Marine trace metal isotope geochemistry

Supervisor:
Prof. E.A. Boyle, Professor of Marine Geochemistry; Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology

Rationale: This work aims to use the isotopic variability of trace metals to understand mechanisms controlling the fluxes of metals through the ocean and their links to biogeochemical processes. Oceanic trace metal isotope variability is caused by (a) radiogenic isotope differences due to varying geological and anthropogenic sources (e.g., Pb isotopes), (b) stable isotope differences created by equilibrium, kinetic, and biological fractionations (e.g. Fe, Zn isotopes).

Methodology: Trace metal clean sampling methods are required at sea; in the laboratory, chemical purification methods and multiple-collector plasma mass spectrometry are used to measure metal isotope ratios.

Wider Implications: The evolving North Atlantic surface boundary condition for Pb isotopes can be used to trace anthropogenic Pb into the deep interior of the ocean at least as far as the South Atlantic Ocean. Fe and Zn are essential for marine life; Fe is known to limit marine biological activity in some regions, and Zn is suspected as limiting as well. The stable isotope ratios of these elements can be used to trace their biogeochemical interactions.

Suitable For: Students with strong laboratory analytical skills.

Training: In addition to acquiring generic oceanographic skills, the student will learn how to conduction trace metal clean fieldwork at sea and gain experience in operating a state-of-the-art plasma mass spectrometer.

Additional Relevant Links:

• http://boyle.mit.edu/~ed
• http://www-eaps.mit.edu/faculty/boyle.htm

References:

• Wu, J.F. and E.A. Boyle (1997) Lead in the western North Alantic Ocean: completed response to leaded gasoline phaseout, Geochim. Cosmochim. Acta 61:3279-3283.
• Wu, J. and E. Boyle (2002) Iron in the Sargasso Sea: implications for the processes controlling dissolved Fe distribution in the ocean, Glob. Biogeochemi. Cycles. 16:1086 (10.1029/2001GB 001453).831.
• Bell, J., J. Betts, and E. Boyle (2002) MITESS: A Moored In-situ Trace Element Serial Sampler for Deep-Sea Moorings, Deep-Sea Research I: 49:2103-2118.