St Louis Vincent L, Sharp Martin J, Steffen Alexandra, May Al, Barker Joel, Kirk Jane L, Kelly David J A, Arnott Shelley E, Keatley Bronwyn, Smol John P
Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2E9.
Environ Sci Technol. 2005 Apr 15;39(8):2686-701. doi: 10.1021/es049326o.
We identified some of the sources and sinks of monomethyl mercury (MMHg) and inorganic mercury (HgII) on Ellesmere Island in the Canadian High Arctic. Atmospheric Hg depletion events resulted in the deposition of Hg(II) into the upper layers of snowpacks, where concentrations of total Hg (all forms of Hg) reached over 20 ng/L. However, our data suggest that much of this deposited Hg(II) was rapidly photoreduced to Hg(0) which then evaded back to the atmosphere. As a result, we estimate that net wet and dry deposition of Hg(II) during winter was lower at our sites (0.4-5.9 mg/ha) than wet deposition in more southerly locations in Canada and the United States. We also found quite high concentrations of monomethyl Hg (MMHg) in snowpacks (up to 0.28 ng/L), and at times, most of the Hg in snowpacks was present as MMHg. On the Prince of Wales Icefield nearthe North Water Polynya, we observed a significant correlation between concentrations of Cl and MMHg in snow deposited in the spring, suggesting a marine source of MMHg. We hypothesize that dimethyl Hg fluxes from the ocean to the atmosphere through polynyas and open leads in ice, and is rapidly photolyzed to MMHgCl. We also found that concentrations of MMHg in initial 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 snow or preferential leaching of MMHg from snow during the initial melt phase. This springtime pulse of MMHg to the High Arctic, in conjunction with climate warming and the thinning and melting of sea ice, may be partially responsible for the increase in concentrations of Hg observed in certain Arctic marine mammals in recent decades. Concentrations of MMHg in warm and shallow freshwater ponds on Ellesmere Island were also quite high (up to 3.0 ng/L), leading us to conclude that there are very active regions of microbial Hg(II) methylation in freshwater systems during the short summer season in the High Arctic.
我们确定了加拿大北极地区埃尔斯米尔岛上甲基汞（MMHg）和无机汞（HgII）的一些来源和汇。大气汞消耗事件导致Hg(II)沉积到积雪的上层，那里总汞（所有汞形态）的浓度超过20 ng/L。然而，我们的数据表明，大部分沉积的Hg(II)迅速光还原为Hg(0)，然后又逸散回大气中。因此，我们估计冬季我们研究地点的Hg(II)净湿沉降和干沉降（0.4 - 5.9 mg/ha）低于加拿大和美国更靠南地区的湿沉降。我们还在积雪中发现了相当高浓度的甲基汞（MMHg）（高达0.28 ng/L），而且有时积雪中大部分汞以MMHg的形式存在。在靠近北水多冰区的威尔士王子冰原上，我们观察到春季积雪中Cl和MMHg的浓度之间存在显著相关性，这表明MMHg有海洋来源。我们推测二甲基汞通过多冰区和冰中的开阔水道从海洋向大气通量传输，并迅速光解为MMHgCl。我们还发现约翰·埃文斯冰川初始融雪水中的MMHg浓度（高达0.24 ng/L）高于积雪中的MMHg浓度（高达0.11 ng/L），这可能是由于雪的升华或在初始融化阶段MMHg从雪中优先淋溶所致。这种春季MMHg向北极地区的脉冲式输入，再加上气候变暖以及海冰变薄和融化，可能是近几十年来在某些北极海洋哺乳动物中观察到汞浓度增加现象的部分原因。埃尔斯米尔岛上温暖且浅的淡水池塘中MMHg的浓度也相当高（高达3.0 ng/L），这使我们得出结论，在北极地区短暂的夏季，淡水系统中存在微生物将Hg(II)甲基化的非常活跃的区域。
