Peroxyacetyl Nitrate in China: Characteristics, Impacts, and Research Perspectives

Peroxyacetyl nitrate (PAN) is a key secondary pollutant formed through atmospheric photochemical reactions and is regarded as a characteristic indicator of photochemical pollution. In China, while primary pollutant concentrations have been effectively controlled in recent years, secondary pollution dominated by ozone (O3) and fine particulate matter (PM2.5) has become increasingly prominent. However, research on PAN’s environmental behavior and mechanisms remains insufficient, and it has not been incorporated into routine air quality monitoring systems, leading to significant gaps in understanding its pollution characteristics. This paper systematically reviews research progress on atmospheric PAN in China, covering its formation mechanisms, spatiotemporal distribution (highlighting high concentrations in economically developed eastern regions and low levels in background areas like the Tibetan Plateau), and its influence pathways on O3 and PM2.5 formation. It also addresses PAN’s complex formation, meteorological regulation of its variations, its role in nitrogen oxide redistribution via regional transport, and its potential health risks. Given limited monitoring data, future efforts should focus on clarifying key influencing factors, expanding monitoring networks, and deepening research on PAN-pollutant interactions to support targeted pollution control.