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Purpose <p>Determining redox state threshold for nitrous oxide (N<sub>2</sub>O) emissions and revealing the indirect regulatory impact of organic carbon on N<sub>2</sub>O production rates helps to further clarify the biogeochemical mechanism of sediment N<sub>2</sub>O emissions in shallow lakes.</p> Methods <p>Different forms of nitrogen (N) and phosphorus (P) in surface and interstitial water, carbon (C), P and iron (Fe) compounds, N<sub>2</sub>O production rate, oxidation-reduction potential (ORP<sub>sed</sub>), as well as functional genes (<i>nirS</i>, <i>nirK</i>, and <i>nosZ</i> genes) in sediments were analyzed.</p> Results <p>Sediment N<sub>2</sub>O production rates changed non-monotonically with the changing of redox state (ORP<sub>sed</sub> and ratio of ferrous ion (Fe(Ⅱ)) and total iron (TFe) (Fe(Ⅱ)/TFe)), forming an inverted V-shaped curve, and with the highest N<sub>2</sub>O production rate at an intermediate ORP<sub>sed</sub> (around 126.5 mV) and Fe(Ⅱ)/TFe (around 0.72) in some light and middle eutrophic lakes. Hypereutrophic lakes showed lower sediment redox states, thus had lower N<sub>2</sub>O production rates, which was attributed to the shift from incomplete to complete denitrification. Sediment redox state was regulated by organic carbon directly or indirectly through the coupling of C, N, P, oxygen (O) and Fe cycling processes. The community structure and function of nitrite-reducing bacteria (i.e. <i>nirS</i> and <i>nirK</i>) and N<sub>2</sub>O-reducing bacteria (i.e. <i>nosZ</i>) were mainly shaped by C, N, P, O, and Fe in sediment, which were all controlled by organic carbon.</p> Conclusion <p>Organic carbon shaped sediment redox state and microbial community structure of N<sub>2</sub>O-producers and N<sub>2</sub>O-reducers directly and indirectly by altering N, P, O and Fe cycles in sediment, and further regulated N<sub>2</sub>O emissions.</p>

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Sediment redox state threshold for N2O emissions and indirect regulatory impact of organic carbon in shallow lakes

  • 期刊论文

  • 发表日期：

    2025年9月18日

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  • Hui Li,
  • Huatang Deng,
  • Yingying Cai,
  • Jianfen Li,
  • Zhenhua Qin,
  • Fangyuan Chen,
  • Xiuyun Cao,
  • Chunlei Song,
  • XinBin Duan

摘要

Purpose

Determining redox state threshold for nitrous oxide (N2O) emissions and revealing the indirect regulatory impact of organic carbon on N2O production rates helps to further clarify the biogeochemical mechanism of sediment N2O emissions in shallow lakes.

Methods

Different forms of nitrogen (N) and phosphorus (P) in surface and interstitial water, carbon (C), P and iron (Fe) compounds, N2O production rate, oxidation-reduction potential (ORPsed), as well as functional genes (nirS, nirK, and nosZ genes) in sediments were analyzed.

Results

Sediment N2O production rates changed non-monotonically with the changing of redox state (ORPsed and ratio of ferrous ion (Fe(Ⅱ)) and total iron (TFe) (Fe(Ⅱ)/TFe)), forming an inverted V-shaped curve, and with the highest N2O production rate at an intermediate ORPsed (around 126.5 mV) and Fe(Ⅱ)/TFe (around 0.72) in some light and middle eutrophic lakes. Hypereutrophic lakes showed lower sediment redox states, thus had lower N2O production rates, which was attributed to the shift from incomplete to complete denitrification. Sediment redox state was regulated by organic carbon directly or indirectly through the coupling of C, N, P, oxygen (O) and Fe cycling processes. The community structure and function of nitrite-reducing bacteria (i.e. nirS and nirK) and N2O-reducing bacteria (i.e. nosZ) were mainly shaped by C, N, P, O, and Fe in sediment, which were all controlled by organic carbon.

Conclusion

Organic carbon shaped sediment redox state and microbial community structure of N2O-producers and N2O-reducers directly and indirectly by altering N, P, O and Fe cycles in sediment, and further regulated N2O emissions.