Liu Shujun, Wang Hong, Hu Zehui, Zhang Xin, Sun Yanjuan, Dong Fan
Research Center for Carbon-Neutral Environmental & Energy Technology, Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 611731, China.
School of Resources and Environment, University of Electronic Science and Technology of China, Chengdu 611731, China.
Proc Natl Acad Sci U S A. 2024 Jul 23;121(30):e2401452121. doi: 10.1073/pnas.2401452121. Epub 2024 Jul 17.
Nitrophenols present on the surface of particulates are ubiquitous in the atmosphere. However, its atmospheric photochemical transformation pathway remains unknown, for which the crucial effect of visible light is largely overlooked, resulting in an incomplete understanding of the effects of nitrophenols in the atmospheric environment. This study delves into the photolysis mechanism of 4-nitrophenol (4NP), one of the most abundant atmospheric nitrophenol compounds, on the surface of photoactive particulates under visible light irradiation. Unexpectedly, the nonradical species (singlet oxygen, O) was identified as a dominant factor in driving the visible photolysis of 4NP. The pathways of HONO and p-benzoquinone (CHO) generation were clarified by acquiring direct evidence of C-N and O-H bond breakage in the nitro (-NO) and hydroxyl (-OH) groups of 4NP. The further decomposition of HONO results in the generation of NO and hydroxyl radicals, which could directly contribute to atmospheric oxidizing capacity and complicate the PM composition. Significantly, the behavior of O-induced visible photolysis of 4NP was universal on the surface of common particulates in the atmosphere, such as A1 dust and FeO. This work advances the understanding of the photochemical transformation mechanism of particulate-phase atmospheric nitrophenols, which is indispensable in elucidating the role of nitrophenols in atmospheric chemistry.
颗粒物表面存在的硝基酚在大气中普遍存在。然而，其大气光化学转化途径尚不清楚，可见光的关键作用在很大程度上被忽视，导致对硝基酚在大气环境中的影响理解不完整。本研究深入探讨了大气中含量最丰富的硝基酚化合物之一4-硝基酚（4NP）在可见光照射下在光活性颗粒物表面的光解机理。出乎意料的是，非自由基物种（单线态氧，O）被确定为驱动4NP可见光解的主要因素。通过获得4NP硝基（-NO）和羟基（-OH）基团中C-N和O-H键断裂的直接证据，阐明了HONO和对苯醌（CHO）的生成途径。HONO的进一步分解导致NO和羟基自由基的产生，这可能直接影响大气氧化能力并使颗粒物成分复杂化。值得注意的是，O诱导的4NP可见光解行为在大气中常见颗粒物表面（如A1粉尘和FeO）上具有普遍性。这项工作推进了对颗粒相大气硝基酚光化学转化机制的理解，这对于阐明硝基酚在大气化学中的作用不可或缺。
