Characteristics of Phosphorous Release from Soil in Periodic Alternately Waterlogged and Drained Environments at WFZ of the Three Gorges Reservoir
三峡库区消落区周期性干湿交替环境对土壤磷释放的影响

The water-fluctuation-zone (WFZ) of reservoir and big river had special environmental characteristics that were a joint of aquicolous and terrestrial ecological system. According to the WFZ' s alternately waterlogged and drained environment, the control experiment for phosphorous release with purple alluvial soil of the water-fluctuation-zone (WFZ) at the Three Gorges Reservoir were carried out. Research was focused on the characteristics of phosphorous release from soil in the WFZ in periodic inundating-draining environment. Results showed that the release of T-P increased after each inundating process, from 15.4 mg x kg(-1) at first time to 26.5 mg x kg(-1) at third time. The activity of each phosphorous fraction at the water-soil interface in alternately inundating-draining conditions followed the sequence of Ca2-P, Fe-P > Ca8-P, Al-P > O-P > Ca10-P. The main impetus of phosphorous release at continuing inundating condition was the solubilization of Ca2-P and the transformation of Fe-P at alternately oxidizing-deoxidizing conditions; and the main impetus of phosphorous release at alternately inundating-draining conditions was the latter. In addition, inundation could not make O-P release from the soil, but it activated O-P which transformed to Fe-P when drained and Fe-P could be released when inundated again. The activeness of Ca2-P was highest among all kinds of phosphorous, and its concentration is from 14 mg x kg(-1) at beginning of inundated process to 5 mg x kg(-1) at end of inundated process. The results showed there was an increase of activated O-P after each waterlogged period, and a decrease after each drained period.