ATMOSPHERIC SCIENCE. Response to Comment on "Missing gas-phase source of HONO inferred from Zeppelin measurements in the troposphere"

Area of Science:

• Atmospheric Chemistry
• Environmental Science

Background:

• Investigating the sources of nitrous acid (HONO) is crucial for understanding atmospheric chemistry and air quality.
• Previous models may have overestimated HONO yields from specific reactions.

Discussion:

• The reaction of HO2·H2O with NO2 yields a maximum of 3% HONO, a lower value than previously assumed.
• Despite new findings on HONO yield, the primary source in the Po Valley remains a gas-phase process involving nitrogen oxides.

Key Insights:

• Nitrous acid (HONO) in the Po Valley is predominantly formed via a gas-phase mechanism consuming nitrogen oxides.
• The established primary HONO source in the region is robust and unaffected by revised reaction yield data.

Outlook:

• Further research should focus on refining the understanding of gas-phase nitrogen oxide chemistry.
• Continued monitoring in the Po Valley is essential to track HONO levels and their atmospheric implications.