Assessment of the mechanism of elemental incorporation into bivalve shells (Arctica islandica) based on elemental distribution at the microstructural scale
Assessment of the mechanism of elemental incorporation into bivalve shells (Arctica islandica) based on elemental distribution at the microstructural scale
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DOI：
10.1016/j.gca.2013.10.050
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发表时间：
2014-02
影响因子：
5
通讯作者：
K. Shirai;B. Schöne;Tsuzumi Miyaji;Pascal Radarmacher;R. Krause;K. Tanabe
中科院分区：
文献类型：
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作者：
K. Shirai;B. Schöne;Tsuzumi Miyaji;Pascal Radarmacher;R. Krause;K. Tanabe
为了解决元素融入北极双壳类岛屿壳的机制，我们使用电子探针在~ 3 μm的空间分辨率下进行了Sr， Mg和S的二维元素映射。这些元素分布与壳的微观结构进行了精确的比较。Sr分布与S浓度和/或壳结构密切相关。Sr表现出明显的年际格局，在年生长线处值较高，在年生长线处值较低。次年生长线附近的Sr和S浓度高于相邻区域，以针状组织（中壳层）或均匀组织（外层）为主。中间壳层Sr浓度低于外层壳层，但两层间S浓度无明显差异。观察到的元素在壳中的分布可以合理地解释为，在钙化部位，即在帽外空间的有机组成，可以促进元素优先结合到碳酸钙中。Sr/Ca比值在壳内表现出微米尺度的变化，表明元素分布分析需要与壳微观结构相当的精细空间分辨率，以避免时间平均，并在过去的环境重建中正确评估壳中成分变化的幅度。
To address the mechanism of elemental incorporation into shells of the bivalveArctica islandica, we performed two-dimensional elemental mapping of Sr, Mg, and S at a ∼3 μm spatial resolution using electron microprobe. These elemental distributions were precisely compared to the shell microstructure. The Sr distribution was intimately linked to the S concentration and/or shell microstructure. Sr showed a clear annual pattern with higher values at the annual growth lines and lower values in annual growth increments. The Sr and S concentrations were higher near sub-annual growth lines than in the adjacent regions, which were dominated by acicular microstructure (middle shell layer) or homogeneous microstructure (outer shell layer). Furthermore, the Sr concentration was lower in the middle shell layer than in the outer shell layer, but there was no clear difference in the S concentration between the two layers. The observed elemental distribution in the shell can be reasonably explained by the hypothesis that the organic composition at the calcification site, i.e. in the extrapallial space, can facilitate the preferential elemental incorporation into calcium carbonate. The Sr/Ca ratio shows micrometer scale variation within the shell, suggesting that fine spatial resolution, comparable to the shell microstructure, is required for the analysis of elemental distribution to avoid time-averaging and to correctly evaluate the magnitude of the compositional variation in the shell for past environmental reconstruction.