Distribution and speciation of dissolved iron in the Sulu Sea and its adjacent waters
Distribution and speciation of dissolved iron in the Sulu Sea and its adjacent waters
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DOI：
10.1016/j.dsr2.2006.08.019
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发表时间：
2007-01-01
影响因子：
3
通讯作者：
Furuya, Ken
中科院分区：
文献类型：
--
作者：
Kondo, Yoshiko;Takeda, Shigenobu;Furuya, Ken
苏禄海是一个深海盆地，被岛屿链和深度不到420米的浅海与周围的海洋隔离开来。2002年11 - 12月测定了苏禄海及其邻近海域（菲律宾海、Celebes海和中国南海）溶解铁（< 0.22 μ m）和天然有机铁络合配体的垂直分布，以阐明水文对溶解铁化学形态的影响。在苏禄海，溶解铁浓度（[D-Fe]）的垂直剖面在深度小于500 m处出现峰值。在低盐度地表水中观察到的高[D-Fe]表明，来自周围岛屿的河流径流可能是苏禄海的重要铁源。500 m以下[D-Fe]值为0.43 ~ 1.68 nM；它们随着深度的增加而减少。在125-500 m深度处检测到最大值。苏禄海深层海水异常升高的温度似乎是导致溶解铁从下沉的有机物中浅层再生的原因。在125-500 m深度附近发现的最大[D-Fe]也部分归因于大陆斜坡的大量颗粒铁在深海中重新悬浮释放的铁。苏禄海天然有机铁络合配体（[L-T]）浓度为0.4 ~ 1.3 nM。在苏禄海，虽然深水水温、盐度和AOU是恒定的，但[D-Fe]和[L-T]的分布在各台站之间存在差异。在邻近海域也观察到这种非均质分布。这些配体对Fe3+ (K-Fe3+L(cond))的条件稳定性常数变化了两个数量级，为10(22.3)~ 10(24.1)；苏禄海与其邻近海域之间没有明显差异。本研究发现，测定的[D-Fe]高于[L-T]；过量的[d -铁]可以以胶体铁和/或与弱配体的有机/无机配合物的形式存在，这在本研究中未被检测到。在邻近海域也观察到过量[D-Fe] [L-T]的存在，这表明深水的高温并不是苏禄海过量[D-Fe]的特征。基于热力学平衡的铁的化学形态表明，铁以有机结合的形式存在于地表水中（> 99%）。500 m处溶解铁的有机络合程度较低（43-92%），说明深水颗粒的铁溶解过程很重要，可能存在胶体铁或弱配体。这些结果表明，[D-Fe]和[L-T]在苏禄海和西里伯斯海的垂直分布与其他开放海和沿海海不同。苏禄海和西里伯斯海附近的岛屿和深盆地等地质特征似乎强烈地影响着铁的动力学。(c) 2006 Elsevier Ltd.版权所有。
The Sulu Sea is a deep ocean basin that is isolated from the surrounding ocean by chains of islands and shallow sills less than 420 m in depth. Vertical distributions of dissolved (< 0.22 mu m) iron and natural organic iron-complexing ligands were determined in November-December 2002 for the Sulu Sea and its adjacent waters (the Philippine Sea, Celebes Sea and South China Sea) to elucidate effects of hydrography on the chemical speciation of dissolved iron. In the Sulu Sea, vertical profiles of dissolved iron concentrations ([D-Fe]) had peaks at less than 500 m depth. High [D-Fe] observed in the low salinity surface waters suggest that river run-off from surrounding islands might be an important iron source for the Sulu Sea. The [D-Fe] values below 500 m were 0.43-1.68 nM; they decreased with increasing depth. The maxima were detected at 125-500 m depths. Unusually elevated temperatures of deep seawater in the Sulu Sea seem to be responsible for the shallow regeneration of dissolved iron from sinking organic matter. The maximum [D-Fe] that were found around 125-500 m depth were also partly attributable to the iron released from large amounts of particulate Fe from the continental slope that were resuspended in the deep seawater. Concentrations of natural organic iron-complexing ligands ([L-T]) in the Sulu Sea were 0.4-1.3 nM. In the Sulu Sea, although water temperature, salinity and AOU were constant in the deep water, distributions of [D-Fe] and [L-T] differed among stations. These heterogenous distributions were also observed in adjacent seas. The conditional stability constants of these ligands for Fe3+ (K-Fe3+L(cond)) varied by two orders of magnitude, with values of 10(22.3)-10(24.1); no significant difference was found between the Sulu Sea and its adjacent seas. This study found that measured [D-Fe] was higher than [L-T]; excess [D-Fe] can exist as colloidal Fe and/or organic/inorganic complexes with weak ligands that were not detectable in this study. The presence of excess [D-Fe] for [L-T] also was observed in adjacent waters, indicating that high temperatures in the deep water did not characterize excess [D-Fe] in the Sulu Sea. The chemical speciation of iron based on the thermodynamic equilibrium shows that iron exists as organically bound (> 99%) in the surface water. The extent of organic complexation of dissolved iron at 500 m is lower (43-92%), suggesting the importance of iron dissolution process from particles in deep waters and the possible existence of colloidal iron or weak ligands. These results suggest that the vertical distributions of [D-Fe] and [L-T] in the Sulu Sea and Celebes Sea differ from those obtained for other open and coastal seas. Geological features such as those near islands and deep basins in the Sulu Sea and Celebes Sea seem to influence the dynamics of iron strongly. (c) 2006 Elsevier Ltd. All rights reserved.