, Volume 35, Issue 2, pp 305–326 | Cite as

Losses of inorganic carbon and nitrous oxide from a temperate freshwater wetland in relation to nitrate loading

  • Claus Paludan
  • Gitte Blicher-Mathiesen


We studied the export of inorganic carbon and nitrous oxide (N2O) from a Danish freshwater wetland. The wetland is situated in an agricultural catchment area and is recharged by groundwater enriched with nitrate (NO3) (∼1000 μM). NO3 in recharging groundwater was reduced (57.5 mol NO3 m−2 yr) within a narrow zone of the wetland. Congruently, the annual efflux of carbon dioxide (CO2) from the sediment was 19.1 mol C m−2 when estimated from monthly in situ measurements. In comparison the CO2 efflux was 4.8 mol C m−2 yr−1 further out in the wetland, where no NO3 reduction occurred. Annual exports of inorganic carbon in groundwater and surface water was 78.4 mol C m−2 and 6.1 mol C m−2 at the two sites, respectively. N2O efflux from the sedimenst was detectable on five out of twelve sampling dates and was significantly (P < 0.0001) higher in the NO3 reduction zone (0.35–9.40 μmol m−2 h−1, range of monthly means) than in the zone without NO3 reduction (0.21–0.41 μmol m−2 h−1). No loss of dissolved N2O could be measured. Total annual export of N2O was not estimated. The reduction of oxygen (O2) in groundwater was minor throughout the wetland and did not exceed 0.2 mol 02 m−2yr−1. Sulfate (SO4−−) was reduced in groundwater (2.1 mol SO4−− m−2 yr−1) in the zone without NO3 reduction. Although the NO3 in our wetland can be reduced along several pathways our results strongly suggest that NO3 loading of freshwater wetlands disturb the carbon balance of such areas, resulting in an accelerated loss of inorganic carbon in gaseous and dissolved forms.

Key words

freshwater wetlands NO3 loading CO2 efflux DIC export N2O efflux 


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Copyright information

© Kluwer Academic Publishers 1996

Authors and Affiliations

  • Claus Paludan
    • 1
  • Gitte Blicher-Mathiesen
    • 1
  1. 1.National Environmental Research InstituteDepartment of Freshwater EcologySilkeborgDenmark

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