Methane transport and oxidation in the unsaturated zone of a Sphagnum peatland
Methane transport and oxidation in the unsaturated zone of a Sphagnum peatland
复制标题
泥炭地不饱和区的甲烷传输和氧化
DOI：
10.1029/91gb02989
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发表时间：
1992
影响因子：
5.2
通讯作者：
H. Hemond
中科院分区：
文献类型：
--
作者：
Elizabeth J. Fechner;H. Hemond
甲烷 (CH4) 的流出速率和氧化速率是在马萨诸塞州康科德市北部泥炭沼泽（即马萨诸塞州康科德的梭罗沼泽）中使用不改变原位条件的梯度方法测量的。设计了一种远程采样技术来获得未受干扰的 CH4 剖面，作为泥炭深度的函数；泥炭中的有效扩散系数通过物理方法和使用丙烷作为示踪剂进行估计。通过结合这些技术，我们估计夏末从深层厌氧产甲烷沉积物到不饱和带的平均 CH4 通量为 3.5 × 10−11 mol cm−2 s−1 (± 1.0 × 10−10 mol cm−2 s−1)，而从该不饱和带到大气的 CH4 通量为 3.7 × 10−12 mol cm−2 s−1 (± 1.0 × 10−10 mol cm−2 s−1)。 5.0 × 10−12 mol cm−2 s−1)。因此，大部分 CH4 通量在到达大气之前就被消耗掉了。大多数 CH4 消耗（可能是通过氧化）发生在地下水位之间，位于沼泽地表以下 12 至 15 厘米处，以及沼泽地表以下约 6 厘米处。在该区域，CH4 浓度和氧化速率分布不均匀，可能遵循饱和区中气泡通过裂缝和管道向上传输 CH4 的模式。在沼泽表面和 6 厘米深度之间，CH4 浓度分布更均匀，很可能是因为该深度范围内水平混合程度更大。分析不饱和泥炭中的 CH4 分布是一种简单实用的技术，可测量 CH4 净流出和 CH4 氧化，同时对泥炭结构和气体交换条件的干扰最小。
Efflux rates and oxidation rates of methane (CH4) were measured in a northern Sphagnum bog, Thoreau's Bog in Concord, Massachusetts, by using a gradient methodology which does not change in situ conditions. A remote-sampling technique was devised to obtain undisturbed CH4 profiles as a function of depth in the peat; effective diffusion coefficients in peat were estimated both physically and by using propane as a tracer. By combining these techniques we estimated the average late summer CH44 flux from deep, anaerobic methanogenic sediments to the unsaturated zone to be 3.5 × 10−11 mol cm−2 s−1 (± 1.0 × 10−10 mol cm−2 s−1), while the CH4 flux from this unsaturated zone to the atmosphere was 3.7 × 10−12 mol cm−2 s−1 (± 5.0 × 10−12 mol cm−2 s−1). Therefore a large fraction of the CH4 flux was consumed before it reached the atmosphere. Most CH4 consumption, presumably by oxidation, occurred between the water table, located 12 to 15 cm below the bog surface, and about 6 cm below the bog surface. In this region, CH4 concentrations and oxidation rates were unevenly distributed, probably following patterns of upward transport of CH4 by bubbles via fissures and tubes in the saturated zone. Between the surface of the bog and 6-cm depth, CH4 concentrations were more uniformly distributed, most likely because of greater horizontal mixing in this depth range. Analysis of CH4 distributions in unsaturated peat is a straightforward and practical technique to measure both net CH4 efflux and CH4 oxidation with minimal disturbance to the peat structure and gas exchange conditions.