Determining the pathways, fate, and flux of atmospherically derived trace elements in the Arctic ocean/ice system
Determining the pathways, fate, and flux of atmospherically derived trace elements in the Arctic ocean/ice system
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确定北冰洋/冰系统中大气衍生微量元素的路径、命运和通量
DOI：
10.1016/j.marchem.2016.04.006
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发表时间：
2016
期刊：
影响因子：
3
通讯作者：
R. Shelley
中科院分区：
文献类型：
--
作者：
D. Kadko;B. Galfond;W. Landing;R. Shelley
气溶胶沉积是将微量元素（包括人为元素）输送到北极的重要途径。在恶劣的北极环境中评估这一过程很困难，有限的实地研究迫使人们依赖约束较差的模型。在这里，我们使用宇宙射线产生的放射性同位素 7Be 来追踪北极水/冰/雪系统内元素的大气沉积，并将气溶胶浓度与通量联系起来。作为 RV Polarstern 的 ARK-XXVI/3 活动的一部分，在 2011 年夏末收集了海水、冰、雪、融水池和气溶胶样本。根据测量的 7Be 库存，我们确定平均 7Be 通量为 109 dpm/m2/d，这与该地区之前的研究结果一致。雪、冰和融水池是 7Be 的重要储存库，整个 8 月下旬，冰中的相对 7Be 库存量有所增加，而融水池库存量随着结冰的开始而减少。在我们的样带中，总（水/冰/雪系统）库存量相对恒定，但随着接近无冰、开放水域，混合层库存量向低纬度地区增加。后一个梯度驱动 7Be 以及可能的其他大气衍生物种向冰覆盖的海洋混合层迁移。这是通过沿跨极漂移的平流输送来模拟的。平均 7Be 气溶胶浓度为 0.0182 dpm/m3。成岩气溶胶元素均未表现出高于地壳成分的显着富集，而污染源元素（Cr、Ni、Cu、Zn、Cd、Sb、Pb）相对于地壳成分则表现出不同程度的富集。历史气溶胶 7Be 数据用于推导 7Be 库存中的季节性周期，该周期已根据本研究中测量的库存进行校准，使用 1350 m/天的有效整体（湿加干）沉积速度。然后使用该沉积速度来估计气溶胶微量元素的季节性大气通量。
Aerosol deposition is an important pathway for delivering trace elements, including those of anthropogenic origin, into the Arctic. Assessment of this process is difficult in the harsh Arctic environment, and limited field studies have forced a reliance on poorly constrained models. Here we use the cosmic ray produced radioisotope,7Be, to trace the atmospheric deposition of elements within the Arctic water/ice/snow system, and link aerosol concentrations to flux. Seawater, ice, snow, melt pond, and aerosol samples were collected during late summer 2011 as part of the RV Polarstern's ARK-XXVI/3 campaign. From the measured7Be inventories we determined an average7Be flux of 109 dpm/m2/d, which is consistent with results from previous studies in the region. Snow, ice and melt ponds represent significant reservoirs of7Be, and the relative7Be inventory in ice increased through late August, as melt pond inventories decreased with onset of freezing. The total (water/ice/snow system) inventory was relatively constant across our transect, but mixed layer inventories increased towards lower latitudes as ice-free, open water was approached. The latter gradient drives transport of7Be, and presumably other atmospherically-derived species, towards the ice-covered ocean mixed layer. This is modeled by advective transport along the Transpolar Drift. The average7Be aerosol concentration was 0.0182 dpm/m3. None of the lithogenic aerosol elements showed any significant enrichment above crustal composition, while the pollution-derived elements (Cr, Ni, Cu, Zn, Cd, Sb, Pb) showed varying degrees of enrichment relative to crustal values. Historical aerosol7Be data was used to derive a seasonal cycle in the7Be inventory that was calibrated to the inventory measured in this study, using an effective bulk (wet plus dry) deposition velocity of 1350 m/day. This deposition velocity was then used to estimate the seasonal atmospheric flux of aerosol trace elements.