Before human beings had ever stepped foot on one of the highest peaks in the Himalayas, we had already contaminated it.
An analysis of ice cores drilled from the Dasuopu glacier in the central Himalayas show traces of toxic metals, by-products of burning coal, embedded in the sample’s layers. By deciphering the timeline of the ice core, the researchers have dated the earliest contamination to the end of the 18th century –the start of the Industrial Revolution.
Published in Proceedings of the National Academy of Sciences, the team from Ohio State University studied an ice core collected in 1997 from the glacier located on Shishapangma, the world’s 14th tallest mountain. Hidden in the cores are clues about the snowfall, atmospheric circulation, and other environmental changes in time. This allows researchers to pinpoint the precise year a layer of the sample was formed.
The core in question was found to have formed between 1499 and 1992. Whilst analyzing the core for a total of 23 trace metals, the researchers found that higher-than-natural levels of cadmium, chromium, nickel, and zinc were present from 1780. All of which could be attributed back to the burning of coal – a key part of industry in Western Europe during the late 18th century, and throughout the 19th and 20th centuries.
“The Industrial Revolution was a revolution in the use of energy,” Paolo Gabrielli, lead author of the study and research scientist at The Ohio State University Byrd Polar and Climate Research Center, said in a statement. “And so the use of coal combustion also started to cause emissions that we think were transported by winds up to the Himalayas.”
In this case humanity’s actions appear to have had far-reaching consequences – approximately the distance between London and the Dasuopu glacier of 10,300 kilometers (6,400 miles), to be exact. Distant not only in geographical location, but also in time. The first summit of Shishapangma, at 8,027 meters (26,335 feet), was in 1964 – hundreds of years after the contamination first appeared.
A further cause of the metal contamination at the world’s highest drilling site (7,200 meters or 23,600 feet above sea level), was also identified by the researchers.
“What happens is at that time, in addition to the Industrial Revolution, the human population exploded and expanded,” Gabrielli continued. “And so there was a greater need for agricultural fields — and, typically, the way they got new fields was to burn forests.”
Although the researchers cannot be sure whether the forest fires were man-made or natural, the presence of zinc, released when trees are burnt, was an indication for this other factor.
Another important point from the study was the distinct difference between “contamination” and “pollution”.
“The levels of metals we found were higher than what would exist naturally, but were not high enough to be acutely toxic or poisonous,” Gabrielli said. “However, in the future, bioaccumulation may concentrate metals from meltwater at dangerous toxic levels in the tissues of organisms that live in ecosystems below the glacier.”
Researchers from the University of Ohio have already found further evidence of humanity’s activities altering the atmosphere. In 2015, the impact of humans mining silver in Peru was studied and found to have contaminated the air in South America around 240 years before the Industrial Revolution.
“What is emerging from our studies, both in Peru and in the Himalayas, is that the impact of humans started at different times in different parts of the planet,” Gabrielli concluded.