State Key Joint Laboratory of Environmental Simulation and Pollution Control; College of Environmental Sciences and Engineering, Peking University , Beijing 100871, China.
Environ Sci Technol. 2014;48(15):8671-8. doi: 10.1021/es501543g. Epub 2014 Jul 9.
Oxidative derivatives of polycyclic aromatic hydrocarbons (PAHs), that is, nitro-PAHs and quinones, are classed as hazardous semivolatile organic compounds but their formation mechanism from the heterogeneous reactions of PAHs adsorbed on atmospheric particles is not well understood. The heterogeneous reaction of NO2 with anthracene adsorbed on NaCl particles under different relative humidity (RH 0-60%) was investigated under dark conditions at 298 K. The formation of the major products, 9,10-anthraquinone (9,10-AQ) and 9-nitroanthracene (9-NANT), were determined to be second-order reactions with respect to NO2 concentration. The rate of formation of 9,10-AQ under low RH (0-20%) increased as the RH increased but decreased when the RH was further increased in high RH (40-60%). In contrast, the rate of formation of 9-NANT across the whole RH range (0-60%) decreased significantly with increasing RH. Two different reaction pathways are discussed for the formation of 9,10-AQ and 9-NANT, respectively, and both are considered to be coupled to the predominant reaction of NO2 with the NaCl substrate. These results suggest that relative humidity, which controls the amount of surface adsorbed water on NaCl particles, plays an important role in the heterogeneous reaction of NO2 with adsorbed PAHs.
多环芳烃（PAHs）的氧化衍生物，即硝基-PAHs 和醌类物质，被归类为危险的半挥发性有机化合物，但它们是如何从吸附在大气颗粒上的 PAHs 的多相反应中形成的，目前还不是很清楚。在 298 K 下，在黑暗条件下研究了不同相对湿度（RH 0-60%）下，NO2 与吸附在 NaCl 颗粒上的蒽的多相反应。主要产物 9,10-蒽醌（9,10-AQ）和 9-硝基蒽（9-NANT）的形成被确定为对 NO2 浓度的二级反应。在低 RH（0-20%）下，9,10-AQ 的形成速率随着 RH 的增加而增加，但当 RH 进一步增加到高 RH（40-60%）时，形成速率会降低。相比之下，9-NANT 的形成速率在整个 RH 范围内（0-60%）都随着 RH 的增加而显著降低。分别讨论了形成 9,10-AQ 和 9-NANT 的两种不同反应途径，这两种途径都被认为与 NO2 与 NaCl 基质的主要反应有关。这些结果表明，相对湿度控制着 NaCl 颗粒表面吸附水的量，在 NO2 与吸附的 PAHs 的多相反应中起着重要作用。
