Dissolved organic matter (DOM) is an important organic matter fraction that affects many biological and chemical processes in soil. Biochar can change soil DOM while the effects were paradoxical, and contributions of biochar to soil DOM was not clear yet. In this study, excitation-emission matrix (EEM) fluorescence spectroscopy was applied to determine the biochar-induced changes of DOM composition. Batch experiments were conducted to quantify the contributions of biochar to soil DOM. Biochars were prepared by pyrolyzing wheat straw (S300/700) and cow manure (M300/700) at 300 and 700 °C, respectively. Generally, biochar increased the humification of soil DOM possibly by the release of indigenous DOM and selective adsorption of the small molecule DOM. Besides, contributions of S300 and M300 to soil DOM (37–91%) were higher than that of S700 and M700 (2–19%) irrespective of application rates. The indigenous DOM released from S300 and M300 was 6.4–12.1 times more than the soil DOM adsorbed by S300 and M300, leading to the increase of DOM content. Contrarily, the DOM from S700 and M700 was only 11–17% of the soil DOM adsorbed by them, resulting in the decrease of DOM content. In addition, contributions of biochar to soil DOM increased as the application rate increased, especially for S300 and M300. This study indicated that the release and adsorption of DOM were the key processes determining the effects of biochar on soil DOM, which were closely related to the pyrolysis temperature and application rate of biochar.

中文翻译：

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生物炭诱导土壤可溶性有机质的变化：生物质炭与土壤对可溶性有机质的释放和吸附


可溶性有机物 （DOM） 是一种重要的有机物组分，影响土壤中的许多生物和化学过程。生物炭可以改变土壤 DOM，而效果是自相矛盾的，生物炭对土壤 DOM 的贡献尚不清楚。在本研究中，应用激发-发射矩阵 （EEM） 荧光光谱来确定生物炭诱导的 DOM 组成变化。通过分别在 300 °C 和 700 °C 下热解小麦秸秆 （S300/700） 和牛粪 （M300/700） 制备生物炭。一般来说，生物炭可能通过释放天然 DOM 和选择性吸附小分子 DOM 来增加土壤 DOM 的腐殖化。此外，无论施用量如何，S300 和 M300 对土壤 DOM 的贡献 （37-91%） 都高于 S700 和 M700 （2-19%）。S300 和 M300 释放的原生 DOM 是 S300 和 M300 吸附的土壤 DOM 的 6.4–12.1 倍，导致 DOM 含量增加。相反，S700 和 M700 的 DOM 仅为它们吸附的土壤 DOM 的 11-17%，导致 DOM 含量降低。此外，随着施用量的增加，生物炭对土壤 DOM 的贡献增加，尤其是 S300 和 M300。本研究表明，DOM 的释放和吸附是决定生物炭对土壤 DOM 影响的关键过程，与生物炭的热解温度和施用速率密切相关。