Assessment of hydrological and biogeochemical effects on N2O emission factors in river networks of eastern China based on long-term study
- 1Zhejiang University, College of Environment and Resources, Hangzhou, China (hmpjerry1991@zju.edu.cn)
- 2Department of Land, Air, and Water Resources, University of California, Davis, CA 95616, USA
The N2O emission factors (EF) in river networks remains a major source of uncertainty due to limited data availability. This study integrated three years of multiple stable isotope (15N-NO3-/18O-NO3- and 2H-H2O/18O-H2O) and hydrochemistry measurements for river water and groundwater to evaluate the effects of hydrological and biogeochemical processes on riverine N2O emission factors in the Yongan watershed (2474 km2) of subtropical eastern China. The EF in groundwater (0.00195 ± 0.00146) was about one magnitude higher than that in surface water (0.00038 ± 0.00020). The N2O EF displayed seasonal and spatial variability in surface water and groundwater. The emission factors in surface water showed negative relationship with N levels and positive relationship with dissolved organic carbon: DIN (C:N) ratio. In contrast, N2O EF in groundwater showed positive relationship with N level and negative relationship with DO concentration, implying quite different processes undergoing in surface water and groundwater. The 2H-H2O/18O-H2O information suggested high base flow contribution (~70%) to rivers, implying the potential N2O contribution from groundwater to riverine N2O. Information from 15N-NO3- and 18O-NO3- indicated that N2O in groundwater were regulated by nitrification and denitrification, while N2O in river networks was mainly derived from nitrification and may be also regulated by hydrological processes. The strong positive relationship between riverine N2O concentrations and that in groundwater may indicate the potential high contribution of groundwater N2O to surface water. This study highlights the importance of combining multiple isotope tracers and hydrochemistry to assess the riverine N2O dynamics, as well as the necessity to consider the potential impact from groundwater N2O contribution during the determination of riverine N2O emission factors in rivers with high groundwater recharge.
How to cite: Hu, M., Dahlgren, R., and Chen, D.: Assessment of hydrological and biogeochemical effects on N2O emission factors in river networks of eastern China based on long-term study, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12362, https://doi.org/10.5194/egusphere-egu2020-12362, 2020
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