Dissolved and particulate trace elements in late summer Arctic melt ponds
Dissolved and particulate trace elements in late summer Arctic melt ponds
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DOI：
10.1016/j.marchem.2018.06.002
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发表时间：
2018-08-20
期刊：
影响因子：
3
通讯作者：
Buck, Clifton S.
中科院分区：
文献类型：
--
作者：
Marsay, Chris M.;Aguilar-Islas, Ana;Buck, Clifton S.
融化池是夏季北极海冰的一个突出特征，在大气、冰冻圈和表层海洋之间的复杂界面中发挥着重要作用。在融化池的形成和发展过程中，来自季节性积累的大气沉积的微量营养素和污染物微量元素（TE）与夹带的沉积物和海洋来源的物质混合，然后在海冰融化期间释放到海洋表层。在这里，我们展示了 2015 年夏末美国北极 GEOTRACES (GN01) 巡航期间从五个融化池采样的颗粒和尺寸分级溶解（真正可溶和胶体）TE 数据。对盐度、δO-18 和 Be-7 的分析表明，融雪、融化的海冰和表层海水对融化池的贡献各不相同。我们的数据强调了夏末北极融化池复杂的 TE 生物地球化学以及不同来源对特定 TE 的不同重要性。溶解的 TE 浓度表明海水入侵对 V、Ni、Cu、Cd 和 Ba 产生强烈影响。超滤方法显示溶解的 Fe、Zn 和 Pb 大部分为胶体 (0.003-0.2 μm)，而 Mn、Co、Ni、Cu 和 Cd 主要为真正可溶的 (< 0.003 μm) 部分。一些熔池中的同位素光溶解铁表明也发生了光化学和/或生物驱动的氧化还原循环。颗粒 TE/Al 比值与平均地壳值的比较表明，受到岩石来源的影响，包括天然气溶胶和/或沉积物质，其中一些元素显着富集，包括 Ni、Cu、Zn、Cd 和 Pb，这可能是由人为气溶胶、生物物质和/或溶解 TE 的原位清除造成的。我们的结果表明，融化池代表了一个过渡环境，其中一些来自大气的TE在释放到表层海洋之前经历了物理和/或化学变化。因此，海冰面积范围、厚度和融化季节长度的持续变化可能会影响北冰洋表面大气TE输入的生物有效性，夏季早些时候，雪和海冰中的物质通过融化池释放出来，并更广泛地直接沉积到海洋表面。
Melt ponds are a prominent feature of Arctic sea ice during the summer and play a role in the complex interface between the atmosphere, cryosphere and surface ocean. During melt pond formation and development, micronutrient and contaminant trace elements (TEs) from seasonally accumulated atmospheric deposition are mixed with entrained sedimentary and marine-derived material before being released to the surface ocean during sea ice melting. Here we present particulate and size-fractionated dissolved (truly soluble and colloidal) TE data from five melt ponds sampled in late summer 2015, during the US Arctic GEOTRACES (GN01) cruise. Analyses of salinity, delta O-18, and Be-7 indicate variable contributions to the melt ponds from snowmelt, melting sea ice, and surface seawater. Our data highlight the complex TE biogeochemistry of late summer Arctic melt ponds and the variable importance of different sources for specific TEs. Dissolved TE concentrations indicate a strong influence from seawater intrusion for V, Ni, Cu, Cd, and Ba. Ultrafiltration methods reveal dissolved Fe, Zn, and Pb to be mostly colloidal (0.003-0.2 mu m), while Mn, Co, Ni, Cu, and Cd are dominated by a truly soluble ( < 0.003 mu m) fraction. Isotopically light dissolved Fe in some melt ponds suggests that photochemical and/or biologically driven redox cycling also takes place. Comparisons of particulate TE/Al ratios to mean crustal values indicate influences from lithogenic sources, including natural aerosols and/or sedimentary material, with significant enrichments for some elements, including Ni, Cu, Zn, Cd and Pb, that may result from anthropogenic aerosols, biogenic material, and/or in situ scavenging of dissolved TEs. Our results indicate that melt ponds represent a transitional environment in which some atmospherically-derived TEs undergo physical and/or chemical changes before their release to the surface ocean. As a result, the ongoing changes in sea ice areal extent, thickness, and melt season length are likely to influence the bioavailability of atmospheric TE input to the surface Arctic Ocean, with material released from snow and sea ice via melt ponds earlier in the summer and with more extensive direct deposition to the ocean surface.