Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean
Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean
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DOI：
10.5194/bg-9-3231-2012
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发表时间：
2012-01-01
期刊：
影响因子：
4.9
通讯作者：
Achterberg, E. P.
中科院分区：
文献类型：
--
作者：
Boye, M.;Wake, B. D.;Achterberg, E. P.
在东南大西洋和南非以南的南大洋，沿着S 34A度至S 57A度的剖面，提供了全面的表层水(低至4000米)溶解镉(Cd)、铜(Cu)、锰(Mn)、铅(Pb)和银(Ag)的天气资料。铜、银的垂直分布与硅酸相似，镉的垂直分布与磷酸盐相似。锰的分布在氧极小区有一次表层最大值，而铅的浓度随深度变化不大。气溶胶的干沉积被认为是靠近南非的地表水中铅的重要来源，而干沉积和降雪可能是高纬度地区铜和锰的重要来源。此外，与大陆边缘接触后富含微量金属的水团平流似乎是东南大西洋表层、中层和深水以及南极绕极洋流中微量元素的重要来源。热液输入可能形成了布维三联海脊深水中痕量金属的来源，这是由于溶解的锰浓度相对增加所表明的。铜和银的生物利用率与硅酸的生物利用率成正比，这表明硅藻对地表水中铜和银的去除起着重要的控制作用。然而，恐龙和纳米鞭毛虫的吸收可能影响了亚热带大西洋区域表层水域中铜和银的分布。镉与磷酸盐(P)有很强的相关性，在磷酸盐浓度低于0.95µM的亚热带表层水域，Cd/P比值较低。与南极绕极流相比，韦德尔环流中观察到的Cd相对于P的消耗更大，这可能是因为在这些高营养-低叶绿素水域，铁限制条件导致了Cd吸收的增加。类似地，在缺铁的条件下，锰吸收的增加可能导致了韦德尔环流表层水中相对于磷的最高的锰的消耗。此外，可能在韦德尔环流中激活了Cd的细胞锰运输通道，这反过来可能导致这些表层水域中的Mn和Cd的枯竭。
Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34A degrees S and 57A degrees S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu and Ag display nutrient-like profiles similar to silicic acid, and of Cd similar to phosphate. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb concentrations are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water masses enriched in trace metals following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source of trace metals to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced dissolved Mn concentrations. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However, uptake by dino- and nano-flagellates may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical surface waters where phosphate concentrations were below 0.95 mu M. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd uptake induced by iron-limiting conditions in these high-nutrient-low-chlorophyll waters. Similarly, an increase of Mn uptake under Fe-depleted conditions may have caused the highest depletion of Mn relative to P in the surface waters of the Weddell Gyre. In addition, a cellular Mn-transport channel of Cd was possibly activated in the Weddell Gyre, which in turn may have yielded depletion of both Mn and Cd in these surface waters.