Distribution and flux of <sup>226</sup>Ra and <sup>228</sup>Ra in the Amazon River estuary

Key, Robert M.; Stallard, Robert F.; Moore, Willard S.; Sarmiento, Jorge L.

doi:10.1029/jc090ic04p06995

Cited by 113 publications

(47 citation statements)

References 22 publications

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“…4b), in agreement with the results of Key et al (1985) for the Amazon. Apart from the two high values of the Ob River and the Lena River, the highest values are reached at a river water percentage of around 20%.…”

Section: The Estuarine Behaviour Of 228 Rasupporting

confidence: 90%

“…It is produced by 234 U in seawater and reaches its highest activities in deepsea sediments. As a consequence of parent distribution and of half life, the oceanographic distribution of 226 Ra (1600 years half-life) is primarily controlled by release from deep-sea sediments (Broecker et al, 1967), whereas the distribution of 228 Ra (5.8 years half-life) is characterized by the high activities that can be reached in the shallow water column over wide continental shelf areas (Moore, 1981;Key et al, 1985). 228 Ra is therefore used as a tracer for continental shelf influence in the open ocean (Moore et al, 1986(Moore et al, , 1995Moore, 1987;Li et al, 1980;Rutgers van der Loeff, 1994;Rutgers van der Loeff et al, 1995;Ku et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

“…Radium is strongly adsorbed on riverine sediment and released to the dissolved state at increasing ionic strength at mid-salinities (Li et al, 1977;Elsinger and Moore, 1980;Moore, 1981;Key et al, 1985). The riverine contribution to 226 Ra in the surface ocean may be as high as 30% (Li et al, 1977).…”

Section: Introductionmentioning

confidence: 99%

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228Ra and 226Ra in the Kara and Laptev seas

Loeff

Kühne

Wahsner

et al. 2003

Continental Shelf Research

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The surface water in the Transpolar Drift in the Arctic Ocean has a strong signature of 228 Ra. In an earlier study of 228 Ra in the open Arctic we showed that the major 228 Ra source had to be in the Siberian shelf seas, but only a single shelf station was published so far. Here we investigate the sources of this signal on the Siberian shelves by measurements of 228 Ra and 226 Ra in surface waters of the Kara and Laptev Sea, including the Ob, Yenisey and Lena estuaries.In the Ob and Lena rivers we found an indication for a very strong and unexpected removal of both isotopes in the early stage of estuarine mixing, presumably related to flocculation of organic-rich material. Whereas 226 Ra behaves conservatively on the shelf, the distribution of 228 Ra is governed by large inputs on the shelves, although sources are highly variable. In the Kara Sea the maximum activity was found in the Baydaratskaya Bay, where tidal resonance and low freshwater supply favour 228 Ra accumulation. The Laptev Sea is a stronger source for 228 Ra than the Kara Sea. Since a large part of Kara Sea water flows through the Laptev Sea, the 228 Ra signal in the Transpolar Drift can be described as originating on the Laptev shelf.The combined freshwater inputs from the Eurasian shelves thus produce a common radium signature with a 228 Ra/ 226 Ra activity ratio of 4.0 at 20% river water. The radium signals of the individual Siberian rivers and shelves cannot be separated, but their signal is significantly different from the signal produced on the Canadian shelf (Smith et al., in press). In this respect, the radium tracers add to the information given by Barium. Moreover, with the 5.8 year half-life of 228 Ra, they have the potential to serve as a tracer for the age of a water mass since its contact with the shelves. r

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Section: The Estuarine Behaviour Of 228 Rasupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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228Ra and 226Ra in the Kara and Laptev seas

Loeff

Kühne

Wahsner

et al. 2003

Continental Shelf Research

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“…Key et al 1985;Burnett et al 2006;Ku and Luo 2008). In freshwater, Ra tends to sorb to particles, whereas in seawater it is found primarily in the dissolved form (Li et al 1977).…”

Section: Introductionmentioning

confidence: 99%

228Ra, 226Ra, 224Ra and 223Ra in potential sources and sinks of land-derived material in the German Bight of the North Sea: implications for the use of radium as a tracer

et al. 2011

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“…The 228Ra/226Ra activity ratio may be used as a tracer of fiver water [Moore et al, 1986]. The technique makes use of the differing chemical behavior and half-lives of the two radium isotopes and is described by Key et al [1985] and Moore and Todd [1993].…”

Section: Methodsmentioning

confidence: 99%