Quantification of the enhancement of PM_2.5 concentration by the downward transport of ozone from the stratosphere.

ABSTRACT: The downward transport of ozone (O₃) stemming from the stratosphere-to-troposphere exchange (STE) can be a significant contributor to background O₃. Such enhancement of background O₃ may also influence ground-level PM_2.5, particularly in polluted regions which have abundant precursor emissions. In this study, we quantified the STE impact on tropospheric O₃ and its subsequent influence on surface PM_2.5 across the northern hemisphere. The sensitivity analyses was conducted by using a comprehensive hemispheric atmospheric modeling system. Results suggest the surface PM_2.5 concentration can be considerably enhanced by the STE in polluted regions including East China, East US, and Europe, mostly in winter and spring. In winter, the PM_2.5 concentrations in East China, East US, and Europe are estimated to be enhanced by 1.3%, 3.5% and 5.5% due to the STE. The STE-enhanced PM_2.5 concentrations are typically higher on high pollution days suggesting likely increasing contributions in regions with the growing pollution levels. During the heavy polluted days, the PM_2.5 concentrations in East China can be enhanced by 2.289 μg/m³ in winter and 2.034 μg/m³ in spring due to the STE. The STE-enhanced PM_2.5 also exhibits strong diurnal variations following a pattern similar to the total PM_2.5 concentration, with high increasing ratio in the morning and low at afternoon, suggesting that the enhancement is most pronounced during peak pollution events. The STE-enhanced PM_2.5 is exclusively contributed by the increase of nitrate, ammonium, and secondary organic aerosol which in-turn are strongly influenced by the atmospheric oxidation capacity.

SUBMITTER: Chen L 

PROVIDER: S-EPMC7441492 | biostudies-literature |

REPOSITORIES: biostudies-literature