Li Xiaofei, Gao Dengzhou, Hou Lijun, Qian Wei, Liu Min, Zeng Hongda, Chen Zhibiao, Tong Chuan
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China; Key Laboratory for Humid Subtropical Eco-geographical Processes of the Ministry of Education, Fujian Normal University, Fuzhou, 350007, China.
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, 200241, China.
Environ Pollut. 2021 May 15;277:116757. doi: 10.1016/j.envpol.2021.116757. Epub 2021 Feb 22.
Estuarine sediment denitrification and anammox in response to increased nitrogen (N) loads remain poorly understood. In this study, we used N isotope tracer approach to investigate the spatial distribution of denitrification and anammox and identified the crucial controls on the partitioning of dinitrogen gas (N) production along the Min River Estuary (MRE), a highly impacted estuary in southeast China. The results indicated that denitrification and anammox rates ranged from 10.5 to 70.7 nmol g h and from 0.44 to 4.31 nmol g h, respectively. Relative contribution of anammox to N production (R) was in a range of 1.04-15.1%, tending to increase toward estuary mouth. Denitrification rates were significantly higher in upper (high N loads) than in lower estuary (low N loads), while anammox rates and R showed inverse distributions along the MRE. Wastewater discharge caused the N point pollution triggering denitrification but inhibiting anammox. The best predictor of the variations in denitrification rates was total nitrogen, whereas pH and NH could explained the variations in anammox rates across the estuary. The crucial predictors for the partitioning of N production between denitrification and anammox were NH and NO. These results suggest that the increase in human activities intensity can alter the partitioning of N production between denitrification and anammox, and the magnitude of this switch can be predicted by N loads in MRE and other highly impacted estuaries.
河口沉积物反硝化作用和厌氧氨氧化作用对增加的氮（N）负荷的响应仍知之甚少。在本研究中，我们采用氮同位素示踪方法研究了反硝化作用和厌氧氨氧化作用的空间分布，并确定了中国东南部一个受严重影响的河口——闽江口（MRE）沿程二氮气体（N₂）产生分配的关键控制因素。结果表明，反硝化作用速率和厌氧氨氧化作用速率分别为10.5至70.7 nmol g⁻¹ h⁻¹和0.44至4.31 nmol g⁻¹ h⁻¹。厌氧氨氧化作用对N₂产生的相对贡献（R）在1.04 - 15.1%范围内，且有向河口口门增加的趋势。河口上段（高氮负荷）的反硝化作用速率显著高于下段（低氮负荷），而厌氧氨氧化作用速率和R沿闽江口呈相反分布。废水排放导致氮点源污染，引发反硝化作用但抑制厌氧氨氧化作用。反硝化作用速率变化的最佳预测指标是总氮，而pH值和NH₄⁺可以解释整个河口厌氧氨氧化作用速率的变化。反硝化作用和厌氧氨氧化作用之间N₂产生分配的关键预测指标是NH₄⁺和NO₃⁻。这些结果表明，人类活动强度的增加会改变反硝化作用和厌氧氨氧化作用之间N₂产生的分配，并且这种转变的幅度可以通过闽江口及其他受严重影响河口的氮负荷来预测。
