Water, Air, & Soil Pollution

, 224:1693

Quantification of In Situ Denitrification Rates in Groundwater Below an Arable and a Grassland System

  • M. M. R. Jahangir
  • P. Johnston
  • K. Addy
  • M. I. Khalil
  • P. M. Groffman
  • K. G. Richards
Article

DOI: 10.1007/s11270-013-1693-z

Cite this article as:
Jahangir, M.M.R., Johnston, P., Addy, K. et al. Water Air Soil Pollut (2013) 224: 1693. doi:10.1007/s11270-013-1693-z
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Abstract

Understanding denitrification rates in groundwater ecosystems can help predict where agricultural reactive nitrogen (N) contributes to environmental degradation. In situ groundwater denitrification rates were determined in subsoil, at the bedrock interface and in bedrock at two sites, grassland and arable, using an in situ ‘push–pull’ method with 15N-labelled nitrate (NO3–N). Measured groundwater denitrification rates ranged from 1.3 to 469.5 μg N kg−1 day−1. Exceptionally high denitrification rates observed at the bedrock interface at grassland site (470 ± 152 μg N kg−1 day−1; SE, standard error) suggest that deep groundwater can serve as substantial hotspots for NO3–N removal. However, denitrification rates at the other locations were low and may not substantially reduce NO3–N delivery to surface waters. Denitrification rates were negatively correlated with ambient dissolved oxygen, redox potential, ks and NO3 (all p values, p < 0.01) and positively correlated with SO42− (p < 0.05). Higher mean N2O/(N2O + N2) ratios at an arable (0.28) site than the grassland (0.10) revealed that the arable site has higher potential to indirect N2O emissions. Identification of areas with high and low denitrification and related site parameters can be a tool to manage agricultural N to safeguard the environment.

Keywords

Denitrification15N-enrichment15N–N2O15N–N2GroundwaterN2O mole fraction

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • M. M. R. Jahangir
    • 1
    • 2
    • 3
  • P. Johnston
    • 2
  • K. Addy
    • 4
  • M. I. Khalil
    • 5
  • P. M. Groffman
    • 6
  • K. G. Richards
    • 1
  1. 1.Teagasc Environment Research CentreJohnstown Castle EstateCo. WexfordIreland
  2. 2.Department of Civil, Structural and Environmental EngineeringTrinity CollegeDublinIreland
  3. 3.Department of Soil ScienceBangladesh Agricultural UniversityMymensinghBangladesh
  4. 4.Department of Natural Resources ScienceUniversity of Rhode IslandKingstonUSA
  5. 5.Environmental Protection AgencyJohnstown Castle EstateCo. WexfordIreland
  6. 6.Cary Institute of Ecosystem StudiesMillbrookUSA