Key Laboratory of the Three Gorges Reservoir Region's Eco-Environment, Ministry of Education, Chongqing University, Chongqing, 400045, China.
College of Urban Construction & Environmental Engineering, Chongqing University, Chongqing, 400045, China.
Environ Sci Pollut Res Int. 2019 Jan;26(3):2898-2907. doi: 10.1007/s11356-018-3716-1. Epub 2018 Nov 29.
Dissolved oxygen (DO) stratification is a natural phenomenon in lakes, which potentially influences nitrogen (N) biogeochemical cycle. However, the specific effects of DO stratification on N speciation and transformation behaviors in different water layers are still poorly understood. Here, we reported that DO stratification remarkably influenced N species and transformation pathways in different water columns by high frequency sampling during summers in Longjing Lake, China. Results showed that DO stratification in the lake created three water layers: epilimnion (1-3 m), oxycline (4-11 m), and hypolimnion (12-20 m). In the epilimnion, N speciation was mainly controlled by phytoplankton assimilation and organic N dominated in this layer. Oxycline was the major place for N transformations and had the most notable N removal capacity (714 kg N from June to August). In the hypolimnion, [Formula: see text] was the major N species, and sediment release contributed nearly 85% hypolimnetic [Formula: see text]. Furthermore, approximately 8 kg of dissolved NO was also accumulated in the hypolimnion, contributing ~ 70% of NO in the whole lake. Overall, our results indicated that DO stratification caused the shifts in N speciation and transformation behaviors among different water columns, which may have a great implication for lake managements for providing separated protection strategies from different water depths.
溶解氧（DO）分层是湖泊中的一种自然现象，它可能会影响氮（N）的生物地球化学循环。然而，DO 分层对不同水层中 N 形态和转化行为的具体影响仍知之甚少。在这里，我们通过在中国龙井湖夏季的高频采样，报道了 DO 分层对不同水柱中 N 物种和转化途径的显著影响。结果表明，DO 分层在湖中形成了三个水层：表水层（1-3 m）、氧跃层（4-11 m）和下水层（12-20 m）。在表水层中，N 形态主要受浮游植物同化控制，该层中有机氮占主导地位。氧跃层是 N 转化的主要场所，具有最显著的 N 去除能力（6-8 月去除 714 kg N）。在下水层中，[Formula: see text]是主要的 N 物种，沉积物释放贡献了下水层中近 85%的[Formula: see text]。此外，下水层中还积累了约 8 kg 的溶解态 NO，占整个湖泊中 NO 的约 70%。总的来说，我们的结果表明，DO 分层导致了不同水层中 N 形态和转化行为的转变，这可能对湖泊管理具有重要意义，为不同水深提供了有针对性的保护策略。
