Aerosol–photolysis interaction reduces particulate matter during wintertime haze events

Abstract

Aerosol–radiation interaction (ARI) plays a significant role in the accumulation of fine particulate matter (PM2.5) by stabilizing the planetary boundary layer and thus deteriorating air quality during haze events. However, modification of photolysis by aerosol scattering or absorbing solar radiation (aerosol–photolysis interaction or API) alters the atmospheric oxidizing capacity, decreases the rate of secondary aerosol formation, and ultimately alleviates the ARI effect on PM2.5 pollution. Therefore, the synergetic effect of both ARI and API can either aggravate or even mitigate PM2.5 pollution. To test the effect, a fully coupled Weather Research and Forecasting (WRF)-Chem model has been used to simulate a heavy haze episode in North China Plain. Our results show that ARI contributes to a 7.8% increase in near-surface PM2.5. However, API suppresses secondary aerosol formation, and the combination of ARI and API results in only 4.8% net increase of PM2.5. Additionally, API increases the solar radiation reaching the surface and perturbs aerosol nucleation and activation to form cloud condensation nuclei, influencing aerosol–cloud interaction. The results suggest that API reduces PM2.5 pollution during haze events, but adds uncertainties in climate prediction.

Vapor isotopic evidence for the worsening of winter air quality by anthropogenic combustion-derived water

“…The WRF-Chem model performed well in simulating particulate pollution in China ( 17 , 37 , 38 ), and reasonably reproduced the observed temporal variations and spatial distributions of [PM 2.5 ], [O 3 ], [NO 2 ], and [SO 2 ] in the GZB and Xi’an city ( SI Appendix , Fig. S7 ) during the simulation period in the present study.…”

Environmental effects of stratospheric ozone depletion, UV radiation, and interactions with climate change: UNEP Environmental Effects Assessment Panel, Update 2020

“…In China, long-term reductions in some emissions [e.g., nitrogen oxides (NO x ) and SO 2 ] have resulted in substantial reductions in aerosol haze, but this has been accompanied by an undesirable increase in ambient ozone [ 377 – 380 ]. Observations show worsening ozone pollution between 2013 and 2017 at urban locations in China [ 379 , 381 , 382 ] and in the North China Plain from 2013 to 2019 [ 383 ].…”

Unexpected air pollution with marked emission reductions during the COVID-19 outbreak in China

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