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

以三峡库区消落区典型江段万州断面为试验基地,以释磷能力较强的紫色土为对象,根据三峡水库消落带的"干湿交替"空间和时间特征,进行万州断面土壤磷释放的实验室模拟试验,分析了周期性"淹水-落干"干湿交替对土壤磷释放的影响.研究发现,在"淹水-落干"干湿交替条件下各形态磷在水土界面释放的活性为:Ca2-P,Fe-P＞Cas-P,Al-P＞O-P＞Ca10-P;T-P在每次淹没时释放量递增,从第1次的15.4 mg·kg-1,到第3次26.5 mg·kg-1;磷在持续淹水状态下释放的主要动力为Ca2-P在水相的溶解和还原状态下Fe-P的释放,其中Ca2-P活性最高,由淹水初期的14 mg·kg-1降至5 mg·kg-1左右;而干湿交替条件下P的释放主要是氧化-还原条件变换下Fe-P的形态转换.淹水并不会使O-P释放,但可以使O-P活化,使其在落干氧化时转化为Fe-P,在下一次淹水时释放.研究发现每次淹水时土壤的有效磷水平都略有增加,每次落干时较上次落干时有效磷水平降低.

Characteristics of Phosphorous Release from Soil in Periodic Alternately Waterlogged and Drained Environments at WFZ of the Three Gorges Reservoir

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.