Evaluation of Leachate Recirculation on Nitrous Oxide Production in the Likang Landfill, China
2002
Lee, Chun Man | Lin, Xue Rui | Lan, Chong Yu | Lo, Samuel Chun Lap | Chan, Gilbert Yuk Sing
Landfill leachate recirculation is efficient in reducing the leachate quantity handled by a leachate treatment plant. However, after land application of leachate, nitrification and denitrification of the ammoniacal N becomes possible and the greenhouse gas nitrous oxide (N₂O) is produced. Lack of information on the effects of leachate recirculation on N₂O production led to a field study being conducted in the Likang Landfill (Guangzhou, China) where leachate recirculation had been practiced for 8 yr. Monthly productions and fluxes of N₂O from leachate and soil were studied from June to November 2000. Environmental and chemical factors regulating N₂O production were also accessed. An impermeable top liner was not used at this site; municipal solid waste was simply covered by inert soil and compacted by bulldozers. A high N₂O emission rate (113 mg m⁻² h⁻¹) was detected from a leachate pond purposely formed on topsoil within the landfill boundary after leachate irrigation. A high N₂O level (1.09 μg L⁻¹) was detected in a gas sample emitted from topsoil 1 m from the leachate pond. Nitrous oxide production from denitrification in leachate-contaminated soil was at least 20 times higher than that from nitrification based on laboratory incubation studies. The N₂O levels emitted from leachate ponds were compared with figures reported for different ecosystems and showed that the results of the present study were 68.7 to 88.6 times higher. Leachate recirculation can be a cost-effective operation in reducing the volume of leachate to be treated in landfill. However, to reduce N₂O flux, leachate should be applied to underground soil rather than being irrigated and allowed to flow on topsoil.
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