A field-based method for simultaneous measurements of the 18 O and 13 C soil CO 2 efflux
A field-based method for simultaneous measurements of the 18 O and 13 C soil CO 2 efflux
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一种同时测量 18 O 和 13 C 土壤 CO 2 流出的现场方法
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
J. Chanton
中科院分区：
文献类型：
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作者：
B. Mortazavi;J. L. Prater;J. Chanton
摘要。比较了三种测定土壤CO外排稳定同位素组成（δ13C和δ18O）的方法。一项新技术采用了微型塔，由顶部开口的管道构成，放置在土壤表面收集土壤排放的二氧化碳。样品沿垂直梯度收集，并分析二氧化碳浓度和同位素组成。这些数据随后被用来制作基林图，以确定从土壤中排放的二氧化碳的δ18O和δ13C。然后将这些结果与另外两种技术测量的土壤呼吸CO2的δ18O和δ13C进行比较：(1)通量室和(2)应用扩散分馏因子估算地下土壤CO2的测量值和二氧化碳与土壤水的平衡δ18O。迷你塔δ18O基林曲线呈线性且极显著（0.81 0.96），而室δ18O基林曲线呈显著曲率，因此需要使用质量天平来计算呼吸CO2的δ18O。在实验室内，土壤呼吸CO2的δ18O值接近与表层土壤水分平衡的CO2值，相对于微型塔的结果和土壤CO2外排的δ18O值，δ18O值明显富集。三种方法测定土壤外排CO2的δ13C值具有较好的一致性。结果表明，微型塔可以有效地用于野外测定土壤呼吸CO2的δ18O和δ13C。
Abstract. Three approaches for determining the stable isotopic composition (δ13C and δ18O) of soil CO efflux were compared. A new technique employed mini-towers, constructed of open-topped piping, that were placed on the soil surface to collect soil-emitted CO2. Samples were collected along a vertical gradient and analyzed for CO2 concentration and isotopic composition. These data were then used to produce Keeling plots to determine the δ18O and δ13C of CO2 emitted from the soil. These results were then compared to the δ18O and δ13C of soil-respired CO2 measured with two other techniques: (1) flux chambers and (2) estimation from the application of the diffusional fractionation factor to measured values of below ground soil CO2 and to CO2 in equilibrium with soil water δ18O. Mini-tower δ18O Keeling plots were linear and highly significant (0.81 0.96), in contrast to chamber δ18O Keeling plots, which showed significant curvature, necessitating the use of a mass balance to calculate the δ18O of respired CO2. In the chambers, the values determined for the δ18O of soil respired CO2 approached the value of CO2 in equilibrium with surficial soil water, and the results were significantly δ18O enriched relative to the mini-tower results and the δ18O of soil CO2 efflux determined from soil CO2. There were close agreements between the three methods for the determination of the δ13C of soil efflux CO2. Results suggest that the mini-towers can be effectively used in the field for determining the δ18O and the δ13C of soil-respired CO2.