†Key Laboratory of the Coastal and Wetland Ecosystems, Ministry of Education, College of Environment and Ecology, Xiamen University, Xiamen, Fujian 361102, China.
‡Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
Environ Sci Technol. 2015 Jun 2;49(11):6919-25. doi: 10.1021/es506330h. Epub 2015 May 14.
In oysters, Cu and Zn concentration can reach extraordinarily high (1-2% of tissue dry weights), leading to intense green or blue colors in oyster tissues. It is thus puzzling how oysters detoxify the excessively accumulated metals. Here, we used X-ray absorption spectroscopy to examine the Cu and Zn speciation in two "colored" oysters (Crassostrea hongkongensis and Crassostrea sikamea) collected from a severely metal-contaminated estuary. In contaminated oysters, we found a much higher proportion of tissue Cu and Zn as oxygen- or nitrogen-bonded species, contrasting to the sulfur-bonded (thiolate) species in normal oysters. Speciation of Cu and Zn in mantle was similar to that in gills, both of which were different from that in the digestive gland. In C. sikamea, the difference of metal speciation between normal and contaminated individuals was of similar pattern but less pronounced than that in C. hongkongensis. In normal oysters, Cu existed mainly as Cu(I) bound to sulfur, whereas in contaminated oysters mainly as Cu(II) bound to oxygen or nitrogen. Our study provided direct and semiquantitative information on the changes of metal speciation in contaminated oysters, indicating that oysters could efficiently detoxify the excessively accumulated Cu and Zn by storing them in oxygen- and nitrogen-bonded complexes in metal-rich environments.
在牡蛎中，Cu 和 Zn 的浓度可以达到非常高的水平（组织干重的 1-2%），导致牡蛎组织呈现出强烈的绿色或蓝色。因此，令人困惑的是，牡蛎如何解毒过量积累的金属。在这里，我们使用 X 射线吸收光谱研究了两种“有色”牡蛎（香港牡蛎和太平洋牡蛎）中 Cu 和 Zn 的形态，这些牡蛎是从一个重金属污染严重的河口采集的。在污染的牡蛎中，我们发现组织中的 Cu 和 Zn 有更高比例的氧或氮结合态，与正常牡蛎中的硫结合态（硫醇）形成鲜明对比。牡蛎套膜和鳃中的 Cu 和 Zn 形态与消化腺中的形态相似，但又有所不同。在太平洋牡蛎中，正常和污染个体之间的金属形态差异模式相似，但不如香港牡蛎那么明显。在正常牡蛎中，Cu 主要以与硫结合的 Cu(I)形式存在，而在污染牡蛎中主要以与氧或氮结合的 Cu(II)形式存在。我们的研究提供了关于污染牡蛎中金属形态变化的直接和半定量信息，表明牡蛎可以通过将过量积累的 Cu 和 Zn 储存在富含金属的环境中的氧和氮结合的复合物中，有效地解毒这些金属。
