Samplings: July–August 2007

Print

Email

Lake Pirhuacocha

Colin A. Cooke

The abundance of pre-Columbian bronze, copper, and silver artifacts in Peru indicates that the region was a center for metallurgy in the New World. But archaeologists have long been puzzled because they have never found remnants of smelting furnaces in the highlands of the Peruvian Andes, the source of much of the region’s mineral reserves. Indeed, seventeenth-century Spaniards were long thought to have been the first metallurgists in the highlands. A new study, however, shows that pre-Columbian civilizations were smelting there after all: metallurgists started polluting a local lake with lead and other metals 1,000 years ago.

When metals were extracted from ore in ancient wind-drafted furnaces, small particles of floating debris would have settled in nearby bodies of water. To detect such ancient pollution, a team led by Colin A. Cooke, a graduate student of environmental science at the University of Alberta in Edmonton, hammered a three-foot-long plastic tube into the muddy floor of Lake Pirhuacocha, in Peru’s Morococha mining region, and withdrew a cylinder of sediment.

Chemical analysis detected signs of smelting in sediments from as early as CE 1000, soon after the decline of the Wari Empire. Most of the early smelting produced copper and bronze. Lead pollution, a sign of silver production, turned up only after CE 1450, first during the Inca reign, later under European colonialism, and finally in modern Peru (a working mine and smelter stand nearby). Cooke thinks the missing furnaces were simply destroyed by landslides, which plague the highlands. (Environmental Science & Technology)