228Ra/226Ra and 226Ra/Ba ratios in the Western Mediterranean Sea: Barite formation and transport in the water column

Beek, Pieter van; Sternberg, E.; Reyss, Jean-Louis; Souhaut, Marc; Robin, Éric; Jeandel, Catherine

doi:10.1016/j.gca.2009.05.063

Cited by 26 publications

(39 citation statements)

References 74 publications

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“…At 15 of the 78 stations completed during the GA01 cruise, up to 22 discrete 10 L seawater samples were collected through the water column from Niskin bottles. Due to gravity, the seawater samples passed through 10 g of acrylic fibers impregnated with MnO 2 (called "Mn fibers"), which quantitatively adsorb radium isotopes (assumed to scavenge 100 % of Ra;van Beek et al, 2010;Moore and Reid, 1973). High-resolution vertical profiles of 226 Ra were thus built to provide a detailed 226 Ra section.…”

Section: Sample Collectionmentioning

confidence: 99%

“…High-resolution vertical profiles of 226 Ra were thus built to provide a detailed 226 Ra section. The samples were unfiltered since particulate 226 Ra activities are typically 2 orders of magnitude lower than the dissolved 226 Ra activities (van Beek et al, 2007(van Beek et al, , 2009. From the same Niskin bottles, 15 mL was collected to determine the Ba concentration, so that Ba and 226 Ra analyses were conducted from the same initial sample, which allows us to investigate the 226 Ra / Ba ratio in the samples.…”

Section: Sample Collectionmentioning

confidence: 99%

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The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

et al. 2018

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Abstract. We report detailed sections of radium-226 (226Ra, T1∕2 =  1602 years) activities and barium (Ba) concentrations determined in the North Atlantic (Portugal–Greenland–Canada) in the framework of the international GEOTRACES program (GA01 section – GEOVIDE project, May–July 2014). Dissolved 226Ra and Ba are strongly correlated along the section, a pattern that may reflect their similar chemical behavior. Because 226Ra and Ba have been widely used as tracers of water masses and ocean mixing, we investigated their behavior more thoroughly in this crucial region for thermohaline circulation, taking advantage of the contrasting biogeochemical patterns existing along the GA01 section. We used an optimum multiparameter (OMP) analysis to distinguish the relative importance of physical transport (water mass mixing) from nonconservative processes (sedimentary, river or hydrothermal inputs, uptake by particles and dissolved–particulate dynamics) on the 226Ra and Ba distributions in the North Atlantic. Results show that the measured 226Ra and Ba concentrations can be explained by conservative mixing for 58 and 65 % of the samples, respectively, notably at intermediate depth, away from the ocean interfaces. 226Ra and Ba can thus be considered conservative tracers of water mass transport in the ocean interior on the space scales considered here, namely, on the order of a few thousand kilometers. However, regions in which 226Ra and Ba displayed nonconservative behavior and in some cases decoupled behaviors were also identified, mostly at the ocean boundaries (seafloor, continental margins and surface waters). Elevated 226Ra and Ba concentrations found in deepwater in the West European Basin suggest that lower Northeast Atlantic Deep Water (NEADWl) accumulates 226Ra and Ba from sediment diffusion and/or particle dissolution during transport. In the upper 1500 m of the West European Basin, deficiencies in 226Ra and Ba are likely explained by their incorporation in planktonic calcareous and siliceous shells, or in barite (BaSO4) by substitution or adsorption mechanisms. Finally, because Ba and 226Ra display different source terms (mostly deep-sea sediments for 226Ra and rivers for Ba), strong decoupling between 226Ra and Ba were observed at the land–ocean boundaries. This is especially true in the shallow stations near the coasts of Greenland and Newfoundland where high 226Ra ∕ Ba ratios at depth reflect the diffusion of 226Ra from sediment and low 226Ra ∕ Ba ratios in the upper water column reflect the input of Ba associated with meteoric waters.

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Section: Sample Collectionmentioning

confidence: 99%

Section: Sample Collectionmentioning

confidence: 99%

The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

et al. 2018

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“…Depletions of [Ba] sw in the upper mixed layer are a result of adsorption/absorption of Ba onto organic particulates (Cardinal et al, 2005;Collier and Edmond, 1984;Hoppema et al, 2010;Jacquet et al, 2008Jacquet et al, , 2007Sternberg et al, 2005). Ba is also removed from deeper waters (100-1000 m) as a result of barite formation in and around aggregates of sinking organic matter, and is released back into the water column following remineralisation (Bishop, 1988;Cardinal et al, 2005;Dehairs et al, 1980;Dymond et al, 1992;Ganeshram et al, 2003;Jacquet et al, 2007;Stroobants et al, 1991;van Beek et al, 2009). Collectively, these effects cause the deep ocean to be enriched in [Ba] sw relative to the surface.…”

Section: Introductionmentioning

confidence: 99%

Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration

et al. 2018

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Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration. Chemge (2018), Abstract Biological productivity and ocean circulation are both important oceanographic variables that control the distribution of dissolved barium in the ocean interior ([Ba] sw ). The ability to accurately reconstruct [Ba] sw will provide key constraints on these processes in the past. The geochemistry of cold-water corals has the potential to unlock paleoceanographic records at spatial and temporal resolutions not available using other sedimentary archives. Previous studies have suggested that the Ba/Ca ratio of coral skeletons is linearly related to [Ba] sw .However, these efforts have used a limited number of species, sparse global seawater databases, or have not explicitly measured the Ba/Ca ratio. Here we investigate the Ba/Ca ratio in a well-constrained set of cold-water scleractinian (aragonitic) corals as a proxy for[Ba] sw , using 58 specimens from 7 coral genera along with co-located measurements of [Ba] sw . We find that traditional chemical cleaning procedures do not significantly affect the Ba/Ca ratio of cold-water coral skeletons, allowing rapid sample throughput. We also determine that intra-sample variation in Ba/Ca ratios can be reduced by using larger sample sizes (e.g. 20 mg). By combining our results with existing data, we find that cold-water coral Ba/Ca is linearly related to [Ba] sw according to the relationship: Ba/Ca µmol/mol = [0.15 ± 0.02] [Ba sw nmol/kg] + [2.5 ± 1.4], (R 2 = 0.7). We observe no species-specific 'vital effects' in cold-water coral Ba/Ca ratios, but site-specific effects could be a factor. Nevertheless, our results highlight the potential of Ba/Ca in cold-water corals to reconstruct biological and physical changes in the ocean interior.

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“…The presence of barite micro‐crystals in oceanic suspended particulate matter is quite ubiquitous, despite the fact that most ocean waters are undersaturated with respect to this mineral [ Monnin et al , 1999]. Several hypotheses have been proposed to explain this conundrum [e.g., Bishop , 1988; Dehairs et al , 1997; Sternberg et al , 2005, 2008; van Beek et al , 2009], most of which call upon biological processes including respiratory activity in the mesopelagic layer [ Dehairs et al , 1992]. A detailed review of these hypotheses is discussed by Sternberg et al [2007], and Jacquet et al [2011] summarize these by reporting that barite precipitates in supersaturated microenvironments during the bacterial degradation of sinking organic matter.…”

Section: Introductionmentioning

confidence: 99%

Barium and carbon fluxes in the Canadian Arctic Archipelago

et al. 2011

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[1] The seasonal and spatial variability of dissolved Barium (Ba) in the Amundsen Gulf, southeastern Beaufort Sea, was monitored over a full year from September 2007 to September 2008. Dissolved Ba displays a nutrient-type behavior: the maximum water column concentration is located below the surface layer. The highest Ba concentrations are typically observed at river mouths, the lowest concentrations are found in water masses of Atlantic origin. Barium concentrations decrease eastward through the Canadian Arctic Archipelago. Barite (BaSO 4 ) saturation is reached at the maximum dissolved Ba concentrations in the subsurface layer, whereas the rest of the water column is undersaturated. A three end-member mixing model comprising freshwater from sea-ice melt and rivers, as well as upper halocline water, is used to establish their relative contributions to the Ba concentrations in the upper water column of the Amundsen Gulf. Based on water column and riverine Ba contributions, we assess the depletion of dissolved Ba by formation and sinking of biologically bound Ba (bio-Ba), from which we derive an estimate of the carbon export production. In the upper 50 m of the water column of the Amundsen Gulf, riverine Ba accounts for up to 15% of the available dissolved Ba inventory, of which up to 20% is depleted by bio-Ba formation and export. Since riverine inputs and Ba export occur concurrently, the seasonal variability of dissolved Ba in the upper water column is moderate. Assuming a fixed organic carbon to bio-Ba flux ratio, carbon export out of the surface layer is estimated at 1.8 ± 0.45 mol C m −2 yr −1. Finally, we propose a climatological carbon budget for the Amundsen Gulf based on recent literature data and our findings, the latter bridging the surface and subsurface water carbon cycles.

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228Ra/226Ra and 226Ra/Ba ratios in the Western Mediterranean Sea: Barite formation and transport in the water column

Cited by 26 publications

References 74 publications

The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration

Barium and carbon fluxes in the Canadian Arctic Archipelago

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228Ra/226Ra and 226Ra/Ba ratios in the Western Mediterranean Sea: Barite formation and transport in the water column

Cited by 26 publications

References 74 publications

The &lt;sup&gt;226&lt;/sup&gt;Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

The &lt;sup&gt;226&lt;/sup&gt;Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

Extended calibration of cold-water coral Ba/Ca using multiple genera and co-located measurements of dissolved barium concentration

Barium and carbon fluxes in the Canadian Arctic Archipelago

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Resources

About

The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01

The <sup>226</sup>Ra–Ba relationship in the North Atlantic during GEOTRACES-GA01