title: Effects of humidity and [NO3]/[N2O5] ratio on the heterogeneous reaction of fluoranthene and pyrene with N2O5/NO3/NO2.
abstract: Atmospheric 2-nitrofluoranthene (2-NFL) and 2-nitropyrene (2-NPY) were two important nitro-polycyclic aromatic hydrocarbons (NPAHs). Especially, 2-NFL was recognized to be the most abundant particle-associated NPAH (Ramdahl et al., 1986). In previous studies, these two products were observed in the gas-phase reaction between N2O5/NO3/NO2 and their parent polycyclic aromatic hydrocarbons (PAHs), while the heterogeneous reaction generated other nitro-PAH isomers (1, 3, 7, 8-NFL and 1-NPY) (Atkinson et al. 1990). To clarify the possible reasons for this difference, the heterogeneous reactions of suspended fluoranthene (FL) and pyrene (PY) particles under different relative humidity (RH; 0.5%-43%) and [NO3]/[N2O5] ratios were carried out. Under low humidity (0.5% RH) or a relatively high ratio of [NO3]/[N2O5], 2-NFL and 2-NPY were observed as the major nitro-FL isomers for the first time in the heterogeneous reaction. Decreasing the humidity or increasing the [NO3]/[N2O5] ratio in the reaction essentially increases the concentration radio of [NO3(g)]/[NO2(+)(aq)] on the particle surface (NO2(+) is derived from the ionization of N2O5). Thus, it can be concluded that under different atmospheric conditions, the change of [NO3(g)]/[NO2(+)(aq)] in the particle surface has an influence on the product distribution of FL and PY in the atmosphere. The experimental results provide evidence for the heterogeneous formations of particle-bound 2-NFL and 2-NPY. However, relative to the gas-phase formation, they will be negligible in the real atmosphere. 2-NFL and 2-NPY observed in the ambient particles should mainly derive from deposition of gas-phase reactions. Additionally, this study also clarifies the reason for different nitro-PAHs isomers observed between gas and particulate reactions.
authors.affiliation: State Key Joint Laboratory of Environment Simulation and Pollution Control, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , Beijing 100085, China.
authors.forename: Peng
authors.initials: P
authors.lastname: Zhang
authors.forename: Wanqi
authors.initials: W
authors.lastname: Sun
authors.forename: Nana
authors.initials: N
authors.lastname: Li
authors.forename: Youfeng
authors.initials: Y
authors.lastname: Wang
authors.forename: Jinian
authors.initials: J
authors.lastname: Shu
authors.forename: Bo
authors.initials: B
authors.lastname: Yang
authors.forename: Liang
authors.initials: L
authors.lastname: Dong
mesh_terms: D001272:Atmosphere / Q000737:chemistry; D002849:Chromatography, Gas; D005449:Fluorenes / Q000737:chemistry*; D006813:Humidity; D013058:Mass Spectrometry; D009566:Nitrates / Q000737:chemistry*; D009573:Nitrites / Q000737:chemistry*; D009589:Nitrogen Oxides / Q000737:chemistry*; D052638:Particulate Matter / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000737:chemistry; D011721:Pyrenes / Q000737:chemistry*
chemical_list: D005449:Fluorenes; D009566:Nitrates; D009573:Nitrites; D009589:Nitrogen Oxides; D052638:Particulate Matter; D011084:Polycyclic Aromatic Hydrocarbons; D011721:Pyrenes; C007738:fluoranthene; C010125:nitrogen pentoxide; C049029:2-nitropyrene; C030984:pyrene; C049030:2-nitrofluoranthene