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TitleNitrate isotopes unveil distinct seasonal N-sources and the critical role of crop residues in groundwater contamination
AuthorSavard, M M; Somers, G; Smirnoff, A; Paradis, D; van Bochove, E; Liao, S
SourceJournal of Hydrology vol. 381, issue 1-2, 2010 p. 134-141,
Alt SeriesEarth Sciences Sector, Contribution Series 20100307
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvincePrince Edward Island
NTS11L/05; 11L/12; 21I/09
Lat/Long WENS-64.5000 -63.5000 46.7500 46.2500
Subjectshydrogeology; geochemistry; groundwater regimes; groundwater pollution; groundwater geochemistry; groundwater; watersheds; environmental studies; environmental analysis; nitrate; Wilmot watershed
Illustrationstables; plots; histograms; location maps
ProgramGroundwater Geoscience
AbstractGlobally, fertilizers are identified as principle sources of nitrate in waters of intensely cultivated areas. Here this general concept is appraised on a seasonal basis over a two year period, under temperate climatic conditions. Water (delta2H and delta18O) and nitrate (delta15N and delta18O) isotopes in surface water and groundwater suggest that freshwater is acting as a transport vector conducting nitrate from agricultural soils to groundwater and ultimately to surface water. Measured nitrate isotopes of organic and inorganic fertilizers and of nitrate in groundwater are used to constrain a conceptual apportionment model quantifying the relative seasonal N contributions in an area of intense potato production. Source inputs differ strongly between the growing (summer and fall) and non-growing (winter and spring) periods. Chemical fertilizers and soil organic matter equally dominate and contribute to the growing period load, whereas soil organic matter dominates the non-growing period load, and accounts for over half of the overall annual nitrogen charge. These findings reveal the magnitude of nitrogen cycling by soil organic matter, and point to the benefits of controlling the timing of its nitrate release from this organic material. We conclude that strategies to attenuate contamination by nitrate in waters of temperate climate row-cropping regions must consider nitrogen cycling by soil organic matter, including the crucial role of crop residues throughout both the growing and non-growing seasons.