Source-specific light absorption and radiative effects decreases and indications due to the lockdown

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Climate Science

Background:

• COVID-19 lockdowns provided a unique, large-scale experiment in emission abatement.
• Understanding source-specific aerosol impacts is crucial for climate and air quality management.
• Aerosol light absorption and direct radiative effect (DRE) are key climate-forcing parameters.

Purpose of the Study:

• To quantify source-specific variations in aerosol light absorption (b_abs) and DRE during and after the COVID-19 lockdown.
• To investigate the influence of emission reductions on aerosol optical properties and radiative effects.
• To assess the effectiveness of emission control strategies on atmospheric radiation.

Main Methods:

• Utilized artificial neural networks (ANN) for data analysis.
• Employed source apportionment environmental receptor models.
• Analyzed variations in b_abs at 370 nm and 880 nm, and DRE during distinct periods.

Main Results:

• All emission sources showed decreased b_abs; traffic emissions reduced by ~90% (lockdown), coal combustion by ~85% (post-lockdown).
• Elevated b_abs at 370 nm for coal/biomass burning during lockdown linked to enhanced atmospheric oxidation.
• b_abs variations at 880 nm post-lockdown attributed to weakened oxidation and reduced secondary precursors.

Conclusions:

• Large-scale emission reductions effectively decreased aerosol light absorption and DRE (34-68%) during lockdowns.
• Primary emission reductions, like traffic, can enhance atmospheric oxidation and UV light absorption efficiency.
• Source-specific emission controls yield varied radiative effects, informing effective climate mitigation strategies.