Riverine source of Arctic Ocean mercury inferred from atmospheric observations

• Main Authors: Jenny A. Fisher, Daniel J. Jacob, Anne L. Soerensen, Helen M. Amos, Ra Steffen, Elsie M. Sunderl
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2012
• Subjects: Arctic; Arctic Ocean; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.353.4544; http://www.nature.com/ngeo/journal/v5/n7/pdf/ngeo1478.pdf

Methylmercury is a potent neurotoxin that accumulates in aquatic food webs. Human activities, including industry and mining, have increased inorganic mercury inputs to terrestrial and aquatic ecosystems. Methylation of this mercury generates methylmercury, and is thus a public health concern. Marine methylmercury is a particular concern in the Arctic, where indigenous peoples rely heavily on marine-based diets. In the summer, atmospheric inorganic mercury concentrations peak in the Arctic, whereas they reach a minimum in the northern mid-latitudes. Here, we use a global three-dimensional ocean–atmosphere model to examine the cause of this Arctic summertime maximum. According to our simulations, circumpolar rivers deliver large quantities of mercury to the Arctic Ocean during summer; the subsequent evasion of this riverine mercury to the atmosphere can explain the summertime peak in atmospheric mercury levels. We infer that rivers are the dominant source of mercury to the Arctic Ocean on an annual basis. Our simulations suggest that Arctic Ocean mercury concentrations could be highly sensitive to climate-induced changes in river flow, and to increases in the mobility of mercury in soils, for example as a result of permafrost thaw and forest fires. Mercury is emitted from anthropogenic and natural sources primarily as elemental mercury (Hg0). The Hg0 atmospheric lifetime of 6–12 months allows transport of this emitted mercury on a hemispheric scale. Eventual oxidation to highly soluble HgII drives deposition in remote regions. Hg0 has