Dissolution of particle‐reactive radionuclides in deposit‐feeder digestive fluids

Shull, David H.; Mayer, Lawrence M.

doi:10.4319/lo.2002.47.5.1530

Cited by 13 publications

(5 citation statements)

References 18 publications

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“…However, it should be pointed out that the TSM-K d correlation given by Honeyman et al (1988) and Luo et al (1995) resulted in a K d value almost two orders of magnitude higher at 1 g L -1 TSM level. A lower K d in the nearshore environment than the extrapolated value based on the TSM-K d relationship obtained from the open ocean, may be a result of the lower affinity of 234 Th for the terrestrial clay mineral than algal detritus (Shull and Meyer, 2002). Here we propose a more appropriate TSM-K d correlation (n = 73, r 2 = 0.51) for the turbid nearshore water: logK d = 6.06-0.95 logTSM.…”

Section: Th Partitioning Between Particles and Watermentioning

confidence: 77%

Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

et al. 2009

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Dissolved and particulate 234 Th activities in surface seawater were determined at 27 stations along the coastline of western Taiwan during 19-23 November 2004. Contrasting scavenging settings were observed between the northern and southern regimes of the nearshore water off western Taiwan, separated by the Cho-Shui River. The northern regime is characterized by a large quantity of suspended load contributed by northward transport of a suspension plume from the Cho-Shui River, while the southern regime, low in suspended load and high in chlorophyll concentration, is a system controlled by biological activity. A scavenging model that takes account of the physical transport was used to estimate the 234 Th budget in order to estimate the scavenging and removal rates from the nearshore water. The scavenging and removal rates ranged from 21 to 127 dpm m -3 d -1 and from 36 to 525 dpm m -3 d -1 , for dissolved and particulate 234 Th, respectively. The removal fluxes of particulate organic carbon (POC) and particulate organic nitrogen (PON) were estimated by multiplying the particulate 234 Th removal flux to the organic carbon/ 234 Th and nitrogen/ 234 Th ratios in suspended particles, which ranged from 4.5 to 275.2 mmol-C m -2 d -1 and from 1.3 to 50.1 mmol-N m -2 d -1 , respectively. These fluxes resulted in residence times of 1~20 days for the POC in the surface water of nearshore water off western Taiwan.mechanism of scavenging and removal processes by which particle-reactive elements are scavenged and removed.The coastal waters of western Taiwan are subject to the influence of four major river systems, characterized by their high suspended loads from high denudation rates of western Taiwan (Dadson et al., 2003). From the north to the south of western Taiwan, the Dan-Shui River (DSR) receives large amounts of sewage effluent discharged from metropolitan Taipei and is severely threatened by environmental degradation (Wen et al., 2008); the Cho-Shui River (CSR) is laden with the highest particulate matter concentration among all rivers of Taiwan; the Jen-Wen River (JWR) is known for its barrier islands and lagoon settings (Liu et al., 2000); and the southernmost Kao-Pin River (KPR) collects the municipal sewage effluents discharged from Kaohsiung, the second largest city of Taiwan, and serves as the major source of fluvial sediments in the shelf-slope region off southwestern Taiwan (Kao et al., 2006).The naturally-occurring isotope 234 Th (t 1/2 = 24.1 days) is one of the most particle-reactive elements with a particle-water distribution coefficient (i.e. K d , the ratio

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Section: Th Partitioning Between Particles and Watermentioning

confidence: 77%

Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

et al. 2009

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“…Compared with Pt, therefore, Pd is more bioavailable (at least indirectly) in GCC particles but less available when added as a solute. These observations require that (i) Pd mobilized from sediment under simulated gastric conditions is largely unavailable for assimilation, perhaps through exceptionally strong complexation with amino acids (21) or readsorption to digested particles (25), and (ii) Pd in GCC undergoes greater mobilization than Pt in estuarine water. The former effect is, qualitatively, consistent with the proposed stabilizing effect of aqueous exudates on Pd behavior in the absence of sediment (Figure 3), while the latter effect concurs with the greater environmental solubility of catalytic Pd (1).…”

Section: Resultsmentioning

confidence: 99%

Mobilization, Adsorption, and Bioavailability of Pt and Pd in Coastal Sediments: The Role of the Polychaete, Arenicola marina

French

Turner²

2008

Environ. Sci. Technol.

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The biogeochemical behavior of Pt and Pd in coastal sediments has been examined in a series of microcosms, both in the presence and absence of the deposit-feeding invertebrate, Arenicola marina. When metals were introduced to the overlying water column as solutes from acidified standards, A. marina dramatically enhanced their sorption to sediment throughout the core depth (14 cm) compared with an unfaunated control by exposing a greater surface area of particles to more rapidly ventilating contaminated water. After a 10 day incubation period, the assimilation efficiency (AE) by A. marina was about 10% for Pt and 1% for Pd. Calculations based on either partition constants or operational measures of metal bioaccessibility in sediment (using the protein, BSA) suggested that both aqueous and dietary sources of metal were important When Pt and Pd were introduced to the sediment-water interface as components of ground catalytic converter particles, significant subduction was effected by A. marina, and metals were solubilized to a greater extent than in an unfaunated control. AE in these experiments was < 0.1% for Pt and about 1% for Pd, and the most important vector for assimilation appeared to be from the aqueous phase via partial solubilization of metal from catalytic material. The findings of this study improve our understanding of the availability, cycling, and fate of Pt and Pd in contaminated estuaries and coastal waters.

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“…No reduction in 210 Pb-based particle mixing rates (per unit volume) was observed within (0.15 cm 2 yr Ϫ1 to 2.9 cm 2 yr Ϫ1 ) compared with that beneath the Oman margin OMZ (1.1 Ϯ 0.62 cm 2 yr Ϫ1 ), but the edge station (0.52 ml l Ϫ1 O 2 ) had an unusually high value (40 cm 2 yr Ϫ1 ) (Smith et al 2000). A longer-lived tracer (Pb-210) was used in this study than in the Peru study and it may be tracking lower quality organic matter (Smith et al 1993) or may have different particle reactivities (Shull & Mayer 2002). The reduced mixed-layer depth without a change in overall mixing intensity suggests that the Oman OMZ sediments must experience only half the bioturbation energy of the oxygenated slope sediments (Smith et al 2000).…”

Section: Ecosystem-level Responses To Omz Conditions Bioturbation and Animal Lifestylesmentioning

confidence: 95%

Oxygen Minimum Zone Benthos: Adaptation and Community Response to Hypoxia

Levin

2003

Oceanography and Marine Biology, an Annual Review, Volume 41

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Mid-water oxygen minima (Ͻ0.5 ml l Ϫ1 dissolved O 2 ) intercept the continental margins along much of the eastern Pacific Ocean, off west Africa and in the Arabian Sea and Bay of Bengal, creating extensive stretches of sea floor exposed to permanent, severe oxygen depletion. These seafloor oxygen minimum zones (OMZs) typically occur at bathyal depths between 200 m and 1000 m, and are major sites of carbon burial along the continental margins. Despite extreme oxygen depletion, protozoan and metazoan assemblages thrive in these environments. Metazoan adaptations include small, thin bodies, enhanced respiratory surface area, blood pigments such as haemoglobin, biogenic structure formation for stability in soupy sediments, an increased number of pyruvate oxidoreductases, and the presence of sulphide-oxidising symbionts. The organic-rich sediments of these regions often support mats of large sulphideoxidising bacteria (Thioploca, Beggiatoa, Thiomargarita), and high-density, low-diversity metazoan assemblages. Densities of protistan and metazoan meiofauna are typically elevated in OMZs, probably due to high tolerance of hypoxia, an abundant food supply, and release from predation. Macrofauna and megafauna often exhibit dense aggregations at OMZ edges, but depressed densities and low diversity in the OMZ core, where oxygen concentration is lowest. Taxa most tolerant of severe oxygen depletion (Ͻ0.2 ml l Ϫ1 ) in seafloor OMZs include calcareous foraminiferans, nematodes, and annelids. Agglutinated protozoans, harpacticoid copepods, and calcified invertebrates are typically less tolerant. High dominance and relatively low species richness are exhibited by foraminiferans, metazoan meiofauna, and macrofauna within OMZs. At dissolved oxygen concentrations below 0.15 ml l Ϫ1 , bioturbation is reduced, the mixed layer is shallow, and chemosynthesis-based nutrition (via heterotrophy and symbiosis) becomes important.OMZs represent a major oceanographic boundary for many species. As they expand and contract over geological time, OMZs may influence genetic diversity and play a key role in the evolution of species at bathyal depths. These ecosystems may preview the types of adaptations, species, and processes that will prevail with increasing hypoxia over ecological and evolutionary time. However, many questions remain unanswered concerning controls on faunal standing stocks in OMZs, and the physiological, enzymatic, metabolic, reproductive and molecular adaptations that permit benthic animals to live in OMZs. As global warming and eutrophication reduce oxygenation of the world ocean, there is a pressing need to understand the functional consequences of oxygen depletion in marine ecosystems.

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Dissolution of particle‐reactive radionuclides in deposit‐feeder digestive fluids

Cited by 13 publications

References 18 publications

Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

Nearshore scavenging phenomenon elucidated by 234th/238u disequilibrium in the coastal waters off Western Taiwan

Mobilization, Adsorption, and Bioavailability of Pt and Pd in Coastal Sediments: The Role of the Polychaete, Arenicola marina

Oxygen Minimum Zone Benthos: Adaptation and Community Response to Hypoxia

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