The first such project is the Seabird Tissue Archival and Monitoring Program (STAMP). STAMP is a multi-agency effort between the U.S. Fish and Wildlife Service (USFWS), the U.S. Geological Survey (USGS), the Bureau of Indian Affairs, and NIST to collect, bank, and analyze seabird tissues from the Alaskan arctic and subarctic to monitor contaminants in the marine ecosystem. Collections date back to 1999, and analyses for mercury have been performed on collections through 2005. A collaboration with the North Pacific Research Board focuses on the Norton Sound region of the Bering Sea where previous analyses showed elevated levels of mercury in eggs relative to the rest of the Bering Sea. Norton Sound is greatly influenced by discharges from the Yukon and Kuskokwim Rivers and has localized areas of historically heavy gold and mercury mining, all of which might contribute to the observed elevated mercury levels in biota. The current work expands on the previous study by investigating whether mercury isotopic patterns in eggs from Norton Sound differ from eggs from other colonies, and whether different fractionation patterns can be resolved among colonies within Norton Sound that may be subject to different local sources and biogeochemical cycling.
As described elsewhere, NIST also supports marine animal health programs conducted by the National Oceanic and Atmospheric Administration (NOAA). NOAA is currently performing an ecosystem health comparison between a superfund site on the Turtle River near Brunswick, Georgia, and the nearby Sapelo Island National Estuarine Research Reserve Site (NERRS). Dolphin skin biopsies and terrapin shell samples have been collected from both of these sites to assess mercury exposures in these indicator species. There is increasing interest in the analytical and environmental communities in the possible use of mercury isotope fractionation patterns to identify source patterns of mercury in the environment. This NOAA collaboration is ideally suited to test whether a large point source (a historical chlor-alkali plant in Brunswick) creates an isotopically distinct mercury signature in the vicinity of its impact. Isotopic patterns in these two indicator species will be assessed near the source and 40 km distant from the source, where atmospheric and natural mercury inputs are presumed to dominate. Potential shifts in the isotopic signature at the two trophic levels represented by these species will also be investigated to assess the consistency of the source fractionation pattern through the food web.
Additional Technical Details:
A similar analytical approach will be used for the isotopic analysis of all tissues. A standard microwave-assisted acid digestion will be performed on a subsample of the tissue. The digest will then be split into two aliquots: one for total mercury quantification by cold vapor isotope dilution inductively coupled plasma mass spectrometry (CV-ID-ICP-MS), and the other for isotopic analysis by CV-multicollector (MC)-ICP-MS. The sample will be injected as a vapor (after reduction with tin chloride) with inline mass bias correction using thallium injected by micro-nebulizer. SRM 3133 Mercury Standard Solution will serve as the isotopic reference standard, providing additional in-house measurements of its isotopic composition to complement the information values currently provided on the certificate. SRM 1947 Lake Michigan Fish Tissue will also be analyzed concurrently with these batches to provide additional mercury isotopic characterization of this material and to monitor instrument reproducibility and drift.
Start Date:August 1, 2007
Lead Organizational Unit:mml
Steven J. Christopher
Related Programs and Projects: