Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, Ocean University of China, Qingdao, 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China; MIT-WHOI Joint Program in Oceanography/Applied Ocean Science & Engineering, Cambridge and Woods Hole, MA, USA.
Frontiers Science Center for Deep Ocean Multispheres and Earth System, Key Laboratory of Marine Chemistry Theory and Technology Ministry of Education, Ocean University of China, Qingdao, 266100, China; Laboratory for Marine Ecology and Environmental Science, Qingdao National Laboratory for Marine Science and Technology, Qingdao, 266237, China.
Environ Res. 2021 Apr;195:110759. doi: 10.1016/j.envres.2021.110759. Epub 2021 Jan 23.
The alterations of nitrogen sources and cycling within the Three Gorges Reservoir (TGR) and downstream the Changjiang were investigated to understand the impacts of the construction of the Three Gorges Dam (TGD) and anthropogenic inputs from the associated watershed. Water samples collected in October 2016 were analyzed for hydrologic parameters, nutrient concentrations, and stable isotopes of nitrate (NO), ammonium (NH) and particulate matter. Nitrate dual stable isotope values ranged from +5.8‰ to +7.1‰ and -1.9‰ to +0.4‰ for δN and δO, respectively. δN values in particulate nitrogen (PN) ranged from +0.5‰ to +8.5‰, with slightly lower values before the dam. δN-NH values ranged between +10.5‰ and +19.4‰, likely reflecting the presence of ammonium assimilation throughout the TGR. The contribution of different nitrogen sources was calculated using a Bayesian mixing model. These sources, including soil organic nitrogen, ammonium fertilizer, and sewage effluent, contributed to elevated DIN concentrations within the TGR (83.2 μM-178.5 μM). The construction of the dam has also likely induced changes in the river environment such as ammonium assimilation in the surface waters and nitrification and/or remineralization within the deep waters of the TGR. Overall, during this investigation period, the TGR acted as a sink of PN (retaining 29%), yet negligibly influenced levels of TDN with ~96.5% of TDN exported to the downstream Changjiang and estuary. It is important to understand the long-term impacts of the TGD on the ecological environment of the Changjiang. This study highlights the influence that anthropogenic nitrogen sources have on the natural biogeochemical cycling within the TGR, showing the urgent need to reduce anthropogenic nitrogen pollution.
本研究调查了三峡水库（TGR）及其下游长江的氮源和循环变化，以了解三峡大坝（TGD）建设和相关流域人为输入的影响。于 2016 年 10 月采集水样，分析了水文参数、营养盐浓度和硝酸盐（NO）、铵（NH）和颗粒态物质的稳定同位素。硝酸盐双稳定同位素值分别为 δN+5.8‰-+7.1‰和 δO-1.9‰-+0.4‰。颗粒态氮（PN）中的 δN 值范围为+0.5‰-+8.5‰，大坝前略低。δN-NH 值范围在+10.5‰-+19.4‰之间，可能反映了整个 TGR 中铵盐同化的存在。不同氮源的贡献通过贝叶斯混合模型计算。这些来源包括土壤有机氮、铵肥和污水，导致 TGR 中 DIN 浓度升高（83.2 μM-178.5 μM）。大坝的建设也可能导致河流环境发生变化，如地表水中的铵盐同化以及 TGR 深部的硝化和/或矿化。总的来说，在调查期间，TGR 作为 PN 的汇（保留 29%），但对 TDN 水平的影响可以忽略不计，约 96.5%的 TDN 被输送到下游长江和河口。了解 TGD 对长江生态环境的长期影响非常重要。本研究强调了人为氮源对 TGR 自然生物地球化学循环的影响，表明迫切需要减少人为氮污染。
