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Ozone ( O 3 ) is a gaseous molecule that is "good" when it is naturally occurring high in the atmosphere, as it shields the Earth against ultraviolet rays from the sun. It is "bad," however, when it occurs close to the ground where it is an irritant that causes lung damage and is the main component of smog. This ground level ozone is a product of reactions involving hydrocarbons and nitrogen oxides in the presence of sunlight.
- Hydrocarbons ( HC ) are chemical compounds that contain hydrogen and carbon. Most motor vehicles and engines are powered by hydrocarbon-based fuels such as gasoline and diesel. Hydrocarbon pollution results when unburned or partially burned fuel is emitted from engines as exhaust and when fuel evaporates into the atmosphere, as when fueling a vehicle. Hydrocarbons include many toxic compounds that cause adverse health effects. Hydrocarbons such as volatile organic compounds react with nitrogen oxides in the presence of sunlight to form ozone.
- Volatile Organic Compounds (VOC's) are chemical substances containing mainly carbon and hydrogen. Hydrocarbons are an important component of the VOC's. VOC's are produced by both natural and anthropogenic (caused by humans) sources. Total emissions from natural sources such as tree s and plants, are much bigger than from anthropogenic ones, but in urban areas it is the anthropogenic one that dominates. The main sources are car exhaust gases and solvent use in industry.
- Nitrogen oxides ( NO x) is a generic term for a group of highly reactive gases that contain nitrogen and oxygen in varying amounts. Most nitrogen oxides are colorless and odorless. One type of nitrogen oxide that can be seen is a very common pollutant called nitrogen dioxide.
- Nitrogen dioxide ( NO 2 ) is a highly reactive oxidant and also a very corrosive one. Nitrogen dioxide can be seen when combined with other particles as a reddish brown layer over many urban areas. The formation of nitrogen oxides is caused by high temperatures and excess oxygen. The primary sources of nitrogen oxides are motor vehicles, electric utilities and other industrial, commercial and residential sources that burn fuels
Remember the following:
• Ozone can be good and it can be bad depending whether it is in the atmosphere or at ground level.
• VOC + NOx + Sunlight = Ozone
• Vehicle use contributes greatly to our ground level ozone issue.
• We can all help by driving and idling less and by refueling after 6:00 PM .
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