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The sources and transport of Sr and Nd isotopes in the Baltic Sea

Andersson, Per S. and Wasserburg, G. J. and Ingri, Johan (1992) The sources and transport of Sr and Nd isotopes in the Baltic Sea. Earth and Planetary Science Letters, 113 (4). pp. 459-472. ISSN 0012-821X. doi:10.1016/0012-821X(92)90124-E.

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We have determined the concentration and isotopic composition of Sr and Nd in waters from the Baltic Sea. The Baltic Sea is an intracontinental, stratified, brackish water, estuarine-like system, and the rivers emptying into it drain a suite of terranes ranging from Proterozoic-Archean in the north to Phanerozoic in the south. The sampled brackish waters range in salinity from seawater (SW) at 35.289‰ to a minimum of 2.460‰ at the surface in the innermost part of the Gulf of Bothnia. The Sr concentrations show generally conservative behavior, indicating a simple two-component mixing. However, small deviations (3–70 ‰) from a perfect mixing line reveal that the imprints from rivers with different Sr concentrations are preserved in the blending. Strontium concentrations from a depth profile across the redoxcline in the Baltic proper indicate that vertical particle transport alters the Sr concentration in the water. Our estimated concentration of Sr in the average freshwater input to the Baltic is ∼ 0.03 ppm, which is only about 0.4% of the SW concentration. The Sr isotopic data range from ε^(Sr)(SW) = 0 in seawater to ε_(Sr)^(BW)(SW) = 7.8 in the least saline Baltic water (BW) sample in the Gulf of Bothnia. The isotopic composition of Sr versus 1/Sr in the Baltic Sea follows an almost perfect mixing line, which shows that seawater Sr is mixed with much more radiogenic components. Calculated end-member values of ε_(Sr)^*(SW) for each sample show that the riverine input into the Gulf of Bothnia has ε_(Sr)^*(SW) = 120–200 and 10–50 ε units in the Baltic proper. These values are in general agreement with direct measurements of river waters in each region. However, the calculated values in the Gulf of Bothnia are lower than the measured river water input in this region, which indicates the presence of less radiogenic Sr, presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with Sr from the Gulf of Bothnia rivers. The Nd concentration in the Baltic Sea is not conservative, varying between 5 and 45 ppt, with the highest concentrations in the bottom waters due to vertical particulate transport. A plot of ε_(Nd)(O) in Baltic water yields a good correlation with the calculated freshwater end member ε_(Sr)^*(SW). The data show that it is possible to unravel the different freshwater sources into the Baltic and to identify the zones of particulate removal of both non-conservative species such as the REE and of quasi-conservative species such as Sr. The use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport. It should also be possible to trace lateral movements of freshwater inputs.

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Wasserburg, G. J.0000-0002-7957-8029
Additional Information:© 1992 Elsevier Science Publishers B.V. Received April 6, 1992; revision accepted August 21, 1992. We acknowledge the advice and aid of D.A. Papanastassiou. We also thank H. Ngo for analytical assistance and advice and Kurt Bostrom for his generous support during this study. In addition, we thank the SMHI (Swedish Meteorological Hydrological Institute) for allowing us to participate in the R.V. Argos cruises; the assistance and hospitality of both the SMHI scientific party and the crew on the Argos are greatly appreciated. We are also grateful for the comments of J.F. Minster and an anonymous reviewer, who contributed to substantial improvement of the manuscript. This work was supported by a grant from the Department of Energy (DEFG03-88ER13851 and the National Science Foundation (NSF OCE 9018534). Per S. Andersson was supported by a post-doctoral fellowship from the Swedish Natural Science Research Council (NFR G-PD 6331-300 and G-GU 6331-301). This is Division Contribution 5131(770).
Funding AgencyGrant Number
Department of Energy (DOE)DEFG03-88ER13851
NSFOCE 9018534
Swedish Natural Science Research CouncilNFR G-PD 6331-300
Swedish Natural Science Research CouncilG-GU 6331-301
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Other Numbering System NameOther Numbering System ID
Caltech Division of Geological and Planetary Sciences5131
Lunatic Asylum Lab770
Issue or Number:4
Record Number:CaltechAUTHORS:20131031-110528692
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Official Citation:Per S. Andersson, G.J. Wasserburg, Johan Ingri, The sources and transport of Sr and Nd isotopes in the Baltic Sea, Earth and Planetary Science Letters, Volume 113, Issue 4, November 1992, Pages 459-472, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:42155
Deposited By: Ruth Sustaita
Deposited On:31 Oct 2013 20:11
Last Modified:10 Nov 2021 16:19

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