Which of the following are components of NOy species in the atmosphere?
A. HNO₃ B. ClONO₂ C. HOONO₂ D. NO₃ E. N₂O₅
Choose the most appropriate answer from the options given below:

Correct option is D

NOy species refer to all reactive nitrogen oxides in the atmosphere, including their oxidized forms. These species play a significant role in atmospheric chemistry, particularly in the formation of ozone and acid rain. The following are components of NOy:
1. A. HNO₃ (Nitric Acid): A major reservoir species of NOy, formed from the reaction of NO₂ with hydroxyl radicals.
2. B. ClONO₂ (Chlorine Nitrate): A reactive nitrogen compound formed in polar stratospheric clouds, acting as a reservoir species in atmospheric chemistry.
3. C. HOONO₂ (Peroxynitric Acid): Another reservoir species of NOy, formed in the atmosphere through reactions involving NO₂ and OH radicals.
4. D. NO₃ (Nitrate Radical): A key reactive nitrogen species involved in nighttime atmospheric chemistry.
5. E. N₂O₅ (Dinitrogen Pentoxide): An important nighttime NOy species, formed from the reaction between NO₃ and NO₂.
Key Explanation: 1. NOy Composition: Includes oxidized nitrogen species such as NO₃, HNO₃, N₂O₅, ClONO₂, and HOONO₂.
2. Reservoir Species: HNO₃, N₂O₅, and ClONO₂ act as temporary reservoirs, storing reactive nitrogen and releasing it under specific conditions.
3. Reactive Roles: NO₃ and N₂O₅ are crucial in nighttime atmospheric chemistry, particularly in ozone formation and loss.
Information Booster: 1. NOy Definition: Refers to the sum of all reactive nitrogen oxides in the atmosphere, excluding N₂O, which is a stable nitrogen compound.
2. Major Sources of NOy:
· Combustion processes (vehicles, industrial emissions).
· Natural processes (lightning, soil emissions).
3. Importance in Atmospheric Chemistry:
· Involved in the formation of tropospheric ozone.
· Contributes to acid deposition (acid rain).
· Participates in stratospheric ozone depletion.
4. Behavior in the Atmosphere:
· NOy species like N₂O₅ are more prominent during nighttime.
· HNO₃ is a key species in wet deposition (acid rain).
Additional Knowledge: · HNO₃ (A): A stable reservoir species, it removes NOx from the atmosphere through wet and dry deposition.
· ClONO₂ (B): Important in the stratosphere, it temporarily stores reactive chlorine and nitrogen.
· HOONO₂ (C): A short-lived species formed from the reaction of OH and NO₂, contributing to the reactive nitrogen pool.
· NO₃ (D): Dominates nighttime nitrogen chemistry, driving reactions with volatile organic compounds (VOCs).
· N₂O₅ (E): A nighttime species that hydrolyzes to form HNO₃, serving as a temporary reservoir of NOx.