Inorganic formation of apatite in brackish seawater from the Baltic Sea: an experimental approach

Gunnars, Anneli; Blomqvist, Sven; Martinsson, Cajsa

doi:10.1016/j.marchem.2004.01.008

Cited by 71 publications

(78 citation statements)

References 43 publications

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“…This suggests that there is no authigenic Ca-P formation in Grevelingen sediments, despite the presence of polyphosphates in cable bacteria and Beggiatoa (SuluGambari et al 2016a) and despite the supersaturation of the pore water with respect to carbonate fluorapatite in the surface sediment (Table S1), which is typical for marine sediments (Ruttenberg 2003). Possible explanations for the lack of authigenic Ca-P formation may include inhibition by Mg 2+ , where these ions take up potential binding sites for Ca 2+ on the apatite precursor surface (Gunnars et al 2004;Martens et al 1978) and undersaturation with respect to octacalcium phosphate, a precursor for carbonate fluorapatite (Oxmann and Schwendenmann 2015); Table S1). Furthermore, we speculate that authigenic Ca-P formed in surface sediments may be redissolved together with Ca-and Mn-carbonates linked to the activity of cable bacteria and the associated acidity of the pore waters (e.g.…”

Section: Discussionmentioning

confidence: 99%

Phosphorus Cycling and Burial in Sediments of a Seasonally Hypoxic Marine Basin

Sulu-Gambari

Hagens

Behrends

et al. 2017

Estuaries and Coasts

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Recycling of phosphorus (P) from sediments contributes to the development of bottom-water hypoxia in many coastal systems. Here, we present results of a year-long assessment of P dynamics in sediments of a seasonally hypoxic coastal marine basin (Lake Grevelingen, the Netherlands) in 2012. Sequential phosphorus extractions (SEDEX) and X-ray absorption spectroscopy (XAS) indicate that P was adsorbed to Fe-(III)-(oxyhydr)oxides when cable bacteria were active in the surface sediments in spring. With the onset of summer h y p o x i a , s u l p h i d e -i n d u c e d d i s s o l u t i o n o f t h e Fe-(III)-(oxyhydr)oxides led to P release to the pore water and overlying water. The similarity in authigenic Ca-P concentrations in the sediment and suspended matter suggest that Ca-P is not formed in situ. The P burial efficiency was ≤ 32%. Hypoxia-driven sedimentary P recycling had a major impact on the water-column chemistry in the basin in 2012. Watercolumn monitoring data indicate up to ninefold higher surface water concentrations of phosphate in the basin in the late 1970s and a stronger hypoxia-driven seasonal P release from the sediment. The amplified release of P from the sediment in the past is attributed to the presence of a larger pool of Febound P in the basin prior to the first onset of hypoxia. Given that P is not limiting, primary production in the basin has not been affected by the decadal changes in P availability and recycling over the past 40 years. The changes in P dynamics on decadal time scales were not recorded in sediment profiles of total P or organic C/total P.

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Section: Discussionmentioning

confidence: 99%

Phosphorus Cycling and Burial in Sediments of a Seasonally Hypoxic Marine Basin

Sulu-Gambari

Hagens

Behrends

et al. 2017

Estuaries and Coasts

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“…Hence, more soluble species might better mirror ongoing processes, whereas sparingly soluble apatite minerals obviously reflect varying conditions over time due to slow precipitation. In accordance with such a kinetic control, OCP has been consequently proposed as a precursor for apatite formation (Gunnars et al, 2004;Krajewski et al, 1994).…”

Section: Sedimentary Ca-p Speciationmentioning

confidence: 97%

“…The precursor hypothesis agrees with earlier reported kinetic barriers but tends to contrast with the often suggested strong undersaturation of seawater with respect to CFAP. If direct nucleation of apatite is kinetically inhibited in marine environments by magnesium (Golubev et al, 1999;Gunnars et al, 2004;Martens and Harriss, 1970), the ambient water must be supersaturated with respect to a precursor to facilitate apatite formation by a less magnesium susceptible pathway. For example, in long-term incubation experiments apatite precipitated from natural brackish seawater only in case of supersaturation with respect to OCP (Gunnars et al, 2004).…”

Section: Sedimentary Ca-p Speciationmentioning

confidence: 99%

“…Thus other Ca-P minerals, such as OCP and amorphous calcium phosphate (ACP), may represent significant sinks during early diagenesis and may influence soluble P levels. Incubation experiments with seawater indicated apatite formation by prior precipitation of metastable precursor phases, and a corresponding mechanism has been suggested for certain phosphorite deposits (Gunnars et al, 2004;Jahnke et al, 1983;Krajewski et al, 1994;Van Cappellen and Berner, 1988;Schenau et al, 2000). Apatite precursors are however difficult to identify, even in relatively simple mixtures without interfering sample matrices.…”

Section: Introductionmentioning

confidence: 99%

“…According to these kinetic considerations, Ca-P precipitation is apparently prevented in the water column (Atlas, 1975;Atlas and Pytkowicz, 1977). Moreover, direct nucleation of apatite was found to be inhibited by magnesium and, thus, spontaneous inorganic precipitation suggested to be kinetically impossible in marine environments (Golubev et al, 1999;Gunnars et al, 2004;Martens and Harriss, 1970). In contrast, magnesium has a lesser inhibitory effect on the precipitation of more soluble precursor phases and therefore selectively stabilizes precursor phases (Gunnars et al, 2004;Johnsson and Nancollas, 1992).…”

Section: Introductionmentioning

confidence: 99%

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Quantification of octacalcium phosphate, authigenic apatite and detrital apatite in coastal sediments using differential dissolution and standard addition

Oxmann

Schwendenmann

2014

Ocean Sci.

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Abstract. 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 % CO 3 ) > CFAP (3.4 % CO 3 ) > CFAP (2.2 % CO 3 ) > 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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Water column particulate matter: A key contributor to phosphorus regeneration in a coastal eutrophic environment, the Chesapeake Bay

Reardon

McKinley

et al. 2017

JGR Biogeosciences

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Particulate phosphorus (PP) in the water column is an essential component of phosphorus (P) cycling in the Chesapeake Bay because P often limits primary productivity, yet its composition and transformation remain undercharacterized. To understand the mobilization of PP and P sequestration in the water column, we studied seasonal variations in particulate organic and inorganic P species at three sites in the Chesapeake Bay, using chemical extractions, 1‐D (31P) and 2‐D (1H‐31P) NMR spectroscopies, and electron microprobe analyses. Our results suggest that an average of 9% and 50% of water column PP was recycled in shallow and deep sites, respectively, primarily through remineralization of organic P, which was 3 times higher than Fe‐bound P remobilization. P recycling efficiency was highest in the warm and anoxic seasons. Organic P compositions and concentrations responded strongly to seasonal and redox variations: orthophosphate monoesters and diesters, and diester‐to‐monoester ratios (D/M) decreased with depth; both esters and D/M ratios were lower in the anoxic waters in July and September. In contrast, pyrophosphate concentration increased with depth and polyphosphate concentration was high in anoxic seasons. Our analyses suggest the presence of Ca‐phosphate minerals (Ca‐P) in the water column but with concentrations comparable to sediment Ca‐P. It is unclear, however, whether authigenic precipitation occurred in the water column or resuspended from sediments. Overall, these results reveal the dominance of internal P cycling particularly via organic P remineralization and controlling P availability in the water column of the Chesapeake Bay.

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Inorganic formation of apatite in brackish seawater from the Baltic Sea: an experimental approach

Cited by 71 publications

References 43 publications

Phosphorus Cycling and Burial in Sediments of a Seasonally Hypoxic Marine Basin

Phosphorus Cycling and Burial in Sediments of a Seasonally Hypoxic Marine Basin

Quantification of octacalcium phosphate, authigenic apatite and detrital apatite in coastal sediments using differential dissolution and standard addition

Water column particulate matter: A key contributor to phosphorus regeneration in a coastal eutrophic environment, the Chesapeake Bay

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