Research Interests:
- Trace metal geochemistry in the marine environment
- Distribution of vanadium (V) redox speciation and its biogeochemical impact in the marine environments including upwelling, hydrothermal input, oxygen minimum zone, dust input and nutrients
- Rare Earth Elements (REE) geochemistry of seawater
My current research topic is focusing on the biogeochemical cycling of trace elements in the global ocean, specifically 1) distribution of vanadium redox species and 2) distribution of anthropogenic trace metals.
Vanadium is known as a redox-sensitive element and strongly hydrolyzed in seawater, present as tetrahedral vanadate (V(V)). In contrast to the oxidized form V(V), the reduced vanadyl V(IV) is highly reactive and forms a large number of strong complexes with inorganic and organic ligands. Vanadium redox species are an essential element for marine bioproductivity, since it is incorporated into enzymes and involved in chlorophyll synthesis and photosynthesis. To elucidate the distribution of vanadium redox species in the marine environment and their biogeochemical impact including upwelling, hydrothermal input, dust input and nutrients, I have been investigating the separation and determination of V redox species in seawater collected during GEOTRACES research projects. Additionally, I have been investigating the distribution of anthropogenic inputs of emerging metal contaminants in the global ocean. I have focused particularly on gadolinium (Gd) in seawater samples collected during GEOTRACES research projects over the last 10 years in a range of ocean regions. Combined with research on other anthropogenically sourced trace metals, such as lead (Pb), platinum (Pt), tellurium (Te), thallium (Tl), and silver (Ag), our study will provide insight into historical and emerging trace element microcontaminants in the global ocean.
Ongoing Projects:
SO289 GEOTRACES-GP21: Dissolved trace element concentration and speciation in the South Pacific Ocean
SO298 GEOTRACES-GP11: Biogeochemistry of trace metals in the equatorial Pacific
SO308 GEOTRACES–GI07: Biogeochemistry of trace metals and their isotopes in the South Indian Ocean
Historical and emerging contaminant trace elements and isotopes. Sources, fluxes and cycling of Pb isotopes, Pt, Tl, Te, Ag and Gd in the oceans – a contribution to GEOTRACES
Previous Projects:
M121 GEOTRACES-GA08: Trace Metal Chemistry in the Water Column of the Angola Basin – A Contribution to the International GEOTRACES Program
M169 TRAM: Tracing origin and distribution of geogenic and anthropogenic dissolved and particlulate critical hightechnology metals in the southern North Sea
Research cruise participation:
METEOR cruise M192, Bridging hydrothermal sites along the Hellenic Arc off Milos from shallow to deep,
August 08 – September 5. 2023, Piräus-Limassol
Selected peer-reviewed publications:
- Kurahashi E., Poehle S. and Koschinsky A., Determination of vanadium redox species V(IV) and V(V) in seawater using chelating resin and inductively coupled plasma mass spectrometry. Deep-Sea Research Part, 206, 104261 (2024). https://doi.org/10.1016/j.dsr.2024.104261.
- Tenner T., Ushikubo T., Kurahashi E., Kita N. T. and Nagahara H., Oxygen isotope systematics of chondrule phenocrysts from the CO3.0 chondrite Yamato 81020: Evidence for two distinct oxygen isotope reservoirs.
- Geochimica et Cosmochimica Acta, volume 102 (2013). 10.1016/j.gca.2012.10.034
- Kurahashi E., Kita N. T., Nagahara H. and Morishita, Y., 26Al–26Mg systematics of chondrules in a primitive CO chondrite. Geochimica et Cosmochimica Acta, volume 72, issue 15, pages 3865-3882 (2008). 10.1016/j.gca.2008.05.038
- Kurahashi E. Contemporaneous chondrule formation: Formation ages of chondrules in carbonaceous and ordinary chondrites with 26Al chronological measurements, The Japanese Society of Planetary Science, 14, 1, 10-16 (2004).
- Sasaki S. and Kurahashi E., Space weathering on Mercury, Advances in Space Research, volume 33, issue 12, pages 2152-2155 (2004). 10.1016/S0273-1177(03)00442-3
- Sasaki S., Kurahashi E., Yamanaka C. and Nakamura K., Laboratory simulation of space weathering: Changes of optical properties and TEM/ESR confirmation of nanophase metallic iron. Advances in Space Research, volume 31, issue 12, pages 2537-2542 (2003). 10.1016/S0273-1177(03)00575-1
- Kurahashi E., Yamanaka C., Nakamura K. and Sasaki S., Laboratory simulation of space weathering: ESR measurements of nanophase metallic iron in laser-irradiated materials. Earth, Planets and Space, volume 54, issue 12, pages e5-e7 (2002). 10.1186/BF03352448
- Kurahashi E., Nakajima Y. and Ogasawara Y., Coesite inclusions and prograde compositional zonation of garnet in eclogite from Zekou in the Su-Lu ultrahigh-pressure terrane, eastern China. Journal of Mineralogical and Petrological Sciences, volume 96, issue 3, pages 100-108 (2001). 10.2465/jmps.96.100