Autoxidized Hydroquinone Mimics the Optical Properties of Chromophoric Dissolved Organic Matter,Environmental Science & Technology Letters

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Autoxidized Hydroquinone Mimics the Optical Properties of Chromophoric Dissolved Organic Matter
Environmental Science & Technology Letters ( IF 8.9 ) Pub Date : 2021-08-02 , DOI: 10.1021/acs.estlett.1c00484
Garrett McKay ₁

Affiliation

One of the most significant knowledge gaps in aquatic chemistry is the chemical composition of chromophores and fluorophores in dissolved organic matter (DOM). While optical measurements have been employed for decades to track DOM quantity and quality, the specific molecular moieties responsible for DOM absorbance and fluorescence remain largely unresolved. In this study, it is demonstrated that autoxidized hydroquinone can reproduce the absorbance and fluorescence spectral shape of humic substance isolates of aquatic, microbial, and terrestrial origin. Furthermore, spectra of autoxidized hydroquinone show responses similar to those of DOM to borohydride reduction and pH titration, two treatments thought to probe the role of charge-transfer interactions. Data presented herein suggest that hydroquinone and p-benzoquinone (formed from hydroquinone autoxidation) interact to form quinhydrone-type charge-transfer contacts that exhibit optical properties highly similar to those of DOM. The similarities observed between DOM and autoxidized hydroquinone support the idea that the charge-transfer model is a viable explanation for DOM photophysical processes. While it is often assumed that the complex mixture of components in DOM is responsible for its optical properties, this study demonstrates that these optical properties can be replicated with a comparatively simple chemical system.

中文翻译：

自氧化对苯二酚模仿发色溶解有机物的光学性质

水生化学中最重要的知识空白之一是溶解有机物 (DOM) 中生色团和荧光团的化学成分。虽然数十年来一直采用光学测量来跟踪 DOM 的数量和质量，但负责 DOM 吸光度和荧光的特定分子部分在很大程度上仍未得到解决。在这项研究中，证明自氧化氢醌可以再现水生、微生物和陆生来源的腐殖质分离物的吸光度和荧光光谱形状。此外，自氧化氢醌的光谱显示出类似于 DOM 对硼氢化物还原和 pH 滴定的响应，这两种处理被认为可以探测电荷转移相互作用的作用。本文提供的数据表明对苯二酚和p-苯醌（由氢醌自氧化形成）相互作用形成醌型电荷转移触点，其光学特性与 DOM 高度相似。在 DOM 和自氧化氢醌之间观察到的相似性支持电荷转移模型是对 DOM 光物理过程的可行解释的观点。虽然通常假设 DOM 中组分的复杂混合物是其光学特性的原因，但这项研究表明，这些光学特性可以用相对简单的化学系统复制。

更新日期：2021-09-14

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