Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi , Kanazawa, Ishikawa 920-1192, Japan.
Environ Sci Technol. 2011 Apr 15;45(8):3325-32. doi: 10.1021/es1042172. Epub 2011 Mar 15.
The formation of hydroxynitropyrene (OHNP) via a photochemical reaction of 1-nitropyrene (1-NP) was demonstrated using a UV irradiation system. The photoreaction of 1-NP in methanol gave products that were hydroxy-substituted at position 1 and mononitro-substituted at positions 2, 3, 5, 6, and 8 [1-hydroxy-x-nitropyrenes (1-OH-x-NPs); x = 2, 3, 5, 6, and 8]. 1-OH-2-NP and 1-OH-5-NP have been identified in ambient airborne particles for the first time. On the contrary, these two OHNP isomers were not found in standard reference materials (SRM) 1650b and SRM 1975, which are typical samples of diesel exhaust particles (DEPs). The concentrations of the other OHNP isomers in the DEP samples were much lower than the concentration of 1-NP, which is a representative nitro-derivative polycyclic aromatic hydrocarbon that is emitted directly from combustion sources. On the other hand, significantly higher concentration ratios of ∑OHNP (=1-OH-3-NP + 1-OH-6-NP + 1-OH-8-NP) to 1-NP were observed in ambient airborne particles than in the DEP samples. In ambient airborne particles, the mean ∑OHNP/1-NP concentration ratio of 1.4 was 35 times higher than that in SRM 1650b and 470 times higher than that in SRM 1975. The diurnal concentration of 1-NP, which was observed at a typical residential area in Osaka, Japan, increased early in the morning and late in the evening, suggesting that automotive emissions contributed to the occurrence of 1-NP. The OHNP concentrations also rose in the morning, and variations of OHNP concentrations similar to those of 1-NP were observed during the daytime. However, the concentrations of OHNPs did not increase in the evening rush hour, and were low at night, i.e., in the absence of sunlight. These results support the idea that atmospheric OHNPs are predominantly formed via secondary formation processes; i.e., photochemical reactions of 1-NP are expected to have a significant effect on the occurrence of OHNPs in the atmosphere.
通过紫外光照射系统，证明了 1-硝基芘（1-NP）的光化学反应可以形成羟基化的硝基芘（OHNP）。在甲醇中的 1-NP 的光反应生成了在 1 位羟基取代和 2、3、5、6 和 8 位单硝基取代的产物[1-羟基-x-硝基芘（1-OH-x-NPs）；x=2、3、5、6 和 8]。1-OH-2-NP 和 1-OH-5-NP 首次在环境空气中颗粒物中被识别出来。相反，这两种 OHNP 异构体在标准参考物质（SRM）1650b 和 SRM 1975 中没有被发现，这两种物质是柴油机排放颗粒（DEP）的典型样品。DEP 样品中其他 OHNP 异构体的浓度远低于直接从燃烧源排放的代表性硝基衍生多环芳烃 1-NP 的浓度。另一方面，在环境空气中颗粒物中，∑OHNP（=1-OH-3-NP+1-OH-6-NP+1-OH-8-NP）与 1-NP 的浓度比值明显高于 DEP 样品。在环境空气中颗粒物中，∑OHNP/1-NP 的平均浓度比为 1.4，是 SRM 1650b 的 35 倍，是 SRM 1975 的 470 倍。在日本大阪的一个典型住宅区观察到的 1-NP 的日浓度在清晨和傍晚较早时增加，表明汽车排放物导致了 1-NP 的出现。OHNP 浓度也在清晨上升，并且在白天观察到 OHNP 浓度与 1-NP 相似的变化。然而，在傍晚交通高峰期，OHNPs 的浓度没有增加，并且在夜间较低，即没有阳光时。这些结果支持这样的观点，即大气中的 OHNPs 主要通过二次形成过程形成；即 1-NP 的光化学反应预计会对大气中 OHNPs 的发生产生重大影响。
