reaction mass of calcium bis(dihydrogenorthophosphate) and calcium hydrogenorthophosphate

Adsorption / desorption

Administrative data

Endpoint:

adsorption / desorption

Type of information:

migrated information: read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

study well documented, meets generally accepted scientific principles, acceptable for assessment

Data source

Reference

Reference Type:

publication

Title:

Biogenic calcium phosphate transformation in soils over millennial time scales

Author:

Sato et al.

Year:

2009

Bibliographic source:

Journal of Soils Sediments (2009) 9:194–205

Materials and methods

Principles of method if other than guideline:

Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from centennial to millennial time scales.

GLP compliance:

no

Test material

Test material information

Constituent 1

Reference substance name:

Calcium phosphate

EC Number:

233-283-6

EC Name:

Calcium phosphate

Cas Number:

10103-46-5

Molecular formula:

Ca.xH3O4P

IUPAC Name:

calcium phosphate

Results and discussion

Any other information on results incl. tables

Changes in bioavailability of phosphorus (P) during pedogenesis and ecosystem development have been shown for geogenic calcium phosphate (Ca-P). However, very little is known about long-term changes of biogenic Ca-P in soil. Materials and methods Long-term transformation characteristics of biogenic Ca-P were examined using anthropogenic soils along a chronosequence from centennial to millennial time scales. Results and discussion Phosphorus fractionation of Anthrosols resulted in overall consistency with the Walker and Syers model of geogenic Ca-P transformation during pedogenesis. The biogenic Ca-P (e.g., animal and fish bones) disappeared to 3% of total P within the first ca. 2,000 years of soil development. This change concurred with increases in P adsorbed on metal-oxides surfaces, organic P, and occluded P at different pedogenic time. Phosphorus K-edge X-ray absorption near-edge structure (XANES) spectroscopy revealed that the crystalline and therefore thermodynamically most stable biogenic Ca-P was transformed into more soluble forms of Ca-P over time. While crystalline hydroxyapatite (34% of total P) dominated Ca-P species after about 600–1,000 years, β-tricalcium phosphate increased to 16% of total P after 900–1,100 years, after which both Ca-P species disappeared. Iron-associated P was observable concurrently with Ca-P disappearance. Soluble P and organic P determined by XANES maintained relatively constant (58–65%) across the time scale studied. Conclusions Disappearance of crystalline biogenic Ca-P on a time scale of a few thousand years appears to be ten times faster than that of geogenic Ca-P.