Brown carbon in biomass burning aerosol enhances HONO production.

Brown carbon in biomass burning aerosol enhances renoxification, boosting HONO formation by up to one order of magnitude in BB-affected regions.

• Why it matters: HONO is a key hydroxyl radical source that drives ozone and aerosol formation, but the mechanism behind elevated HONO in biomass burning plumes is unclear.
• What they did: Flow tube experiments with biomass burning aerosol samples and proxies tested renoxification, showing brown carbon promotes electron transfer to nitrate as an alternative to surface-enhanced nitrate photolysis.
• The result: A new parameterization indicates BrC-enhanced renoxification can raise surface HONO production above 1 part per trillion per hour where aerosol nitrate is high, and these impacts may increase as biomass burning intensifies in a warming climate.

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