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WHAT A PROVOCATIVE caption for a graph; “The fortunes of kings, written in ice.” The graph, shown later here, accompanied “Lead Pollution Traces the Rise and Fall of Medieval Kings,” by Ann Gibbons, in Science, April 3, 2020. Here, in Parts 1 and 2 today and tomorrow, are tidbits gleaned from the article and my usual Internet sleuthing.
Lead, the Element Pb, a Culprit Since Antiquity. Ann Gibbons writes, “Most people associate lead pollution with the Industrial Revolution, when lead became widely used in paints, pipes, and ceramics. But researchers have long known that the Romans also absorbed high levels of lead as they smelted silver and other ores.”
According to Wikipedia, “Silver is mentioned in the Book of Genesis, and slag heaps found in Asia Minor and on the islands of the Aegean Sea indicate that silver was being separated from lead as early as the 4th millennium B.C.” A typical ore contains 0.085 percent silver and 0.5 percent lead. That is, in smelting silver, there’s almost six times more lead left over.
Follow the Money. Silver leaves a documented history in coinage and extravagant uses. Lead’s historical traces are more subtle, but accessible in things like glacier ice cores. Chris Loveluck at England’s University of Nottingham and colleagues studied ice cores in a Swiss glacier and reported their findings in “Alpine Ice-core Evidence for the Transformation of the European Monetary System, AD 640–670,” Antiquity, Volume 92, Issue 366.
“The seventh-century AD switch from gold to silver currencies transformed the socio-economic landscape of North-west Europe,” they wrote in the paper’s Abstract.
Gibbons notes, “Lead tracks silver production because it is often found in the same ore, and the team found that the far-flung lead pollution was a sensitive parameter of the medieval English economy.”
As shown in the graphs, “… lead spiked when kings took power, minted silver coins, and built cathedrals and castles. Levels plunged when plagues, wars, or other crises slowed mining and the air cleared.”
The Researchers’ Methodology. The study involved Loveluck and colleagues, Harvard University historians, and glaciologist Paul Mayewski and his team from the University of Maine, Orono.
Back in 2013, an ice core 236-ft deep was extracted from the Colle Gniffeti Glacier in southern Switzerland, several miles south of Zermatt. Gibbons notes, “The 72-meter-long core preserves more than 2000 years of fallout from pollution, volcanoes, and Saharan dust storms.”
Gibbons continues, “To decipher this record at the highest possible resolution, the team used a laser to carve 120-micron [about 0.005-in.] slivers of ice, each representing just a few days or weeks of snowfall, along the length of the core. They analyzed the samples, some 50,000 of them, for about a dozen elements, including lead.”
Tomorrow, in Part 2, we encounter some recent history and some medieval history, helped along by these ice-core findings. ds
© Dennis Simanaitis, SimanaitisSays.com, 2020