Oldest Known Mercury-Pollution Evidence Found

Laguna Warmicocha (pictured), high in the Peruvian Andes, was the base camp for researchers studying pollutants in nearby lakebed sediments. The team discovered that mercury mining in the region dates back to 1400 B.C., much longer ago than previously believed, according to a study released today and funded in part by the National Geographic Society's Committee for Research and Exploration.

The finding suggests demand for vermilion, a bright red pigment made from crushed cinnabar--the source of mercury--may have helped nurture the rise of the Chavin, the earliest complex and stratified society to take root in the Andes. (Read full story.)

Previously, researchers had thought mercury mining began when Spanish colonists arrived in the 16th century and used liquid mercury to extract silver from ore.



University of Alberta geologist and project leader Colin Cooke holds a sediment core retrieved from one of several mountain lakes near Huancavelica, Peru, home to the world's second largest mercury deposit.

Cooke's team analyzed mercury pollutants in several cores to create a time line of mercury mining, from the Chavin culture through Inca and Spanish-colonial times to the industrial era.

By 1450, long after the Chavin had collapsed and as the Incas were expanding their reach, the type of pollution recorded there shifted from cinnabar dust to mercury vapor, Cooke's May 2009 study shows. This suggests the mercury was being heated, though it's unclear why.



Colonial ruins at Huancavelica, Peru, are reminders of the harsh conditions local miners endured under Spanish rule.

Cave-ins and mercury poisoning were rampant and helped earn the main mine the nickname Mina de la Muerte (Mine of Death).

Radiocarbon dates suggest that by 1450, as the Incas were expanding their reach, cinnabar smelting generated gaseous mercury, according to the May 2009 study. That would have been more toxic than the cinnabar dust that resulted from earlier efforts to produce vermilion pigment.