南京轿子山生活垃圾填埋场温室气体释放的变化规律

垃圾填埋场是全球温室气体释放的重要来源. 在南京轿子山生活垃圾填埋场3个具有不同填埋龄(4~13 a)、覆土深度(30~100 cm)和有无填埋气收集系统的平台,采用静态箱气相色谱法对填埋场CH₄和N₂O的释放规律进行了研究. 结果表明:填埋龄与覆土深度对填埋场CH₄和N₂O的释放影响显著,与其他2个平台相比,填埋龄(10~15 a)长、覆土深度(80~100 cm)大且无填埋气收集系统的平台1的CH₄和N₂O四季及昼夜释放通量均相对较小,相差为2个数量级；虽然3个平台温室气体释放通量的昼夜和季节性变化规律并不一致,但在春季均出现最小值,CH₄和N₂O的最小释放通量分别约为30和186.49 μg/(m2·h). 夏季、秋冬季交替及冬春季交替时期,CH₄和N₂O的释放通量均出现峰值,晚上的释放量约占全天释放总量的70%左右. 垃圾填埋场是高度异质性体系,相关性分析表明,CH₄释放通量与覆土温度、覆土含水率无显著相关性,而N₂O释放通量却与这2个指标呈显著相关. CH₄释放通量季节和昼夜性变化较稳定,变异系数范围分别为13%~405%和43%~429%. N₂O释放通量的季节性和昼夜性变异水平较高,变异系数范围分别为15%~1 005%和17%~1 552%,因此有必要进行全时段监测. 

Study on the Variation Regularity of Greenhouse Gas Release from Jiaozishan Mountain Municipal Solid Waste Landfill

Greenhouse gas emissions (CH₄ and N₂O) from municipal solid waste landfills were investigated using the gas chromatography (GC)-static chamber method. The diurnal variations of CH₄ and N₂O emissions in three different landfill areas were monitored. In addition, greenhouse gas emissions under different conditions of landfill lifts, landfill age (4-13 a), cover soil type (80-100 cm), and gas collection systems were investigated. The rhythms of CH₄ and N₂O fluxes from MSW landfills were studied diurnally, and under over four selected seasons. The results showed that CH₄ and N₂O emissions varied substantially with landfill age and depth. Compared with the oldest landfill age (10-15 a) and the deepest depth (80-100 cm), the minimum emissions observed varied by two orders of magnitude. The landfill showed significant spatial and temporal variations, due to great natural heterogeneities. Although the diurnal and seasonal variations of CH₄ and N₂O fluxes in the three selected landfill sites were different from each other, the least emission fluxes were observed in spring, with the CH₄ flux of 30 and N₂O flux of 186.49 μg/(m2·h). CH₄ and N₂O fluxes were higher in summer and during the transitions of the autumn/winter and winter/spring. About 70% of the greenhouse gases were emitted in the evening. The landfill is a highly heterogeneous system. CH₄ fluxes were not significantly correlated with soil temperature and soil water content during the measurement, while N₂O fluxes were positively correlated with soil temperature and soil water content. The diurnal and seasonal variations of CH₄ fluxes showed better stability, with variation coefficients in the range of 13% to 405% and 43% to 429% separately. There were great diurnal and seasonal variations of N₂O emissions, with variation coefficients in the range of 15% to 1005% and 17% to 1552% separately. This implies that low frequency measurements are likely resulting in greatly over-or under-estimated N₂O emissions. It is necessary to provide full-time monitoring and control of greenhouse gas emissions.