Radiocesium reaction with illite and organic matter in marine sediment
Department of Chemistry, Kyungpook National University, Daikyū, Daegu, South Korea Marine Pollution Bulletin
(Impact Factor: 2.99).
06/2006; 52(6):659-65. DOI: 10.1016/j.marpolbul.2005.10.017
The mineralogical effect on the (137)Cs reaction with marine sediment has not been systematically studied yet, even though illite has been known to adsorb Cs preferentially on its frayed edge sites in a low Cs concentration. Ninety-three marine sediment samples were collected near Yangnam, Korea for quantitative X-ray-diffraction (XRD), gamma-ray, and total organic carbon (TOC) analysis. Illite content was in the range of 0-23 wt.% and those of (137)Cs and TOC were minimum detectable activity (MDA) approximately 7.19 Bq/kg-dry and approximately 3.32%, respectively. The illite content in the marine sediment showed a good relationship with the (137)Cs content (R(2)=0.69), but with an increase in the illite content, the relationship became less linear. This trend can be clearly shown in two groups of samples with different size fractions (< and >5Mdvarphi). For the samples of larger particle sizes (low contents of illite), the relationship is linear, but for the samples of the smaller particle sizes (high illite content) it is less linear with a decreased slope, indicating that increase in illite content does not significantly contribute to the fixation of (137)Cs in marine sediment. Rather, the TOC has a more linear relationship with (137)Cs content with no slope change in all particle size ranges. This may indicate that humic materials in marine sediment block the access of (137)Cs to the frayed edge site and reduces the adsorption of (137)Cs on illite and that the organic materials in marine sediment play more important roles in adsorbing Cs than illite.
Available from: Vladimir Maderich
- "It is worth noting that organic content in the shelf of Fukushima and Ibaraki Prefectures varies in the range of 0.1-25% (Otosaka and Kobayashi, 2013;Ambe et al., 2014;Ono et al., 2015). The preferential adsorption of 137 Cs on organic matter can be explained by the partial coverage of fine mineral sediment by organic substances and subsequent blocking of sorption (Kim et al., 2006;Ono et al., 2015). Comparison of the concentration of 137 Cs in the sediment and benthic invertebrates(Sohtome et al., 2014) and in the demersal fishes (Buesseler et al., 2012;Wada et al., 2013;Tateda et al., 2013) suggests that the continual ingestion of organic matter from sediments can be an important contamination pathway for all components of the benthic food web. "
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ABSTRACT: After the earthquake and tsunami on 11 March, 2011 damaged the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), an accidental release of a large amount of radioactive isotopes into both the air and the ocean occurred. Measurements provided by the Japanese agencies over the past four years show that elevated concentrations of 137Cs still remain in sediments, benthic organisms and demersal ﬁshes in the coastal zone around the FDNPP. These observations indicate that there are 137Cs transfer pathways from bottom sediments to the marine organisms. To describe the transfer quantitatively, the dynamic food chain model BURN has been extended to include benthic marine organisms. The extended model takes into account both pelagic and benthic marine organisms grouped into several classes based on their trophic level and type of species: phytoplankton, zooplankton, and ﬁshes (two types: piscivorous and non-piscivorous) for the pelagic food chain; deposit feeding invertebrates, demersal ﬁshes feeding by benthic invertebrates and bottom omnivorous predators for the benthic food chain; crustaceans, molluscs and coastal predators feeding on both pelagic and benthic organisms. Bottom invertebrates ingest organic parts of bottom sediments with adsorbed radionuclides which then migrate up through the food chain. All organisms take radionuclides directly from water as well as food. The model was implemented into the compartment model POSEIDON-R and applied to the Northwestern Paciﬁc for the period of 1945–2010 and then for the period of 2011–2020 to assess the radiological consequences of releases of 137Cs due to FDNPP accident. The model simulations for activity concentrations of 137Cs in both pelagic and benthic organisms in the coastal area around the FDNPP agree well with measurements for the period of 2011–2015. The decrease constant in the ﬁtted exponential function of simulated concentration for the deposit ingesting invertebrates (0.45 y–1) is close to the decrease constant for the sediment observations (0.44 y–1), indicating that the gradual decrease of activity in the demersal ﬁsh (decrease constant is 0.46 y–1) was caused by the transfer of activity from organic matter deposited in bottom sediment through the deposit feeding invertebrates. The estimated from model transfer coefﬁcient from bulk sediment to demersal ﬁsh in the model for 2012–2020 (0.13) is larger than that to the deposit feeding invertebrates (0.07) due to the biomagniﬁcation effect. In addition, the transfer of 137Cs through food webs for the period of 1945–2020 has been modelled for the Baltic Sea that was essentially contaminated due to global fallout and the Chernobyl accident. The model simulation results obtained with generic parameters are also in good agreement with available measurements in the Baltic Sea. Due to weak water exchange with the North Sea of the semi-enclosed Baltic Sea the chain of water-sediments- biota slowly evolves into a quasi-equilibrium state unlike the processes off the open Paciﬁc Ocean coast where the FDNPP is located. Obtained results demonstrate the importance of the benthic food chain in the long-term transfer of 137Cs from contaminated bottom sediments to marine organisms and the potential of a generic model for the use in different regions of the World Ocean.
Available from: Jennifer Coston-Guarini
- "Cs measured activities measured in Central Atlantic water (1.4 ± 0.2 mBq L −1 , n = 5; WOMARS, 2005) and considering that it will be exported to the deep ocean along the water column at low sedimentation rates (~ 0.5 to 4.4 cm ky −1 ), we infer that 137 Cs marine inputs will be insignificant in lobe sediments with respect to terrestrial inputs. Thus, for the core COL-C-CS-06, the significant positive correlation between OC and 137 Cs activity (R 2 = 0.5; p b 0.05; n = 38) suggests a continental source for particles and for OC associated to these particles and suggest that they were transported by the same physical (erosion, transport and deposition) processes to the lobe complex (Kim et al., 2006). "
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ABSTRACT: The terminal lobe complex of the Congo River submarine fan sits on the abyssal Atlantic plain, at 5000 m water depth, 760 km offshore from the river mouth estuarine area. While most rivers deliver particulate material to the continental shelf, particulate matter from the Congo River largely bypasses the shelf and is transported by turbidity currents through the Congo submarine canyon system. We determined the quantity and quality of the organic matter reaching the terminal lobe complex at five sites with marked morphological differences that may influence the distribution of organic matter. A suite of bulk geochemical (% OC, δ13Corg, δ15N, C: N), 137Cs and palynofacies analyses were done on cores collected from the terminal lobe area. These results were also compared to the composition of sediments collected upstream at the Malebo Pool (Congo River).
Available from: Qiaohui Fan
- "The decrease in RIP with increasing OM content can be attributed to the blocking effect of OM on the access of Cs þ to FES and interlayer sites; such blocking results in the high mobility and bioavailability of Cs þ in organic-rich environments (Rigol et al., 1998, 1999, 2002; Dumat and Staunton, 1999; Staunton et al., 2002; Kim et al., 2006; Fan et al., 2014). Kim et al. (2006) "
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ABSTRACT: This study examined the radiocesium (RCs) interception potential (RIP), cation exchange capacity (CEC), total organic carbon (TOC) content, and adsorption species in soils and minerals by using extended X-ray absorption fine structure (EXAFS) spectroscopy. The RIP related to Cs(+) adsorption by frayed-edge site (FES) has often been used to measure the mobility and bioavailability of RCs in the environment. This study found that the presence of organic matter (OM) can reduce RIP to a certain extent. The adsorption amount (=Q(T)) in soil was obviously correlated to RIP at a small [Cs(+)] region, whereas a linear relationship between Q(T) and CEC was observed at a large [Cs(+)] region. Both the inner-sphere (IS) and outer-sphere (OS) complexes of Cs(+) were observed through EXAFS at a molecular scale. The linear correlation between log (RIP/CEC) and the ratio of the coordination number (CN) of IS (=CNIS) and OS (=CNOS) complexes noted as CNIS/(CNIS + CNOS) suggested that the ratio of CN is very sensitive to Cs(+) adsorption species with variable RIP and CEC. The adsorption species of Cs(+) in soil was mainly dependent on the clay mineral content of soil. RIP was affected not only by FES but also by other strong adsorption sites, such as the interlayers and cavities identified as the IS complex in EXAFS analysis. Findings indicated that the EXAFS approach is a powerful and efficient tool to explore the behavior of Cs(+) in a given environment.
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