Temporal Source Apportionment of PM2.5 Over the Pearl River Delta Region in Southern China.

The key problems in addressing air pollution include determining the source of the pollutants and developing a means to control them. In addition to the source area and source category of pollutants, the contributions of pollutants emitted during various periods is an important factor that must be better understood for effective and efficient policymaking. A temporal source apportionment module in the Comprehensive Air Quality Model with Extensions was developed and applied to analyze the temporal contributions of emissions to the concentration of atmospheric particulate matter with a diameter ≤2.5 μm (PM2.5) in the Pearl River Delta (PRD) region. The results showed that in addition to cross‐boundary transport, the PM2.5 concentration in the PRD region was generally influenced by emissions on the current day and previous day. Local emissions from 06:00–17:59 on the current day accounted for approximately 30% of the PM2.5 concentration, whereas regional sources (cross‐city transport) had greater contributions during earlier emission periods. During the periods of episodic pollution, a weak wind situation hindered the transportation and diffusion of pollutants; thus, pollutants from 2 days earlier were trapped within the PRD region. When only the emissions from the PRD region were considered, particulate nitrate was more affected by regional emissions from the previous day, whereas the main contributors of other major components of PM2.5 were emissions from the current day. Our results suggest that emission control measures should be implemented 2 days in advance when adverse meteorological conditions are predicted. Plain Language Summary: In addition to the source area and source category of air pollutants, the contributions of pollutants emitted during various periods is an important factor that must be better understood for effective and efficient policymaking. The air quality model was further developed and applied to analyze the temporal contribution of emissions to the concentration of atmospheric particulate matter with a diameter ≤2.5 μm (PM2.5) in the Pearl River Delta (PRD) region. The PM2.5 concentration in the PRD region was generally influenced by emissions on the current day and previous day. The emissions from 06:00–17:59 on the current day in the local city accounted for approximately 30% of the PM2.5 concentration. During the pollution period, pollutants from 2 days earlier were trapped within the PRD region because of the lower wind speed. These findings suggest that emission control measures should be implemented 2 days in advance when adverse meteorological conditions are predicted. Key Points: The contributions of emissions released at different periods to the particulate matter with a diameter ≤2.5 μm (PM2.5) concentration in the Pearl River Delta region were quantifiedThe PM2.5 concentration in the Pearl River Delta region was largely affected by emissions on the current and previous dayThe emissions in different periods contributed to major components of PM2.5 at varying degrees [ABSTRACT FROM AUTHOR]