Spatial and temporal dynamics of diffusive methane emissions in the Okavango Delta, northern Botswana, Africa
Spatial and temporal dynamics of diffusive methane emissions in the Okavango Delta, northern Botswana, Africa
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DOI：
10.1007/s11273-013-9323-5
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发表时间：
2014-02-01
影响因子：
1.8
通讯作者：
Masamba, Wellington R. L.
中科院分区：
文献类型：
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作者：
Gondwe, Mangaliso J.;Masamba, Wellington R. L.
全球变暖与大气中二氧化碳、甲烷和一氧化二氮等温室气体浓度的持续增加有关。湿地是世界上大气CH 4最大的单一自然来源，在503-610 Tg年（-1）的总预算中贡献了100 - 231 Tg年（-1），其中约60%来自热带湿地。我们进行了扩散CH 4排放测量，使用静态室在河道，洪泛平原和泻湖在永久性和季节性沼泽在奥卡万戈三角洲，博茨瓦纳。扩散性甲烷排放率在0.24和293 mg CH 4 m（-2）h（-1）之间变化，平均（+/- SE）排放量为23.2 +/- A 2.2 mg CH 4 m（-2）h（-1）或558 +/- A 53 mg CH 4 m（-2）day（-1）。这些排放率在其他热带湿地报告的范围内。永久性沼泽的排放率显著高于季节性沼泽（P < 0.007）。河道的平均通量最高，为31.3 +/- A 5.4 mg CH 4 m（-2）h（-1），高于洪泛区（20.4 +/- A 2.5 mg CH 4 m（-2）h（-1））和泻湖（16.9 +/- A 2.6 mg CH 4 m（-2）h（-1））。三角洲的扩散CH 4排放可能受温度的调节，因为排放量最高（20-300 mg CH 4 m（-2）h（-1））和最低（0.2-3.0 mg m（-2）h（-1））分别在温暖多雨和寒冷的冬季。2010年12月至2012年1月的地表水温从冬季的15.3 A度到夏季的33 A度不等。假设平均淹没9，000 km（2），三角洲的年扩散排放量估计为1.8 +/- A 0.2 Tg，占全球热带湿地CH 4排放总量的2.8 +/- A 0.3%。
Global warming is associated with the continued increase in the atmospheric concentrations of greenhouse gases; carbon dioxide, methane (CH4) and nitrous oxide. Wetlands constitute the largest single natural source of atmospheric CH4 in the world contributing between 100 and 231 Tg year(-1) to the total budget of 503-610 Tg year(-1), approximately 60 % of which is emitted from tropical wetlands. We conducted diffusive CH4 emission measurements using static chambers in river channels, floodplains and lagoons in permanent and seasonal swamps in the Okavango Delta, Botswana. Diffusive CH4 emission rates varied between 0.24 and 293 mg CH4 m(-2) h(-1), with a mean (+/- SE) emission of 23.2 +/- A 2.2 mg CH4 m(-2) h(-1) or 558 +/- A 53 mg CH4 m(-2) day(-1). These emission rates lie within the range reported for other tropical wetlands. The emission rates were significantly higher (P < 0.007) in permanent than in seasonal swamps. River channels exhibited the highest average fluxes at 31.3 +/- A 5.4 mg CH4 m(-2) h(-1) than in floodplains (20.4 +/- A 2.5 mg CH4 m(-2) h(-1)) and lagoons (16.9 +/- A 2.6 mg CH4 m(-2) h(-1)). Diffusive CH4 emissions in the Delta were probably regulated by temperature since emissions were highest (20-300 mg CH4 m(-2) h(-1)) and lowest (0.2-3.0 mg m(-2) h(-1)) during the warmer-rainy and cooler winter seasons, respectively. Surface water temperatures between December 2010 and January 2012 varied from 15.3 A degrees C in winter to 33 A degrees C in summer. Assuming mean inundation of 9,000 km(2), the Delta's annual diffusive emission was estimated at 1.8 +/- A 0.2 Tg, accounting for 2.8 +/- A 0.3 % of the total CH4 emission from global tropical wetlands.