- Trace metal geochemistry of seawater: Analytics, chemical speciation and geochemical cycling
- Rare Earth Elements (REE) and High Field Strength Elements (HFSE) geochemistry of seawater/river water
- Method development for determination of vanadium chemical speciation in seawater
- Method development with seaFAST for HFSE elements in seawater
Research Projects: T
- Trace Metal Chemistry in the Water Column of the Angola Basin – A Contribution to the International GEOTRACES Program (M121 cruise)
- Tracing origin and distribution of geogenic and anthropogenic dissolved and particulate critical high-technology metals in the southern North Sea (TRAM cruise)
Trace metals play an important role for the biogeochemical cycles in the world’s oceans. The research program M121 cruise (GA08 Section Cruise) in the SE Atlantic, one of the official programs of the international GEOTRACES (www.geotraces.org), was conducted to obtain an improved understanding of the sources, sinks, speciation and biogeochemical cycling of trace elements in the SE Atlantic region. The sampling location included both open ocean offshore sections and regions close to land on the nearshore which are influenced by upwelling, continental dust input, and influx from the Congo River.
Vanadium is an essential element for marine bioproductivity since it is incorporated into enzymes and involved in chlorophyll synthesis and photosysnthesis. Hence, the bioavailability of V depends on the redox species emphasizes the need to investigate their behavior under varying oxygen conditions in marine environment. My current research topic is to determine the distribution of vanadium and its main redox species, V(IV) and V(V), in open and coastal seawaters to get a better understanding of potential sources, sinks or processes at the sediment/water interface and the interaction of V in biogeochemical cycling.
The distribution of dissolved trace metals (e.g. Ti, W, Nb, Hf, Zr, V and Mo) in the open/coastal/river waters are also investigated in the on-going projects. High Field Strength elements (HFSE; Hf, Zr, Nb) are known as particle-reactive elements. However, their concentration in natural waters (seawater, river water) and its behavior in biogeochemical cycling are still less investigated.
Filtered seawater samples collected during M121 will be analyzed aiming to gain more insights into sources for the HFSE (e.g. riverine, dust inputs and mobilization from shelf sediments). Comparison of seawater collected in offshore with those in nearshore allows to reveal regional sources and get a better understanding of biogeochemical cycling of these trace metals in seawater.
In addition, HFSE elements in seawater/river water samples collected during TRAM cruise will be analyzed to determine the concentrations in the rivers (Ems, Weser and Elbe) as well as the seawater in southern North Sea. It is important to assess the role of rivers in the input of high-technology metals such as REE, Sc, Ge, Ga, Ti and Zr into the southern North Sea, because these metals are increasingly used in new industrial and medicinal applications and can be assumed to be potential emerging contaminants into the nature.
Inductively Coupled Plasma Mass Spectrometry (ICP-MS)*
seaFAST (Automated preconcentration system for undiluted seawater)*
Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES)*
Pressure digestion using Pico Trace DAS system*
Preconcentration of trace elements using SPE (Solid Phase Extraction)*
Column chromatography (Lu, Hf, Sm, Nd, Mg, Fe)
Thermal Ionization Mass Spectroscopy (TIMS)
Secondary Ion Mass Spectroscopy (SIMS)
Electron Microprobe Analysis (EPMA)
Scanning electron microscope (SEM/FE-SEM)
*operated in the laboratory of Jacobs University Bremen
Selected peer-reviewed publications:
- Tenner T., Ushikubo T., Kurahashi E., Kita N. and Nagahara H. (2013): Oxygen isotope systematics of chondrule phenocrysts from the CO3.0 chondrite Yamato 81020: Evidence for two distinct oxygen isotope reservoirs. Geochimica et Cosmochimica Acta, 102, 226-245.
- Hezel D., Needham W. A., Armytage R., Georg B., Abel L. R., Kurahashi E., Coles J. B., Rehkämper M. and Russell S. (2010): A nebula setting as the origin for bulk chondrule Fe isotope variations in CV chondrites. Earth and Planetary Science Letters, 296, 423-433.
- Kurahashi E., Kita T.N., Nagahara H. and Morishita Y. (2008): 26Al-26Mg systematics of chondrules in a primitive CO chondrite. Geochimica et Cosmochimica Acta, 72, 3865-3882.
- Kurahashi E. (2004): 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.
- Kurahashi E., Yamanaka C., Nakamura K. and Sasaki S. (2002): Laboratory simulation of space weathering: ESR measurements of nanophase metallic iron in laser-irradiated materials. Earth Planets Space, 54, e5-e7.
- Sasaki S., Nakamura K., Hamabe Y., Kurahashi E., and Hiroi T. (2001): Production of iron nanoparticles by laser irradiation in a simulation of lunar-like Space weathering, Nature, 410, 6828, 555-557.
- Kurahashi. E, Nakajima Y. and Ogasawara Y. (2001): Coesite inclusions and prograde compositional zonation of garnet in eclogite from Zekou in the SuLu ultrahigh-pressure terrane, eastern China, Journal of Mineralogical and Petrological Sciences, 96, 3, 100-108.