Rivers and streams in Alaska are changing colors—from a clean, clear blue to a rust y orange—because of the toxic metal s released by thawing permafrost(融化的冻土), according to a new study.
The finding surprised researchers who conducted tests at 75 locations in the waterways of Alaska's Brooks Range. The rivers and streams in the range appeared to rust and became cloudy and orange over the past five to 10 years, according to the study published in the journal Communications: Earth & Environment.
The discoloration(变色) and cloudiness are being caused by metal s such as iron and lead, some of which are toxic to the river and stream ecosystems—as permafrost thaws and exposes the waterways to minerals locked away underground for thousands of years.
"We're used to seeing this in parts of California where we have mining history. This is a classic process that happens in rivers here for over 100 years," said Brett Poulin, a co-author of the study and a professor of environmental toxicology at UC Davis. "But it's very shocking to see it in some of the most remote wilderness and far from a mine source," Brett added.
Arctic soils naturally contain organic carbon, nutrients and metals within their permafrost. High temperatures have caused these minerals and the water sources around them to meet as permafrost melts. The Arctic is warming four times faster than the rest of the world. "It's really an unexpected consequence of climate change," said Brett.
This discoloration has been linked to dramatic declines in sea life, raising concerns about how the continued melting of permafrost will affect communities that rely on those waterways for drınkıng and fishing.
These studies have extended beyond the US in the past. Similar research on increases in metal and rare earth element concentrations in mountain rivers and streams has been done in the European Alps and the Pyrenees in northern Spain. Although some of these areas have been exposed to mining sites and thus have seen metal concentrations in rivers and streams over the years, the noted increases raise questions about how climate change will continue to impact mountain water sources.
