21-32. Isotope geochemistry applications for improved coastal and marine risk mitigation

Please communicate with individual Research Advisor(s) on the right to discuss project ideas and answer specific questions about the Research Opportunity.

How to Apply

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Isotopes of many elements are powerful tracers and geochronometers in coastal and marine studies (Ivanovich and Harmon, 1992; Bourdon et al., 2003). For example, some short-lived radionuclides such, as ²²²Rn or ²²⁴Ra, are produced in situ by decay of long-lived isotopes and uniquely identify and quantify fluid flux into the ocean (Porcelli and Swarzenski 2003). Pb-210, ¹³⁷Cs and ⁷Be are proven geochronometers (Goldberg, 1963; Appleby and Oldfield, 1992) that can yield important time-stamp information to assess rates of deposition and accumulation of fine-grained material in coastal and marine environments (Moore and Sackett, 1964), which has relevance also to Blue Carbon stocks and the fate of a cocktail of contaminants. Other isotopes can be used as ocean circulation (e.g., ²³⁴Th, ²³⁸U) or atmospheric (e.g., ⁷Be, ¹⁴C) tracers (Broecker, 1974). Variations in isotope ratios yield information on fractionation processes that can be used to identify specific chemical processes involved. Radioactive decay also imparts distinctive isotopic signatures in rocks and sediment (Borole et al., 1982; Cochran, 1982) that can be used to fingerprint source terms and provide key information to track ‘ridge-to-reef’ processes.  

The Pacific Coastal and Marine Science Center (Santa Cruz, CA) uses several techniques to measure different isotopes depending on the decay mechanism, the half-life, and the overall abundance. Applications of isotope geochemistry can provide key information to many existing CMHRP and PCMSC projects including, WildFire Impacts (Takesue), Marine Minerals (Gartman), Coral Reefs (Storlazzi), Alaska Coastal Processes and Hazards Project (Erikson and Gibbs), Integrated Climate-Driven Coastal Hazards (Barnard), Coastal Habitats in Puget Sound (Grossman), and Cascadia Subduction Zone Marine Geohazards (Brothers).  Cross-USGS mission area (interdisciplinary), cross-CMHRP Science Center (Woods Hole, St. Petersburg), other DOI agencies, and tribal, federal, and external partner collaborations are encouraged to be developed. Future progress in the field will follow developments in analytical instrumentation and in the creative application of isotopic tools to support cutting edge coastal and marine studies that help reduce ecological and societal risk, and also support efforts in environmental justice.  

We seek a Mendenhall Postdoctoral Scholar to develop and apply state of the art isotopic methods to advance our understanding of sediment and water exchange processes in ecologically and societally sensitive coastal and marine settings, with direct implications for risk mitigation.  Collection and detailed analyses of isotopic data will be utilized to gain knowledge of the physical processes that underpin and control many modern environmental stressors, such as climate change induced impacts, urbanization, eutrophication, pollution, and a suite of geohazards. 

The candidate is encouraged to explore a wide range of topics, including but not limited to: 

• Sediment transport processes, including U/Th radionuclide-derived geochronologies, deposition, accumulation, and erosion, Blue Carbon assessments;  

• Subsurface fluid flux estimates, including hydrothermal vent- and submarine groundwater-discharge with Ra and Rn;

• Pore fluid controls on geohazards, including landslide formation; and 

• Atmospheric exchange processes.  

Interested applicants are strongly encouraged to contact the Research Advisor(s) early in the application process to discuss project ideas. 

References: 

Appleby, P. G., and F. Oldfield. (1992). Application of lead-210 to sedimentation studies. In: Uranium-Series Disequilibrium: Applications to Earth, Marine, and Environmental Sciences (Eds M. Ivanovich and R. S. Harmon). Clarendon Press, Oxford, pp. 731–778. 

Borole, D. V., S. Krishnaswami, and B. L. K. Somayajulu. (1982). Uranium isotopes in rivers, estuaries and adjacent coastal sediments of western India: Their weathering, transport and oceanic budget. Geochimica et Cosmochimica Acta, 46, 125–137 

Bourdon, B., G. M. Henderson, C. C. Lundstrom, and S. P. Turner. (2003). Uranium-series geochemistry. Reviews in Mineralogy and Geochemistry, 52, 656pp 

Broecker, W. S. (1974). Chemical Oceanography. Harcourt Brace and Jovanovich, New York, 214pp 

Chen, J. H., R. L. Edwards, and G. J. Wasserburg. (1992). Mass spectrometry and application to uranium-series disequilibrium. In: Uranium-Series Disequilibrium: Applications to Earth, Marine and Environmental Sciences (Eds M. Ivanovich and R. S. Harmon). Clarendon Press, Oxford,pp. 174–206. 

Cochran, J. K. (1982). The oceanic chemistry of U- and Th-series nuclides. In: Uranium Series Disequilibria: Applications to Environmental Problems (Eds M. Ivanovich and R. S. Harmon). Clarendon, Oxford, pp. 663–680. 

Goldberg, E. D. (1963). Geochronology with lead-210. In: Radioactive Dating. IAEA, Vienna, pp. 121–131.  

Ivanovich, M., and R. S. Harmon. (1992). Uranium-Series Disequilibrium: Applications to Earth, Marine, and Environmental Sciences. Clarendon Press, Oxford, 910pp. 

Moore, W. S., and W. M. Sackett. (1964). Uranium and thorium series in equilibrium in sea water. Journal of Geophysical Research, 69, 5401–5405. 

Porcelli, D, and P.W. Swarzenski. (2003). The Behavior of U- and Th-series Nuclides in Groundwater. Reviews in Mineralogy and Geochemistry, 52 (1), 317–361. 

Proposed Duty Station(s): Santa Cruz, California 

Areas of PhD: Isotope geochemistry, geochemistry, chemical oceanography, biogeochemistry, sedimentology, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may also be considered). 

Qualifications: Applicants must meet one of the following qualifications: Research Oceanographer, Research Geologist, or Research Chemist.  

(This type of research is performed by those who have backgrounds for the occupations stated above.  However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of the position will be made by the Human Resources specialist.) 

Human Resources Office Contact:  Victor Mendoza, 650-439-2454, vjmendoza@usgs.gov

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