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

Quantifying the weathered fluxes to the ocean is far from over: the overlooked role of rock coast erosion

This study reveals that cliff derived sediment supply is only three times less than the solid discharge of rivers for Europe.

21.01.2022

Science Highlights

Contrasting distributions of dissolved manganese, nickel, cadmium and zinc in the Mediterranean Sea

Extensive trace metal clean sampling during the Dutch GEOTRACES cruise in the Mediterranean Sea allowed Middag and his colleagues to establish the basin scale distribution of these trace metals.

19.01.2022

Science Highlights

Specific features characterize the dissolved iron distribution in the North Western Indian Ocean

Venkatesh Chinni and Sunil Kumar Singh propose dissolved iron profiles along two meridional transects realized during spring and fall seasons between the Arabian Sea and the sub-tropical western Indian Ocean…

07.01.2022

Science Highlights

Anthropogenic aerosol has become a dominant source of zinc in the deep water of the Northern South China Sea

Liao and colleagues determined zinc concentrations and isotope compositions in sinking particles collected in the Northern South China Sea…

24.11.2021

Rechercher