The night-time tropospheric chemistry is dominated by which of the following chemical species?

Correct option is B

Explanation:
Night-time tropospheric chemistry is significantly influenced by nitrate radicals (NO₃). These radicals are formed during the reaction of nitrogen dioxide (NO₂) with ozone (O₃) at night. Unlike hydroxyl radicals, which are prevalent during the daytime due to photochemical processes driven by sunlight, nitrate radicals dominate the night-time atmosphere as they can react with various pollutants, leading to the formation of secondary pollutants like organic nitrates. This is crucial for understanding atmospheric chemistry and its impact on air quality, particularly in urban areas where emissions of nitrogen oxides (NOₓ) are high.
Information Booster:
· Nitrate radicals are short-lived species that are effective oxidants in the night-time atmosphere.
· They play a critical role in the chemistry of secondary organic aerosol formation.
· The formation of nitrate radicals increases when sunlight is absent, leading to distinct chemical processes compared to daytime.
· Hydroxyl radicals are primarily responsible for the degradation of pollutants during the day.
· Nitrate ions are more stable than nitrate radicals and do not directly participate in atmospheric reactions at night.
· Ozone molecules can also react during the night but are less dominant in chemical processes compared to nitrate radicals.
Additional Information:
· Option (a): Hydroxyl radicals are prevalent during the day and are responsible for the oxidation of many atmospheric compounds.
· Option (c): Nitrate ions are stable and primarily exist in the aqueous phase rather than actively participating in gas-phase night-time chemistry.
· Option (d): Ozone molecules play a role in daytime chemistry and can react at night, but they do not dominate night-time processes like nitrate radicals do.