Mongolia’s ancient silver mines highly polluting: study
A team of American and Chinese scientists has revealed that pollution from heavy metals like lead, zinc and cadmium spiked between 1271AD and 1368AD in the Yunnan region, affecting several of southwest China’s water reservoirs.
Writing in the journal Environmental Science and Technology, geologists from the University of Pittsburgh and the Chinese Academy of Sciences argue that large amounts of silver smelting ended up contaminating the area. And they attribute the high volumes to Mongolia’s hunger for the precious metal, used to make coins, jewellery and art.
“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,” writes Aubrey Hillman, who led the study.
She said that one surprising finding was to see that the concentrations of lead were close to levels at which harmful effects may be observed in aquatic organisms. Yet, she added that levels of pollution remained relatively low until 1271AD, around the time when Kublai Khan founded the Yuan dynasty and became Emperor of China.
The Mongols established their first government-operated silver mine in Yuan around 1290AD and taxes from silver production came to account for 47% of the national revenue.
The Yuan area is still known for being rich in mineral resources, with important deposits of copper, tin, gold, silver and iron ore.