[Effects of leachate-loading and irrigation depth on N2O and CO2 emissions from leachate-irrigated soil]

By using prefabricated probe and static chamber, the N2O concentration at different depths along the soil columns irrigated by landfill leachate as well as the N2O and CO2 fluxes were determined. The results showed that leachate irrigation could promote the N2O emission. Within the first 24 hours after irrigation, the N2O fluxes from the soil columns were significantly correlated with the N2O concentrations in the columns at the depths of 10 cm (r = 0.944, P < 0.01), 20 cm (r = 0.799, P < 0.01), 30 cm (r = 0.666, P < 0.01), and 40 cm (r = 0.482, P < 0.05), and the correlation decreased along the depths. Landfill leachate irrigation also promoted the CO2 emission from the soil columns. There was no significant correlation between the emissions of N2O and CO2 (P > 0.05). The irrigation loading of landfill leachate had a predominant effect on the total greenhouse gas emissions (including N2O and CO2 fluxes, based on CO2-equivalent emissions). When the irrigation loading was 6 mm x d(-1), the total greenhouse gas emissions from the soil columns were 2 times higher than those when the irrigation loading was 2 mm x d(-1). 47% of the total greenhouse gas emissions were reduced from the soil columns when the leachate irrigation depth was at 20 cm, compared with the depth being at 10 cm. Within the 14 days under leachate irrigation, 57.0%-91.0% of the total greenhouse gas emissions were originated from N2O emission.