The distribution of lead concentrations and isotope compositions in the eastern Tropical Atlantic Ocean
The distribution of lead concentrations and isotope compositions in the eastern Tropical Atlantic Ocean
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DOI：
10.1016/j.gca.2018.01.018
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发表时间：
2018-03-15
影响因子：
5
通讯作者：
Achterberg, Eric P.
中科院分区：
文献类型：
--
作者：
Bridgestock, Luke;Rehkaemper, Mark;Achterberg, Eric P.
在过去的世纪，人为排放一直是海洋铅的主要来源。在这里，我们提出了铅浓度和同位素组成的海洋深度剖面收集在热带大西洋东部（GEOTRACES节GA 06），跟踪转移到海洋内部的人为铅。铅浓度和同位素组成的变化与水文的变化。根据历史上人为Pb排放的Pb同位素数据，南半球通风的水团通常具有较低的Pb-206/Pb-207和Pb-208/Pb-207比北方半球通风。铅浓度和同位素组成的分布在北方来源的沃茨是一致的，其通风时间尺度的差异。例如，铅浓度最大值在中间深度（600-900 m，35 pmol kg（-1）），与Pb同位素组成有关（Pb-206/Pb-207 = 1.1818-1.1824，Pb-208/Pb-207 = 2.4472-2.4483）表明北方半球在1950年代和1960年代接近含铅汽油使用高峰时的排放量，和类似于50-60年的过渡时间。相比之下，北大西洋深水（2000-4000 m水深）Pb含量和同位素组成较低（Pb-206/Pb-207 = 1.176 2-1.184，Pb-208/Pb-207 = 2.4482-2.4545），表明1910年代和1930年代期间北方半球的排放量，以及类似于80-100年的过境时间。这支持的概念，即短暂的人为铅输入主要是转移到海洋内部的水质量运输。然而，解释铅浓度和同位素组成分布的通风时间尺度和途径是复杂的（1）铅在海洋中的化学反应，（2）混合沃茨通风在不同的时间段。水团混合对Pb分布的复杂影响在南半球通风的热带大西洋海水中尤为明显。特别是，南大西洋中央水和南极中层水占主导地位的人为铅排放在过去的50-100年，尽管在这一地区的平均通风年龄估计更老。(C)2018作者（S）出版社：Elsevier Ltd
Anthropogenic emissions have dominated marine Pb sources during the past century. Here we present Pb concentrations and isotope compositions for ocean depth profiles collected in the eastern Tropical Atlantic Ocean (GEOTRACES section GA06), to trace the transfer of anthropogenic Pb into the ocean interior. Variations in Pb concentration and isotope composition were associated with changes in hydrography. Water masses ventilated in the southern hemisphere generally featured lower Pb-206/Pb-207 and Pb-208/Pb-207 ratios than those ventilated in the northern hemisphere, in accordance with Pb isotope data of historic anthropogenic Pb emissions. The distributions of Pb concentrations and isotope compositions in northern sourced waters were consistent with differences in their ventilation timescales. For example, a Pb concentration maximum at intermediate depth (600-900 m, 35 pmol kg(-1)) in waters sourced from the Irminger/Labrador Seas, is associated with Pb isotope compositions (Pb-206/Pb-207 = 1.1818-1.1824, Pb-208/Pb-207 = 2.4472-2.4483) indicative of northern hemispheric emissions during the 1950s and 1960s close to peak leaded petrol usage, and a transit time of similar to 50-60 years. In contrast, North Atlantic Deep Water (2000-4000 m water depth) featured lower Pb concentrations and isotope compositions (Pb-206/Pb-207 = 1.176 2-1.184, Pb-208/Pb-207 = 2.4482-2.4545) indicative of northern hemispheric emissions during the 1910s and 1930s and a transit time of similar to 80-100 years. This supports the notion that transient anthropogenic Pb inputs are predominantly transferred into the ocean interior by water mass transport. However, the interpretation of Pb concentration and isotope composition distributions in terms of ventilation timescales and pathways is complicated by (1) the chemical reactivity of Pb in the ocean, and (2) mixing of waters ventilated during different time periods. The complex effects of water mass mixing on Pb distributions is particularly apparent in seawater in the Tropical Atlantic Ocean which is ventilated from the southern hemisphere. In particular, South Atlantic Central Water and Antarctic Intermediate Water were dominated by anthropogenic Pb emitted during the last 50-100 years, despite estimates of much older average ventilation ages in this region. (C) 2018 The Author(s). Published by Elsevier Ltd.