冰中和水中羟基多环芳烃光化学转化行为的比较：动力学、溶解性物质影响与转化产物
Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products
Linke Ge, Shengkai Cao, Crispin Halsall, Junfeng Niu, Dongxiao Bai, Guangkai He, Peng Zhang*, Hongrui Ma
https://doi.org/10.1016/j.jes.2021.11.002
摘要
冰雪是一类重要普遍的环境介质，冰雪环境光化学是一门新兴的学科。与表层水体相比，冰雪环境体系更加复杂。在相同光照条件下比较冰中和水中有机污染物的光化学行为，有助于揭示冰雪环境光化学与水环境光化学之间的异同。羟基PAHs (OH-PAHs)等多环芳烃衍生物是目前公认的新型污染物，已在多个国家和地区大气、水体等环境多介质中被监测到。本研究选取2种OH-PAHs [2-羟基芴(2-OHFL)和9-羟基芴(9-OHFL)]作为模型化合物，比较研究冰中和水中光化学转化的动力学、主要溶解性物质的影响，以及转化产物和路径。结果表明，相同模拟日光(λ > 290 nm)照射下，OHFLs在冰中的光降解比在相同水溶液中更快，这归因于结冰引起的物质浓缩效应。并且，纯水、淡水和海水的水相和冰相中光降解相对快慢不尽相同。进一步发现，相同光照条件下，不同相中某一溶解物质[如Cl−、腐殖酸钠(HASS)、NO3−和Fe(III)]对光降解动力学的影响(增强或抑制)并不完全一样，这取决于基质相中存在的溶解性物质的量、特定OHFL异构体，以及基质类型(冰或水溶液)，表明这些溶解性物质相关的水环境光化学和冰雪环境光化学存在差异。基于衍生化技术和GC-MS/MS分析，比较了冰、水中光降解产物和转化路径，发现水中易于发生多羟基化 (multi-hydroxylation) 反应，生成二羟基或三羟基代的产物，而在冰中只是检测到单羟基化的产物。以上结果揭示了冰中和水中OH-PAHs光化学转化行为的异同，这对于准确评价寒冷环境中此类新型污染物的归趋具有重要意义。
亮点
揭示了冰环境光化学与水环境光化学的异同，发现新污染物OH-PAHs在纯水、淡水、海水中光降解的相对快慢顺序与相应冰相中不同，不同相中溶解性物质对光降解动力学的影响并不完全一样，冰相中的转化产物相对“简单”。
Abstract
The photochemical behavior of organic pollutants in ice is poorly studied in comparison to aqueous photochemistry. Here we report a detailed comparison of ice and aqueous photodegradation of two representative OH-PAHs, 2-hydroxyfluorene (2-OHFL) and 9-hydroxyfluorene (9-OHFL), which are newly recognized contaminants in the wider environment including colder regions. Interestingly, their photodegradation kinetics were clearly influenced by whether they reside in ice or water. Under the same simulated solar irradiation (λ > 290 nm), OHFLs photodegraded faster in ice than in equivalent aqueous solutions and this was attributed to the specific concentration effect caused by freezing. Furthermore, the presence of dissolved constituents in ice also influenced photodegradation with 2-OHFL phototransforming the fastest in ‘seawater’ ice (k = (11.4 ± 1.0) × 10−2 min−1) followed by ‘pure-water’ ice ((8.7 ± 0.4) × 10−2 min−1) and ‘freshwater’ ice ((8.0 ± 0.7) × 10−2 min−1). The presence of dissolved constituents (specifically Cl−, NO3−, Fe(III) and humic acid) influences the phototransformation kinetics, either enhancing or suppressing phototransformation, but this is based on the quantity of the constituent present in the matrixes, the specific OHFL isomer and the matrix type (e.g., ice or aqueous solution). Careful derivation of key photointermediates was undertaken in both ice and water samples using tandem mass spectrometry. Ice phototransformation exhibited fewer by-products and ‘simpler’ pathways giving rise to a range of hydroxylated fluorenes and hydroxylated fluorenones in ice. These results are of importance when considering the fate of PAHs and OH-PAHs in cold regions and their persistence in sunlit ice.
作者简介
第一作者
葛林科，毕业于大连理工大学，荣获辽宁省优秀博士学位论文。现任陕西科技大学环境科学与工程学院教授，博士生导师。主要从事新型有机污染物的环境光化学与LC-MS/MS分析技术研究，承担国家自然科学基金项目3项，在Environ. Sci. Technol., Water Res., J. Environ. Sci.等期刊发表论文40余篇。曾6次参加中国南北极科学考察，在兰卡斯特大学作访问学者、高级研究学者。荣获教育部自然科学一等奖、第十三届陕西青年科技奖等省部级奖励4项。
原文链接
https://www.sciencedirect.com/science/article/abs/pii/S1001074221004587
引用格式
Linke Ge, Shengkai Cao, Crispin Halsall, Junfeng Niu, Dongxiao Bai, Guangkai He, Peng Zhang, Hongrui Ma, 2023. Photodegradation of hydroxyfluorenes in ice and water: A comparison of kinetics, effects of water constituents, and phototransformation by-products. J. Environ. Sci. 124, 139-145.
