Spanish conquerors were polluters

Greed for silver left heavy metals even on distant Andean peaks

View of the ice cap of the Quelccaya in Peru © Paolo Gabrielli / The Ohio State University
Read out

The Spanish conquerors not only brought down the Inca empire, they also already destroyed and polluted the environment in the Andes region: as early as the 16th century, the silver mining they had forced on them released large amounts of toxic heavy metals. Their tracks have now been detected in a glacier in the Peruvian Andes. They are the earliest evidence of anthropogenic air pollution in South America.

The Andes are rich in mineral resources, especially gold, silver and copper have been promoted here for hundreds of years. Also in the realm of the Inca there were already some mining areas in Bolivia and Peru. When the Spanish conquerors arrived, they not only robbed the Incas of their gold, they also took over some of these mines. The largest of them was Cerro Rico de Potosi in southern Bolivia. There, they forced local workers to promote silver for them.

Mercury and lead in rough amounts

The Spaniards introduced a new technique: they imported mercury from Mexico and used the liquid heavy metal to dissolve the silver from the previously ground leaded ore. The toxic relics of this mining practice can still be detected in local lake sediments. Researchers around Lonnie Thompson at Ohio State University in Columbus have now discovered that environmental pollution far exceeded the local level.

For their study, the researchers had taken ice cores from the Quelccaya Glacier in Peru - a 5, 600-meter-high mountain peak that is more than 800 kilometers from the Potosi Mine. The egg layers in this core date back to the year 793. Each year, the snowfall added another layer, including small air bubbles in the ice. Like little time capsules, they still preserve the atmosphere of the time.

In the mines of Potosi in Bolivia, silver-bearing ore is still mined © Albert Backer / CC-by-sa 3.0

Significant growth after arrival of the Spaniards

The analyzes of these inclusions show a clear cut: Before the middle of the 16th century, the inclusions contained hardly any heavy metals, only a few short-term spikes caused by volcanic eruptions can be seen. But from about 1540, the concentrations of lead, but also of arsenic, antimony and other heavy metals increase significantly, as the researchers report. display

"Showing ice pollution in such a remote high mountain location shows how strong and widespread it was at the time, " says co-author Paolo Gabriello of Ohio State University. From the composition of trace metals, the researchers conclude that the main source of this pollution was the Potosi Mines. The inclusions reflect the three phases of the most intense silver mining around 1600, around 1700 and around 1800 very well.

Pollution long before the industrial revolution

"This proves that the human impact on the environment was significant even before the industrial revolution, " notes Gabrielli. The heavy metals detected in the Andes glacier speak for a true flag of pollution, which rose from the silver mines and was carried by the wind over a hundred kilometers after all, about 240 years before the industrialization.

This makes these glacier enclosures the earliest evidence of environmental pollution in South America. However, the extent of pollution since the 20th century does not reach these early traces by far. (Proceedings of the National Academy of Sciences, 2015; doi: 10.1073 / pnas.1421119112)

(Ohio State University / PNAS, 10.02.2015 - NPO)