EAGER: Mercury and methylmercury isotope tracing in high-dissolved organic matter high-salinity environments

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Mercury accumulation in wildlife is a major concern for both ecosystem health and the health of humans who hunt and consume mercury-impacted prey (e.g., fish, ducks, and other animals). Tracing the pathways by which mercury enters the food chain and propagates to animals is successfully done by measuring mercury isotopes in the ecosystem (e.g., water, soil, fish, birds) and in different potential mercury sources (e.g., wastewaters). This project seeks to develop new methods to allow measurement of mercury isotopes in saline waters that also have high organic carbon (e.g., estuaries, marine systems, and inland salt lakes) since the co-occurrence of salinity and high organic carbon interfere with current measurement methods for mercury isotopes. Mercury accumulation is often a major concern in saline waters with high organic carbon, and so development of methods to allow mercury isotope measurements in these waters will allow mercury tracking in these settings across the globe. This collaborative research between University of Utah and the US Geological Survey concerns the current inability of mercury researchers globally to utilize isotopic methods to elucidate pathways to biota for: a) total mercury in saline high dissolved organic matter (DOM) waters; and b) methyl mercury in natural waters where low ambient methyl mercury concentrations inhibit application and method development for isotope measurements. Saline high-DOM systems are important locations globally for mercury contaminant burdens in biota, including marine systems such as the Black Sea, inland waters such as Great Salt Lake (GSL), and estuarine systems such as the Florida Everglades, San Francisco Bay, Chesapeake Bay, and many other urbanized estuaries worldwide. Developing a method to overcome the interfering effects of DOM in saline waters will allow elucidation of mercury pathways to biota in these systems. Application of the newly-developed methodology to elucidate mercury pathways to the simple food web in Great Salt Lake (Utah) will serve as a proof of concept to spur application in other locales. The elevated total mercury and methyl mercury concentrations at GSL, the simple ecosystem at GSL, and the tractable size and depth of GSL, make it an ideal incubator for the proposed methodology.Broader impacts include training of a Ph.D. assistant, as well as teachers-in-training as candidates in the Masters of Science in Secondary School Science Teaching (MSSST) graduate program at the University of Utah, who will be mentored during summer-fall internships. The program engages middle and high school biology, chemistry, and earth science teachers in six-week long summer internships that culminate at the end of the fall semester in a teacher-developed series of grade-appropriate lesson plans through which teachers will impact over 600 students.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.