Deep time perspectives on watershed-scale uranium hydrobiogeochemistry in Unaweep Canyon, CO
EMSL Project ID
50689
Abstract
We request rapid-access approval to support the analysis of one each of red, green, and bleached Cutler Formation sedimentary rock samples by Mössbauer spectroscopy by Dr. Ravi Kukkadapu of the EMSL. We request support for instrument time and time for Dr. Kukkadapu to interpret the data and fit isomer shifts, quadrupole splitting parameters, etc. to determine the oxidation state, mineralogy, and general coordination environments of iron atoms in the samples. Samples were selected from those collected by our team. We will/have perform(ed) powder X-ray diffraction (bulk and oriented/ clay fraction), Raman microspectroscopy, electron probe microanalysis, optical petrography, laser particle size analysis, etc. to interpret their mineralogical, geochemical, and textural characteristics that relate to reactivity. We anticipate that Mössbauer spectroscopy will provide critical information regarding the oxidation state, mineral hosts, and coordination environments of iron in the samples. Mössbauer results will be used for (1) interpreting the present-day redox state and history of reducing/oxidizing fluid alteration of the Cutler Formation strata and (2) interpretation and understanding of data from planned experiments investigating the reactivity of Cutler Formation strata towards contaminants of DOE interest (e.g., uranium, chromium). We will use these data to support DOE-OBER research proposals and a peer-reviewed publication describing the chemistry and mineralogy of iron redox interfaces in Cutler Formation sediments. Future work will quantify the impact of deep-time hydrothermal reducing fluids, consequences for the modern Unaweep Canyon hydrobiogeochemical system, and implications for uranium immobilization over geologic time. Our study of hydrothermally reduced sediments will address the molecular-scale immobilization capacity of groundwater metals such as Cr and U in a complex natural system over time scales previously unaddressed by the DOE research portfolio, but societally relevant for understanding contaminant sequestration over 103-106-year time scales. Furthermore, our field site contains a geographically constrained watershed that includes organic-rich and organic-poor flowpaths. A combination of springs and streams access groundwater of different ages, allowing us to link organic matter, nutrients, and metal transport to a range of hydrobiogeochemical processes.
Project Details
Project type
Limited Scope
Start Date
2019-02-19
End Date
2019-04-21
Status
Closed
Released Data Link
Team
Principal Investigator