Tue, Aug 16, 2022: 5:00 PM-6:30 PM
ESA Exhibit Hall
Background/Question/MethodsNitrogen (N) is limiting in boreal ecosystems, which shouldn’t allow for losses of N via leaching into waterways or via gaseous pathways. However, high concentrations of nitrate in streams, and extremely high ammonium in lakes and permafrost has been measured in permafrost influenced regions, indicating the potential for loses of N. One fate of N lost is as nitrous oxide (N2O), a greenhouse gas (GHG) with a global warming potential ~265 times greater than carbon dioxide (CO2), but N2O is understudied at high latitudes leaving the true magnitude of emissions unknown. In late summer 2021, along 3 transects in a palsa-forming peatland near Kuujjuarapik, QC, we measured in-situ flux of N2O, CO2 and CH4 using static chambers to calculate a linear flux, collected ancillary environmental data, and measured dissolved gas concentrations in thermokarst ponds and groundwater. In winter 2022, we will measure in-situ N2O, CO2 and CH4 concentrations in the soil and snowpack using gas-wells, and measure dissolved gas concentrations in the ponds. We will also collect continuous soil temperature data for correlation with the gas-well data, measure snow density to calculate potential fluxes out of the snow, and collect winter water chemistry data for correlation with dissolved gases.
Results/ConclusionsWe found no measurable N2O production at most sites along our transects extending from a thermokarsting palsa (underlain by permafrost) to three thermokarst ponds (no permafrost). However, one site on the downstream side of a pond produced a low flux of N2O, and we did find high linear production of CO2 at every site indicating that our method was working. In the ponds, N2O was undersaturated relative to atmospheric concentration (320 ppb), and concentrations declined at deeper depths suggesting denitrifiers were reducing N2O to N2. Extremely low nitrate and high ammonium concentrations in the ponds and groundwater, indicate that nitrification is likely not occurring. This means no N2O emissions from “leaky” nitrification, and no denitrification reducing nitrate to produce N2O. In most groundwater samples N2O was undersaturated, but in an area of active permafrost thaw groundwater was oversaturated with N2O (18.76 ppmv) relative to atmospheric concentration, indicating permafrost thaw could contribute to high N2O production by either nitrification or denitrification. However, we measured no N2O emissions at the surface above this oversaturated groundwater, indicating that N2O produced at depth is likely reduced to N2 before it is emitted. Our results indicate some boreal peatlands are likely consuming, not producing, N2O.
Results/ConclusionsWe found no measurable N2O production at most sites along our transects extending from a thermokarsting palsa (underlain by permafrost) to three thermokarst ponds (no permafrost). However, one site on the downstream side of a pond produced a low flux of N2O, and we did find high linear production of CO2 at every site indicating that our method was working. In the ponds, N2O was undersaturated relative to atmospheric concentration (320 ppb), and concentrations declined at deeper depths suggesting denitrifiers were reducing N2O to N2. Extremely low nitrate and high ammonium concentrations in the ponds and groundwater, indicate that nitrification is likely not occurring. This means no N2O emissions from “leaky” nitrification, and no denitrification reducing nitrate to produce N2O. In most groundwater samples N2O was undersaturated, but in an area of active permafrost thaw groundwater was oversaturated with N2O (18.76 ppmv) relative to atmospheric concentration, indicating permafrost thaw could contribute to high N2O production by either nitrification or denitrification. However, we measured no N2O emissions at the surface above this oversaturated groundwater, indicating that N2O produced at depth is likely reduced to N2 before it is emitted. Our results indicate some boreal peatlands are likely consuming, not producing, N2O.