Abstract:

Based on the antiseasonal operation mode of storing the clean and discharging the muddy,the changes of soil phosphorous forms and contents were analyzed through drywet cycling for the first time in TGRA (Three Gorges Reservoir area),which reveals phosphorous distribution characteristics and its release laws.In summer,total phosphorous contents in the overlying water in lowwaterlevel mode was much higher than that in highwaterlevel mode in winter. Moreover,total phosphorous contents in the overlying water in the upstream and that in the downstream fluctuated remarkably due to the large runoff in flood period.Soil phosphorous in different form distributed in a uniform law. Active phosphorous and organic phosphorous contents changed fiercely,which were the main source of endogenous phosphorus load in the overlying water.Additionally,organic phosphorous was the primary contributor for soil endogenous phosphorus load after the water level went up to 175 m for the first time.In the early submerged period,soil phosphorous contents in different form in drywet cycling did not differ significantly.Soil phosphorous release level showed significant linear correlation to soil total phosphorous,organic phosphorous and active phosphorous.Therefore,the newly emerged fluctuating zone,a potential phosphorous source,had little impact on water quality in the initial period of TGRA operation.