Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Fujian Provincial Key Laboratory of Soil Environmental Health and Regulation, College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Water Res. 2022 Aug 1;221:118731. doi: 10.1016/j.watres.2022.118731. Epub 2022 Jun 9.
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. O· and HO 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 已经被越来越多地记录下来，并且它会导致自然系统中微塑料（MPs）的老化或降解。然而，尽管腐殖质氧化还原循环在交替缺氧-好氧环境中普遍存在，但它对·OH 生成和 MPs 转化的贡献以前一直被忽视。在这项工作中，首次研究了腐殖酸（HA）氧化还原转化过程中·OH 生成的综合途径，以及这种·OH 对 MPs 转化的贡献。结果发现，通过嗜热芽孢杆菌 SgZ-8 介导的外源 HA 依赖性和非依赖性途径，HA 的连续氧化还原转化过程中可以连续产生·OH。鉴定出 O·和 HO 是关键的中间物种，它们是通过微生物需氧呼吸和 HA 氧化产生的。HA 氧化还原循环产生的·OH 可以通过氧化降解导致 PS-MPs 在 8 周的缺氧-好氧孵育过程中失重 18.1%。HA 的 EDC 与·OH 的生成密切相关，这可能会对暂时缺氧环境系统中各种 HA 氧化还原循环中 PS-MPs 的氧化降解效果产生很大影响。这些发现为交替缺氧-好氧环境中微生物驱动的腐殖质氧化还原循环中·OH 形成和 MPs 转化提供了新的见解。
