Humans may have begun to pollute the atmosphere earlier than we thought. So says recent research conducted at the Quelccaya Ice Cap in Peru, where scientists drilled into the ice to pull out cores, which they could read like ancient texts.
Those cores show widespread traces of copper and lead starting in about A.D. 1540, which corresponds to the end of the Inca empire and a period of mining and metallurgy when the areas that are now Peru and Bolivia became part of the Spanish Empire. The findings, published by Paolo Gabrielli and colleagues in February in the Proceedings of the National Academy of Sciences, suggest for the first time that the Anthropocene, the geological epoch defined by massive and widespread human impacts on the planet, began about 240 years before the industrial age arrived on the scene with its steam engines and its coal plants.
Scientists have long used glacier ice cores to learn about the Earth’s climates and air pollution and reconstruct pollution histories. In Greenland, for example, they have traced metals found in ice cores back to ancient Greek and Roman mining operations. The pattern of climate changes and air quality are recorded in the ice itself as glaciers grow, accumulating layer after layer of ice, year after year. For example, winter layers are often thicker and lighter in color, while summer layers are often thinner and darker because of less snowfall and more dust in summer. Scientists can read these layers much in the same way they read tree rings to calculate historical environmental conditions, including snowfall and atmospheric composition.
Once the scientists have removed the ice cores from a glacier, they can analyze the trace elements in the ice itself. They also study the air bubbles trapped in those cores at the time of their formation to learn about the chemical components of the atmosphere. According to Paolo Gabrielli, an Earth scientist at Ohio State University, anything in the air at the time the glacier layer was formed, such as soot particles, dust and a wide variety of chemicals, will be trapped in the ice layers as well. Gabrielli says there are no glaciers on Earth in which traces of anthropogenic air pollution cannot be detected.
Gabrielli and his team found that lead levels in the Quelccaya ice core doubled between 1450 and 1900, while the amount of chemical element antimony (Sb) in the ice was 3.5 times greater than before. They also compared data from a peat bog in Tierra del Fuego, Chile, and from sedimentary lake records from regions including Potosí and other mines throughout Bolivia and Peru to determine the path the pollution took, and found that most of the pollution was carried to the Quelccaya Ice Cap in Peru by the wind.
In the 16th century, the Spanish colonial authorities forced the indigenous populations in South America to extract ore and refine silver from the mountaintop mines of Potosi. They introduced mercury amalgamation, a new technology, to expand silver production, which lead to dramatic increases in the amounts of trace metals released into the atmosphere.
“This evidence supports the idea that human impact on the environment was widespread even before the industrial revolution,” Gabrielli said in a statement on Ohio State University’s website.
While the industrial economies in 20th century produced more pollution than any other time in human history, colonial mining should be considered the beginning of the Anthropocene, according to these new findings.
For more information about Quelccaya, look here.