<div><p> </p>
<p>Partition coefficient of 234Th, 233Pa, 210Pb, 210Po, and 7Be<br />
Activity concentrations of 234Th, 233Pa, 210Pb, 210Po, and 7Be were measured by gamma counting the 63.5, 312, 46.5, and 477.6 keV lines, respectively, on a Canberra ultra-highpurity germanium well-type detector. The 210Po activity was analyzed by liquid scintillation counting (Beckman Model 8100 Liquid Scintillation Counter). The filter samples (> 0.2 um particulate phase) were soaked with 1 mol L-1 HCl for 20 min in a counting vial, and the filtrate samples (< 0.2 um dissolved phase) were transferred into counting vials directly. Both filter and filtrate samples were then counted for activities of each radionuclide. All reported activities were decay and geometry corrected. 233Pa was added in equilibrium with 237Np. Under a wide range of environmental conditions, aqueous neptunium speciation is believed to be dominated by the pentavalent cation NpO2+. Np(V) is relative soluble and tends to remain in the water phase, unlike other actinides, such as Pu and Am, which are readily adsorbed by particles in the environment (Atwood 2013). In our absorption experiments, 237Np activities could be found only in the dissolved phase for all samples, supporting the assumption that 237Np would not adsorb onto particles during the time for which decay and in-growth corrections of 233Pa were applied. Traditional partition coefficients (Kd) between dissolved and particulate phases were used to quantify the sorption of radionuclides onto different particles in different experimental systems. Kd was defined here as</p>
<p>Kd = Ap x (Ad x Cp)^-1 (1)</p>
<p>where Ap and Ad represent particulate and dissolved activities (Bq L-1) of radionuclides and Cp is the particle concentration (kg L-1; Honeyman and Santschi 1989; Guo and Santschi 1997).</p></div>
Laboratory studies of radionuclides (234Th, 233Pa, 210Po, 210Pb, and 7Be) binding with fractions from cultured diatom, Phaeodactylum tricornutum
<div><p>Laboratory studies were conducted to examine the sorption of selected radionuclides (234Th, 233Pa, 210Po,<br />
210Pb, and 7Be) onto inorganic (pure silica and acid-cleaned diatom frustules) and organic (diatom cells with or<br />
without silica frustules) particles in natural seawater and the role of templating biomolecules and exopolymeric<br />
substances (EPS) extracted from the same species of diatom, Phaeodactylum tricornutum, in the sorption process.<br />
The range of partition coefficients (Kd, reported as logKd) of radionuclides between water and the different<br />
particle types was 4.78–6.69 for 234Th, 5.23–6.71 for 233Pa, 4.44–5.86 for 210Pb, 4.47–4.92 for 210Po, and 4.93–7.23 for 7Be, similar to values reported for lab and field determinations. The sorption of all radionuclides was<br />
significantly enhanced in the presence of organic matter associated with particles, resulting in Kd one to two<br />
orders of magnitude higher than for inorganic particles only, with highest values for 7Be (logKd of 7.2). Results<br />
further indicate that EPS and frustule-embedded biomolecules in diatom cells are responsible for the sorption<br />
enhancement rather than the silica shell itself. By separating radiolabeled EPS via isoelectric focusing, we found<br />
that isoelectric points are radionuclide specific, suggesting that each radionuclide binds to specific biopolymeric<br />
functional groups, with the most efficient binding sites likely occurring in acid polysaccharides, iron hydroxides,<br />
and proteins. Further progress in evaluating the effects of diatom frustule–related biopolymers on binding,<br />
scavenging, and fractionation of radionuclides would require the application of molecular-level characterization<br />
techniques.</p></div>
Log_Kd
<div><p>BCO-DMO Processing Notes:<br />
- added conventional header with dataset name, PI name, version date<br />
- modified parameter names to conform with BCO-DMO naming conventions<br />
- combined the two submitted tables together on the pH column, indicating percent activity and percent composition in the parameter names.</p>
<p> </p></div>
764664
Log_Kd
2019-04-10T13:32:05-04:00
2019-04-10T13:32:05-04:00
2023-07-07T16:10:26-04:00
urn:bcodmo:dataset:764664
Partition coefficient of 234Th, 233Pa, 210Pb, 210Po, and 7Be
Laboratory studies were conducted to examine the sorption of selected radionuclides (234Th, 233Pa, 210Po, 210Pb, and 7Be) onto inorganic (pure silica and acid-cleaned diatom frustules) and organic (diatom cells with or without silica frustules) particles in natural seawater and the role of templating biomolecules and exopolymeric substances (EPS) extracted from the same species of diatom, Phaeodactylum tricornutum, in the sorption process. The range of partition coefficients (Kd, reported as logKd) of radionuclides between water and the different particle types was 4.78–6.69 for 234Th, 5.23–6.71 for 233Pa, 4.44–5.86 for 210Pb, 4.47–4.92 for 210Po, and 4.93–7.23 for 7Be, similar to values reported for lab and field determinations. The sorption of all radionuclides was significantly enhanced in the presence of organic matter associated with particles, resulting in Kd one to two orders of magnitude higher than for inorganic particles only, with highest values for 7Be (logKd of 7.2). Results further indicate that EPS and frustule-embedded biomolecules in diatom cells are responsible for the sorption enhancement rather than the silica shell itself. By separating radiolabeled EPS via isoelectric focusing, we found that isoelectric points are radionuclide specific, suggesting that each radionuclide binds to specific biopolymeric functional groups, with the most efficient binding sites likely occurring in acid polysaccharides, iron hydroxides, and proteins. Further progress in evaluating the effects of diatom frustule–related biopolymers on binding, scavenging, and fractionation of radionuclides would require the application of molecular-level characterization techniques.
false
Santschi, P., Quigg, A., Schwehr, K., Xu, C. (2019) Partition coefficient of 234Th, 233Pa, 210Pb, 210Po, and 7Be. Biological and Chemical Oceanography Data Management Office (BCO-DMO). (Version 1) Version Date 2019-04-10 [if applicable, indicate subset used]. doi:10.1575/1912/bco-dmo.764664.1 [access date]
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10.1575/1912/bco-dmo.764664.1
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2019-04-10
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