The purpose of this study is to analyze the effects of different straw returning modes on the structure of humic acid (HA) in soil by fluorescence spectroscopy and infrared (IR) spectroscopy. Four different straw returning modes, including straw returning to topsoil (St), straw returning to subsoil (Ss), straw mixing with topsoil (Smt), and straw mixing with subsoil (Sms), were used in this study; the soil HA was analyzed after 12 months of corn straw returning by a combination of fluorescence spectroscopy and IR spectroscopy. Based on the results, it was established that IR spectroscopy can estimate the complication and oxidation degree of soil HA and also evaluate its aliphaticity and aromaticity. Monodimensional fluorescence spectroscopy could preliminarily determine the changes in the humification of HA through the fluorescence intensities. The intensity ratio of I₄₅₆/I₃₈₀ calculated from synchronous-scan fluorescence spectra could be used to evaluate the humification degree of soil HA. The total luminescence spectra of HAs provided more information on the fluorophores in the structure, including the amount and peak position of lignin-like structures and phenol-like or naphthol-like structures. Among the four straw returning modes, Ss is the most beneficial for reducing the oxidation degree and increasing the aromatization and humification degree of subsoil HA. It is believed that fluorescence spectroscopy and IR spectroscopy are relatively simple and sensitive methods for analyzing soil HA.

中文翻译：

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通过荧光光谱和红外光谱分析不同玉米秸秆还田模式下土壤腐殖酸的结构。

本研究的目的是通过荧光光谱法和红外光谱法分析不同秸秆还田方式对土壤中腐殖酸（HA）结构的影响。本研究使用了四种不同的秸秆还田方式，包括秸秆还田（Sts），秸秆还田（Ss），秸秆与表土混合（Smt）以及秸秆与底土混合（Sms）。玉米秸秆还田12个月后，通过荧光光谱和红外光谱相结合的方法对土壤HA进行了分析。根据这些结果，可以确定红外光谱可以估算土壤HA的复杂性和氧化程度，并可以评估其脂肪族和芳香族。一维荧光光谱可以通过荧光强度初步确定HA的腐殖化变化。由同步扫描荧光光谱计算得到的₄₅₆ / I ₃₈₀可用于评估土壤HA的腐殖化程度。HA的总发光光谱提供了有关结构中荧光团的更多信息，包括木质素样结构和酚样或萘酚样结构的数量和峰位置。在四种秸秆还田方式中，Ss最有利于降低土壤HA的氧化度，增加其芳构化程度。相信荧光光谱法和IR光谱法是分析土壤HA的相对简单和灵敏的方法。