首页|Linking Water Age, Nitrate Export Regime, and Nitrate Isotope Biogeochemistry in a Tile-Drained Agricultural Field

Linking Water Age, Nitrate Export Regime, and Nitrate Isotope Biogeochemistry in a Tile-Drained Agricultural Field

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  • NETL
  • NSTL
  • Amer Geophysical Union
Accurately quantifying and predicting the reactive transport of nitrate (NO_3~- ) in hydrologic systems continues to be a challenge, due to the complex hydrological and biogeochemical interactions that underlie this transport. Recent advances related to time-variant water age have led to a new method that probes water mixing and selection behaviors using StorAge Selection (SAS) functions. In this study, SAS functions were applied to investigate storage, water selection behaviors, and NO_3~- export regimes in a tile-drained corn-soybean field. The natural abundance stable nitrogen and oxygen isotopes of tile drainage NO_3~- were also measured to provide constraints on biogeochemical NO_3~- transformations. The SAS functions, calibrated using chloride measurements at tile drain outlets, revealed a strong young water preference during tile discharge generation. The use of a time-variant SAS function for tile discharge generated unique water age dynamics that reveal an inverse storage effect driven by the activation of preferential flow paths and mechanically explain the observed variations in NO_3~- isotopes. Combining the water age estimates with NO_3~- isotope fingerprinting shed new light on NO_3~- export dynamics at the tile-drain scale, where a large mixing volume and the lack of a strong vertical contrast in NO_3~- concentration resulted in chemostatic export regimes. For the first time, NO_3~- isotopes were embedded into a water age-based transport model to model reactive NO_3~- transport under transient conditions. The results of this modeling study provided a proof-of-concept for the potential of coupling water age modeling with NO_3~- isotope analysis to elucidate the mechanisms driving reactive NO_3~- transport.

Zhongjie Yu、Yinchao Hu、Lowell E. Gentry、Wendy H. Yang、Andrew J. Margenot、Kaiyu Guan、Corey A. Mitchell、Minpeng Hu

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Department of Natural Resources and Environmenlal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Department of Plant Biology, University of Illinois at Urbana-Champaign, Urbana, IL, USA||Department of Earth Science & Environmental Change, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Department of Crop Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA

Department of Natural Resources and Environmenlal Sciences, University of Illinois at Urbana-Champaign, Urbana, IL, USA||Agroecosystem Sustainability Center, University of Illinois at Urbana-Champaign, Urbana, IL, USA

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2023

10.1029/2023WR034948

Water resources research

Water resources research

EISCI
ISSN：0043-1397
年,卷(期)：2023.59(12)
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