Variability in nocturnal nitrogen oxide processing and its role in regional air quality
S S Brown1, T B Ryerson, A G Wollny
1National Oceanic and Atmospheric Administration (NOAA) Earth System Research Laboratory, R/CSD2, 325 Broadway, Boulder, CO 80305, USA. steven.s.brown@noaa.gov
Science (New York, N.Y.)
|January 10, 2006
Summary
The uptake of dinitrogen pentoxide (N2O5) by aerosols is highly variable, depending on sulfate content. This finding impacts ozone pollution models and highlights sulfur-nitrogen interactions.
Area of Science:
- Atmospheric Chemistry
- Tropospheric Ozone Dynamics
- Aerosol-Gas Interactions
Background:
- Nitrogen oxides (NOx) drive ozone (O3) production during the day.
- At night, NOx species like dinitrogen pentoxide (N2O5) are involved in ozone removal and aerosol formation.
- Heterogeneous reactions on aerosol surfaces are critical for N2O5 removal.
Purpose of the Study:
- To investigate the nocturnal heterogeneous hydrolysis of N2O5 on atmospheric aerosols.
- To determine the factors influencing the N2O5 uptake coefficient, g(N2O5).
- To assess the implications for regional ozone production and NOx-SOx interactions.
Main Methods:
- Aircraft-based measurements of nitrogen trioxide (NO3) and N2O5 concentrations.
- Analysis of aerosol composition, with a focus on sulfate content.
- Quantification of the N2O5 uptake coefficient (g(N2O5)) based on field data.
Main Results:
- The N2O5 uptake coefficient (g(N2O5)) on aerosol particles exhibits significant variability.
- Aerosol composition, particularly the sulfate fraction, strongly influences g(N2O5).
- Observed variability suggests a greater interplay between anthropogenic sulfur and nitrogen oxide emissions.
Conclusions:
- Aerosol composition is a critical determinant of nocturnal ozone removal pathways.
- Current models may underestimate the impact of sulfur emissions on nitrogen oxide chemistry and ozone pollution.
- Understanding N2O5 heterogeneous chemistry is vital for accurate air quality and climate projections.
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