USGS Grant Number: G19AP00003
Year Established: 2018 Start Date: 2018-11-20 End Date: 2021-10-31
Total Federal Funds: $193,831 Total Non-Federal Funds: $193,831
Principal Investigators: James P. Hurley
Abstract: Mercury (Hg) cycling in the environment has received significant attention over the past few decades as scientists continue to apply new and emerging techniques for chemical and biological analysis of key pools, processes and pathways. Development of techniques to assess trace-metal clean, sub-nanogram per liter levels of total (HgT) and the more bioaccumulative and toxic methyl Hg (MeHg) have led to a better understanding of key processes affecting biotransformation and bioaccumulation. The recent development of techniques amenable for the application of ultra-high precision mass spectroscopy has increased recently, enabling the adetermination of isotopic fingerprints of many elements, including Hg. Specifically, with the application of multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS), scientists have a new tool to identify sources, pathways and processes of Hg through highly resolved isotopic signatures. While the use of Hg stable isotopes is increasing, we are at the initial stages of applying the technique to understand aquatic cycling due to the fact that microgram levels of HgT are needed for analysis, which requires significant preconcentration for natural samples from background settings. Furthermore, techniques are still emerging for accurately quantifying MeHg isotopes, truly a necessary measurement to understand bioaccumulation in aquatic systems. Our proposed project links field and laboratory studies to investigate the effects that chemical transformations and biological uptake processes may have on Hg isotopic ratios. A strength of Hg isotopic analyses is that disparate sources exhibit different mass dependent fractionation and mass independent fractionation of Hg isotopes. If we are to use Hg isotopes in sediments or in fish, we need to understand how Hg isotopes partition and fractionate in phytoplankton, zooplankton and fish. Equally important is knowing to what extent MeHg isotopic fingerprints are preserved or transformed during bioaccumulation. Our results are intended to assist resource managers in determining the reactivity of different Hg sources.