Nitrated polycyclic aromatic compounds in the atmospheric environment: A review

Abstract

Nitrated polycyclic aromatic compounds (Nitro-PACs) are a class of aromatic compounds with at least one nitro-(NO₂) functional group on the aromatic ring of polycyclic aromatic hydrocarbons and phenols, including nitrated polycyclic aromatic hydrocarbons (nitro-PAH) and nitrophenols (NPs). Due to their mutagenicity, carcinogenicity and light absorption ability, the emission sources, toxicity, optical properties and radiative forcing effects of nitro-PACs have attracted global attention. In this study, we review the spatial and temporal variation patterns of nitro-PACs worldwide, and highlight the current emission hotspots. The changes in emissions of nitro-PACs under clean energy strategies are compiled, and the optical properties and possible climatic impacts of nitro-PACs are illustrated in detail. Finally, we provide some recommendations for future research, such as further investigation into the determination of nitro-PACs in heavily polluted South Asia and Brazil, the mechanisms of nitro-PACs during photochemical formation and photodegradation processes, the optical properties of nitro-PACs in cloud or fog droplets, and the contribution of nitro-PACs to the total radiative forcing of brown carbon. This review summarizes our understanding of the environmental and climatic effects of nitro-PACs.

Graphical abstract

Keywords:

• Nitro-PACs
• nitro-PAHs
• emissions reduction

Additional information

Funding

This study was supported by the National Natural Science Foundation of China (41701083 and 41925032), the Strategic Priority Research Program of the Chinese Academy of Sciences, the Pan‐Third Pole Environment Study for a Green Silk Road (Pan‐TPE; XDA2004050202), and the China Postdoctoral Science Foundation (2018T110146).