三峡库区消落带淹水—落干过程土壤磷吸附—解吸及释放研究

FLOODING AND SUBSEQUENT AIR-DRYING ON ADSORPTION, DESORPTION AND RELEASE OF PHOSPHORUS OF SOIL IN DRAWDOWN AREAS IN THREE GORGES RESERVOIR

选取三峡库区消落带典型区土壤作为测试土壤，研究了淹水-落干对土壤磷的等温吸附解吸特性，以及土壤吸附一定的磷后再次淹水向上覆水体释磷的规律。研究表明：①三峡库区消落带土壤淹水-落干后吸磷能力增强，由淹水-落干前的256mg／kg增加到淹水-落干后的625mg／kg，磷零点吸持平衡浓度（EPC0）由淹水前的0．46mg／L增加到淹水后的1．47mg／L；②淹水-落干处理后土壤磷的解吸率降低，由淹水-落干前的73．3％～80．3％降低到67．3％～69．6％；③三峡库区消落带土壤吸附一定磷后，再淹水磷会再次逐渐释放到上覆水当中，且土壤吸附外源磷越多，磷淹水释放强度越大；④淹水-落干使吸附一定外源性磷的土壤淹水条件下释放更多的磷。

In this paper, the typical kind of soil in the Three Gorges Reservoir region was taken from Kaixian County to make two types of soil samples （original soil sample and flooded-dried soil sample）, to examine the relationship between alternative flooding-drying condition and the isothermal adsorption of the P from the soil samples, and to compare the P release patterns of the flooded-dried soil samples with original soil samples. The maximum P adsorption capacity （Xm） from Langmuir isotherm equation was first studied in this paper, and then the two types of soil samples were treated by KH2PO4 of 10% Xm, 30% Xm, 50% Xm, and 80% Xm. All the treated soil samples were deposited for 15 days before the subsequent flooding experiments. The adsorption capacity of the soil can be enhanced by flooding and subsequent airdrying condition. The adsorption capacity of the P increased from 256 mg/kg （original soil samples） to 625 mg/kg （flooded and dried soil samples）, and the EPC0 was from 0.46 mg/L to 1.47 mg/L respectively after flooding condition. The ratio of desorption of the soil samples decreased from 73.3%～80.3% to 67. 3%～69.6% after flooding. It is predicted that phosphorus adsorbed by the soils in drawdown area of Three Gorges area may then be released under the conditions similar to the flooding conditions employed in the present study. The release amount of P will vary synchronously with the P amount absorbed by soils before flooding. The alternative flooding-drying condition will cause the soil release more phosphorus.