New research has just revealed that mercury concentrations in meltwater from Greenland’s glaciers are similar to those found in highly polluted rivers in industrial China. This unexpected finding, published in the journal Nature Geoscience , raises many questions about the effects of melting glaciers as a result of climate change.
The study consisted, initially, in taking measurements of the waters of three rivers and two fjords near the Greenland glaciers to study the quality of the meltwater and its influence on the nutrient cycles in this area, which is also an importer of seafood internationally. One of the elements they measured was mercury, a potentially toxic compound, but they did not expect to find such high concentrations in that particular area.
To get an idea, the average mercury content in an unpolluted river is between one and ten nanograms per liter, which is equivalent to an amount of the element the size of a grain of salt in an Olympic swimming pool. However, dissolved mercury levels in excess of 150 nanograms per liter have been found in the rivers sampled. Furthermore, particulate mercury carried by glacial flour – the sediment that gives glacial rivers a milky appearance – was found in very high concentrations, of more than 2,000 nanograms per liter.
What is the origin of mercury?
As we have already discussed, scientists did not expect this finding, and its discovery raises many questions. “Naturally, we have hypotheses as to what is causing these high concentrations of mercury, but these findings have raised a host of questions for which we do not yet have the answers, ” explains Rob Spencer, one of the authors.
To begin with, the researchers are not clear if such high amounts were found in areas farther from the ice sheet, or if this detected mercury is entering the aquatic food web, in which case it would become even more concentrated. “We have been doing fieldwork in this region west of Greenland for many years and we know that glaciers export nutrients to the ocean, but the discovery that they can also release potentially toxic elements reveals a disturbing new dimension of the influence of melting glaciers. in water quality. It is necessary to investigate it more ”, argue the authors.
Fishing is Greenland’s main industry and the country is a major exporter of cold-water shrimp, halibut, and cod. The finding underscores the complicated reality of the rapid melting of ice sheets around the world: It is estimated that approximately 10% of the Earth’s land surface is covered by glaciers, and these environments are undergoing very rapid changes as a result of the increase. temperatures . Scientists around the world are working to understand how warming temperatures, and thus more rapidly melting glaciers, will affect geochemical processes critical to life on Earth.
New sources of mercury
Another noteworthy aspect that the study reveals has to do with the sources of mercury in the oceans, which until now were attributed almost exclusively to human industrial activity. “All efforts to manage mercury so far have come from the idea that the increasing concentrations that we have been seeing throughout the Earth system are mainly coming from direct anthropogenic activity, such as industry,” explains Jon Hawkings, postdoctoral researcher. at Florida State University. “But mercury from climate-sensitive environments like glaciers could be a much more difficult source to manage.”
