7.2 - Photochemical Smog

photochemical oxidants

a class of air pollutants formed as a result of sunlight acting on compounds such as nitrogen oxides

Role of sunlight in smog formation

Breaks an oxygen atom off of NO2, driving the formation of ozone (O3)

Environmental factors affecting smog formation

Surrounding mountains can block air flow from dispersing smog. Geographical basins are also susceptible to smog formation that isn't dispersed by wind.

Nitrogen oxide

(NOx) Major source is auto exhaust. Primary and secondary effects include acidification of lakes, respiratory irritation, leads to smog and ozone. Reduced using catalytic converters in cars

VOCs (volatile organic compounds)

group of primary pollutants that are carbon-based and easily evaporate at room temperature. gasoline, formaldehyde, dry-cleaning fluids, naturally from coniferous trees ; component of photochemical smog

Formaldehyde and gasoline

Potent VOCs that are present in high concentrations in urban areas. Especially volatile during warmer summer months as heat drives faster evaporation

Natural VOCs sources

Coniferous (pine) trees

Respiratory irritation

Damage, irritation, inflammation in the respiratory pathways like the trachea, bronchioles, and aveoli (air sacs in the lungs). Caused by SOx, PM, Ozone, Smog

Eye irritation

Redness and itching in the eyes from PM, SOx, Ozone, Smog

Photochemical smog reduction

Any methods that reduce vehicle emissions like carpooling, electric cars, buses, biking/walking. Increased vehicle efficiency.

Methods that target sources of VOCs also help reduce smog. Less car use, less gasoline evaporation from gas stations. Fewer industrial petrochemical plants, dry-cleaning laundromats, etc.