(HW 9)Tropospheric Chemistry and Ozone Production Mechanisms

Hydroxyl radicals (OH)

Acting as the primary oxidant that removes pollutants from the atmosphere.

Photochemical ozone production linked to Los Angeles smog

Smog worsened as air drifted downwind, showing photochemical ozone formation.

Primary CO oxidation pathway in the troposphere

CO + OH → CO₂ + H

Importance of NOₓ for tropospheric ozone production

It regenerates radicals that sustain ozone formation.

Tropospheric ozone vs stratospheric ozone replenishment

Stratospheric ozone is primarily formed by photolysis of O₂, not from tropospheric sources.

Significance of Hanwant Singh's research on methylchloroform (CH₃CCl₃)

It helped infer global OH concentrations based on CH₃CCl₃ decay.

Primary OH production mechanism in the troposphere

Photolysis of ozone producing O(¹D), which reacts with water vapor.

Lightning as a source of tropospheric ozone

It releases large amounts of NOₓ, which drive ozone formation.

Role of NOₓ in tropospheric ozone production

It catalyzes the production of ozone via its photochemical cycle.

Ozone concentration change in NOₓ-limited regime

Ozone concentration increases as NOₓ increases.

Difference between NOₓ-limited and VOC-limited ozone regimes

In NOₓ-limited, ozone increases with NOₓ; in VOC-limited, ozone decreases with more NOₓ.

Satellite observations of tropospheric NO₂ in the 21st century

NO₂ emissions have decreased significantly, especially in the U.S.

Factors affecting OH production

OH production is faster in a polluted, humid urban environment.

Calculating [NO]/[NO₂] at photostationary state

Use the ratio jNO₂ / (kNO + O₃ × [O₃]) to find [NO]/[NO₂].

Determining steady-state O₃ from NO, NO₂, and jNO₂

Use the steady-state equation: [O₃] = jNO₂ × [NO₂] / (kNO + O₃ × [NO]).