Comparison of different chamber techniques for measuring soil CO2 efflux
Comparison of different chamber techniques for measuring soil CO2 efflux
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DOI：
10.1016/j.agrformet.2003.12.001
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发表时间：
2004-06-20
影响因子：
6.2
通讯作者：
Hari, P
中科院分区：
文献类型：
--
作者：
Pumpanen, J;Kolari, P;Hari, P
20个测量土壤CO2流出的腔室与已知的CO2通量进行了比较，通量范围为0.32至10.01 μ mol CO2 m（-2）s（-1），并由专门开发的校准罐产生。分别在粒度为0.05-0.2 mm和0.6 mm的细、粗均质石英砂上对腔室进行了测试。通过将细石英砂润湿至约25%体积含水量来测试土壤水分对室测量的影响。非稳态通流腔室低估或高估了-21至+33%的通量，这取决于腔室的类型和在腔室顶部空间内混合空气的方法。然而，当所有系统的测试结果取平均值时，通量在参考值的4%以内。非稳态非通流室低估或高估了-35%至+6%的通量。平均而言，细砂的低估率约为13-14%，粗砂为4%。当测量周期的长度增加时，由于腔室顶部空间内的浓度升高，低估增加，这降低了土壤内的扩散梯度。稳态通流室几乎同样适用于本研究中使用的所有砂类型。他们平均高估了2- 4%的通量。总体而言，腔室的可靠性与测量原理本身无关。即使是相同的腔室，不同的衣领设计，显示出高度可变的结果。室内空气的混合可能是误差的主要来源。室内的过度湍流会导致CO2从土壤中大量流入室内。腔室顶部空间浓度也通过改变土壤和腔室之间的浓度梯度来影响通量。(C)2003 Elsevier B. V.保留所有权利。
Twenty chambers for measurement of soil CO2 efflux were compared against known CO2 fluxes ranging from 0.32 to 10.01 mumol CO2 m(-2) s(-1) and generated by a specially developed calibration tank. Chambers were tested on fine and coarse homogeneous quartz sand with particle sizes of 0.05-0.2 and 0.6 mm, respectively. The effect of soil moisture on chamber measurements was tested by wetting the fine quartz sand to about 25% volumetric water content. Non-steady-state through-flow chambers either underestimated or overestimated fluxes from -21 to +33% depending on the type of chamber and the method of mixing air within the chamber's headspace. However, when results of all systems tested were averaged, fluxes were within 4% of references. Non-steady-state non-through-flow chambers underestimated or overestimated fluxes from -35 to +6%. On average, the underestimation was about 13-14% on fine sand and 4% on coarse sand. When the length of the measurement period was increased, the underestimation increased due to the rising concentration within the chamber headspace, which reduced the diffusion gradient within the soil. Steady-state through-flow chambers worked almost equally well in all sand types used in this study. They overestimated the fluxes on average by 2-4%. Overall, the reliability of the chambers was not related to the measurement principle per se. Even the same chambers, with different collar designs, showed highly variable results. The mixing of air within the chamber can be a major source of error. Excessive turbulence inside the chamber can cause mass flow of CO2 from the soil into the chamber. The chamber headspace concentration also affects the flux by altering the concentration gradient between the soil and the chamber. (C) 2003 Elsevier B.V. All rights reserved.