Barrons AP Environmental Science

(Marvins-Underground-K-12) #1
2NO + O 2 → 2NO 2

■ 11 A.M.– 4 P.M.

As the sunlight becomes more intense, nitrogen dioxide is broken down and
the concentration of ozone increases:


uv
NO 2 → NO + O
O 2 + O → O 3

Nitrogen dioxide also reacts with water vapor to produce nitric acid and
nitric oxide:


3NO 2   +   H 2 O   →   2HNO 3  +   NO

Nitrogen dioxide can also react with VOCs released by vehicles, refineries,
gas stations, and so on to produce toxic PANs (peroxacyl nitrates):


NO 2    +   VOCs    →   PANs

■ 4 P.M.–Sunset


As the sun goes down, the production of ozone is halted.


Net result: NO  +   VOCs    +   O 2     +   uv  →   O 3     +   PANs
Free download pdf