Arctic rivers become a strange orange, and that’s why

Researchers have long believed that frozen environments slow down chemical reactions, but new research question this belief.

In a study published last month in the journal PNA, the researchers demonstrated that ice can dissolve iron minerals better than liquid water, with implications for the many arctic rivers which mysteriously rotate orange when the planet warms up.

More specifically, Jean-François Boily, co-author of the study and chemist at Umeå University, and his colleagues revealed that ice at 14 degrees Fahrenheit (-10 degrees Celsius) unlocks more iron from common minerals than liquid water at 39 degrees Fahrenheit (4 degrees Celsius).

Iron dissolves more effectively

“It may seem counterattack, but ice is not a passive frozen bloc,” said Boily in a university statement. “Freezing creates microscopic pockets of liquid water between ice crystals. These act as chemical reactors, where compounds become concentrated and extremely acidic.

They studied Goethite (a common iron oxide mineral) with a natural organic acid, revealing that repeated freezing cycles and thaw dissolve iron more effectively. Indeed, the organic compounds formerly trapped in the ice are released during frost and thaw, generating additional chemical reactions. The team also noted that, while brackish and soft water has deepened dissolution, salty sea water can control it.

These results bear important applications for acidic environments, according to researchers, including mine drainage sites, frozen dust in the atmosphere, acid sulfate soils on the Baltic Sea coast or any acid frozen frozen environment where iron minerals and biological products interact. To move forward, Boily and the researchers work to find out if their results apply to all the ice containing iron.

“While the climate warms up, gel-degel cycles become more frequent,” said Angelo Pio Sebaly, a graduate in university chemistry and the first author of the study. “Each cycle releases floors and permafrosts in water. This can affect water quality and aquatic ecosystems in large areas. ”

Ice is an active player

In particular, this could also have something to do with the reasons why the Arctic rivers run an alarming orange. “By solving chemical controls on the dissolution of minerals in the ice, this work can help explain how gel-degel events provide new strength of iron soluble to nature,” wrote researchers in the study.

The document also highlights the ice as a “active player”, according to the declaration, as opposed to a “passive storage support”, confirming another element that we should monitor closely because climate change disrupts environments around the world.