Abstract A novel method coupling pyrolysis with mid-infrared spectroscopy (Py-MIRS) was developed to characterize soil organic matter (SOM) chemistry in soils. The pyrolyzer was interfaced to the MIR spectrometer by means of a Brill cell™ (CDS Analytica). The set-up generates pyrolysis fingerprint spectra from which individual pyrolysis products can be related to SOM bulk chemistry. Py-MIRS development involved the testing of experimental conditions like pyrolysis temperature (550, 700, 1000 °C), heating rate (20 °C s−1 and 20 °C ms−1) and time (15, 30 and 60 s) using reference standard compounds ranging from carbohydrates to phenols varying in chemical and structural composition like levoglusogan, gluten, tannin, syringol, pectin and leucine falling within different compound categories (carbohydrates, amino acids, proteins, phenols, etc.) as well as soil samples. Pyrolysis yields of prominent specific functional groups, like aliphatics (C H stretching at 2930 cm−1) and C C aromatics (1510 cm−1), varied with pyrolysis temperature, heating rate and time. The preferred settings for high pyrolysis yield and minimized secondary reactions were obtained at a pyrolysis temperature of 700 °C, heating rate of 20 °C ms−1 and heating time of 30 s. The suitability of Py-MIRS to detect changes in SOM composition was evaluated by comparing Py-MIRS results to Diffuse Reflectance Fourier Transform mid-Infrared Spectroscopy (DRIFTS) results. Soil samples taken from the Static Fertilization Experiment, Bad Lauchstadt, Germany (Chernozem) revealed a major SOM contribution of the peak at 1750 cm−1 (C O), followed by peaks at 950 (C H), 1510 (C C), 1176 (C H, O H) cm−1, with smaller contributions from the 2930 (C H) and 3015 (CH4) cm−1 peaks, apart from a dominant CO2 peak. Using the preferred pyrolysis settings, Py-MIRS as well as DRIFTS results further indicated that soils receiving organic (e.g. farmyard manure) inputs were highly enriched in aliphatic groups, while their absence favored the accumulation of carboxyl and aromatic groups as well as polysaccharides. Py-MIRS allowed via semi-quantification of pyrolysis products a rapid monitoring of SOM bulk chemistry with a high degree of reproducibility. It was concluded that Py-MIRS represents a fast, effective and reproducible technique to characterize changes in the SOM bulk chemistry as a result of management practices. It also allows to minimize acknowledged constraints of other analytical techniques used to characterize SOM bulk chemistry such as mineral interferences and associated secondary reactions.

中文翻译：

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将热解与中红外光谱 (Py-MIRS) 结合以指纹土壤有机质整体化学

摘要 开发了一种新的热解与中红外光谱 (Py-MIRS) 耦合方法来表征土壤中的土壤有机质 (SOM) 化学。热解器通过 Brill cell™ (CDS Analytica) 连接到 MIR 光谱仪。该设置生成热解指纹谱，从中单个热解产物可以与 SOM 本体化学相关。Py-MIRS 开发涉及实验条件的测试，如热解温度（550、700、1000 °C）、加热速率（20 °C s-1 和 20 °C ms-1）和时间（15、30 和 60 s）使用从碳水化合物到酚类的参考标准化合物，化学和结构组成不同，如左旋葡聚糖、麸质、单宁、丁香醇、果胶和亮氨酸，属于不同的化合物类别（碳水化合物、氨基酸、蛋白质、酚类等）。) 以及土壤样品。突出的特定官能团的热解产率，如脂肪族（CH 在 2930 cm-1 处拉伸）和 CC 芳族（1510 cm-1），随热解温度、加热速率和时间而变化。在 700 °C 的热解温度、20 °C ms-1 的加热速率和 30 s 的加热时间下获得了高热解产率和最小化二次反应的优选设置。通过将 Py-MIRS 结果与漫反射傅立叶变换中红外光谱 (DRIFTS) 结果进行比较，评估了 Py-MIRS 检测 SOM 组成变化的适用性。从静态施肥实验中提取的土壤样本，德国巴德劳赫施塔特（黑钙土）揭示了 1750 cm-1 (CO) 峰值的主要 SOM 贡献，其次是 950 (CH)、1510 (CC)、1176 (CH) 的峰值, OH) cm−1, 除了主要的 CO2 峰外，2930 (CH) 和 3015 (CH4) cm-1 峰的贡献较小。使用首选的热解设置，Py-MIRS 以及 DRIFTS 结果进一步表明，接受有机（例如农家肥）输入的土壤富含脂肪族群，而它们的缺失有利于羧基和芳香族基团以及多糖的积累。Py-MIRS 允许通过热解产物的半定量快速监测 SOM 批量化学，具有高度的重现性。得出的结论是，Py-MIRS 代表了一种快速、有效和可重复的技术，用于表征由于管理实践而导致的 SOM 本体化学变化。