典型有机肥溶解态有机质分子量组分特征

Characteristics of Molecular Mass Fractions of Dissolved Organic Matter in a Typical Organic Fertilizer

    摘要
  • 摘要:
    目的 溶解态有机质（DOM）是有机肥料的关键活性组分，其特性在很大程度上主导着有机肥的功能。因此，探究有机肥中DOM的特性，是准确评估其对土壤肥力影响的重要基础。
    方法 本研究选择广东省常用的商品有机肥（维地康），通过超滤离心的方法，将有机肥料中的DOM，按照分子量大小分为3个组分：分子量小于3 kDa (DOM<3k)、分子量为3 ~ 10 kDa (DOM3k-10k) 和分子量大于10 kDa (DOM>10k)；比较分析其化学组成、紫外可见光谱和荧光光谱特征。
    结果 组分DOM>10k的有机碳含量为三者最高，含量为22.51 g L−1。紫外光谱分析显示，SUVA254与SUVA280的比值随着DOM组分的分子量增大而提高，在表征芳香性与腐殖化程度的关键指标SUVA254上，DOM>10k和DOM<3k组分的数值分别是DOM3k-10k组分的5.2倍和5.7倍，显著高于后者，这表明其具有更高的芳香性和腐殖化程度。热质联用分析进一步揭示了不同分子量DOM的化学组成差异，DOM<3k 组分在官能团上以醚类和酯类为主，且其碳骨架多为芳香结构；DOM3k-10k 组分则以醇类和酯类为主导。值得注意的是，DOM>10k 组分无论相对含量还是化合物种类，均以复杂的芳香族化合物为主。三维荧光光谱结合PARAFAC分析表明，DOM<3k 组分主要由类腐殖酸组成，DOM>10k 组分主要由类腐殖酸和富里酸组成。荧光指数和腐殖化指数显示DOM具有强烈的腐殖质特征，腐殖化程度高，随着分子量增大，自生源成分逐渐减少，受微生物的影响减弱。
    结论 有机肥的DOM主要是DOM>10k组分，其腐殖化程度高。基于组分特性推测，DOM<3k 的高活性(如富含小分子醚类、酯类)可能为土壤微生物提供易利用碳源，进而潜在改善土壤健康质量；DOM>10k 的高稳定性(如高芳香缩合度)可能延长其在土壤中的留存时间，利于土壤固碳。具体功能需进一步通过土壤培养或田间试验验证。

     

    Abstract:
    Objectives Dissolved organic matter (DOM), as a critical component of organic fertilizers, significantly determines their multiple functions. Understanding the DOM characteristics of organic fertilizer thus becomes fundamental in estimating the impacts of organic fertilizer on soil fertility.
    Methods In this study, three DOM fractions with different molecular mass of DOM<3k, DOM3k-10k and DOM>10k were obtained by ultrafiltration centrifugation from a typical organic fertilizer commonly used in Guangdong Province and then were characterized their chemical compositions, UV-visible and fluorescence spectral characteristics.
    Results The DOM>10k fraction had the highest organic carbon content (22.51 g L−1). UV spectral analysis showed that the ratio of SUVA254 to SUVA280 increased with increasing molecular mass. The SUVA254 value, a key indicator of aromaticity and humification, were 5.2 and 5.7 times higher in DOM>10k and DOM<3k than those in DOM3k-10k, indicating significantly greater aromaticity and humification. Thermogravimetry-mass spectrometry (TG-MS) further revealed compositional differences: the DOM<3k fraction was rich in ethers and esters, with aromatic carbon structures, while DOM3k-10k was dominated by alcohols and esters. Notably, DOM>10k was predominantly composed of complex aromatic compounds in both relative abundance and variety. Three-dimensional fluorescence spectroscopy combined with PARAFAC analysis showed that DOM<3k was primarily composed of humic-like substances, whereas DOM>10k contained both humic-like and fulvic-like components. Fluorescence and humification indices indicated strong humic characteristics and a high degree of humification. As molecular weight increased, autochthonous contributions decreased, suggesting reduced microbial influence.
    Conclusions The DOM in the organic fertilizer was dominated by the DOM>10k fraction, which exhibited a high degree of humification. Based on compositional features, the high reactivity of DOM<3k (e.g., rich in small-molecule ethers and esters) may provide readily available carbon sources for soil microorganisms, potentially improving soil health. In contrast, the high stability of DOM>10k (e.g., high aromatic condensation) may prolong its persistence in soil, potentially enhancing carbon sequestration. These hypothesized functions require further validation through soil incubation or field experiments.

     

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