title: Atmospheric formation of hydroxynitropyrenes from a photochemical reaction of particle-associated 1-nitropyrene.
abstract: 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.
authors.affiliation: Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi , Kanazawa, Ishikawa 920-1192, Japan. kameda@p.kanazawa-u.ac.jp
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kameda
authors.forename: Ayuko
authors.initials: A
authors.lastname: Akiyama
authors.forename: Akira
authors.initials: A
authors.lastname: Toriba
authors.forename: Ning
authors.initials: N
authors.lastname: Tang
authors.forename: Kazuichi
authors.initials: K
authors.lastname: Hayakawa
mesh_terms: D000393:Air Pollutants / Q000032:analysis / Q000737:chemistry*; D001272:Atmosphere / Q000737:chemistry*; D002274:Carcinogens, Environmental / Q000032:analysis / Q000737:chemistry; D004784:Environmental Monitoring; D052638:Particulate Matter / Q000032:analysis / Q000737:chemistry; D055668:Photochemical Processes; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis / Q000737:chemistry; D011721:Pyrenes / Q000032:analysis / Q000737:chemistry*; D001335:Vehicle Emissions / Q000032:analysis
chemical_list: D000393:Air Pollutants; D002274:Carcinogens, Environmental; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; D001335:Vehicle Emissions; C032668:1-nitropyrene