Department of Chemical and Biochemical Engineering, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark.
Rapid Commun Mass Spectrom. 2013 Jul 15;27(13):1417-28. doi: 10.1002/rcm.6584.
Pulse-labeling with (13)CO2 and the subsequent analysis of (13)C-carbon via isotope ratio mass spectrometry (IRMS) have been shown to be an excellent method to investigate the terrestrial carbon cycle. Improving (13)CO2 manipulation experiments will facilitate our understanding of carbon cycling processes.
A mobile field setup for in situ (13)CO2 pulse-labeling was developed for low vegetation field experiments. Two pulse-labeling experiments were conducted in a Danish heathland in September 2010 (Exp1) and May 2011 (Exp2). A flow-through system was developed where labeling chambers were supplied with (13)CO2-enriched air from a gas reservoir. Reservoir and chamber air was sampled over the course of the experiments and analyzed for CO2 concentration and isotopic composition on a GasBench II interfaced with an isotope ratio mass spectrometer. The soil CO2 efflux and the atom% excess in soil respiration were assessed after the (13)CO2-pulse to verify the setup performance.
The carbon dioxide concentrations and (13)CO2 enrichments were stable during the experiments. The CO2 concentrations conformed to the aimed values, whereas the (13)CO2 enrichments were lower than expected. The sources of error for the deviation in observed atom% (13)CO2 values are discussed, and a measurement procedure is suggested for samples highly enriched in (13)C by using adjusted resistor settings of the mass spectrometer. However, more work has to be done. Enrichment patterns in soil respiration agree with published observations indicating satisfactory performance of the developed system.
A mobile flow-through system suitable for continuous in situ (13)CO2 pulse-labeling was successfully developed that is easily applicable in remote natural ecosystems.
通过（13）CO2 脉冲标记和随后通过同位素比质谱（IRMS）分析（13）C 碳已被证明是研究陆地碳循环的极好方法。改进（13）CO2 操作实验将有助于我们理解碳循环过程。
为低植被野外实验开发了一种用于现场（13）CO2 脉冲标记的移动现场设置。2010 年 9 月（Exp1）和 2011 年 5 月（Exp2）在丹麦石南荒原进行了两次脉冲标记实验。开发了一种流动系统，其中标记室由来自气体储层的（13）CO2 富集空气供应。在实验过程中对储层和腔室空气进行采样，并在与同位素质谱仪接口的 GasBench II 上分析 CO2 浓度和同位素组成。在（13）CO2 脉冲后评估土壤 CO2 通量和土壤呼吸中的原子%过剩，以验证设置性能。
在实验过程中，二氧化碳浓度和（13）CO2 富集稳定。CO2 浓度符合目标值，而（13）CO2 富集低于预期。讨论了观察到的原子%（13）CO2 值偏差的误差源，并提出了一种用于高度富集（13）C 的样品的测量程序，方法是调整质谱仪的电阻器设置。但是，还有更多的工作要做。土壤呼吸中的富集模式与已发表的观察结果一致，表明所开发系统的性能令人满意。
成功开发了一种适用于连续现场（13）CO2 脉冲标记的移动流动系统，该系统易于在偏远的自然生态系统中应用。
