Examining the role of nanoparticles in the formation and degradation of methylated mercury in the ocean

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In this project funded by the Environmental Chemistry Program in the Chemistry Division at the National Science Foundation, Professors Robert Mason and Jing Zhao of the University of Connecticut examine the role of nanoparticles in controlling the reactions between various forms of mercury in the ocean. Specifically, in contrast to freshwater environments, dimethylmercury is found in all ocean waters where measurements have been made. There is little information on its formation mechanisms. The investigators have preliminary evidence to indicate that it may be formed by reactions that involve nanoparticles and other surfaces. It is known that methylmercury, an organic form of mercury found in the ocean, is mostly formed by bacteria that react with inorganic mercury. Reactive surfaces are also be important in the degradation of methylmercury. The project trains a graduate student in diverse aspects of environment chemistry, and engages undergraduates and high school students, providing avenues for research, teaching and outreach. The investigators incorporate the research into ongoing outreach programs. They use the information generated from the project in developing their graduate and undergraduate teaching curricula. The results are published in the peer-reviewed literature, with the graduate student as the lead author. The investigators conduct laboratory experiments with both commercially manufactured and natural nanomaterials to examine the potential importance of metal nanoparticles in forming metallic and organic forms of mercury under conditions applicable to the ocean. Techniques used in these experiments include UV-visible and fluorescence spectroscopy, electron microscopy and mass spectrometry. Mercury analyses require instruments that are specifically designed for measurement of the different forms of mercury at low concentrations. The results of this research enhance our understanding of the processes that form methylated mercury in the ocean which, when bioaccumulated into seafood is an important human health concern. Professors Mason and Zhao incorporate their findings into their outreach communications with managers and regulators interested in mitigating the impacts of anthropogenic mercury emissions on the biosphere through such treaties as the Minamata Convention.