GEOSCAN, résultats de la recherche


TitreEvaluating the sources and fate of anthropogenic dissolved inorganic nitrogen (DIN) in two contrasting North Sea estuaries
AuteurAhad, J M E; Ganeshram, R S; Spencer, R G M; Uher, G; Upstill-Goddard, R C; Cowie, G L
SourceScience of the Total Environment vol. 372, 2006 p. 317-333,
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110087
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Lat/Long OENS -2.0000 -1.0000 56.0000 54.0000
Sujetsmilieu côtièr; études côtières; estuaires; dépôts estuairiens; études estuairiennes; nitrate; azote; isotopes; etudes isotopiques; rapports isotopiques; géologie marine
Illustrationslocation maps; plots
Résumé(disponible en anglais seulement)
Nitrogen isotope ratios (delta15N) were used to help elucidate the sources and fate of ammonium (NH4+) and nitrate (NO3-) in two northeastern English estuaries. The dominant feature of NH4+ in the heavily urbanised Tyne estuary was a plume arising from a single point source; a large sewage works. Although NH4 + concentrations (ranging from 30 - 150 Mu M) near the sewage outfall varied considerably between surveys, the sewage-derived delta15N-NH4 + signature was remarkably constant (+10.6±0.5permil) and could be tracked across the estuary. As indirectly supported by 15N-depleted delta15N-NO3- values observed close to the mouth of the Tyne, this sewage-derived NH4+ was thought to initiate lower estuarine and coastal zone nitrification. In the more rural Tweed, NH4+
concentrations were low (b7 Mu M) compared to those in the Tyne and delta15N-NH4+ values were consistent with mixing between
riverine and marine sources. The dominant form of dissolved inorganic nitrogen (DIN) in the Tweed was agricultural soil-derived
NO3-. A decrease in riverine NO3- flux during the summer coinciding with an increase in delta15N-NO3- values was mainly attributed to
enhanced watershed nutrient processing. In the Tyne, where agricultural inputs are less important compared to the Tweed, light
delta15N-NO3- (ca. 0permil) detected in the estuary during one winter survey pointed to a larger contribution from precipitation-derived NO3- during high river discharge. Regardless of the dominant sources, in both estuaries most of the variability in DIN concentrations and delta15N values was explained by simple end-member mixing models, implying very little estuarine processing.