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Fluoride (F-)-substituted B-type carbonate hydroxyapatite (CHAP) powders were prepared for application as bone substitute materials having the ability to enhance bone formation and to suppress bone resorption due to the therapeutic effect of F-. F- was adsorbed on CHAP in a sodium fluoride solution followed by heating at 700 degrees C in carbon dioxide flow to substitute F- for the hydroxyl ion in the CHAP structure. The F- contents in the F-substituted CHAP powders were 16-22 times greater than that in normal adult human bones. The carbonate ion contents in the F-substituted CHAP powders corresponded to or were higher than that in normal adult human bones. F-substituted CHAP powder with CO3(2-) and F- contents of 11.03 and 0.66 wt%, respectively, slowly released F- in a physiological salt solution to a sufficiently high F- level. The F- concentration slowly increased and reached 67.20 +/- 4.81 microg l(-1), which was 1.5-9.3 times higher than that in the body fluid of normal adult humans, near the therapeutic window of F-, and far lower than the estimated toxic level. Therefore, the F-substituted CHAP can promote bone formation. The present F-substituted CHAP has the advantage of slow F- release over sodium fluoride and sodium monofluorophosphate which are highly soluble salts and cannot be sintered into a ceramic body.

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Soil organic phosphorus (P) is an important P source for biota especially in P-limited forests. Organic P has various chemical formations which differ in bioavailability and these organic P can be degraded by phosphatase enzymes. Here, we report soil P fractions inferred from solution 31 P-NMR spectroscopy and soil phosphatase activities of two tropical rain forests on contrasting parent materials; sedimentary and ultramafic igneous (serpentinite) rocks. Compared to the sedimentary soils and previous studies, P fractions of the serpentinite soils have distinctly high proportions of pyrophosphate and scyllo-inositol hexakisphosphate (scyllo-IP 6). The accumulation of pyrophosphate and scyllo-IP 6 may be related to strong sorptive capacity of iron oxides present in the serpentinite soils, which implies a consequent low P availability in the serpentinite soils. Mean value of soil phosphatase activities was higher in the serpentinite soils than in the sedimentary soils, suggesting that biota in these serpentinite forests depend more on soil organic P as a P source.

An incubation study was conducted to test the effects of phosphorus (P) addition on nitrous oxide (N2O) emissions from the soils taken from two tropical rain forests established on different parent materials [meta-sedimentary (MS) and ultrabasic (UB) rock] on Mt. Kinabalu, Borneo. Earlier studies suggest that the forest on UB soils is more strongly limited by P than that on MS soils is. In MS soils, P addition significantly reduced N2O emissions. Since neither ammonium (NH4+) nor nitrate (NO3−) contents were reduced by P addition, we assumed that the decrease in N2O emissions were not due to the previously-reported mechanism: P addition stimulated microbial nitrogen (N) immobilization and collateral inorganic N consumption, reducing resources for producing N2O. Since P addition enhanced the ratios of microbial biomass to CO2 and N2O emissions (indicators of nitrifying and/or denitrifying respiratory efficiency), it was suggested that the N required for the respiration of nitrifying and/or denitrifying bacteria was reduced, leading to reduced N2O emissions. On the other hand, P addition had no effects on N2O emissions in UB soils. The respiratory efficiency did not change significantly by P addition, possibly because the microbial community in the highly-P-depleted UB soils shifted by P addition, with which the enhancement of respiration efficiency did not co-vary. We concluded that (1) P addition may control N2O emissions through increasing respiratory efficiency, and (2) the effects may be different depending on the differences in P availability.