题目：筑坝对河流锶地球化学行为的影响
Effect of damming on riverine strontium geochemical behavior
主讲人：2019级博士 仇晓龙
时间：11月10日（周四）中午12：00
地点：16教学楼221会议室
摘要：
筑坝改变了河流营养元素的地球化学循环，但其对Sr的影响现在还没有定论。为此，我们以中国西南喀斯特梯级水库为研究对象，利用87Sr/86Sr手段调查了其中溶解态、颗粒态Sr的情况。结果表明水库的溶解态Sr浓度在剖面上发生了明显的分层，这种分层由浮游植物和方解石的结晶/溶解过程引起，分层强度由水库水力负荷控制。因此，随时间积累（十年尺度）筑坝可能造成河流Sr2+浓度的增加，但对溶解态87Sr/86Sr无影响。溶解态87Sr/86Sr在水库剖面分布均匀，与无机颗粒态87Sr/86Sr表现相似。水库中浮游植物将继承水体中溶解态87Sr/86Sr的信号，控制了水库剖面有机颗粒87Sr/86Sr的变化。由于溶解态87Sr/86Sr远低于陆源有机颗粒结合的87Sr/86Sr，水库颗粒态87Sr/86Sr可作为区分水库自源和外源颗粒物的依据。本研究表明筑坝显著影响了河流锶的地球化学行为，丰富了筑坝河流锶的生物地球化学理论体系。
River damming alters biogeochemical cycles in river continuum. Yet, its effect on the geochemical behavior of riverine strontium (Sr) is still unclear. Here, we measured 87Sr/86Sr in dissolved and particulate phases of Southwest China. The results show that dissolved Sr concentrations were stratified and increased with depth in the reservoir profile. This stratification was likely caused by phytoplankton bioactivity and the precipitation and dissolution of calcite, with the stratified strength largely controlled by reservoir hydraulic loads. A long-term river damming could result in a significant increase in dissolved Sr concentrations rather than 87Sr/86Sr. The dissolved 87Sr/86Sr were rather homogeneous across the water body and nearly identical to inorganic particulate-bound 87Sr/86Sr. Reservoir phytoplankton 87Sr/86Sr would inherit dissolved 87Sr/86Sr and were lower than terrestrial particulate organic 87Sr/86Sr, implying that organic particulate-bound 87Sr/86Sr has the potential to distinguish autochthonous and allochthonous sources of particulate organic matter in reservoirs. This study demonstrated that damming influences riverine Sr geochemical behavior and thus will deepen the understanding of Sr biogeochemistry in dammed rivers.
