Assessing chemical inputs and mixing


Chemical inputs (e.g. iron) to the oceans have significant impacts on biogeochemical processes and marine productivity. However, their sources and fluxes are not well constrained. Chemical distribution and transport are also controlled by mixing processes in the oceans. Assessing ocean mixing rates could provide important information about the fluxes of trace metals into, out of, and within the ocean. Such information would help us to understand the correlation between biological activity and micronutrient supply in the oceans.


Trace-metal inputs to the oceans have multiple sources and pathways, for instance atmospheric dust input, river runoff, submarine groundwater discharge, sediments and hydrothermal input. U-Th series nuclides provide unique isotopic fingerprints and different half-lives, which can be used as powerful tracers to identify trace-metal sources and to quantify their fluxes to the oceans. 




Recent work

Using seawater 232Th and 230Th as improved tracers to accurately constrain dust input to the surface ocean.

Analytical development of high precision measurements of seawater 228Ra by MC-ICP-MS

Using the Ra quartet, 228Ra, 226Ra, 224Ra and 223Ra to trace water mixing, nutrient inputs and Ra fluxes in the oceans. 


Natural Environment Research Council

People Involved

Yu-Te (Alan) Hsieh  (MIT)

Alex Thomas  (University of Edinburgh)

Gideon Henderson 


Walter Geibert (University of Edinburgh)


Hsieh, Y.-T., Henderson, M.G., and Thomas, L.A. (2011) Combining seawater 232Th and 230Th concentrations to determine dust fluxes to the sufrace ocean. Earth Planet Sci. Lett., 312. 280-290.

Hsieh, Y.-T. and Henderson, G. (2011) Precise measurement of 228Ra/226Ra ratios and Ra concentrations in seawater samples by multi-collector ICP mass spectrometry. J. Anal. At. Spectrom. 26. 1338-1346.