Despite the widespread use of photochemical and optical properties to characterize dissolved organic matter (DOM), a significant gap persists in our understanding of the relationship among these properties. This study infers the molecular basis for the optical and photochemical properties of DOM using a comprehensive framework and known structural moieties within DOM. Utilizing Suwannee River Fulvic Acid (SRFA) as a model DOM, carboxylated aromatics, phenols, and quinones were identified as dominant contributors to the absorbance spectra, and phenols, quinones, aldehydes, and ketones were identified as major contributors to radiative energy pathways. It was estimated that chromophores constitute ∼63% w/w of dissolved organic carbon in SRFA and ∼47% w/w of overall SRFA. Notably, estimations indicate the pool of fluorescent compounds and photosensitizing compounds in SRFA are likely distinct from each other at wavelengths below 400 nm. This perspective offers a practical tool to aid in the identification of probable chemical groups when interpreting optical and photochemical data and challenges the current “black box” thinking. Instead, DOM photochemical and optical properties can be closely estimated by assuming the DOM is composed of a mixture of individual compounds.

中文翻译：

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推断溶解有机物光化学和光学性质的分子基础


尽管广泛使用光化学和光学特性来表征溶解有机物（DOM），但我们对这些特性之间关系的理解仍然存在很大差距。本研究利用 DOM 内的综合框架和已知结构部分推断 DOM 光学和光化学性质的分子基础。利用苏万尼河黄腐酸 (SRFA) 作为 DOM 模型，羧化芳香族化合物、酚类和醌类被确定为吸收光谱的主要贡献者，酚类、醌类、醛类和酮类被确定为辐射能量路径的主要贡献者。据估计，发色团占 SRFA 中溶解有机碳的 63% w/w，占整个 SRFA 的 47% w/w。值得注意的是，估计表明 SRFA 中的荧光化合物和光敏化合物池在低于 400 nm 的波长下可能彼此不同。这种观点提供了一种实用工具，可以在解释光学和光化学数据时帮助识别可能的化学基团，并挑战当前的“黑匣子”思维。相反，可以通过假设 DOM 由单个化合物的混合物组成来仔细估计 DOM 的光化学和光学特性。