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- Title
Different Response Mechanisms of N‐Bearing Components to Emission Reduction Across China During COVID‐19 Lockdown Period.
- Authors
Li, Rui; Zhang, Lijia; Gao, Yining; Wang, Gehui
- Abstract
The response characteristics of secondary inorganic aerosols to COVID‐19 lockdown measures have been extensively reported, while spatial disparities of these response characteristics across China and key deriving mechanisms still remained poorly understood. In our study, a chemical transport model (GEOS‐Chem) was applied to simulate the national concentrations of four N‐bearing components during lockdown periods in 2020 and business‐as‐usual (BAU) period (the same period in 2019). Three distinct regional response mechanisms were distinguished across China. The increases of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\,\text{and}\,{{\text{NH}}_{4}}^{+}$ levels in the northern part of Beijing‐Tianjin‐Hebei (BTH) might be attributable to increased relative humidity (RH) and abundant ammonia (NH3) level (13.5 μg/m3). The dramatic decreases of secondary inorganic nitrogen in Southeast China were contributed by substantial emission reduction (−15.3%) and slightly favorable (pollutant removal) meteorological conditions (−4.36%). The consistent increases of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\,\text{and}\,{{\text{NH}}_{4}}^{+}$ levels, but decreased NH3 levels in tropical regions suggested extremely high RH (84%) and enhanced atmospheric oxidation capacity were dominant factors. The response mechanisms of secondary N‐bearing components showed the distinct characteristics between urban and rural regions, which might be closely associated with variations of emission reduction and meteorology during the COVID‐19 period. The natural experiment demonstrates priority control of NH3 emission might be the primary target for BTH, while the coordinated controls of VOCs and NOx emissions should be exerted in Southeast China especially the tropical regions. Plain Language Summary: Previous studies focused on the regional response mechanisms of secondary inorganic aerosol to COVID‐19 lockdown measures in China. However, how many response mechanisms across China are still unknown. Here, we employed CTM to reveal different response characteristics of four N‐bearing components and clarified the major factors. In Northeast China, the enhanced atmospheric oxidation capacity (AOC), high RH, and abundant NH3 level significantly elevated the concentrations of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\,\text{and}\,{{\text{NH}}_{4}}^{+}$. In tropical regions such as Hainan Island, extremely high RH coupled with strong AOC promoted the increase of secondary aerosol though they are NH3‐limited region. In Southeast China and West China, the consistent decreases of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\,\text{and}\,{{\text{NH}}_{4}}^{+}$ might be attributable to the dramatic decreases of precursor emissions and slightly favorable meteorological conditions. The result highlighted the different measures should be implemented based on the local meteorological conditions and emission characteristics. Key Points: Three distinct response mechanisms of N‐bearing components were revealed in China during the lockdown periodIncreased relative humidity (RH) and abundant NH3 promoted the simultaneous increases of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\text{and}\,{{\text{NH}}_{4}}^{+}$ in Northeast ChinaStrong atmospheric oxidation capacity coupled with high RH promoted the increases of NO3−andNH4+ ${{\text{NO}}_{3}}^{-}\text{and}\,{{\text{NH}}_{4}}^{+}$ despite low NH3 level
- Subjects
CHINA; HAINAN Sheng (China); COVID-19 pandemic; GREENHOUSE gas mitigation; MICROBIOLOGICAL aerosols; STAY-at-home orders; CHEMICAL models; SECONDARY forests; NITROGEN oxides emission control
- Publication
Journal of Geophysical Research. Atmospheres, 2023, Vol 128, Issue 22, p1
- ISSN
2169-897X
- Publication type
Article
- DOI
10.1029/2023JD039496