School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People's Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, Guangdong 510006, People's Republic of China.
School of Environment and Energy, South China University of Technology, Guangzhou, Guangdong 510006, People's Republic of China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, South China University of Technology, Guangzhou, Guangdong 510006, People's Republic of China.
Sci Total Environ. 2021 Apr 1;763:142937. doi: 10.1016/j.scitotenv.2020.142937. Epub 2020 Oct 14.
The properties and composition of soil dissolved organic matter (DOM) are highly affected by the adsorption and desorption of organic matter (OM) on soil minerals and heterotrophic microbial respiration. Organic acids (e.g., oxalic acid), components of root exudates, have been revealed to liberate organic matter (OM) by the dissolution of protective mineral phases and stimulate microbial degradation of OM. However, the effects of organic acids on the properties and composition of soil DOM molecules and the related mechanisms are still poorly understood. In this study, we conducted microcosm incubation experiments with and without oxalic acid addition, and aimed to elucidate the variations of DOM properties and composition, employing a combination of Fourier transform ion cyclotron resonance mass spectrometry, optical spectroscopy, and bacterial community composition analysis. Our results indicated that the released OM from the direct dissolution of protective mineral phases by oxalic acid further stimulated the microbial reductive release of Fe mineral-associated OM under anoxic conditions. Furthermore, the addition of oxalic acid enhanced the degradation of aliphatic compounds and lignins with low O/C ratios, and increased the accumulation of lignins with high O/C ratios, tannins, and condensed aromatics. Linking the bacterial community composition to DOM molecular properties and composition further suggested that the enhanced reductive release of Fe mineral-associated OM was highly related to the increased abundances of Proteobacteria and Actinobacteria. Overall, oxalic acid induced long-lasting impacts on soil DOM properties and composition under anoxic soil conditions in our study. We expect that our results will contribute to understanding the dynamics of soil DOM molecules in the environment.
土壤溶解性有机质 (DOM) 的性质和组成受到有机质 (OM) 在土壤矿物上的吸附和解吸以及异养微生物呼吸的强烈影响。已发现有机酸（如草酸）通过溶解保护性矿物相释放有机质 (OM)，并刺激 OM 的微生物降解。然而，有机酸对土壤 DOM 分子的性质和组成的影响及其相关机制仍知之甚少。在这项研究中，我们进行了添加和不添加草酸的微宇宙培养实验，旨在阐明 DOM 性质和组成的变化，采用傅里叶变换离子回旋共振质谱、光学光谱和细菌群落组成分析相结合的方法。我们的结果表明，草酸直接溶解保护性矿物相释放的 OM 进一步刺激了缺氧条件下微生物对 Fe 矿物结合 OM 的还原性释放。此外，添加草酸增强了低 O/C 比的脂肪族化合物和木质素的降解，并增加了高 O/C 比、单宁和缩合芳烃的木质素积累。将细菌群落组成与 DOM 分子性质和组成联系起来进一步表明，Fe 矿物结合 OM 的增强还原性释放与变形菌门和放线菌门丰度的增加密切相关。总的来说，在本研究的缺氧土壤条件下，草酸对土壤 DOM 性质和组成产生了持久的影响。我们期望我们的结果将有助于理解环境中土壤 DOM 分子的动态。
