Environ Sci Technol. 2020 Jul 21;54(14):8558-8567. doi: 10.1021/acs.est.0c01150. Epub 2020 Jul 8.
Modifications of the physicochemical properties and oxidative potential (OP) of soot due to visible-light irradiation and its underlying mechanisms during atmospheric aging have not been elucidated. In this study, two types of soot obtained using different air/fuel ratios (A/F) were aged under visible light with or without ozone (O) at an atmospherically relevant level in an environmental chamber. Physicochemical characteristics and OP of aged soot were systematically measured using the dithiothreitol (DTT) assay (OP). Regardless of the presence of O, visible light markedly promoted oxidation of soot, which led to consumption of polycyclic aromatic hydrocarbons, formation of oxygen-containing functional groups, and enhancement of OP values. Compared to low-A/F soot, high-A/F soot contained more elemental carbon but less organic carbon and was more sensitive to visible light by exhibiting greater changes. It was proposed that elemental carbon in soot under visible-light irradiation initiated an inside-to-outside oxidation pathway, where reactive oxygen species played an important role. This study clarified the solar irradiation-triggered self-oxidation process in soot, which is important to its atmospheric and health effects.
由于可见光照射，烟尘的物理化学性质和氧化潜力（OP）发生了变化，而在大气老化过程中，其潜在机制尚不清楚。在本研究中，使用两种不同的空气/燃料比（A/F）在环境室中以大气相关水平在可见光下或有臭氧（O）存在下对两种类型的烟尘进行老化。使用二硫苏糖醇（DTT）测定法（OP）系统地测量了老化烟尘的物理化学特性和 OP。无论 O 是否存在，可见光都明显促进了烟尘的氧化，导致多环芳烃的消耗、含氧官能团的形成以及 OP 值的提高。与低 A/F 烟尘相比，高 A/F 烟尘含有更多的元素碳，但有机碳较少，并且通过表现出更大的变化，对可见光更为敏感。据推测，烟尘中的元素碳在可见光照射下引发了从内到外的氧化途径，其中活性氧物质发挥了重要作用。本研究阐明了烟尘中太阳辐射引发的自氧化过程，这对其大气和健康影响很重要。
