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| Titel |
Quantification of octacalcium phosphate, authigenic apatite and detrital apatite in coastal sediments using differential dissolution and standard addition |
| VerfasserIn |
J. F. Oxmann, L. Schwendenmann |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 10, no. 3 ; Nr. 10, no. 3 (2014-06-30), S.571-585 |
| Datensatznummer |
250117010
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| Publikation (Nr.) |
 copernicus.org/os-10-571-2014.pdf |
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| Zusammenfassung |
| Knowledge of calcium phosphate (Ca-P) solubility is crucial for
understanding temporal and spatial variations of phosphorus (P)
concentrations in water bodies and sedimentary reservoirs. In situ relationships
between liquid- and solid-phase levels cannot be fully explained by dissolved
analytes alone and need to be verified by determining particular sediment P
species. Lack of quantification methods for these species limits the
knowledge of the P cycle. To address this issue, we (i) optimized a
specifically developed conversion–extraction (CONVEX) method for P species
quantification using standard additions, and (ii) simultaneously determined
solubilities of Ca-P standards by measuring their pH-dependent contents in
the sediment matrix. Ca-P minerals including various carbonate fluorapatite
(CFAP) specimens from different localities, fluorapatite (FAP), fish bone
apatite, synthetic hydroxylapatite (HAP) and octacalcium phosphate (OCP)
were characterized by XRD, Raman, FTIR and elemental analysis. Sediment
samples were incubated with and without these reference minerals and then
sequentially extracted to quantify Ca-P species by their differential
dissolution at pH values between 3 and 8. The quantification of solid-phase
phosphates at varying pH revealed solubilities in the following order: OCP > HAP > CFAP (4.5% CO3) > CFAP
(3.4% CO3) > CFAP (2.2% CO3) > FAP.
Thus, CFAP was less soluble in sediment than HAP, and CFAP solubility
increased with carbonate content. Unspiked sediment analyses together with
standard addition analyses indicated consistent differential dissolution of
natural sediment species vs. added reference species and therefore verified
the applicability of the CONVEX method in separately determining the most
prevalent Ca-P minerals. We found surprisingly high OCP contents in the
coastal sediments analyzed, which supports the hypothesis of apatite
formation by an OCP precursor mechanism. |
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