The impact of sea ice on the air-sea exchange of mercury in the Arctic Ocean
The impact of sea ice on the air-sea exchange of mercury in the Arctic Ocean
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DOI：
10.1016/j.dsr.2018.12.001
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发表时间：
2019-02-01
影响因子：
2.4
通讯作者：
Moore, Chris
中科院分区：
文献类型：
--
作者：
DiMento, Brian P.;Mason, Robert P.;Moore, Chris
大气沉积是汞(Hg)进入海洋的主要输入，即使在北极等偏远地区也是如此。此外，元素汞(汞程度)的逃逸是海洋汞的主要汇。因此，海气交换是海洋汞循环的重要组成部分。为了研究北冰洋汞的海气交换，我们在2015年8月9日至10月12日期间，使用连续采样系统对北冰洋表层水域的汞含量和大气中汞的形态进行了高分辨率测量。此外，还采集了样品，用于测量湿沉积和大量气溶胶以及地面雪和海冰中的总汞和甲基溴汞(CH3Hg)。我们使用这些在水和大气中进行的测量来估计从海洋到大气的汞的通量。在无冰水域(32+/-30 fm)中，溶解汞(Hedi)的浓度接近饱和，生成的通量很低；然而，在连续冰(101+/-98 fm，高达544 fm)下，汞高度浓缩，这表明即使在冰覆盖的情况下，水中仍有汞的持续形成。在这些区域(这些是冰下位置的潜在逃逸速率)预测的逃避通量高达492pmom(-2)h(-1)。大气汞浓度平均为1.2+/-0.1 ng m-3，在航行过程中几乎没有变化，即使在汞含量(DISS)升高的水域也是如此，这表明海冰对海-气交换起到了屏障作用。对降水和气溶胶中汞的测量低于北极更多沿海地区的汞含量。我们使用这些浓度来估计汞和甲烷汞在巡航期间的沉降量。总体而言，湿沉降占CH3Hg通量的88%，占HGT通量的38%。我们的通量估计证实了大气-海洋交换在北极汞循环中的重要性，并表明逃避大于沉积，表明在此期间来自北极的汞净损失或本研究期间未测量到的其他来源的存在。此外，我们的结果表明，近海水域的通量低于北极沿海地区的通量。根据这些估计，我们预测汞浓度可能如何应对未来冰盖的变化，以及气候变化对这一重要海洋区域汞动态和食物网生物积累的其他潜在影响。
Atmospheric deposition is the main input of mercury (Hg) to the ocean, even in remote locations such as the Arctic. Furthermore, evasion of elemental Hg (Hg degrees) is the major sink for oceanic Hg. As a result, air-sea exchange is an important part of the oceanic Hg cycle. To examine the air-sea exchange of Hg in the Arctic Ocean we made high resolution measurements of Hg degrees in surface waters and Hg speciation in the atmosphere using continuous sampling systems during the 2015 U.S. Arctic GEOTRACES cruise from August 9 to October 12. Additionally, samples were obtained for measurement of total Hg and methybriercury (CH3Hg) in wet deposition and bulk aerosols as well as surface snow and sea ice. We used these measurements made in the water and the atmosphere to estimate fluxes of Hg degrees from the ocean to the atmosphere. Concentrations of dissolved Hg (Hedi,) were near saturation in ice-free waters (32 +/- 30 fM) and resultant fluxes were low; however, Hg was highly enriched under contiguous ice (101 +/- 98 fM, up to 544 fM) suggesting the continual formation of Hg in waters even when ice covered. Predicted evasion fluxes in these regions (these being potential rates for locations under ice) were as high as 492 pmol m(-2) h(-1). Atmospheric Hg concentrations averaged 1.2 +/- 0.1 ng m-3 with little variation over the course of the cruise even above waters with elevated Hg degrees(diss) indicating that sea ice acts as a barrier to air-sea exchange. Measurements of Hg in precipitation and aerosols were lower than have been found in more coastal regions of the Arctic. We used these concentrations to estimate deposition of Hg and CH3Hg during the time of the cruise. Overall, wet deposition represented 88% of the CH3Hg flux and 38% of the HgT flux. Our flux estimates confirm the importance of air-sea exchange in Hg cycling in the Arctic and suggest that evasion was greater than deposition, indicating a net loss of Hg from the Arctic during this period or the presence of other sources not measured during this study. Additionally, our results suggest that fluxes for offshore waters are lower than found in coastal regions of the Arctic. From these estimates, we predict how Hg concentrations may respond to future changes in ice cover and other potential impacts of climate change on Hg dynamics and food web bioaccumulation in this important ocean region.