Some Sources and Sinks of Monomethyl and Inorganic Mercury on Ellesmere Island in the Canadian High Arctic

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• 作者：Vincent L. St. Louis ; Martin J. Sharp ; Alexandra Steffen ; Al May ; Joel Barker ; Jane L. Kirk ; David J. A. Kelly ; Shelley E. Arnott ; Bronwyn Keatley ; and John P. Smol
• 刊名：Environmental Science & Technology
• 出版年：2005
• 出版时间：April 15, 2005
• 年：2005
• 卷：39
• 期：8
• 页码：2686 - 2701
• 全文大小：1375K
• 年卷期：v.39,no.8(April 15, 2005)
• ISSN：1520-5851

文摘

We identified some of the sources and sinks of monomethylmercury (MMHg) and inorganic mercury (HgII) on EllesmereIsland in the Canadian High Arctic. Atmospheric Hgdepletion events resulted in the deposition of Hg(II) intothe upper layers of snowpacks, where concentrations oftotal Hg (all forms of Hg) reached over 20 ng/L. However, ourdata suggest that much of this deposited Hg(II) wasrapidly photoreduced to Hg(0) which then evaded back tothe atmosphere. As a result, we estimate that net wetand dry deposition of Hg(II) during winter was lower at oursites (0.4-5.9 mg/ha) than wet deposition in more southerlylocations in Canada and the United States. We alsofound quite high concentrations of monomethyl Hg (MMHg)in snowpacks (up to 0.28 ng/L), and at times, most of theHg in snowpacks was present as MMHg. On the Prince ofWales Icefield near the North Water Polynya, we observeda significant correlation between concentrations of Cland MMHg in snow deposited in the spring, suggesting amarine source of MMHg. We hypothesize that dimethylHg fluxes from the ocean to the atmosphere through polynyasand open leads in ice, and is rapidly photolyzed to MMHg-Cl. We also found that concentrations of MMHg ininitial snowmelt on John Evans Glacier (up to 0.24 ng/L)were higher than concentrations of MMHg in the snowpack(up to 0.11 ng/L), likely due to either sublimation of snowor preferential leaching of MMHg from snow during the initialmelt phase. This springtime pulse of MMHg to the HighArctic, in conjunction with climate warming and the thinningand melting of sea ice, may be partially responsible forthe increase in concentrations of Hg observed in certainArctic marine mammals in recent decades. Concentrationsof MMHg in warm and shallow freshwater ponds onEllesmere Island were also quite high (up to 3.0 ng/L),leading us to conclude that there are very active regionsof microbial Hg(II) methylation in freshwater systemsduring the short summer season in the High Arctic.