杭州城市内河底泥磷污染与磷释放水力模拟

在分析杭州城市内河东新河底泥磷污染的基础上，采用加长型环形水槽动态模拟水体流速（0.002～0.02 m·s^-1）、上覆水质（水体总磷本底值分别为0.18、 0.072和0.007 mg·L^-1）及上覆水深（5、 10 cm）对底泥磷释放的影响，并定量分析了不同流速下底泥磷的释放速率.结果表明，东新河底泥的pH值、含水率、磷含量等理化性质有利于磷的释放.在动态水力条件下底泥磷主要以悬浮颗粒态形式向上覆水体释放.流速对底泥磷释放的影响较为显著，模型流速为0.008 m·s^-1（原型流速为0.05 m·s^-1）时对应底泥的“少量动”，此时底泥磷释放速率趋于最大，达147.36 g·(m²·h)^-1.上覆水质影响底泥磷的释放，尤其显著影响磷的初期释放，内河水较自来水更有利于底泥磷的释放，可能是由于内河水与底泥构成了良好的磷交换关系.在浅水水体中，上覆水深对底泥磷释放影响不大.因此，可以通过调节水力学条件和水质来抑制或强化河流底泥磷的释放.

Phosphorus Pollution of the Sediment from Hangzhou Urban River and Hydraulic Simulation of Phosphorus Release

The phosphorus pollution of the sediment from Dongxin River, an urban river in Hangzhou, was surveyed. Phosphorus release under various flow velocity(0.002-0.02 m·s^-1), quality of overlying water (the total phosphorus concentration: 0.18, 0.072 and 0.007 mg·L^-1), depth of overlying water (5, 10 cm) were carefully studied in a hydraulic simulation setup. The results indicate that phosphorus was feasible to release from the sediment with high ratio of water content (40.09%-68.57%) under alkali condition (pH 7.2-8.3). The phosphorus release was also influenced by high content of phosphorus (1.04-2.51 g·kg^-1) in the sediment. Phosphorus release was mainly in the form of suspended solid under dynamic hydraulic condition, and depended definitely on flow velocity. The release rate reached 147.36 g·(m²·h)^-1, which approached the maximum value, at flow velocity 0.008 m·s^-1 (i.e. 0.05 m·s^-1 in archetype). Phosphorus release, especially the initial release rate, was obviously affected by the quality of overlying water. Phosphorus tended to release under river water than tap water. However, the depth of overlying water had little influence on phosphorus release in shallow water. Therefore, it is possible to restrain or enhance phosphorus release by adjusting the hydraulic conditions and the quality of overlying water.