深水水库内源磷化氢释放、迁移与环境效应研究

Endogenous phosphorus release and transport mainly in terms of molecule diffusion in waterbody. Endogenous phosphorus transporting velocity decrease with water depth. Therefore, in traditional theory, endogenous phosphorus in deep reservoirs has little influence on phosphorus load. Phosphine could transport from sediments to the surface in the way of bubble flotation, which is of higher transportation velocity than molecule diffussion, and be oxdized to phosphate in photic zone under sunlight.Therefore, endogenous phosphine transportation may be an important supplement to endogenous phosphorus cycle in deep reservoirs.It also might trigger harmful algae blooms in phosphorus-limited waterbody. However, environmental behavior of endogenous phosphine in deep reservoirs has not recerived systematic research. High concentration of phosphine has been detected in the sediments of the Three Gorges Reservoir. This program selects the backwater area of the Xiangxi River in the Three Gorges Reservoir as studying area, which is rich in phosphorus, investigates the levels and distribution characteristics of endogenous phosphine release, the phosphine trasportation characteristics in different depth and interface, phosphours load and algaedistribution characteristics in photic zone, carries out in-door experiments to study release mechanism, transportation mechanism and fate of endogenous phosphine in deep reservoirs, illustrates the environmental effect of endogenous phosphine in deep reservoirs, identifies the role of endogenous phosphorus cycle with phosphine as gaseous carrier in deep reservoirs in phosphorus regional transportation and phosphorus biogeochemical cyle.

水体内源磷释放迁移主要采取分子扩散方式，迁移速率随水深增大而减小，因此一般认为深水水库内源磷对真光层磷负荷影响较小。磷化氢可以通过迁移速率远大于分子扩散的气泡漂浮过程迁移，从底泥进入真光层后在光照下氧化为磷酸盐，因此以磷化氢为载体的内源磷迁移过程可能是深水水库内源磷循环的重要补充，并可能诱发磷限制水体富营养化。但是深水水体内源磷化氢的环境行为尚未得到系统研究。三峡水库底泥已检测到较高浓度基质结合态磷化氢，因此本项目选择高含磷背景的三峡水库香溪河回水区为研究区域，系统观测研究区域内源磷化氢的释放水平分布特征、不同深度和界面磷化氢迁移特征、真光层磷负荷与藻类分布特征，并利用模拟装置研究深水水库内源磷化氢的释放机理、迁移规律、真光层的归趋过程，阐明深水水库内源磷化氢的环境效应，识别以磷化氢为气态载体的深水水库内源磷循环途径在区域磷的迁移输送中的作用和在生物地球化学循环中的意义。

深水水库沉积物中释放的气态磷化氢，可能以气泡形式、通过迁移速率远大于分子扩散的气泡漂浮过程，从底泥进入真光层并发生光化学氧化，转化为极易被浮游植物利用的正磷酸盐，从而影响真光层的磷负荷。因此以磷化氢为载体的内源磷迁移过程可能是深水水库内源磷循环的重要补充，并可能诱发磷限制水体富营养化。为探索深水水体内源磷化氢的环境行为和环境效应，本项目选择高含磷背景的三峡水库香溪河回水区为研究区域，系统观测研究区域内源磷化氢的释放水平分布特征、不同深度和界面磷化氢迁移特征、真光层磷负荷分布特征，并利用模拟装置研究深水水库内源磷化氢的释放机理、迁移规律、真光层的归趋过程。研究结果包括：（1）发现了三峡水库香溪河回水区存在活跃的内源磷化氢释放、迁移、转化活动，证实了深水水体中存在较为活跃的、以气态磷化氢为载体的、内源磷进入表层水体的途径，确定了内源磷在真光层磷收支中的作用。（2）通过模拟实验等手段，获得了典型深水水库水体香溪河回水区中沉积物-水界面气态磷化氢释放通量（包括不同水位下的释放通量）、不同深度水柱的气态磷化氢垂向迁移速率、真光层气态磷化氢迁移速率和转化速率，并获得了具体过程的相关参数。