The influence of particle composition on Thorium scavenging in the Mediterranean Sea

Roy‐Barman, Matthieu; Lemaître, C.; Ayrault, Sophie; Jeandel, Catherine; Souhaut, Marc; Miquel, Juan Carlos

doi:10.1016/j.epsl.2009.07.018

Cited by 48 publications

(22 citation statements)

References 62 publications

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“…The role of SPM composition in TEI scavenging has been studied for the naturally occurring, strongly particle-reactive thorium isotopes ( 234 Th, 228 Th, and 230 Th), but there is not yet consensus over which phase exerts the most influence in scavenging. It has been variously proposed that the scavenging efficiency of 230 Th is controlled by CaCO 3 (Chase et al, 2002(Chase et al, , 2003, lithogenic material (Luo and Ku, 2004;Roy-Barman et al, 2009), and/ or Mn oxyhydroxides (Roy-Barman et al, 2005). All of these studies were conducted on sinking particles collected by sediment traps, where the identification of a single controlling factor can be confounded by fortuitous correlations between multiple factors (e. g., CaCO 3 and MnO 2 Roy- Barman et al, 2005), and may help explain the contradictory conclusions reached by various studies (Jeandel et al, in press;Roy-Barman et al, 2005).…”

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confidence: 99%

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Lam

Ohnemus

Auro

2015

Deep Sea Research Part II: Topical Studies in Oceanography

147

148

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Opal Biogenic silica POC Ballast Dust Lithogenic material a b s t r a c tThe concentration and the major phase composition (particulate organic matter, CaCO 3 , opal, lithogenic matter, and iron and manganese oxyhydroxides) of marine particles is thought to determine the scavenging removal of particle-reactive TEIs. Particles are also the vector for transferring carbon from the atmosphere to the deep ocean via the biological carbon pump, and their composition may determine the efficiency and strength of this transfer. Here, we present the first full ocean depth section of sizefractionated (1-51 mm, 4 51 mm) suspended particulate matter (SPM) concentration and major phase composition from the US GEOTRACES North Atlantic Zonal Transect between Woods Hole, MA and Lisbon, Portugal conducted in 2010 and 2011. Several major particle features are notable in the section: intense benthic nepheloid layers were observed in the western North American margin with concentrations of SPM of up to 1648 mg/L, two to three orders of magnitude higher than surrounding waters, that were dominated by lithogenic material. A more moderate benthic nepheloid layer was also observed in the eastern Mauritanian margin (44 mg/L) that had a lower lithogenic content and, notably, significant concentrations of iron and manganese oxyhydroxides (2.5% each). An intermediate nepheloid layer reaching 102 mg/L, an order of magnitude above surrounding waters, was observed associated with the Mediterranean Outflow. Finally, there was a factor of two enhancement in SPM at the TAG hydrothermal plume due almost entirely to the addition of iron oxyhydroxides from the hydrothermal vent. We observe correlations between POC and CaCO 3 in large (4 51 mm) particles in the upper 2000 m, but not deeper than 2000 m, and no correlations between POC and CaCO 3 at any depth in small ( o51 mm) particles. There were also no correlations between POC and lithogenic material in large particles. Overall, there were very large uncertainties associated with all regression coefficients for mineral ballast ("carrying coefficients"), suggesting that mineral ballast was not a strong predictor for POC in this section.

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confidence: 99%

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Lam

Ohnemus

Auro

2015

Deep Sea Research Part II: Topical Studies in Oceanography

147

148

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“…Changing proportions of particle types over geologic time may overprint other influences on the Pa/Th sediment record such as the AMOC. While previous work has demonstrated a particle composition effect on Pa/Th scavenging, there is still debate about what are the major carrier phases (Chase and Anderson, 2004;Chuang et al, 2013;Luo and Ku, 2004;Roy-Barman et al, 2009) and the importance of chemical fractionation during scavenging on basin-wide radionuclide budgets (Hayes et al, 2014;Lippold et al, 2012;Luo et al, 2010;Siddall et al, 2007). Here we present measurements of dissolved and particulate (adsorbed) 230 Th and 231 Pa from the U. S. GEOTRACES North Atlantic transect in conjunction with measurements of the mass concentration and major chemical composition of the suspended particles.…”

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confidence: 99%

Intensity of Th and Pa scavenging partitioned by particle chemistry in the North Atlantic Ocean

et al. 2015

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The natural radionuclides 231 Pa and 230 Th are incorporated into the marine sediment record by scavenging, or adsorption to various particle types, via chemical reactions that are not fully understood. Because these isotopes have potential value in tracing several oceanographic processes, we investigate the nature of scavenging using trans-Atlantic measurements of dissolved (<0.45 µm) and particulate (0.8-51 µm) 231 Pa and 230 Th, together with major particle composition. We find widespread impact of intense scavenging by authigenic Fe/Mn (hydr)oxides, in the form of hydrothermal particles emanating from the Mid-Atlantic ridge and particles resuspended from reducing conditions near the seafloor off the coast of West Africa.Biogenic opal was not found to be a significant scavenging phase for either element in this sample set, essentially because of its low abundance and small dynamic range at the studied sites. Distribution coefficients in shallow (< 200 m) depths are anomalously low which suggests either the unexpected result of a low scavenging intensity for organic matter or that, in water masses containing abundant organic-rich particles, a greater percentage of radionuclides exist in the colloidal or complexed phase. In addition to particle concentration, the oceanic distribution of particle types likely plays a significant role in the ultimate distribution of sedimentary 230 Th and 231 Pa.4

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“…In reality, the distribution of 230 Th depends also on variations in the flow field and resulting changes in nutrient availability, and consequently changes in particle production as well as flux. Also the effect of boundary scavenging (Anderson et al, 1983;Roy-Barman et al, 2009), i.e. the transport of dissolved 230 Th from areas of low particle concentrations to those with high particle concentrations (especially at ocean margins 15 at shelf seas) is not spatially resolved in our model.…”

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confidence: 93%

The potential of <sup>230</sup>Th for detection of ocean acidification impacts on pelagic carbonate production

Heinze¹,

Ilyina²,

Gehlen³

2017

Preprint

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Abstract. Concentrations of dissolved230 Th in the ocean water column increase with depth due to scavenging 10 and downward particle flux. Due to the 230 Th scavenging process, any change in the calcium carbonate (CaCO 3 ) fraction of the marine particle flux due to changes in biological CaCO 3 hard shell production as a consequence of progressing ocean acidification would be reflected in the dissolved

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The influence of particle composition on Thorium scavenging in the Mediterranean Sea

Abstract: International audienc

Cited by 48 publications

References 62 publications

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Intensity of Th and Pa scavenging partitioned by particle chemistry in the North Atlantic Ocean

The potential of <sup>230</sup>Th for detection of ocean acidification impacts on pelagic carbonate production

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The influence of particle composition on Thorium scavenging in the Mediterranean Sea

Abstract: International audienc

Cited by 48 publications

References 62 publications

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Size-fractionated major particle composition and concentrations from the US GEOTRACES North Atlantic Zonal Transect

Intensity of Th and Pa scavenging partitioned by particle chemistry in the North Atlantic Ocean

The potential of &lt;sup&gt;230&lt;/sup&gt;Th for detection of ocean acidification impacts on pelagic carbonate production

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The potential of <sup>230</sup>Th for detection of ocean acidification impacts on pelagic carbonate production