The river is pumping three to 32 times more mercury into the environment than similarly sized river basins, based on limited data. And while scientists don't know the reason for the Yukon's big mercury load, they say evidence points strongly to two suspects: Melting permafrost, and the Yukon basin's unique placement as a catchment for pollution from Asia and Europe.
"What has been happening in that part of the world for the past 30 years has been unprecedented in terms of environmental pollution," said Paul Schuster, a USGS hydrologist who was the lead author of the study, published in the journal Environmental Science and Technology.
"What we might be seeing is a combination of the release of (mercury) reserves from thawing permafrost and the more recent anthropogenic contamination."
Mercury is a potent neurotoxin and takes several different forms in the environment. Methylated mercury - the type most easily absorbed and therefore harmful to food webs and humans - was found in the Yukon River but at very low levels.
The vast bulk of the Yukon's mercury load - upwards of 90 percent of what scientists measured - consists of less bio-available "particulate mercury:" mercury bound to an organic compound like carbon. Such mercury isn't as readily available to organisms, but it is important nonetheless, Schuster cautioned. Read the full report here.
Source: by Douglas Fischer and Daily Climate, Scientific American.
