The production of ·OH during transformation of redox active substances has been increasingly documented, and it causes the ageing or degradation of microplastics (MPs) in natural systems. However, the contribution of the humus redox cycle to ·OH generation and MPs transformation has previously been overlooked, even though it is ubiquitous in alternating anoxic-oxic environments. In this work, the integrated pathways of ·OH generation during the redox transformation of humic acids (HAs) and the contribution of this ·OH to the transformation of MPs were investigated for the first time. It was found that ·OH could be produced continuously during successive cycles of redox transformation of HAs mediated by Bacillus thermotolerans SgZ-8 through exogeneous HAs dependent and independent pathways. O₂·⁻ and H₂O₂ were identified as the key intermediate species, which were produced by both microbial aerobic respiration and HA oxidation. The ·OH generated by HA redox cycles could lead to a weight loss of PS-MPs of 18.1% through oxidative degradation during a period of 8 weeks of anoxic-oxic incubation. The EDC of HAs is closely related to ·OH production, which could have a large influence on the effectiveness of oxidative degradation of PS-MPs during various HAs redox cycles in temporarily anoxic environmental systems. These findings provide new insights into ·OH formation and MPs transformation through microbially driven humus redox cycles in alternating anoxic-oxic environments.

在氧化还原活性物质转化过程中产生 ·OH 的记录越来越多，它会导致自然系统中的微塑料 (MPs) 老化或降解。然而，腐殖质氧化还原循环对·OH 生成和 MPs 转化的贡献以前被忽视了，尽管它在交替缺氧-好氧环境中无处不在。在这项工作中，首次研究了腐植酸（HAs）氧化还原转化过程中·OH生成的综合途径以及该·OH对MPs转化的贡献。结果表明，在耐热芽孢杆菌SgZ-8介导的HAs氧化还原转化的连续循环中，可以通过外源HAs依赖和独立途径连续产生·OH 。氧₂· ^-和H ₂ O ₂被确定为关键的中间物种，它们是由微生物有氧呼吸和HA氧化产生的。在 8 周的缺氧-好氧培养期间，HA 氧化还原循环产生的·OH 可通过氧化降解导致 PS-MPs 的重量损失 18.1%。HAs的EDC与·OH的产生密切相关，这可能对PS-MPs在临时缺氧环境系统中各种HAs氧化还原循环中氧化降解的有效性有很大影响。这些发现为通过微生物驱动的腐殖质氧化还原循环在缺氧-好氧交替环境中形成·OH 和 MPs 转化提供了新的见解。