Binding of Th, Pa, Pb, Po and Be radionuclides to marine colloidal macromolecular organic matter Academic Article

abstract

• 2014 Elsevier B.V. To study the binding mechanisms of radionuclides to organic moieties in colloidal organic matter (COM), marine colloids (1kDa-0.2m) were isolated by cross-flow ultrafiltration from seawater of the west Pacific Ocean and the northern Gulf of Mexico. For the same purpose, exopolymeric substances (EPS) produced by laboratory-cultured diatoms were collected as well. In our study areas, colloidal organic carbon (COC) concentrations ranged from 6.5 to 202g-C/L in the Pacific Ocean, and were 808g-C/L in the Gulf of Mexico. The COM compositions (organic carbon, organic nitrogen, proteins, total hydrolysable amino acids, total polysaccharides, uronic acids, hydroxamate siderophores, hydroquinone) were quantified to examine the relationships between partition coefficients (Kc) of five different radionuclides, ²³⁴Th, ²³³Pa, ²¹⁰Pb, ²¹⁰Po and ⁷Be, and concentration ratios to COC of individual chelating biomolecules that could potentially act as a chelating moiety. The range of partition coefficients (Kc, reported as logKc) of radionuclides between water and the different colloidal materials was 5.12 to 5.85 for ²³⁴Th, 5.19 to 6.01 for ²³³Pa, 4.21 to 4.85 for ²¹⁰Pb, 4.87 to 5.68 for ²¹⁰Po, and 4.49 to 4.92 for ⁷Be, similar to values previously reported for lab and field determinations under different particle concentrations. While any relationship obtained between Kc and abundance of specific moieties could not be taken as proving the existence of colloidal organic binding ligands for the different radionuclides, it could suggest possible organic moieties involved in the scavenging of these natural radionuclides. Together with results from isoelectric focusing of radiolabeled COM, we conclude that binding to different biomolecules is nuclide-specific, with colloidal hydroxamate siderophoric moieties being important for the binding of Th and Pa radionuclides. Hydroquinones/quinone (HQ/Q) facilitated redox and chelation reactions seem to be involved in the binding of Pa and Be. However, the actual mechanisms are not clear. Individual amino acids, proteins, total polysaccharides and uronic acids did not yield significant relationships with logKc values of the different radionuclides. Nonetheless, our results provide new insights into the relative importance of different potential ligand moieties in COM in the binding and possible scavenging of specific radionuclides in the ocean.
• © 2014 Elsevier B.V. To study the binding mechanisms of radionuclides to organic moieties in colloidal organic matter (COM), marine colloids (1kDa-0.2μm) were isolated by cross-flow ultrafiltration from seawater of the west Pacific Ocean and the northern Gulf of Mexico. For the same purpose, exopolymeric substances (EPS) produced by laboratory-cultured diatoms were collected as well. In our study areas, colloidal organic carbon (COC) concentrations ranged from 6.5 to 202μg-C/L in the Pacific Ocean, and were 808μg-C/L in the Gulf of Mexico. The COM compositions (organic carbon, organic nitrogen, proteins, total hydrolysable amino acids, total polysaccharides, uronic acids, hydroxamate siderophores, hydroquinone) were quantified to examine the relationships between partition coefficients (Kc) of five different radionuclides, ²³⁴Th, ²³³Pa, ²¹⁰Pb, ²¹⁰Po and ⁷Be, and concentration ratios to COC of individual chelating biomolecules that could potentially act as a chelating moiety. The range of partition coefficients (Kc, reported as logKc) of radionuclides between water and the different colloidal materials was 5.12 to 5.85 for ²³⁴Th, 5.19 to 6.01 for ²³³Pa, 4.21 to 4.85 for ²¹⁰Pb, 4.87 to 5.68 for ²¹⁰Po, and 4.49 to 4.92 for ⁷Be, similar to values previously reported for lab and field determinations under different particle concentrations. While any relationship obtained between Kc and abundance of specific moieties could not be taken as proving the existence of colloidal organic binding ligands for the different radionuclides, it could suggest possible organic moieties involved in the scavenging of these natural radionuclides. Together with results from isoelectric focusing of radiolabeled COM, we conclude that binding to different biomolecules is nuclide-specific, with colloidal hydroxamate siderophoric moieties being important for the binding of Th and Pa radionuclides. Hydroquinones/quinone (HQ/Q) facilitated redox and chelation reactions seem to be involved in the binding of Pa and Be. However, the actual mechanisms are not clear. Individual amino acids, proteins, total polysaccharides and uronic acids did not yield significant relationships with logKc values of the different radionuclides. Nonetheless, our results provide new insights into the relative importance of different potential ligand moieties in COM in the binding and possible scavenging of specific radionuclides in the ocean.

authors

• Quigg, Antonietta
• Santschi, Peter
• Schwehr, Kathleen

published proceedings

• MARINE CHEMISTRY

author list (cited authors)

• Chuang, C., Santschi, P. H., Wen, L., Guo, L., Xu, C., Zhang, S., ... Schumann, D.

citation count

• 37

complete list of authors

• Chuang, Chia-Ying||Santschi, Peter H||Wen, Liang-Saw||Guo, Laodong||Xu, Chen||Zhang, Saijin||Jiang, Yuelu||Ho, Yi-Fang||Schwehr, Kathleen A||Quigg, Antonietta||Hung, Chin-Chang||Ayranov, Marin||Schumann, Dorothea

publication date

• July 2015

publisher

• Elsevier  Publisher
• Elsevier BV  Publisher

published in

• Marine Chemistry  Journal

keywords

• Beryllium
• Colloidal Hydroxamate Siderophoric Moieties
• Exopolymeric Substances
• Lead
• Marine Colloids
• Particle Reactive Radionuclides
• Polonium
• Protactinium
• Thorium

Digital Object Identifier (DOI)

• 10.1016/j.marchem.2014.10.014

start page

• 320

end page

• 329

volume

• 173