Are We Baking with Volcanic Ash?
I was trawling the USGS photo archive for upcoming Friday Rock Blog candidates when I came across this scanning electron micrograph of wheat. It’s from a gargantuan volume published in 1981, full of initial reports about the eruption of Mt. St. Helens.
Why is there a picture of wheat in a book about a volcano?
It turns out people were curious about how quickly material from the ash would be incorporated into the soil nutrient supply, and particularly into crops. So a month after the eruption, USGS scientists sampled wheat and soil from fields that had been ashed on.
The answer? Wheat from sites with 20mm or more of ashfall had slightly elevated sulfur content. I do not know if this means that bread made from Washington wheat in 1980-1981 was more or less delicious than it would have been otherwise. Worrisome things like cadmium and other heavy metals were apparently not affected by the eruption, at least not in the 1980 wheat crop.
But before they could get to this conclusion, they had to carefully wash all the tiny bits of ash off the wheat. You can see in this picture how the ash tends to hide in little crannies on the wheat, so if you’re not careful, your analysis will just tell you the bulk composition of wheat + ash, which is not useful. So what you do first is to hang the wheat stalk upside-down in a beaker of distilled water, and whack it with some ultrasonic vibration to knock the ash off.
L.P. Gough, R.C. Severson, F.E. Lichte, J.L. Peard, M.L. Tuttle, C.S.E. Papp, T.F. Harms, and K.S. Smith, Ash-fall effects on the chemistry of wheat and the Ritzville soil series, eastern Washington, in USGS Professional Paper 1250 which is available for purchase or free download from the USGS publications warehouse.