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| Titel |
Could organic phosphorus compounds contaminate the analysis of phosphate oxygen isotopes in freshwater matrices? |
| VerfasserIn |
Ceri Davies, Ben Surridge, Daren Gooddy |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250093151
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| Publikation (Nr.) |
 EGU/EGU2014-7620.pdf |
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| Zusammenfassung |
| Variation in the stable isotope composition of oxygen within dissolved phosphate (δ18Op)
represents a novel and potentially powerful environmental tracer, providing insights into the
sources of phosphorus and the extent to which phosphorus from different sources is
metabolised. The analysis of δ18Opwithin freshwater matrices requires isolation of the
phosphate ion from possible sources of contaminant oxygen within the bulk matrix, prior to
pyrolysis (usually of a silver phosphate precipitate) and analysis of the oxygen isotope
composition. The majority of published research uses co-precipitation of phosphate
with brucite (Mg(OH)2) as an initial step in the isolation of the phosphate ion.
However, freshwater matrices also contain a wide range of organic phosphorus
compounds, including adenosine 5’-triphosphate (ATP) and phosphonates such as
2-aminoethylphosphonic acid. In this paper, we initially examine the potential for
co-precipitation of organic phosphorus compounds with brucite. Our data indicate that ATP,
sodium pyrophosphate and inositol hexakisphosphate are almost entirely removed from
solution through co-precipitation with brucite, whilst glucose-6-phosphate and
2-aminoethylphosphonic acid are less readily co-precipitated. Subsequently, we
assessed the potential for acid-hydrolysis of organic phosphorus compounds during
re-dissolution of the brucite precipitate, using a range of acid systems. Our data indicate that
up to 17% of ATP and up to 5% of sodium pyrophosphate can be hydrolysed by
concentrated acetic acid, yielding fresh phosphate ions in solution. Our findings have
potentially significant implications for analysis of δ18Opbecause the fresh phosphate ions
produced following acid hydrolysis will be subjected to inheritance and kinetic
isotope fractionations, likely altering the bulk δ18Op within a freshwater sample. |
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