Research
| Title： | Sediment redox state threshold for N2O emissions and indirect regulatory impact of organic carbon in shallow lakes |
|---|---|
| First author： | Li, Hui; Deng, Huatang; Cai, Yingying; Li, Jianfen; Qin, Zhenhua; Chen, Fangyuan; Cao, Xiuyun; Song, Chunlei; Duan, XinBin |
| Journal： | JOURNAL OF SOILS AND SEDIMENTS |
| Years： | 2025 |
| DOI： | 10.1007/s11368-025-04129-0 |
| Abstract： | PurposeDetermining 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.MethodsDifferent 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.ResultsSediment 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.ConclusionOrganic 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. |
