Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, Rimouski, 310, allée des Ursulines, QC, Canada G5L 3A1.
Chemosphere. 2012 Feb;86(6):680-3. doi: 10.1016/j.chemosphere.2011.11.023. Epub 2011 Dec 7.
External shell surface (ESS) of bivalve mollusks is known to adsorb various metals dissolved in ambient water in high concentration. It is hypothesized here that the surface microtopography of the thin organic coating layer, periostracum, or calcareous shell (if periostracum was destroyed) plays a major role in the adsorption of actinides on ESS. Thorium (natural alpha-emitter) was used in short-term biosorption experiment with shell fragments of five bivalve mollusks. After a 72 h exposure to Th (~6 kBq L(-1)), thorium concentration was measured on ESS using laser ablation inductively coupled plasma mass spectrometry; the distribution and density of alpha tracks were subsequently visualized by α-track autoradiography. A trend in reduced Th concentrations on the ESS was observed depending upon the species tested: (group 1 ~4000 μg g(-1)) Chlamys islandica (M.), Mercenaria mercenaria (L.), Dreissena polymorpha (P.)>(group 2 ~1200 μg g(-1)) Crassostrea virginica (G.)≫(group 3 ~150 μg g(-1)) Mytilus edulis L. The microtopography of ESS was characterized by scanning electron microscopy revealing the high porosity of the calcareous surface of C. islandica and M. mercenaria, lamellate surface of periostracum in D. polymorpha, uneven but a weakly porous surface of periostracum of C. virginica, and a nearly smooth surface of the periostracum of M. edulis. This work has demonstrated, for the first time, the presence of a strong correlation between concentration of adsorbed Th and ESS microtopography, and the role of the periostracum in this process is discussed.
双壳类软体动物的外壳表面（ESS）已知能够高浓度地吸附溶解在环境水中的各种金属。这里假设薄的有机覆盖层（壳皮或钙质壳，如果壳皮被破坏）的表面微观形貌在 ESS 上吸附锕系元素方面起着主要作用。在使用五种双壳类软体动物贝壳碎片的短期生物吸附实验中，使用了钍（天然α发射体）。在 72 小时暴露于 Th（6 kBq L(-1)) 后，使用激光烧蚀电感耦合等离子体质谱法测量 ESS 上的钍浓度；随后通过α-track 放射自显影观察α轨迹的分布和密度。根据测试的物种，观察到 ESS 上的 Th 浓度呈降低趋势：（第 1 组4000 μg g(-1)) 冰岛扇贝（M.)、海湾扇贝（L.)、圆背角无齿蚌（P.)>(第 2 组1200 μg g(-1)) 美洲帘蛤（G.)≫（第 3 组150 μg g(-1)) 贻贝（L.）。ESS 的微观形貌通过扫描电子显微镜进行了表征，揭示了 C. islandica 和 M. mercenaria 的钙质表面的高孔隙率、D. polymorpha 中壳皮的层状表面、C. virginica 中壳皮的不均匀但多孔性较弱的表面以及 M. edulis 中壳皮的几乎光滑表面。这项工作首次证明了吸附 Th 的浓度与 ESS 微观形貌之间存在强烈相关性，并且讨论了壳皮在这一过程中的作用。
