『Abstract
Background, aim, and scope 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.
Keywords: Adsorption; Amazonian dark earths; Anthrosols; Dissolution;
Organic phosphorus; Oxisols; Phosphorus transformation; speciation;
Terra Preta de Indio（Iの頭に´）; XANES (X-ray
absorption near-edge structure)』
1. Background, aim, and scope
2. Materials and methods
2.1. Site and soil descriptions and soil analyses
2.2. Phosphorus sequential fractionation
2.3. X-ray absorption near-edge structure spectroscopy analysis
2.4. Statistical analyses
3. Results
3.1. Soil properties
3.2. Phosphorus fractions
3.3. Phosphorus species from XANES analyses
4. Discussion
5. Conclusions
Acknowledgements
References