Sprenger Matthias, Tetzlaff Doerthe, Soulsby Chris
Northern Rivers Institute, School of Geosciences, University of Aberdeen, Elphinstone Road, Aberdeen, AB24 3UF, UK.
Rapid Commun Mass Spectrom. 2017 Mar 15;31(5):430-436. doi: 10.1002/rcm.7815.
It was recently shown that the presence of CO affects the stable isotope (δ H and δ O values) analysis of water vapor via Wavelength-Scanned Cavity Ring-Down Spectroscopy. Here, we test how much CO is emitted from soil samples and if the CO in the headspace influences the isotope analysis with the direct equilibration method by Off-Axis Integrated Cavity Output Spectroscopy (OA-ICOS).
The headspace above different amounts of sparkling water was sampled, and its stable isotopic composition (δ H and δ O values) and CO concentration were measured by direct equilibration and by gas chromatography, respectively. In addition, the headspace above soil samples was analyzed in the same way. Furthermore, the gravimetric water content and the loss on ignition were measured for the soil samples.
The experiment with the sparkling water showed that CO does not influence the stable isotope analysis by OA-ICOS. CO was emitted from the soil samples and correlated with the isotopic fractionation signal, but no causal relationship between the two was determined. Instead, the fractionation signal in pore water isotopes can be explained by soil evaporation and the CO can be related to soil moisture and organic matter which both enhance microbial activity.
We found, despite the high CO emissions from soil samples, no need for a post-correction of the pore water stable isotope analysis results, since there is no relation between CO concentrations and the stable isotope results of vapor samples obtained with OA-ICOS. © 2016 The Authors. Rapid Communications in Mass Spectrometry Published by John Wiley & Sons Ltd.
最近研究表明，一氧化碳（CO）的存在会通过波长扫描腔衰荡光谱法影响水蒸气的稳定同位素（δH和δO值）分析。在此，我们测试了土壤样品中会释放多少CO，以及顶空中的CO是否会通过离轴积分腔输出光谱法（OA - ICOS）的直接平衡法影响同位素分析。
对不同量的苏打水上方的顶空进行采样，分别通过直接平衡法和气相色谱法测量其稳定同位素组成（δH和δO值）以及CO浓度。此外，以同样的方式分析土壤样品上方的顶空。此外，还测量了土壤样品的重量含水量和烧失量。
苏打水实验表明，CO不会影响OA - ICOS的稳定同位素分析。土壤样品释放出CO，且与同位素分馏信号相关，但未确定两者之间存在因果关系。相反，孔隙水同位素中的分馏信号可以用土壤蒸发来解释，而CO可能与土壤湿度和有机质有关，这两者都会增强微生物活性。
我们发现，尽管土壤样品释放出大量CO，但无需对孔隙水稳定同位素分析结果进行校正，因为CO浓度与通过OA - ICOS获得的蒸汽样品的稳定同位素结果之间没有关系。© 2016作者。《质谱快报》由约翰·威利父子有限公司出版
