【他山之石】阴永光研究员团队：火诱导的泥炭土壤有机质电子传递能力的多重变化——官能团、石墨碳和铁的作用

第一作者：杨佩杰

通讯作者：刘艳伟 助理研究员、阴永光 研究员

通讯单位：国科大杭州高等研究院、中国科学院生态环境研究中心

论文DOI: 10.1021/acs.est.4c06586

图文摘要

成果简介

全文速览

引言

图文导读

PSOM燃烧导致其EEC降低，EC增强

Figure 1. (A, B) Change in electron-donating capacity (EDC), electron-accepting capacity (EAC), and electron exchange capacity (EEC) with burning temperature. (C) Change in electrical conductivity with burning temperature. A-pyPSOM and N-pyPSOM represent oxic and anoxic burnt samples, respectively. PPS represents unburnt PSOM and N150-N450 represents anoxic burnt samples at 150‒450℃. TT₁ and TT₂ represent the temperatures at which EEC begins to lose and stabilize again, respectively.

通过模拟泥炭土壤燃烧，发现燃烧显著改变了PSOM的电子传递特性。250℃内燃烧，PSOM的电子传递特性主要由EEC贡献，但随着温度升高，EEC降低，EC增强，电子传递特性由EEC和EC共同驱动。EEC具一定的有热抗性，使其在200℃（TT₁）可保持稳定。但随温度的进一步升高，EEC迅速降低，在350℃（TT₂）后，再次保持稳定。值得注意的是，氧气可显著影响燃烧过程中EEC的演变。TT₂后，有氧燃烧的PSOM（A-pyPSOM）EEC是缺氧燃烧（N-pyPSOM）EEC的1.5倍。这一差异由有氧燃烧过程中氧气向PSOM中并入形成更多醌导致。

火后PSOM的电子传递活性由官能团及石墨碳共同驱动

Figure 2. (A) Correlation between electron-accepting capacity (EAC_MER) and electron-accepting moieties (assigned as EAC_Na2S2O4). (B) Correlation between electron-donating capacities (EDC) and electron-donating moieties (i.e., total phenols). (C) Correlation between aromaticity index (AI) and electrical conductivity. (D) Change in EAC with I_D/G (the intensity ratio of D bond and G bond in Raman spectrum). A-pyPSOM and N-pyPSOM represent oxic and anoxic burnt samples, respectively.

Fe(II)可贡献大量的EDC，但燃烧过程中形成的杂环氮可抑制其活性

Figure 3. (A) Changes in electron-donating capacity (EDC) with E_H and pH conditions. (B) Effect of the ligand on the EDC of Fe₃O₄nanoparticles at E_H = +0.61 V and +0.73 V, respectively. (C, D) Correlation of difference value between EDC_{EH =+0.73 V, pH 7.0} and EDC_{EH =+0.73 V, pH 9.0} (ΔEDC) and Fe(II) content. Gray numbers represent the contribution of Fe(II) to EDC at +0.61 V, which was obtained by calculating the ratio of [ΔEDC −Fe(II)] to EDC_{EH = 0.61 V, pH 7}. When phenols are the main eletron-donating capacity, EDC_{EH = +0.73 V, pH 7.0} ≈ EDC_{EH = +0.61 V, pH 9.0}. A-yPSOM and N-pyPSOM represent oxic and anoxic burning samples.

Fe(II)是PSOM中主要的铁物种，可贡献大量的EDC。高电位下（E_H= +0.73 V），EDC与总酚含量相关性较差，推测高电位下，EDC主要由酚和Fe(II)共同驱动。基于EDC与pH-E_H相关分析及小分子模型进一步评估，发现200℃内，Fe(II)可在低电位下（E_H= +0.61 V）贡献EDC，温度进一步升高，由于杂环N与Fe(II)结合，其EDC受到抑制，仅能在高电位下贡献EDC。

PSOM燃烧减缓了微生物铁还原及甲烷生成，但增强的EC可能在火后的生物地球化学过程中发挥重要作用

Figure 4. Effect of peat burning on PSOM-mediated microbial FeNPs reduction and methanogenesis. (A) Change in reduction extent of Fe(III) in the presence of oxic burnt samples (0.1 mg mL^-1). (B) Correlation between electron-accepting capacity (EAC) and reduction rate (0-3 h) of Fe(III). (C) Change in CH₄ production in the presence of PPS (unburnt PSOM, 1 g L^-1), N500 (anoxic burnt PSOM at 500℃, 1 g L^-1), and quinone model (AQDS, 1 mM) in the pure-cultural and co-cultural systems. The α-Fe₂O₃ and acetate concentrations were 1 and 30 mM, respectively. G. sulfurreducens PCA: GS; Methanosarcina barkeri: MB. The inoculum concentration is 5% both of GS and MB.  The v, v₁, and v₂ are CH₄production rates.

PSOM可通过电子穿梭作用增强微生物铁还原速率，燃烧显著削弱了PSOM在微生物铁还原中的电子穿梭作用（还原速率降低）。通过相关性分析发现，这一电子穿梭作用主要由EAC驱动。值得注意的是，低温PSOM添加组（A250）中铁还原达到平衡后，高温PSOM添加组（A500）中铁还原仍继续进行，提示了高温燃烧后随着官能团的消耗，增强的EC可继续提供电子穿梭作用，增强铁还原，进一步证实了火灾后PSOM的电子传递特性由EEC和EC共同驱动。此外，火诱导的PSOM电子传递能力的变化也削弱了CH₄生成速率。燃烧后，由于EAC的降低，CH₄生成速率由94.99 ± 1.71 µmol d^-1降低至12.75 ± 1.22 µmol d^-1 ，但在受电子基团消耗完后，由于EC增强，CH₄生成速率再次增加至74.91 ± 3.01 µmol d^-1。

小结

这项工作揭示了PSOM的电子传递特性随火灾温度的动态变化，强调了官能团及石墨碳在火灾后电子传递中的重要作用，进一步增强了对火灾后泥炭生物地球化学过程的理解。燃烧通过消耗醌酚基团导致EEC损失，但通过形成石墨碳结构增强其EC。燃烧重塑了贡献EEC的活性官能团组分。燃烧后EAC主要由醌和杂环氮驱动，EDC则由酚类基团和结合的Fe(II)贡献，但由与Fe(II)与杂环氮的高亲和力，其活性在火后受到抑制。重要的是，火灾诱导的EAC降低削弱了PSOM的电子穿梭效应，EC的增强可能在火后泥炭地CH₄生成中发挥重要作用。该工作为探究火后泥炭地CH₄排放机制提供了新思路。

作者介绍

Peijie Yang, Shuai Wang, Tianran Sun, Tao Jiang, Yifan Cui, Guangliang Liu, Yingying Guo, Yanwei Liu, Ligang Hu, Jianbo Shi, Qinghua Zhang, Yongguang Yin, Yong Cai, Guibin Jiang, Fire-Induced Multiple Changes in Electron Transfer Properties of Peat Soil Organic Matter: The Role of Functional Groups, Graphitic Carbon, and Iron, Environ. Sci. Technol. 2024, DOI: 10.1021/acs.est.4c06586

https://pubs.acs.org/doi/10.1021/acs.est.4c06586