Muddy Rain Across South Texas
On March 18, 2008, residents across South Texas were surprised to find their cars coated with a thick film of tan-colored mud from the recent rain. The National Weather Service told the San Antonio Express-News that the material was ash from fires in Mexico. The San Antonio TV meteorologists reported the material was from a massive dust storm across northern Mexico.
Who was right?
Here’s a report about this event that I sent to Bryan Lambeth at the Texas Commission on Environmental Quality and Peter Bella at AACOG
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March 18, 2008
Bryan and Pete,
I swabbed material from the window using an alcohol pad and transferred some to a flat microscope slide.
The material is predominantly tan to translucent tan mineral dust ranging in size from sub micron to 20 microns.
The material includes some pollen and large black carbon particles, the latter being up to 20 microns across. A spherical nigrospora was noted. Various vegetative matter was observed.
The large black carbon suggests outdoor burning or, more likely, a brush fire origin.
Some pollen (there isn’t much) closely matches Quercus virginiana (live oak) based on my copy of E. Grant Smith’s “Sampling and Identifying Allergenic Pollens and Molds.”
Looks like I need to visit the USDA solar instruments at Texas Lutheran University that I manage for Colorado State before solar noon to remove this matter.
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The TV weather people got it right.
As for the sunlight instruments that I manage for Colorado State, they were coated! The visible wavelengths were attenuated by about 10 percent before I cleaned them.
March 21st, 2008 at 6:06 am
Hi Forrest, You say that the TV people were right. But isn’t the NWS correct? They attributed the dust to fires, and you say your investigation showed large black carbon, which “suggests outdoor burning or, more likely, a brush fire origin.” Or is it the difference between ash and dust? Either way, it’s pretty incredible that dust can travel over such long distances before settling!
March 21st, 2008 at 8:50 am
Good point. Today (March 21, 2008) Graeme Zielinski of the San Antonio Express-News reported that the National Weather Service took another look at this and proclaimed that the material was indeed dust.
The story is titled “Just ash with rain? Not so fast” and it opens with:
“The strange stuff that fell Tuesday, griming up windows and lining the pockets of carwash owners, has had the additional effect of setting up a sort of meteorological whodunit.
“Just what, some scientific sleuths want to know, commingled with the rain as it fell onto vehicles from San Antonio to Corpus Christi, from Austin to Houston?”
The story goes on to quote various weather people and includes this comment I gave them:
“Forrest Mims III, a science consultant and a freelance columnist for the Express-News, took a sample of the stuff from his window and put it under the microscope, forwarding some of his findings to TCEQ.
“‘There’s one black spore and there are three possible soot particles and everything else is dirt, dust, sand. I would say that it’s probably less than 1 percent smoke, and that’s being generous,’ he said.”
All in an all a rather intriguing story.
Forrest M. Mims III
March 22nd, 2008 at 3:24 pm
Forrest:
Is there an organization to which someone could send a dust sample to, in order to have it analyzed, as you have described above?
There’s another question that has troubled me for a number of years, which I hope you can shed some light on:
Are trees that were alive during the time of atmospheric nuclear testing repositories for this form of radiation? And is there radioactivity present in the ashes of the wood when the tree is burned? We did a story on this for Pulse of the Planet in 1992 with a scientist named Stewart Farber, but I’ve never heard anything else about this matter. It this something that you’ve investigated?
Cheers;
Jim Metzner
March 30th, 2008 at 10:05 pm
Jim,
There are labs that will evaluate dust, bacteria and mold spore samples.
Yes, tree rings can store information about nuclear tests. This is not my field of expertise, but I do know that wood ash is slightly radioactive due to naturally occurring isotopes. Coal ash is also slightly radioactive.
Forrest M. Mims III