CAS Key Laboratory for Biomedical Effects of Nanomaterials and Nanosafety, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China.
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.
Environ Sci Technol. 2022 Apr 19;56(8):4961-4969. doi: 10.1021/acs.est.1c06558. Epub 2022 Apr 7.
As a major entry point of mercury (Hg) to aquatic food webs, algae play an important role in taking up and transforming Hg species in aquatic ecosystems. However, little is known how and to what extent Hg reduction, uptake, and species transformations are mediated by algal cells and their exudates, algal organic matter (AOM), under either sunlit or dark conditions. Here, using (CV) as one of the most prevalent freshwater model algal species, we show that solar irradiation could enhance the reduction of mercuric Hg(II) to elemental Hg(0) by both CV cells and AOM. AOM reduced more Hg(II) than algal cells themselves due to cell surface adsorption and uptake of Hg(II) inside the cells under solar irradiation. Synchrotron radiation X-ray absorption near-edge spectroscopy (SR-XANES) analyses indicate that sunlight facilitated the transformation of Hg to less bioavailable species, such as β-HgS and Hg-phytochelatins, compared to Hg(Cysteine)-like species formed in algal cells in the dark. These findings highlight important functional roles and potential mechanisms of algae in Hg reduction and immobilization under varying lighting conditions and how these processes may modulate Hg cycling and bioavailability in the aquatic environment.
作为汞 (Hg) 进入水生食物网的主要入口之一，藻类在水生生态系统中吸收和转化 Hg 物种方面发挥着重要作用。然而，对于在光照或黑暗条件下，藻类细胞及其分泌物（藻源有机质，AOM）如何以及在何种程度上介导 Hg 的还原、吸收和物种转化，我们知之甚少。在这里，我们使用（CV）作为最普遍的淡水模式藻类物种之一，表明太阳辐射可以增强 CV 细胞和 AOM 对二价汞 (Hg(II)) 到零价汞 (Hg(0)) 的还原。由于细胞表面吸附和细胞内 Hg(II)的吸收，AOM 比藻类细胞本身还原更多的 Hg(II)。同步辐射 X 射线吸收近边光谱（SR-XANES）分析表明，与在黑暗中形成的藻类细胞中的 Hg（半胱氨酸）样物质相比，阳光促进了 Hg 向生物利用度较低的物质如 β-HgS 和 Hg-植物螯合肽的转化。这些发现强调了藻类在不同光照条件下 Hg 还原和固定中的重要功能作用和潜在机制，以及这些过程如何调节水生环境中的 Hg 循环和生物利用度。
