Spatial distribution characteristics of dissolved n2o in unconfi ned groundwater of an agricultural catchment affected by signifi cant fertilizer application

Koki Onishi, Shin Ichi Onodera, Mitsuyo Saito, Yuta Shimizu, Masashi Yoshikawa

Research output: Contribution to journalArticle


Spatial distribution characteristics of nitrous oxide (N2O) in an unconfi ned aquifer were examined, based on changes in concentrations of N2O, nitrate-nitrogen (NO3--N) and other chemical components with the groundwater fl ow of an agricultural catchment affected by signifi cant fertilizer application. N2O concentrations were about 4μgN L-1 in the upstream area, and were positively correlated with NO3--N concentrations. These results suggest that the nitrifi cation process infl uences N2O concentrations in upstream areas. In the downstream area, N2O concentrations in deeper groundwater (> 15 m) were signifi cantly higher (13 μgN L-1), but they were very low in shallower groundwater (< 15 m), below the detection limit. Spatial distributions of dissolved oxygen (DO) and dissolved organic carbon (DOC) suggest that shallower groundwater is characterized by a strong reducing condition and high organic carbon content compared to deeper groundwater. These results suggest that a complete denitrifi cation process (NO3- → N2) occurs in shallower groundwater, whereas an incomplete denitrifi cation process causes the increase of N2O concentrations found in deeper groundwater.

Original languageEnglish
Pages (from-to)1-11
Number of pages11
JournalJapanese Journal of Limnology
Issue number1
Publication statusPublished - Jan 1 2014



  • Agricultural catchment
  • Denitrifi cation
  • Groundwater
  • N2O
  • Nitrifi cation

ASJC Scopus subject areas

  • Aquatic Science
  • Ecology
  • Water Science and Technology

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