Coprecipitation of phosphate with calcite.

Ishikawa, Masamichi; Ichikuni, Masami

doi:10.2343/geochemj.15.283

Cited by 53 publications

(21 citation statements)

References 20 publications

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“…The only other element recorded in significant amounts was P (Table 3). Although P may be substituted into the calcite lattice under certain conditions (Ishikawa and Ichikuni 1981), the relatively high concentration appears unusual and probably reflects the occurrence of trace quantities of (acid‐soluble) apatite (Ca 5 [PO 4 ] 3 ). Apatite was not identified in the diffraction pattern of NBS 18, but fluorapatite (Ca 5 [PO 4 ] 3 F) is a common constituent of carbonatites from the Fen district (Barth and Ramberg 1966, Barber and Wenk 1984, Hornig‐Kjarsgaard 1998).…”

Section: Results and Interpretationmentioning

confidence: 99%

Mineralogical and Chemical Composition of International Carbon and Oxygen Isotope Calibration Material NBS 19, and Reference Materials NBS 18, IAEA‐CO‐1 and IAEA‐CO‐8

Crowley

2010

Geostandard Geoanalytic Res

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International carbon and oxygen isotope calibration material NBS 19 and reference materials NBS 18, International Atomic Energy Agency (IAEA)‐CO‐1 and IAEA‐CO‐8 are prepared from naturally occurring rock specimens of marble and carbonatite. Mineralogical and chemical analysis showed that only NBS 19 and IAEA‐CO‐1 represent essentially pure samples of calcite containing < and minimal (< 1%) quantities of quartz. In contrast, both NBS 18 and IAEA‐CO‐8, although primarily composed of calcite, are contaminated by a range of additional phases. NBS 18 was estimated to contain 1% Fe‐dolomite and trace (< 1%) quantities of apatite and quartz. IAEA‐CO‐8 was estimated to contain at least 4% non‐carbonate material (including apatite, barite, biotite and magnetite). NBS 18 and IAEA‐CO‐8 are both derived from samples of carbonatite and the calcite component of each material is characterised by appreciable substitution of Mg + Mn + Sr ± Fe ± Ba (Σ ≈ 14000–15000 μg g‐1) for Ca. The observations reported in this study complement data in the literature detailing significant grain‐scale isotopic heterogeneity in NBS 18 and IAEA‐CO‐8. Both data sets highlight the need for careful characterisation of calibration materials prior to distribution.

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Section: Results and Interpretationmentioning

confidence: 99%

Mineralogical and Chemical Composition of International Carbon and Oxygen Isotope Calibration Material NBS 19, and Reference Materials NBS 18, IAEA‐CO‐1 and IAEA‐CO‐8

Crowley

2010

Geostandard Geoanalytic Res

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“…The SK P calculated for SC4 by using the range of values for P and Ca concentration in the drip water, and the range of P concentration in the stalagmite (from 4000 and 8000 ppm), varies from 4 to 8, values which are within the range of, or slightly higher than, the theoretical K P (Ishikawa and Ichikuni, 1981) (Fig. S1).…”

Section: Phosphorus Incorporation and Its Significance In Sc4mentioning

confidence: 90%

A re-evaluation of the palaeoclimatic significance of phosphorus variability in speleothems revealed by high-resolution synchrotron micro XRF mapping

et al. 2012

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Abstract. Phosphorus (P) is potentially a very important environmental proxy in speleothem palaeoclimate reconstructions. However, the transfer of P to a speleothem seems to vary between cave sites. Therefore, it is important to investigate the source of P and the way it is incorporated into a speleothem on a site-by-site basis before it can be used as a robust palaeoclimate proxy.In this paper, the distribution of P in one modern and two Early Pliocene speleothems formed in coastal caves on Christmas Island (Indian Ocean) and the Nullarbor Plain (southern Australia) is investigated using microscopy and ultra-high resolution chemical mapping.Phosphorus has been found to be both incorporated in the lattice and present as diverse P-rich phases. Monitoring data from Christmas Island suggest that co-precipitation of P-rich phases occurs when 'prior calcite precipitation' decreases following recharge, even if the drip rate decreases. Microbial mediation may also play a role, which complicates a direct climate relationship between P and hydrology. We find that some P-enriched layers contain dissolution features, with possible involvement of microbial mats which colonise pores during reduced drip rates associated with prolonged dry spells.In the two Early Pliocene speleothems the relationship between P and microbial laminae is clearer. Both petrographic and chemical data suggest that phosphorus-rich phases in the microbial laminae mark intervals of reduced drip rates, which may indicate dry intervals during the otherwise wet palaeoclimate of the Early Pliocene.We develop a speleothem distribution coefficient for phosphorus (SK P ) rather than the thermodynamic partition coefficient (K P ) to account for the presence of crystalline phosphate inclusions. SK P describes P enrichment in speleothems regardless of the process, as similar mechanisms of phosphate co-precipitation may be in operation in biotic and abiotic conditions.The most important implication of our study is that variability in P concentration may be related to diverse processes which can be recognized through petrographic observations and chemical mapping. In particular, there may not be a direct relation between an increase in P concentration and seasonal infiltration as has been found in some previous studies, especially if the source of this element is not the labile phosphate released through leaching during seasonal vegetation dieback in temperate climates.

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“…Based on the above analysis, we believe that CaHPO 4ðaqÞ 0 is the primary species that adsorbs on the calcite surface and inhibits calcite precipitation, although H 2 PO 4 À and other negatively charged species might still contribute to a small fraction of phosphate adsorption through an anion exchange mechanism (Ishikawa and Ichikuni, 1981;. The reaction responsible for the adsorption of phosphate and the subsequent inhibition of calcite precipitation can therefore be expressed as follows:…”

Section: Key Reaction For the Inhibition Of Calcite Precipitation By mentioning

confidence: 98%

“…Successful immobilization of phosphorus has also been artificially achieved by the introduction of calcite seed or lime in eutrophic lakes (Dittrich et al, 1997;Prepas et al, 2001;Berg et al, 2004;Walpersdorf et al, 2004). Phosphate has long been recognized as an inhibitor of calcite precipitation (Reddy, 1977;Ishikawa and Ichikuni, 1981;Mucci, 1986;Giannimaras and Koutsoukos, 1987;House, 1987;Burton and Walter, 1990). The adsorption of phosphate on the calcite surface blocks active crystalgrowth sites and retards calcite precipitation.…”

Section: Introductionmentioning

confidence: 98%

Inhibition of calcite precipitation by orthophosphate: Speciation and thermodynamic considerations

Lin

Singer

2006

Geochimica et Cosmochimica Acta

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Coprecipitation of phosphate with calcite.

Cited by 53 publications

References 20 publications

Mineralogical and Chemical Composition of International Carbon and Oxygen Isotope Calibration Material NBS 19, and Reference Materials NBS 18, IAEA‐CO‐1 and IAEA‐CO‐8

Mineralogical and Chemical Composition of International Carbon and Oxygen Isotope Calibration Material NBS 19, and Reference Materials NBS 18, IAEA‐CO‐1 and IAEA‐CO‐8

A re-evaluation of the palaeoclimatic significance of phosphorus variability in speleothems revealed by high-resolution synchrotron micro XRF mapping

Inhibition of calcite precipitation by orthophosphate: Speciation and thermodynamic considerations

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