Significant Contribution of Solid Organic Matter for Hydroxyl Radical Production during Oxygenation,Environmental Science & Technology

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Significant Contribution of Solid Organic Matter for Hydroxyl Radical Production during Oxygenation
Environmental Science & Technology ( IF 10.8 ) Pub Date : 2022-08-07 , DOI: 10.1021/acs.est.2c02766
Chenglong Yu ₁ , Yuxi Lu ₁ , Yanting Zhang ₁ , Ao Qian ₁ , Peng Zhang ₁ , Man Tong ₁ , Songhu Yuan _{1,

2}

Affiliation

Dark formation of hydroxyl radicals (•OH) from soil/sediment oxygenation has been increasingly reported, and solid Fe(II) is considered as the main electron donor for O₂ activation. However, the role of solid organic matter (SOM) in •OH production is not clear, although it represents an important electron pool in the subsurface. In this study, •OH production from oxygenation of reduced solid humic acid (HA_red) was investigated at pH 7.0. •OH production is linearly correlated with the electrons released from HA_red suspension. Solid HA_red transferred electrons rapidly to O₂ via the surface-reduced moieties (hydroquinone groups), which was fueled by the slow electron transfer from the reduced moieties inside solid HA. Cycling of dissolved HA between oxidized and reduced states could mediate the electron transfer from solid HA_red to O₂ for •OH production enhancement. Modeling results predicted that reduced SOM played an important or even dominant role in •OH production for the soils and sediments possessing high molar ratios of SOC/Fe(II) (e.g., >39). The significant contribution of SOM was further validated by the modeling results for oxygenation of 88 soils/sediments in the literature. Therefore, reduced SOM should be considered carefully to comprehensively understand •OH production in SOM-rich subsurface environments.

中文翻译：

氧化过程中固体有机物对羟基自由基产生的重要贡献

越来越多的报道来自土壤/沉积物氧化形成的暗羟基自由基 (•OH)，并且固体 Fe(II) 被认为是 O ₂活化的主要电子供体。然而，固体有机物 (SOM) 在 •OH 生产中的作用尚不清楚，尽管它代表了地下的一个重要电子池。在这项研究中，研究了在 pH 7.0条件下还原固体腐植酸（HA_{红色）氧化产生的 •OH。}_{•OH 的产生与HA红}悬浮液释放的电子呈线性相关。固体 HA_红色将电子快速转移到 O ₂通过表面还原的部分（氢醌基团），这是由固体 HA 内的还原部分的缓慢电子转移推动的。溶解的HA在氧化态和还原态之间的循环可以介导从固体HA_红到O ₂的电子转移，从而提高•OH的产生。模拟结果预测，对于具有高 SOC/Fe(II) 摩尔比（例如，>39）的土壤和沉积物，减少的 SOM 在 •OH 产生中起重要甚至主导作用。文献中对 88 种土壤/沉积物的氧化建模结果进一步验证了 SOM 的显着贡献。因此，应仔细考虑减少的 SOM，以全面了解富含 SOM 的地下环境中的 •OH 生产。

更新日期：2022-08-07

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