堆肥腐殖酸形成及其电化学活性

为探究堆肥腐殖酸形成过程及腐殖酸的氧化还原性能，以城市生活垃圾不同堆肥阶段提取的腐殖酸样品为研究对象，运用现代色谱学技术、光谱学方法和电化学分析，研究了堆肥过程不同形态氮和碳官能团形成腐殖酸的特征，探究了堆肥腐殖酸的氧化还原性能及影响因素. 结果表明:堆肥腐殖酸中50%~75%的氮为氨基酸态氮，检出的15种氨基酸中酸性氨基酸(Asp和Glu)含量(高于100 mg/g)最高、丝氨酸(Ser)含量(3.78 mg/g)最低. 与堆肥腐殖酸中其他组分和官能团相比，氨基酸易被生物降解和利用，其含量随着发酵的进行呈下降趋势，后期氨基酸态氮占比逐渐降低. 腐殖酸中碳有多种形态，包括苯环、羧基、脂肪族等多种官能团，随着堆肥发酵的进行，木质纤维素降解形成腐殖酸，脂肪族官能团亦被氧化降解；与之相反的是，腐殖酸中羧酸类、醛、酮及苯环等官能团不断增加，导致腐殖酸氧化还原性能增强. 氧化和还原过程中，腐殖酸得失电子均会造成部分官能团结构破坏，大分子腐殖酸被降解和转化为小分子有机物. 研究显示，堆肥腐殖酸活性较高，可利用腐殖酸修复环境过程，但需要适当补充活性腐殖酸，防止腐殖酸因修复氧化还原过程导致降解后只能作为碳源. 

Formation and Electrochemical Activity of Humic Acid in Compost

Humic acids in the compost have a variety of environmental functions, and play an important role in maintaining the stability of soil structure and improving the water holding capacity. It is speculated that humic acids are mainly formed by amino acids and lignocellulose, but the composition of amino acids in the composting process and the reaction characteristics between humic acids with lignocellulose are still not clear. Hence, the effect of redox process on the formation of composting humic acids cannot be evaluated. In order to explore the formation process of humic acids during composting and their redox performance, the humic acid samples extracted at different composting stages of municipal solid waste were used as the research object, and different forms of nitrogen and carbon functional groups, the redox performance of humic acids and its influencing factors in composting were explored using modern chromatography technology, spectroscopy and electrochemical analysis. The results showed that about 50% to 75% of the nitrogen in humic acids of the compost was amino acid nitrogen. Among the 15 amino acids detected, the contents of acidic amino acids (Asp and Glu) were the highest, which were greater than 100 mg/g, and the content of Serine (Ser) was the lowest, with the average concentration of only 3.78 mg/g. Compared with other components and functional groups in humic acids of the compost, amino acids were more easily biodegraded and utilized. As the fermentation of composting proceeded, the proportion of amino acid nitrogen decreased in the later stage. The carbon in humic acids existed in many forms, including benzene ring, carboxyl group, aliphatic and other functional groups. The lignocellulose was degraded and transformed into humic acids, and aliphatic functional groups were also oxidized and degraded during the fermentation process. On the contrary, the increase of carboxylic acids, aldehydes, ketones and benzene rings in humic acids lead to the enhancement of redox performance of humic acids. In the redox process, humic acids gained and lost electrons, which would damage part of the functional group structure, and the macromolecular humic acids were degraded and converted into small molecular organic matters. Due to their high activity, active humic acids are needed to be appropriated supplemented in the process of environmental repairing, which will prevent humic acids from being used just as a carbon source after the degradation of the redox process. The findings above provide a theoretical basis for improving the fertilizer efficiency and environmental remediation performance of composting products.