Collaborative Research: A GEOTRACES Intercalibration of Collection, Handling and Analysis Methods for Mercury Species in Seawater

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Hg is present at very low concentrations in the open ocean (fM - pM) and is subject to a complex biogeochemical cycling. To understand this cycling, determination of the major species of Hg found in the ocean (mercuric ion, elemental Hg, monomethylHg and dimethylHg; Hg(II), Hgº, MMHg and DMHg, respectively), is necessary but poses daunting analytical challenges. These forms can be volatile and photoactive, and their low concentrations make even small amounts of contamination ruinous. But there are important benefits to studying Hg in the ocean, including increased understanding of the source and bioaccumulation dynamics of a toxic metal, the formation of organometallic compounds (including those of Ge, Se, Po, As) in the ocean, assessing the impact of an anthropogenically mobilized element, and the possible development of a paleoproductivity proxy. With funding from this award, researchers at the Woods Hole Oceanographic Institution, University of Connecticut, Battelle Memorial Institute, and Wright State University will participate in the upcoming GEOTRACES Intercalibration cruises in order to initiate a comprehensive, multi-investigator/laboratory comparison of the determination of mercury (Hg) species in seawater. Such an Intercalibration is a critical first step prior to full fledged GEOTRACES cruise activities, so that the various investigators studying the chemical oceanography of Hg in the context of that project, which is intended to be decentralized and of such scope that no one lab would likely be capable of completing the whole effort, may compare their results. The project will consist of both a shore based and field (participation in the two cruises) components. In the laboratory, the team will test the cleanliness of bottles made from plastics other than Teflon, and the prospects of long-term storage of samples collected during the cruises for total and speciation measurements. This award will support only the field component of the project, with the remaining effort facilitated by on-going support from other sources. The broader impacts of this work, and that of the subsequent GEOTRACES studies, include a greater understanding of a serious human and ecosystem health threat in the form of MMHg accumulation in fish. In addition, and as with GEOTRACES in general, this Intercalibration exercise will forge and maintain bonds of international collaboration. Finally, the four PIs in this effort are engaged in, and in many cases seeking additional leveraging funds to help support, educational efforts at the undergraduate, graduate and post-graduate level.