The pristine rivers of Alaska are changing face. The crystalline water has given way to orange sewage, saturated metals toxic metals for flora and aquatic fauna. And in this case, it is not about pollution. Or at least, not directly: the fault is in fact of the increase in temperatures linked to global warming, which is dissolving the ice cream soil (known as permafrost), distorting the geochemical balance of the region, and pouring enormous quantities of metals in the waterways. A phenomenon that is not limited to Alaska alone, but is affecting all areas of the Arctic, and which has recently been described in an article published on Acts of the National Academy of Sciences US.
The River of Salmon
The research analyzed in detail the situation of the Salmon River, a river located in a remote area of north-western Alaska. But as we said, the phenomenon described is unfortunately widespread in all areas where global warming is dissolving the permafrost remained frozen for millennia: at least 75 the waterways that have colored orange described to date in Alaska, many more, probably, in the entire Arctic region.
In the case of the Salmon River, the ecologist of the UNINVITY of the Alaska Paddy Sullivan, during a scientific expedition in this remote area of the country, was first aware that something had changed. The waters suddenly painted orange attracted the attention of the scientist, pushing him to set up a team of colleagues with whom to analyze the causes of the phenomenon, and its consequences.
The effect of heating
Their research has made it possible to confirm the presence of heavy metals – such as cadmium, nickel, aluminum and zinc – at potentially toxic levels for animals and aquatic plants. For many of the metals found, the concentrations exceeded the safety thresholds of the American environmental protection agency. And the situation was so critical as to remember, according to the authors of the research, those that can be seen in the case of environmental contaminations produced by the waste discharges of some mines. Indeed, even worse: “If a mine was operating on the banks of that river and similar levels of metals in the waters were found – Sullivan ensures – the mine would be in large troubles”.
In this case, pollution is not due to human neglect, if not indirectly: in fact, global warming is responsible, through a chain of events that the Sullivan team has managed to reconstruct with its own analyzes. The dissolution of the permafrost exposes the underlying rocks, which for millennia have remained protected by ice, to the action of the elements. If this rocky substrate is rich in sulfur, contact with water can produce the formation of sulfuric acid, which in turn erodes the rock and dissolves the metals contained inside, which therefore accumulate in the waterways.
An irreversible process
“This story is not limited to Salmon River,” explains Tim Lyons, a biochemical of the University of California in River who participated in the study. “It is happening everywhere in the Arctic. Wherever there is the right type of rocks and the dissolution of the permafrost, the process can start. And when it starts, there is no way to stop it: it is another irreversible change caused by the heating of the planet”.
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