The rivers in Greenland can transport unusually high concentrations of heavy metals, including copper, zinc, gold, silver, platinum, lead and mercury. Many of these heavy metals are toxic. However, in low concentrations, some of them are important and necessary nutrients for microorganisms, just as they are for humans. For these metals, only excessive concentrations are harmful, endangering life in the Arctic environment and the entire food web, from plankton to fish and humans.
A large proportion of the heavy metals come from natural sources, as Greenland is naturally rich in metals. However, mining activities have also contributed to high local concentrations in the past, as previous studies have shown. Recently, interest in industrial mining has increased as global warming is melting the glaciers and exposing more and more ground. This makes extraction easier logistically and economically. As a result, more and more licences are being issued for the surveying and mining of metals.
David Janssen, head of the Aquatic Geochemistry research group at the aquatic research institute Eawag, is now investigating how local human activity such as mining and agriculture as well as global anthropogenic environmental changes such as climate change affect the concentrations of heavy metals. "We want to understand where high concentrations occur in Greenland and whether they are of natural origin or due to human intervention," explains David Janssen. "We are also interested in how these metals may impact coastal waters, either by being deposited directly at the estuary or being carried out to sea."
In the past summers of 2022 and 2023, with support from the Swiss Polar Institute and the Leister Foundation, the chemist and a field team therefore investigated numerous rivers in southern and eastern Greenland. "We loaded our minimal field equipment into small boats or helicopters every day and set off for the fjords on the southern and eastern coasts of Greenland," says David Janssen. The field team collected water samples there using a telescopic pole and carried out measurements of water conductivity and temperature. The researchers filtered the water samples on site and prepared them for various analyses back at Eawag.
