They were feared as barbarians who built one of the largest empires in the world from horseback, but it appears the Mongolian emperors were also some of the planet’s biggest polluters.
A new study into the silver mines of Kublai Khan, the grandson of Genghis Khan, shows that the people produced four times as much pollution as modern industrial mining activities.
It is thought to be one of the few examples where pre-industrial period pollution has exceeded modern day levels. Geologists from the University of Pittsburgh and the Chinese Academy of Sciences have found pollution from heavy metals like lead, zinc and cadmium spiked between 1271AD and 1368AD in the Yunnan region of south west China.
They say that this pollution was caused by large amounts of silver smelting driven by the Mongolian hunger for the precious metal, which they used to make coins, jewellery and art.
Writing in the journal Environmental Science and Technology, Aubrey Hillman, who led the work, said that the impact of this pollution was still being felt today by the wildlife and environment in the area.
She said: ‘Culminating during the rule of the Mongols, known as the Yuan Dynasty, these metal concentrations approach levels three to four times higher than those from industrialised mining activity occurring within the catchment.
‘Notably, the concentrations of lead approach levels at which harmful effects may be observed in aquatic organisms.
‘The persistence of this lead pollution over time created an environmental legacy that likely contributes to known issues in modern-day sediment quality.’
Miss Hillman and her colleagues extracted sediment cores from Lake Erhai in Yunnan. The mud within these sediments catalogued around 4,500 years of debris deposited on the floor of the lake.
By scanning the cores for heavy metals they were able to determine how pollution levels had changed through out the areas history.
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