First combined distributions of dissolved Neodymium (Nd) – Hafnium (Hf) concentrations and isotope compositions from the Baltic Sea

The central Baltic Sea is a marginal brackish basin, in which anoxic bottom waters prevail either seasonally or permanently and which is surrounded by continental landmasses comprising a large variety of compositions and ages of rocks. This allows the investigation of water mass mixing using radiogenic isotope compositions of Nd and Hf, as well as the geochemical cycling of these elements in the water column. Tianyu Chen and co-workers present the first combined distributions of dissolved Neodymium (Nd) and Hafnium (Hf) concentrations and their isotopic compositions from the Baltic Sea obtained during a cruise onboard the Polish RV Oceania in the frame of a process study of the GEOTRACES program.

2013 Chen FrankFigure: Neodymium-hafnium isotope systematics of the central Baltic Sea, in comparison with published Nd-Hf isotope data of terrestrial rocks, seawater (<0.45 μm), and Fe-Mn crusts (for sources of the data see publication).

The results document a pronouncedly different behavior of Nd and Hf. The Nd isotopes effectively trace the mixing between more radiogenic saline waters from the Atlantic and unradiogenic fresh waters from the northern Baltic Sea, which helps to understand Nd isotopes as water mass tracer in the open ocean. In contrast the dissolved Hf isotope signatures show a large variability but no consistent mixing trends, suggesting a shorter oceanic residence time of Hf than of Nd and thus a larger influence of local and highly variable weathering inputs. Nevertheless all data plot very close to the seawater array in Nd-Hf isotope space suggesting that continental incongruent weathering alone is most likely sufficient to explain the oceanic Hf isotope compositions without the involvement of hydrothermal contributions, which is also supported by the extreme Hf isotope composition of the Kalix river from northern Sweden.

Reference:

Chen, T.-Y., Stumpf, R., Frank, M., Beldowski J. and Staubwasser, M. (2013): Contrasting geochemical cycling of hafnium and neodymium in the central Baltic Sea. Geochimica et Cosmochimica Acta. 123, 166-180 DOI:10.1016/j.gca.2013.09.011

Latest highlights

Science Highlights

Dissolved iron II deep concentrations re-estimated considering oxidation kinetic effets

Gonzalez-Santana and his collaborators demonstrated that the oxidation kinetic of the samples combined with analysis of triplicate subsamples led iron (II) concentrations to decrease with time.

31.03.2023

Science Highlights

Decline of the anthropogenic lead imprint to the ocean confirmed by data from the South West Atlantic Ocean

This study reveals that the mean lead concentrations in the surface waters of the western South Atlantic Ocean decreased by 34 % between the 1990s and 2011.

29.03.2023

Science Highlights

Irradiance-normalized non-photochemical quenching (NPQ): a new proxy of iron stress for phytoplankton

Ryan-Keogh and his colleagues used NPQ to fingerprint the photo-physiological response of phytoplankton to their environment.

06.03.2023

Science Highlights

Exhaustive modelling study of the oceanic neodymium parameters

The conclusion of this study reinforces the important role of the solid particles in driving the neodymium oceanic cycle.

02.03.2023

Rechercher