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Article

Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization

Juelich Research Centre, Agrosphere Institute (IBG-3), 52425 Juelich, Germany
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Water 2020, 12(10), 2918; https://doi.org/10.3390/w12102918
Received: 12 August 2020 / Revised: 13 October 2020 / Accepted: 16 October 2020 / Published: 19 October 2020
(This article belongs to the Section Wastewater Treatment and Reuse)
Soils are the dominant source of atmospheric nitrous oxide (N2O), especially agricultural soils that experience both waterlogging and intensive nitrogen fertilization. However, soil heterogeneity and the irregular occurrence of hydrological events hamper the prediction of the temporal and spatial dynamics of N2O production and transport in soils. Because soil moisture influences soil redox potential, and as soil N cycling processes are redox-sensitive, redox potential measurements could help us to better understand and predict soil N cycling and N2O emissions. Despite its importance, only a few studies have investigated the control of redox potential on N2Oemission from soils in detail. This study aimed to partition the different microbial processes involved in N2O production (nitrification and denitrification) by using redox measurements combined with isotope analysis at natural abundance and 15N-enriched. To this end, we performed long-term laboratory lysimeter experiments to mimic common agricultural irrigation and fertilization procedures. In addition, we used isotope analysis to characterize the distribution and partitioning of N2O sources and explored the 15N-N2O site preference to further constrain N2O microbial processes. We found that irrigation, saturation, and drainage induced changes in soil redox potential, which were closely related to changes in N2O emission from the soil as well as to changes in the vertical concentration profiles of dissolved N2O, nitrate (NO3) and ammonium (NH4+). The results showed that the redox potential could be used as an indicator for NH4+, NO3, and N2O production and consumption processes along the soil profile. For example, after a longer saturation period of unfertilized soil, the NO3 concentration was linearly correlated with the average redox values at the different depths (R2 = 0.81). During the transition from saturation to drainage, but before fertilization, the soil showed an increase in N2O emissions, which originated mainly from nitrification as indicated by the isotopic signatures of N2O (δ15N bulk, δ18O and 15N-N2O site preference). After fertilization, N2O still mainly originated from nitrification at the beginning, also indicated by high redox potential and the increase of dissolved NO3. Denitrification mainly occurred during the last saturation period, deduced from the simultaneous 15N isotope analysis of NO3 and N2O. Our findings suggest that redox potential measurements provide suitable information for improving the prediction of soil N2O emissions and the distribution of mineral N species along the soil profile under different hydrological and fertilization regimes. View Full-Text
Keywords: water table fluctuations; isotope; soil redox potential; soil geochemistry; N-cycle; N2O emissions water table fluctuations; isotope; soil redox potential; soil geochemistry; N-cycle; N2O emissions
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MDPI and ACS Style

Wang, J.; Bogena, H.R.; Vereecken, H.; Brüggemann, N. Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization. Water 2020, 12, 2918. https://doi.org/10.3390/w12102918

AMA Style

Wang J, Bogena HR, Vereecken H, Brüggemann N. Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization. Water. 2020; 12(10):2918. https://doi.org/10.3390/w12102918

Chicago/Turabian Style

Wang, Jihuan, Heye R. Bogena, Harry Vereecken, and Nicolas Brüggemann. 2020. "Stable-Isotope-Aided Investigation of the Effect of Redox Potential on Nitrous Oxide Emissions as Affected by Water Status and N Fertilization" Water 12, no. 10: 2918. https://doi.org/10.3390/w12102918

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