Deep Sea Research Part II: Topical Studies in Oceanography
234Th and particle cycling in the central equatorial Pacific
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Cited by (57)
Seasonal variability in carbon:<sup>234</sup>thorium ratios of suspended and sinking particles in coastal Antarctic waters: Field data and modeling synthesis
2022, Deep-Sea Research Part I: Oceanographic Research PapersCitation Excerpt :However, such approaches are complicated by the multitude of factors – many of which are not typically measured by the biogeochemists who study 234Th – that influence C:234Th ratios. Indeed, existing models used to study particle-thorium dynamics do not even agree about whether first-order kinetics (i.e., thorium scavenging rates are independent of particle concentration, Dunne et al., 1997; Lerner et al., 2016) or second-order kinetics (i.e., thorium scavenging rates are linearly dependent on particle concentration, Resplandy et al., 2012; Stukel and Kelly, 2019) are most appropriate to model thorium adsorption onto particles. Few attempts have been made to incorporate other information, such as particle size spectra, phytoplankton community composition or physiological status, or zooplankton dynamics (despite the presumed importance of these and other parameters), because of a paucity of studies that have quantified their impact.
The Carbon:<sup>234</sup>Thorium ratios of sinking particles in the California current ecosystem 1: relationships with plankton ecosystem dynamics
2019, Marine ChemistryCitation Excerpt :However, there is also substantial uncertainty associated with our use of a simple steady-state, one-layer, two-box model, without aggregation processes mediated by colloidal particles. More complex models (e.g.Burd et al., 2007; Dunne et al., 1997) may more accurately explain 234Th-particle dynamics, but could not be constrained with our in situ data. Despite the simplicity of the model used in Eq. (3), the results (when computed using the median adsorption coefficient of k1, 0.013), showed good agreement to the measured data for predicted values of C:234Th < 15 μmol dpm−1 (Fig. 10b).
The carbon: <sup>234</sup>Thorium ratios of sinking particles in the California current ecosystem 2: Examination of a thorium sorption, desorption, and particle transport model
2019, Marine ChemistryCitation Excerpt :Multiple Th sorption models have been applied to marine systems (Savoye et al., 2006, and references therein). Dunne et al. (1997) used a series of coupled phytoplankton-particle-234Th models to investigate particle cycling in the Equatorial Pacific. They found that calculations of particle sorption were dependent on model assumptions about the processes driving remineralization and that 234Th was cycled between the particulate and dissolved phases multiple times prior to sinking from the euphotic zone.
Uranium-Thorium Radionuclides in Ocean Profiles
2019, Encyclopedia of Ocean Sciences, Third Edition: Volume 1-5Marine Microgels
2015, Biogeochemistry of Marine Dissolved Organic Matter: Second EditionParticle sinking dynamics and POC fluxes in the Eastern Tropical South Pacific based on <sup>234</sup>Th budgets and sediment trap deployments
2013, Deep-Sea Research Part I: Oceanographic Research PapersCitation Excerpt :They infer that this similarity indicates the >53 μm fraction dominates the sinking flux. However, it is important to note that results from sequential size fractionating in situ pump studies have also shown that particles from size classes<53 μm can have POC:234Th ratios that: are smaller than the >53 μm fraction (Maiti et al., 2008; Benitez-Nelson et al., 2001; Buesseler, 1998), are larger than the >53 μm fraction (Gustafsson et al., 2006; Bacon et al., 1996), or have no consistent correlation with particle size (Lepore et al., 2009; Dunne et al., 1997) or sinking speed (Stewart et al., 2007; Trull et al., 2008). Thus, sediment traps could potentially bias POC:234Th ratios of the truly sinking particulate in either direction.