干湿交替下植物单种与混种对土质覆盖层甲烷减排的影响

EFFECTS OF METHANE EMISSION REDUCTION IN EARTHEN LANDFILL COVER BY SINGLE AND MIXED PLANT SPECIES DURING DRYING-WETTING CYCLES

为研究干湿交替下植物单种(百慕大草)与混种(鹅掌柴和百慕大草)对土质覆盖层甲烷(CH_(4))减排的影响,设计3层土质覆盖层分别由机制砂尾料混合10%膨润土层、碎石层和粉砂层组成。一共开展4次干-湿交替试验,试验期间记录植物生长、土柱各层土体含水量及气压变化规律,监测各组分气体浓度。试验结果表明:填埋气对植物生长具有胁迫作用,可导致植物叶片枯萎、光合及蒸腾速率下降;混种组的CH_(4)氧化能力强于单种组,单种的CH_(4)去除率为混种组的69%~89%;混种组与单种组土体CH_(4)氧化能力差值随着干湿交替次数增加而提高;4次干湿交替后,混种组与单种组CH_(4)氧化能力均下降,分别为第1次干旱峰值的45%与34%;植物根系提高了土体的CH_(4)氧化能力,根系区土体的CH_(4)氧化能力大于根系区外土体。该研究揭示了干湿交替下植物组合方式对土质覆盖层CH_(4)氧化的影响,研究结果为垃圾填埋场CH_(4)减排提供理论参考。

The effects of single-species(Cynodon dactylon) and mixed-species(Schefflera and Cynodon dactylon) on methane emission reduction in landfill cover were studied under the drying-wetting cycles.Three-layer landfill cover consists of a machine-made sand tailing mixed with 10% bentonite,gravel layer and silty sand layer.A total of four drying-wetting cycle tests were conducted.Throughout these tests,measurements were taken for plant growth,soil moisture content,and gas pressure changes in each layer of soil column.Additionally,gas concentration of each component was monitored.The results demonstrate that landfill gas inhibited the plants growth,causing leaf wilting and reduced photosynthesis and transpiration rates.The mixed-species group showed a higher methane oxidation capacity,compared to the single-species group.The methane removal rate of the single-species was approximately 69%~89% of that observed in the mixed-species group.The difference in methane oxidation capacity between the mixed-species group and single-species group increased with the increase in drying-wetting cycle number.After four drying-wetting cycles,both the mixed-species and single-species group showed a decrease in methane oxidation capacity.The mixed-species group reached approximate 45% of its peak value from the first drought,while the single-species group achieved around 34% of its initial peak value.Plant roots enhanced the soil's methane oxidation capacity,and the methane oxidation capacity inside the root zone was greater than that outside the root zone.This study elucidated the influence of plant combinations on methane oxidation under drying-wetting cycles.The test results provide a solid basis for mitigating methane emissions in landfills.