近日，南京水利科学研究院陈求稳和张建云教授探讨了水电站水库瀑布是否会损害下游营养体系这一问题。相关论文于2024年1月8日发表在《科学通报》杂志上。

在这项研究中，研究人员对水库是否可以改善下游的营养状况进行了调查。主要工作为对5年来湄公河上游水库瀑布的水合沉积物中不同种类的氮、磷以及微生物功能进行了测量，并对各水库中氮和磷种类的流入和流出进行了模拟。虽然水库保留了部分总氮和总磷，但增加了下游铵和可溶性活性磷(SRP)的通量。流出和流入之间的铵和可溶性活性磷的增加与水库瀑布的水力停留时间呈线性正相关；可溶性活性磷与溶解无机氮的比值沿水库瀑布的增大而增加。

水库的自然环境促进了藻类介导的硝酸盐向地表水中铵的转化；缺氧条件和藻类诱导有机质的启动效应，促进了沉积物中铵的释放；微生物磷酸化、还原条件和沉积物地球化学性质的协同作用增加了可溶性活性磷的释放。该研究首次提供了确凿的证据，证明水电站水库通过保留—转化—运输过程改善下游养分的生物有效性和氮—磷平衡，并可能会利于初级生产力。研究强调，这些发现可以促进人们对河流筑坝的生态环境影响的理解。

据了解，人们认为河流筑坝在很大程度上拦截了营养物质(特别是保留了更多的磷(P)而不是氮(N))，损害了初级生产力、渔业捕捞和下游的粮食安全，严重制约了全球水电开发和不发达地区的扶贫工作，并可能引发跨境河流沿岸国家之间的地缘政治争端。

附：英文原文

Title: Does a hydropower reservoir cascade really harm downstream nutrient regimes

Author: Qiuwen Chen, Yuchen Chen, Yuqing Lin, Jianyun Zhang, Jinren Ni, Jun Xia, Lin Xiao, Tao Feng, Honghai Ma

Issue&Volume: 2024/01/08

Abstract: River damming is believed to largely intercept nutrients, particularly retain more phosphorus (P) than nitrogen (N), and thus harm primary productivity, fishery catches, and food security downstream, which seriously constrain global hydropower development and poverty relief in undeveloped regions and can drive geo-political disputes between nations along trans-boundary rivers. In this study, we investigated whether reservoirs can instead improve nutrient regimes downstream. We measured different species of N and P as well as microbial functions in water and sediment of cascade reservoirs in the upper Mekong River over 5 years and modelled the influx and outflux of N and P species in each reservoir. Despite partially retaining total N and total P, reservoirs increased the downstream flux of ammonium and soluble reactive phosphorus (SRP). The increase in ammonium and SRP between outflux and influx showed positive linear relationships with the hydraulic residence time of the cascade reservoirs; and the ratio of SRP to dissolved inorganic nitrogen increased along the reservoir cascade. The lentic environment of reservoirs stimulated algae-mediated conversion of nitrate into ammonium in surface water; the hypoxic condition and the priming effect of algae-induced organic matter enhanced release of ammonium from sediment; the synergy of microbial phosphorylation, reductive condition and sediment geochemical properties increased release of SRP. This study is the first to provide solid evidence that hydropower reservoirs improve downstream nutrient bioavailability and N-P balance through a process of retention-transformation-transport, which may benefit primary productivity. These findings could advance our understanding of the eco-environmental impacts of river damming.

DOI: 10.1016/j.scib.2024.01.007

Source: https://www.sciencedirect.com/science/article/pii/S2095927324000124