Porous tubing for use in monitoring soil CO2 concentrations
Porous tubing for use in monitoring soil CO2 concentrations
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DOI：
10.1016/j.soilbio.2006.04.022
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发表时间：
2006-09-01
影响因子：
9.7
通讯作者：
Parkin, Timothy B.
中科院分区：
文献类型：
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作者：
DeSutter, Thomas M.;Sauer, Thomas J.;Parkin, Timothy B.
土壤大气的组成是生物过程的一个指标，土壤CO2梯度已被用来估计CO2从地表流出。用透气材料制成的土壤大气采样器已被用来量化土壤CO2浓度。所使用的材料类型会影响土壤中二氧化碳的实时浓度。以前的工作没有直接比较相同条件下不同类型的材料。本研究的目的是确定通过几种材料的CO2的扩散系数（D）和95%的平衡时间（t（eq）），并评估长期土埋（183天）对扩散特性的影响。受试材料包括硅胶、膨胀聚四氟乙烯（ePTFE）和超高分子量聚乙烯（PE）管路。使用闭环系统测定每种材料的D，该系统由富CO2（7800 ppm）室、CO2分析仪和放置在室内的内管（实验管）组成。空气通过内管再循环，随着CO2从腔室扩散到管中，分析仪记录浓度的增加。硅胶管的D值范围为8.64至5.80 x 10（-6）cm（2）s（-1），相应的teq为3.9至9.7 h。ePTFE（1.25 x 10（-4）cm（2）s（-1））和PE（7.70 x 10（-4）cm（2）s（-1））材料的扩散系数大2个数量级，t（eq）< 6 min。暴露于土壤环境183天不会明显劣化材料或显著影响D或t（eq）值。使用ePTFE或PE材料，而不是硅胶材料，可以更好地表征土壤中的动态CO2浓度，因为这些材料的D值更大，t（eq）值更小。由爱思唯尔有限公司发布
The composition of the soil atmosphere is an indicator of biological processes, and soil CO2, gradients have been used to estimate CO2 efflux from the surface. Soil atmosphere samplers, constructed with gas-permeable materials, have been used to quantify soil CO2 concentrations. The type of material used can influence the perceived real-time concentrations of CO2 in the soil. Previous works have not directly compared different types of materials under the same conditions. The objective of this study was to determine the diffusion coefficient (D) and time of 95% equilibrium (t(eq)) of CO2 through several materials, and to evaluate the effect of long-term soil burial (183 days) on diffusion characteristics. Materials tested included silicone, expanded Teflon (ePTFE), and ultra high molecular weight polyethylene (PE) tubing. The D of each material was determined using a closed-loop system consisting of a CO2-enriched (7800 ppm) chamber, a CO2 analyzer and an inner tube (experimental tubing) placed inside the chamber. Air was re-circulated through the inner tube, and as CO2 diffused from the chamber into the tubing, the analyzer recorded the increase in concentration. The silicone tubes had values of D ranging from 8.64 to 5.80 x 10(-6) cm(2) s(-1) with corresponding teq between 3.9 and 9.7 h. Diffusion coefficients of the ePTFE (1.25 x 10(-4) cm(2) s(-1)) and PE (7.70 x 10(-4) cm(2) s(-1)) materials were 2 orders of magnitude greater, with t(eq) < 6 min. Exposure to the soil environment for 183 days did not visibly deteriorate the materials or significantly affect the D or t(eq) values. Use of the ePTFE or PE materials, over the silicone materials, may allow for better characterization of dynamic CO2 concentrations in the soil based on the greater D and lesser t(eq) values of these materials. Published by Elsevier Ltd.