Characteristics of Secondary PM2.5 Under Different Photochemical Reactivity Backgrounds in the Pearl River Delta Region

Abstract

With the increasing control of air pollution, the levels of atmospheric particulates in the Pearl River Delta (PRD) region are gradually decreasing. However, ozone pollution has become more and more serious, and the problem of secondary aerosol pollution caused by photochemical reactions cannot be ignored. Based on the observation data of environmental and meteorological stations in the nine cities of the PRD during 2019, we investigated the variations of secondary PM2.5 (PM2.5-sec) in the PRD under different photochemical reactivity backgrounds. It was shown that the photochemical reactivities appeared more significant in the central and western areas than those in the eastern areas of the PRD and appeared more significant in inland areas than those in coastal areas. The days of moderate and high photochemical reactivities mainly appeared from August to November. PM2.5-sec concentrations were the highest in autumn, during which the regional discrepancies appeared most significantly with the highest levels in the southern areas. With the enhancement of the photochemical reactivity background, the PM2.5-sec level at each station increased significantly, which appeared significantly higher in coastal areas than in inland areas. Both PM2.5-sec and ozone concentrations showed single-peak variations, which appeared higher in the daytime than at night with the peak occurring at about 15:00. For each pollutant, the average maximum concentration appeared higher for polluted stations than for clean ones, indicating that the atmospheric oxidation background was conducive to the formation of PM2.5-sec.

Climatological Characteristics of Cold Fronts and Their Impacts on Air Quality in Cold Seasons Over the Eastern China

“…On the other hand, high humidity on rainy days is reported to have a promoting effect on the secondary formation of particulate matter, which could serve the increase of PM 2.5 (T. Y. Wang et al., 2020; Xie et al., 2015). To discuss the impacts of these two aspects, here we show the relative humidity (RH) and the PM 2.5 /CO ratio for BTH and YRD in Figure 10, as the ratio of PM 2.5 to CO could be used to indicate the intensity of the secondary formation of aerosols (Chang & Lee, 2007; Luo et al., 2022; Yu et al., 2022). Overall, the variations of RH follow the precipitation changes.…”

“…Xie et al, 2015). To discuss the impacts of these two aspects, here we show the relative humidity (RH) and the PM 2.5 /CO ratio for BTH and YRD in Figure 10, as the ratio of PM 2.5 to CO could be used to indicate the intensity of the secondary formation of aerosols (Chang & Lee, 2007;Luo et al, 2022;Yu et al, 2022). Overall, the variations of RH follow the precipitation changes.…”

Spatio-temporal characteristics of PM2.5 and O3 synergic pollutions and influence factors in the Yangtze River Delta

“…The rapid increase of secondary particulate matter can lead to heavy pollution events with high PM 2.5 loadings (Dao et al, 2021). In addition, atmospheric precursors experience complex (Cui et al, 2013;Jia et al, 2017;Gu et al, 2022;Yao et al, 2022;Yu et al, 2022), and research has proven that the method of CO tracer is able to screen primary PM 2.5 and estimate urban-scale secondary PM 2.5 concentration.…”

“…The primary aerosols were estimated using hourly CO concentrations under different photochemical activity levels. Meanwhile, the secondary aerosols were calculated by deducting primary PM 2.5 from observed PM 2.5 (Cui et al, 2013;Li K. et al, 2020;Yu et al, 2022).…”