| The distributions and the mobility-transformation of phosphorus (P) fractions in wetland soil play an important role in the water eutrophication and ecological balance of the wetland. Yeyahu wetland natural reserve with the largest area in Beijing is critical to the water quality of Guanting reservoir and climate changes. Thus Yeyahu wetland is selected as the objects. The distribution characteristics of P fractions, the adsorption behaviors and mechanism of the inorganic and organic P, the transformation of P fraction on the soil-water interface under different simulating conditions were investigated.The chemical sequential extraction method was performed in the research of the distribution characteristics of P fractions as the seasonal variations and the soil profile depth. And the mathematical statistical method was used for the correlation analysis between soil properties and P fractions. The results showed that the total P was in the range of 352.3～836.1 mg·kg-1, and the inorganic and organic P accounted for 72.76% and 27.24% of total P, respectively; total P and most of P fractions decreased with the soil profile depths. Occluded P (Oc-P) as the inorganic P fraction showed obvious decrease with soil depth, which was probably due the transformation to the Al-bound P (Al-P) and Fe-bound P (Fe-P), and the exchangeable P (Ex-P) was derived from the decomposition of Oc-P and residual P (Re-P). Total P and most P fractions were significantly correlated with the growth cycle of the vegetations. In the growth period, the concentration of P was lower, while in the litter period, P was much higher. Furthermore, Oc-P in the surface soil was the highest in the litter period, which indicated that P in vegetations was the main source to Oc-P in the soil. The resistant organic P (OP) was the main occurrence of OP in soil, accounting for 90.28% of total OP, and it was negatively correlated with the pH value and positively with water contents and organic matter, however, the other OP fractions were not correlated with soil properties. It also revealed that OP fractions in soil could be interchangeable under particular conditions.The results of the nuclear magnetic resonance (NMR) revealed orth-P and mono-P were the major occurrence of P in Yeyahu wetland soil, and indicated the resistance OP accounting for 92.98% of total OP occurred in the form of mono-P in wetland soil.The behaviors of P and the transformation of P fractions were studied by static adsorption experiments and dynamic adsorption experiments, respectively. The results of the static adsorption revealed that the kinetic adsorption process of inorganic P and phytate could be described by second order kinetic equation; and the isothermal adsorption process of inorganic P, phytate, andβ-glycerophosphate could be well described by Langmuir cross-shaped adsorption isothermal equation. The water pH had an impact on the P adsorption, with the increase of pH, the adsorption capability slowly increased in the beginning, subsequently, the capability decreased sharply. The optimum pH of inorganic P, phytate, andβ-glycerophosphate adsorption were about 8. The adsorption of P could be promoted in the water with lower dissolved organic matter (DOM), the adsorption capabilities of inorganic P and phytate were higher in the water of 100mg·L-1 DOM, while that ofβ-glycerophosphate was higher in the water of 50mg·L-1 DOM; the specific surface area of soil particles decreased after the adsorption, and the absorbed P aggregated in micro- and meso-pore; according to the hysteresis loop of adsorption, the pore structure of soil particles was inferred as slit pore formed by schistose ion accumulation; by the SEM-EDS, the adsorbed P on the soil surface was distributed on the raised part with much more permanent charges and functional groups; the results obtained by FT-IR and XRD indicated that kaolinite in soil participated the adsorption process of inorganic and organic P.The results of dynamic adsorption revealed that the surface soil was readily effected by the properties of the overlying water; Ex-P, Al-P and Fe-P as labile P fractions in soil remarkably increased with the P concentration of overlying water, while the resistant fractions Oc-P and Ca-P increased inconspicuously; with the increase of the DOM in overlying water, Ex-P and Fe-P increased in soil, for the reason that micro-organism multiplied in the situation with sufficient organic matter and absorbed amount of P in overlying water; the contents of Ex-P, Al-P and Fe-P was larger in sterilized soil than that in unsterilized soil due to the greater specific surface area, more micropore and the change of mineral composition of the sterilized soil. The second water-lying and soil drying could influence the absorption behavior of P and the distribution of P fractions. In the second waterlying, the relationship between Ex-P and DOM varied, and Ex-P decrease with the concentration increase of DOM; after soil drying, Ex-P, Al-P, Fe-P and Oc-P in soil showed different variation patterns due to the different former properties of the overlying water, soil micro-organism and soil redox conditions.
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