adjacent to the planted field. If its been raining, I'd
not expect to see any. Yards at any distance from field, it would have to
be a really dry with a hard wind for any significant exposure.
I've three Hi-Volume Air Samplers that could answer this question - but it
should also be relatively easy for the engineers to model.
Jerry
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