Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, Perth 6102, Australia.
Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 10085, China.
Sci Total Environ. 2022 Oct 10;842:156959. doi: 10.1016/j.scitotenv.2022.156959. Epub 2022 Jun 26.
The ubiquitously present dissolved organic matter (DOM) greatly influence the efficiency of UV-based technologies due to its reactivity to UV irradiation. In this work, UV-induced changes within three hydrophobic DOM fractions isolated from different surface waters were investigated. Analysis on UV absorbance at 254 nm, electron donating capacity, fluorescence intensity and carbon content revealed small changes in DOM bulk properties associated with the UV-induced photochemical reactions. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) was further used to explore the modification of the molecular distribution based on H/C and O/C ratios, m/z and DBE. The molecular-level investigation revealed that an average of 296 aromatic and lignin-like molecules were degraded, leading to the production of around 306 new molecules. The UV-reactive community were identified as CHO molecules with higher DBE (>10) and carbon number (>25) which could be readily transformed into smaller saturated molecules. Molecules containing nitrogen (N) or sulfur (S) atom, independent of aromaticity and molecular weight (m/z), were also highly UV susceptible and transformed into molecules with larger DBE and m/z. Possible reaction pathways responsible for the observations were discussed. The results indicated that UV-reactivity and subsequent transformation of DOM are remarkably correlated with its molecular composition and characteristics. Though the changes in bulk properties of DOM following UV irradiation were observed to be very small, the significant alteration in its molecular structures would have a profound impact on the UV-based treatment processes.
由于其对紫外线辐照的反应性，普遍存在的溶解有机物 (DOM) 极大地影响了基于紫外线的技术的效率。在这项工作中，研究了从不同地表水分离的三种疏水性 DOM 分数在紫外线照射下的变化。对 254nm 处的紫外吸收、电子给体能力、荧光强度和碳含量的分析表明，与紫外线诱导的光化学反应相关的 DOM 整体性质发生了微小变化。傅里叶变换离子回旋共振质谱 (FT-ICR MS) 进一步用于基于 H/C 和 O/C 比、m/z 和 DBE 来探索分子分布的修饰。分子水平的研究表明，平均有 296 个芳香族和木质素样分子被降解，产生了大约 306 个新分子。UV 反应性群落被鉴定为 CHO 分子，具有更高的 DBE（>10）和碳原子数（>25），这些分子很容易转化为更小的饱和分子。含氮（N）或硫（S）原子的分子，不依赖于芳香度和分子量（m/z），也具有很高的 UV 敏感性，并转化为具有更大 DBE 和 m/z 的分子。讨论了可能导致这些观察结果的反应途径。结果表明，DOM 的 UV 反应性和随后的转化与其分子组成和特征密切相关。尽管 DOM 在紫外线照射后其整体性质的变化非常小，但它的分子结构的显著改变将对基于紫外线的处理过程产生深远的影响。
