A new paper, led by Jon Hawkings from Florida State University and published in Nature Geoscience, shows very high concentrations of the toxic element mercury in rivers and fjords connected to the southwestern part of the Greenland Ice Sheet, comparable to those in rivers in industrial China.
Samples of meltwaters were collected between 2013-18 from three different rivers and two fjords next to the ice sheet to gain a better understanding of meltwater water quality from the glacier and how nutrients in these meltwaters may sustain coastal ecosystems. CryoEco members contributed to the field sampling and analysed the genetic potential of Greenland subglacial microbes for in situ mercury cycling.
Typical dissolved mercury content in rivers are about 1 – 10 ng L-1 . In the glacier meltwater rivers sampled in Greenland, scientists found dissolved mercury levels in excess of 150 ng L-1, far higher than an average river. Particulate mercury carried by glacial flour (the sediment that makes glacial rivers look milky) was found in very high concentrations of more than 2000 ng L-1. The source of mercury is very likely coming from the local rock itself, as opposed to a fossil fuel combustion or other industrial source. It is unclear if the mercury levels will dissipate farther away from the ice sheet and whether this mercury is making its way into the aquatic food web, where it can often concentrate further.
Hawkings JR, Linhoff BS, Wadham JL, Stibal M, Lamborg CH, Carling GT,
Lamarche-Gagnon G, Kohler TJ, Ward R, Hendry KR, Falteisek L, Kellerman AM, Cameron K, Hatton JE, Tingey S, Holt A, Vinšová P, Hofer S, Bulínová M, Větrovský T, Meire L, Spencer RGM (2021) Large meltwater source of mercury from the southwestern margin of the Greenland Ice Sheet. Nature Geoscience 14:496-502 doi:10.1038/s41561-021-00753-w