| Aim at various defects of some past researches on both release characteristic of phosphorus from flooding soil or periodically flooding soil and its environmental effect, typical soils from water level fluctuating zone of the Three Gorges Reservoir were studied in this research, by conducting release and sorption experiments of phosphorus under simulated inundation condition,release speed and load of soil were confirmed. Furthermore, after systematically determination of soil character under periodically flooded condition, combined with the results from sorption-desorption experiments, we studied the release mechanism of phosphorus from different soil type and land using, and some indexes could represent phosphorus transportation in water-soil interface were also proposed.Results showed, during simulated flooding periods, the relationship between pH of water column and pH of soil was positively correlation, while the specific conductance climbed up with the prolonging flooding periods. The main metal ions, which released from soil were Ca2+ and Mg2+, and the concentrations of released Fen+ and Mn2+ were relatively low, while K+ showed negative-desorption.Alternately dried and flooded condition has significant influence on the redox potentials (Eh), pH of soil and amorphous oxides, and the change of soil character under that condition differed from different soil type, as well as land using. During flooding periods, soil pH tends to be neutral, and its Eh drops down significantly. For soil has a high organic matter (OM) content, the decrease speed and range are high, which could drop to the extend of -250-300 mV. When the inundated soils were dried, the value of its pH and Eh could resume to a level before inundation. Besides, the oxalate-extractable iron (Feox) concentration in soil increased significantly after flooding. The mean value of Feox in 30 soils sampling increased 121% compared with that of before flooding. The increase range of Feox of upland soils is higher than that of paddy soils. After 15 upland soils were flooded, the mean value of Feox raised from 1070mg/kg to 4030mg/kg, which increased 277% compared with that of before flooding. However, after the soil flooding was dried, its Feox content is similar with the value before floodong. Compare to the flooding effect on Feox, the concerning effect on the oxalate-extractable aluminum (Alox) is not so evident, flood could increase the Alox concentration in soil, however, the change is insignificant. After the flooding soil was dried, its Alox concentration dropped down, which is significantly different from the value before flooding and during flooding periods. The degree of saturation with phosphorus (DPS) shows significant difference under alternately dried and flooded conditions. DPS decreased during flooding periods, and increased after the soil flooding was dried.Alternately dried and flooded condition also has significant impact on Olsen P in soil. Soil with different type, as well as different land using, shows various levels of Olsen P increase during flooding periods. After the flooding soil was dried, its Olsen P content resumed to the level beforeflooding. However, for upland soils, the samples after flooding had a lower Olsen P level than that of before flooding. The influence of dried-flooded cycle on alkaline yellow soil is insignificant. During the whole procedure (135 days) ,phosphorus applied to soils mainly transformed to Ca2-P, Ca8-P, Al-P and Fe-P, while only a tiny fraction transformed into O-P and Ca10-P. Flooding could increase the concentration of Ca2 -P,Ca8-P and Al-P, while drying could increased Fe-P concentration.Alternately dried and flooded condition has significant influence on soils isothermal sorption-desorption ability of phosphorus. The adsorption maximum of phosphorus (qm) and the maximum buffer capacity (MBC) of soil follow the order of flooding > drying after flooding > unflooding. The qm of upland purple soil increased 413% after floodig, while the MBC of paddy yellow soils soil increased 10...
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