Wintertime N₂O₅ uptake coefficients over the North China Plain

Area of Science:

• Atmospheric Chemistry
• Environmental Science

Background:

• Heterogeneous hydrolysis of dinitrogen pentoxide (N2O5) significantly impacts nitrogen oxide (NOx) regulation.
• Understanding N2O5 uptake coefficients is vital for atmospheric chemistry models.

Purpose of the Study:

• To determine the N2O5 uptake coefficient (γ(N2O5)) in suburban Beijing during winter.
• To investigate factors influencing γ(N2O5) and compare findings with previous studies.

Main Methods:

• Utilized an iterative box model constrained by observational data from February to March 2016.
• Calculated 2289 individual γ(N2O5) values.

Main Results:

• Derived average γ(N2O5) of 0.0046 ± 0.0039, significantly lower than reported values for Hong Kong and the U.S. East Coast.
• Identified low aerosol liquid water content (ALWC), high particulate nitrate (pNO3-), and specific particle morphology (inorganic core/organic shell) as key factors for low γ(N2O5) in the North China Plain.
• Observed suppression of γ(N2O5) by pNO3- and organics, and enhancement by ALWC, consistent with laboratory findings.

Conclusions:

• Low winter γ(N2O5) in Beijing is attributed to a combination of aerosol properties.
• A revised parameterization method incorporating aerosol size distribution, ALWC, and coatings accurately reproduced the field-derived γ(N2O5) values.
• This suggests the feasibility of comprehensive parameterization for N2O5 uptake in the North China Plain during winter.