A grant has been awarded to Drs. Xiahong Feng, Carol Folt and Stefan Sturup at Dartmouth College to purchase a Gas Chromatography-Inductively Coupled Plasma Mass Spectrometry (GC-ICPMS) system. The unique feature of this instrument is that it provides an interface between a GC and an ICPMS. This makes it possible to simultaneously measure chemical speciation and isotope ratios of inorganic and organic metal containing compounds. For example, one can determine 201Hg/202Hg ratios in inorganic mercury and methylmercury of water or biological samples. Such analytical power offers a variety of opportunities for innovative observations and experiments, involving volatile metal compounds, with important applications in environmental and health sciences. Most organometallic compounds are significantly more toxic than the corresponding inorganic forms. Therefore, the importance of specific determination in environmental and biomedical samples is widely appreciated. This instrument will be installed at the Dartmouth Trace Element Analysis Core Facility (TEA Core), joining an existing High Resolution-ICPMS and an ion chromatography (IC) system. The Dartmouth TEA Core serves a large number of PIs and students doing interdisciplinary research in environmental and health sciences. The new instrument will promote our research activities in three ways. First, it provides new analytical capabilities, such as mercury speciation and isotope analysis and isolation of Se from selenoproteins. Second, it improves the quality of some elemental measurements (e.g., rare earth elements). Finally, it will share the analytical load of our HR-ICPMS, so that technical development work (e.g., As speciation) can be carried out using additional machine time. A new project enabled by this instrument is a study of the biomagnification of heavy metals, especially mercury, in aquatic food webs. Methylmercury in the tissue of plankton and fish from more than 20 lakes with different food web structures will be compared. Quantitative estimates of the influence of zooplankton species, size and relative abundance on the buildup of toxic mercury in fish from each lake will used construct a predictive model for mercury trophic transfer across lakes. Laboratory experiments with stable isotopes of mercury will be used to develop mechanistic models for trophic transfer at the low levels of mercury found in natural systems. Other new and existing projects that will benefit from this equipment include human health effects of exposure to toxic elements, interaction of toxic metal with cellular proteins, mechanisms of contaminant transport through watersheds, and reconstructions of chemical and climatic history of the earth. By becoming a part of Dartmouth's TEA Core, the new GC-ICPMS will offer expanded opportunities for graduate and undergraduate education in the area of emerging technology. The TEA core is served as major foci for interdisciplinary research and scientific communication among experts in many departments within Dartmouth. Dartmouth's TEA core is open for student research from first year undergraduates to Ph.D. students. Eighteen graduate students/postdocs and 15 undergraduate students have used the instruments of the facility. The lab has also been used for classroom education in a few Dartmouth classes, including undergraduate level Environmental Geology, and graduate level Watershed Hydrochemistry and Analytical Chemistry and Instrumental Analysis.
