Nighttime radical observations and chemistry

Area of Science:

• Atmospheric Chemistry
• Environmental Science
• Chemical Kinetics

Background:

• The nitrate radical (NO(3)) and dinitrogen pentoxide (N(2)O(5)) are key nitrogen oxides in the nocturnal atmosphere.
• These species exist in thermal equilibrium and participate in numerous atmospheric chemical reactions.

Purpose of the Study:

• To review the essential features of NO(3) and N(2)O(5) atmospheric chemistry.
• To summarize field observations of these species and related atmospheric radicals.

Main Methods:

• Literature review encompassing over three decades of research.
• Synthesis of field, laboratory, and modeling studies.
• Analysis of NO(3), N(2)O(5), OH, and peroxy radical observations.

Main Results:

• NO(3) reactions with VOCs and sulfur species are dominant oxidation pathways.
• NO(3) and N(2)O(5) chemistry influences nighttime radical production and cycling.
• Heterogeneous N(2)O(5) chemistry drives nitrogen oxide removal and halogen cycling.
• Reactions contribute to organic nitrate and secondary organic aerosol formation.
• NO(3)/N(2)O(5) chemistry plays a role in regulating tropospheric and stratospheric ozone.

Conclusions:

• NO(3) and N(2)O(5) are central to nocturnal atmospheric processes.
• Understanding their chemistry is vital for air quality and ozone regulation.
• This review consolidates knowledge on their atmospheric significance.