Molecular level characterization of diatom-associated biopolymers that bind super(234)Th, super(233)Pa, super(210)Pb, and super(7)Be in seawater: A case study with Phaeodactylum tricornutum

In order to investigate the importance of biogenic silica associated biopolymers on the scavenging of radionuclides, the diatom Phaeodactylum tricornutum was incubated together with the radionuclides super(234)Th, super(233)Pa, super(210)Pb, and super(7)Be during their growth phase. Normalized affin...

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Published in:Journal of geophysical research. Biogeosciences 2015-09, Vol.120 (9), p.1858-1869
Main Authors: Chuang, Chia-Ying, Santschi, Peter H, Xu, Chen, Jiang, Yuelu, Ho, Yi-Fang, Quigg, Antonietta, Guo, Laodong, Hatcher, Patrick G, Ayranov, Marin, Schumann, Dorothea
Format: Article
Language:English
Subjects:
Affinity
Bacillariophyceae
Biopolymers
Concerts
Ethylene
Geophysics
Magnetic resonance
Marine
Phaeodactylum tricornutum
Scavenging
Sea water
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Summary:In order to investigate the importance of biogenic silica associated biopolymers on the scavenging of radionuclides, the diatom Phaeodactylum tricornutum was incubated together with the radionuclides super(234)Th, super(233)Pa, super(210)Pb, and super(7)Be during their growth phase. Normalized affinity coefficients were determined for the radionuclides bound with different organic compound classes (i.e., proteins, total carbohydrates, uronic acids) in extracellular (nonattached and attached exopolymeric substances), intracellular (ethylene diamine tetraacetic acid and sodium dodecyl sulfate extractable), and frustule embedded biopolymeric fractions (BF). Results indicated that radionuclides were mostly concentrated in frustule BF. Among three measured organic components, Uronic acids showed the strongest affinities to all tested radionuclides. Confirmed by spectrophotometry and two-dimensional heteronuclear single quantum coherence-nuclear magnetic resonance analyses, the frustule BF were mainly composed of carboxyl-rich, aliphatic-phosphoproteins, which were likely responsible for the strong binding of many of the radionuclides. Results from this study provide evidence for selective absorption of radionuclides with different kinds of diatom-associated biopolymers acting in concert rather than as a single compound. This clearly indicates the importance of these diatom-related biopolymers, especially frustule biopolymers, in the scavenging and fractionation of radionuclides used as particle tracers in the ocean. Key Points * The interactions between diatom-associated biopolymers and radionuclides * The importance of frustule biopolymers in the scavenging of radionuclides * Nuclides sorption with biopolymers acting in concert rather than as a single compound
ISSN:2169-8953
2169-8961
DOI:10.1002/2015JG002970