Elemental Mercury Concentrations and Fluxes in the Tropical Atmosphere and Ocean
Elemental Mercury Concentrations and Fluxes in the Tropical Atmosphere and Ocean
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DOI：
10.1021/es503109p
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发表时间：
2014-10-07
影响因子：
11.4
通讯作者：
Sunderland, Elsie M.
中科院分区：
文献类型：
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作者：
Soerensen, Anne L.;Mason, Robert P.;Sunderland, Elsie M.
元素汞(Hg0)的海-气交换是全球生物地球化学汞循环的重要组成部分。为了更好地了解大气和海洋汞-0的变异性，我们收集了太平洋(北纬20度-S 15度)海水温度、盐度和生产力的大梯度的高分辨率测量数据。我们使用海洋大气环流模式(MITgCM)和大气化学输送模式(GEOS-Chem)模拟了表层海洋汞的输入和损失。观测到的表层海水Hg-0浓度比大气浓度变化更大。在太平洋热带辐合带(ITCZ)观测到的海水汞-0峰值浓度(类似于130fm)类似于周围地区的3倍(类似于50fm)。这与来自大西洋的观测结果相似。北太平洋ITCZ的峰值规避是周围地区的四倍，位于高风速和高海水Hg-0的交汇处。模拟结果表明，ITCZ增强降水的高输入和该地区浅海混合层的高输入推动了海水Hg0浓度的升高。模拟的海水汞-0浓度再现了大西洋和太平洋ITCZ的观测峰值，但低估了其大小，可能是由于对对流层上部氧化汞的深层对流清除不足所致。我们的结果证明了上层大气中活性汞的清除的重要性，推动了热带海洋生物生产区海水汞-0和净汞输入的变化。
Air-sea exchange of elemental mercury (Hg-0) is a critical component of the global biogeochemical Hg cycle. To better understand variability in atmospheric and oceanic Hg-0, we collected high-resolution measurements across large gradients in seawater temperature, salinity, and productivity in the Pacific Ocean (20 degrees N-15 degrees S). We modeled surface ocean Hg inputs and losses using an ocean general circulation model (MITgcm) and an atmospheric chemical transport model (GEOS-Chem). Observed surface seawater Hg-0 was much more variable than atmospheric concentrations. Peak seawater Hg-0 concentrations (similar to 130 fM) observed in the Pacific intertropical convergence zone (ITCZ) were similar to 3-fold greater than surrounding areas (similar to 50 fM). This is similar to observations from the Atlantic Ocean. Peak evasion in the northern Pacific ITCZ was four times higher than surrounding regions and located at the intersection of high wind speeds and elevated seawater Hg-0. Modeling results show that high Hg inputs from enhanced precipitation in the ITCZ combined with the shallow ocean mixed layer in this region drive elevated seawater Hg-0 concentrations. Modeled seawater Hg-0 concentrations reproduce observed peaks in the ITCZ of both the Atlantic and Pacific Oceans but underestimate its magnitude, likely due to insufficient deep convective scavenging of oxidized Hg from the upper troposphere. Our results demonstrate the importance of scavenging of reactive mercury in the upper atmosphere driving variability in seawater Hg-0 and net Hg inputs to biologically productive regions of the tropical ocean.