On the presence of organic phosphate in some Camargue sediments: evidence for the importance of phytate

Abstract

The organic phosphate pool of some Camargue sediments (South of France) was studied, after removal of inorganic phosphate, with Ca-NTA/dithionite (Fe bound phosphate) and Na-EDTA (Ca bound phosphate). The organic phosphate was divided into an acid soluble organic phosphate fraction (ASOP) and a residual organic phosphate fraction (ROP). The extraction of organic matter with 2.0 M NaOH (90 C) from ROP yielded considerable quantities of Org-P. In this extract the presence of phytate (inositol hexa phosphate) could be demonstrated using phytase to hydrolyse the phytate. Phytate was shown to account for a considerable part of organic phosphate in sediments of freshwater marsh sediments as well as in the sediment of the brackish/salt water lake 'Etang de Vaccares'. In laboratory experiments phytate was found to precipitate with all poly-valent cations tested. Furthermore, phytate was found to be strongly adsorbed onto Fe(OOH), which may explain its accumulation and its stability in sediments.Considerable quantities of ASOP were found; the chemical stucture of this pool remains unknown.Abbreviations: In this paper the standard abbreviations are used, as suggested by the editor (see page vi):chem-Xphys (inorg-Pdiss, Tot-Nsed)Additional abbreviations used: ASOP = acid soluble organic phosphate CaCO 3 ; P = calcium bound phosphateFe(OOH) P = iron bound phosphate NaOHextr-P = phosphate extracted with NaOH (90 C) after ASOP extraction.Phyt-P = phytate bound phosphate ROP = residual organic phosphate 118

The C:N:P:S stoichiometry of soil organic matter

“…3), occurs under conditions in which adsorption is most likely strongest, suggesting adsorption as the mechanism by which NRSOM accumulates. This is consistent with the high-density (mineral-rich) fraction of SOM usually having low C:N ratios (Baisden et al 2002;Sollins et al 2006;von Lützow et al 2007;Schrumpf et al 2013), and the known strong adsorption by mineral surfaces of proteins (Kleber et al 2007) and phytic acid (Anderson et al 1974;De Groot and Golterman 1993;Celi and Barberis 2006). Adsorption by mineral matter is thought to stabilise SOM by rendering it less accessible to microbial attack (von Lützow et al 2006;Schmidt et al 2011;Kleber et al 2011).…”

Identification of inositol hexakisphosphate binding sites in soils by selective extraction and solution 31P NMR spectroscopy

“…Most Fe-IP 6 and Al-IP 6 precipitates are soluble in 0.05 M EDTA (Degroot and Golterman, 1993), so it is likely that oxalate also dissolves these precipitates. However, the high recoveries of IP 6 in the oxalate extracts of the forest and grassland soils suggest that IP 6 from Al precipitates is extracted by oxalate, or that the precipitation process is less pronounced in soils as it is in sorption experiments (Yan et al, 2014a).…”

Organic phosphorus in Madagascan rice soils

“…Anaerobic conditions appear critical, because inositol phosphates in marine sediments from Tokyo Bay were hydrolyzed much more rapidly when incubated under anaerobic conditions compared to parallel samples incubated aerobically (Suzumura and Kamatani, 1995). A caveat is that anaerobic reduction of complexes between iron and inositol hexakisphosphate was reported to form insoluble Fe 4 -phytate rather than solubilizing the free inositol hexakisphosphate (De Groot and Golterman, 1993). This could account for the observed decreases in inositol phosphate following submergence of rice soils, but only if, as seems unlikely, the complex remains insoluble in the strong alkali used to extract inositol phosphates.…”