Abstract
Intensive nitrous oxide (N2O) emissions usually occur at the working face of landfills. However, the specific amounts and contributions of the multiple pathways to N2O emissions are poorly understood. N2O emissions and the mutual conversions of N-species in both open and sealed simulated landfill reactors filled with fresh refuse were examined during a 100-h incubation period, and N2O sources were calculated using 15N isotope labelling. N2O peak fluxes were above 70μgNkg−1 waste h−1 for both treatments. The sealed incubation reactors became a N2O sink when N2O in the ambient environment was sufficient. The total amount of N2O emissions under sealed conditions was 2.15±0.56mgNkg−1 waste, which was higher than that under open conditions (1.91±0.34mgNkg−1 waste). The NO2− peak appeared prior to the peak in N2O flux. The degree and duration of total nitrogen reduction in open incubations were larger and longer than those of sealed incubations and could possibly be due to oxygen supplementation. Denitrification (DF) was a major source of N2O generation during these incubations. The contribution of the DF pathway decreased from 89.2% to 61.3% during the open incubations. The effects of nitrification (NF) and nitrification-coupled denitrification (NCD) increased during the increasing phase and the decreasing phase of N2O flux, contributing 24.1–37.4% and 31.7–34.4% of total N2O emissions, respectively. In sealed treatments, the DF pathway accounted for more than 90% of the total N2O emission during the entire incubation.
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