Widespread nitrous oxide undersaturation in farm waterbodies creates an unexpected greenhouse gas sink

Jackie R. Webb*, Nicole M. Hayes, Gavin L. Simpson, Peter R. Leavitt, Helen M. Baulch, Kerri Finlay

*Corresponding author af dette arbejde

Publikation: Bidrag til tidsskrift/Konferencebidrag i tidsskrift /Bidrag til avisTidsskriftartikelForskningpeer review

18 Citationer (Scopus)

Abstract

Nitrogen pollution and global eutrophication are predicted to increase nitrous oxide (N2O) emissions from freshwater ecosystems. Surface waters within agricultural landscapes experience the full impact of these pressures and can contribute substantially to total landscape N2O emissions. However, N2O measurements to date have focused on flowing waters. Small artificial waterbodies remain greatly understudied in the context of agricultural N2O emissions. This study provides a regional analysis of N2O measurements in small (<0.01 km2) artificial reservoirs, of which an estimated 16 million exist globally. We show that 67% of reservoirs were N2O sinks (−12 to −2 μmol N2O·m−2·d−1) in Canada’s largest agricultural area, despite their highly eutrophic status [99 ± 289 μg·L−1 chlorophyll-a (Chl-a)]. Generalized additive models indicated that in situ N2O concentrations were strongly and nonlinearly related to stratification strength and dissolved inorganic nitrogen content, with the lowest N2O levels under conditions of strong water column stability and high algal biomass. Predicted fluxes from previously published models based on lakes, reservoirs, and agricultural waters overestimated measured fluxes on average by 7- to 33-fold, challenging the widely held view that eutrophic N-enriched waters are sources of N2O.

OriginalsprogEngelsk
TidsskriftProceedings of the National Academy of Sciences
Vol/bind116
Nummer20
Sider (fra-til)9814-9819
Antal sider6
ISSN0027-8424
DOI
StatusUdgivet - 14 maj 2019

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