Question

(9) In the troposphere two key reactions responsible for ozone (Os) formation are NO2+ hv -+NO+O 0+ O2+MO+M If the only source of ozone is photolysis of nitrogen dioxide (NO2), what role, if any, is played by Volatile Organics Compounds (VOCs) in O3 formation? Be as specific as you can and give chemical reactions.

Answer 1

Tropospheric ozone (O3) is an important secondary air pollutant formed as a result of photochemical reactions between primary pollutants, such as nitrogen oxides (NOx), and volatile organic compounds (VOCs).

Volatile organic compounds (VOCs) such as hydrocarbons are involved in ozone formation. “Volatile” refers to an extreme readiness to vaporize. Ozone formation in the troposphere requires both NOx and VOCs. In a highly simplified version of tropospheric ozone-forming reactions,

NOx + VOC + Sunlight -------------------> O3 (and other bi-products)

The formula above represents several series of reactions that do not lend themselves to simple depiction. They involve the oxidation of VOCs in reactions that also involve NOx.