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What is Surface Ozone?. Ozone occurs naturally in Earth’s atmosphere wherever sunlight or chemical reactions break apart oxygen molecules (O 2 ) [O 2 ] + [O] [O 3 ]
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What is Surface Ozone? • Ozone occurs naturally in Earth’s atmosphere wherever sunlight or chemical reactions break apart oxygen molecules (O2) [O2] + [O] [O3] • Most of the ozone in the atmosphere is in the stratosphere, 8 to 50 km above the Earth’s surface • Screens out the most of the sun's harmful ultraviolet rays. • Ozone near the surface is a problem • Reacts strongly with surfaces, including living tissue and inorganic structures.
Why Measure Surface Ozone Concentration? • Ozone is a major product of air pollution and globally its abundance is unknown • The amount of ozone present affects many other trace gases in the air • Knowing the amount of ozone helps assess the degree to which it is an environmental problem
How to Measure Surface Ozone • Use a chemical test-strip that changes color in the presence of ozone • Expose the chemical test-strip to outside airfor one hour • Read the test-strip using a hand-held scanner • The unit of measurement is a part per billion • Cloud conditions, wind direction and current atmosphere temperature must also measured to help data interpretation • Knowing relative humidity is helpful as well
Significant Values • Average concentrations range from almost 0 ppb to over 150 ppb depending on time of year and geographic location • In extremely polluted conditions ozone can reach 200 ppb and more • Levels of surface ozone exceeding 80 ppb for 8 hours or longer are considered harmful for most living things