Download Ozone in Our Atmosphere: Presence, Location, and Abundance and more Study notes Earth, Atmospheric, and Planetary Sciences in PDF only on Docsity! Q.4 Section I: OZONE IN OUR ATMOSPHERE Q1 Ozone is a gas that is naturally present in our atmosphere. Each ozone molecule contains three atoms of oxygen and is denoted chemically as O3. Ozone is found primarily in two regions of the atmosphere. About 10% of atmospheric ozone is in the troposphere, the region closest to Earth (from the surface to about 10–16 kilometers (6–10 miles)). The remaining ozone (about 90%) resides in the stratosphere between the top of the troposphere and about 50 kilometers (31 miles) altitude. The large amount of ozone in the stratosphere is often referred to as the “ozone layer.” What is ozone and where is it in the atmosphere? Ozone is a gas that is naturally present in our atmos phere. Ozone has the chemical formula O3 because an ozone molecule contains three oxygen atoms (see Figure Q1-1). Ozone was discovered in laboratory experiments in the mid- 1800s. Ozone’s presence in the atmosphere was later discov- ered using chemical and optical measurement methods. The word ozone is derived from the Greek word óζειν (ozein), meaning “to smell.” Ozone has a pungent odor that allows it to be detected even at very low amounts. Ozone reacts rapidly with many chemical compounds and is explosive in concen- trated amounts. Electrical discharges are generally used to produce ozone for industrial processes such as air and water purification and bleaching of textiles and food products. Ozone location. Most ozone (about 90%) is found in the stratosphere, which begins about 10–16 kilometers (6–10 miles) above Earth’s surface and extends up to about 50 kilo- meters (31 miles) altitude. The stratospheric region with the highest ozone concentration is commonly known as the “ozone layer” (see Figure Q1-2). The ozone layer extends over the entire globe with some variation in altitude and thickness. The remaining ozone, about 10%, is found in the troposphere, which is the lowest region of the atmosphere, between Earth’s surface and the stratosphere. Ozone abundance. Ozone molecules have a low relative abundance in the atmosphere. In the stratosphere near the peak concentration of the ozone layer, there are typically a few thousand ozone molecules for every billion air molecules (1 billion = 1,000 million). Most air molecules are either oxygen (O2) or nitrogen (N2) molecules. In the troposphere near Earth’s surface, ozone is even less abundant, with a typical range of 20 to 100 ozone molecules for each billion air mole- cules. The highest surface values result when ozone is formed in air polluted by human activities. As an illustration of the low relative abundance of ozone in our atmosphere, one can imagine bringing all the ozone mole cules in the troposphere and stratosphere down to Earth’s surface and uniformly distributing these molecules into a layer of gas extending over the globe. The resulting layer of pure ozone would have an average thickness of about three millimeters (about one-tenth inch) (see Q4). Nonethe- less, this extremely small fraction of the atmosphere plays a vital role in protecting life on Earth (see Q3). Figure Q1-1. Ozone and oxygen. A molecule of ozone (O3) contains three oxygen (O) atoms bound together. Oxygen molecules (O2), which constitute 21% of the gases in Earth’s atmosphere, contain two oxygen atoms bound together. Oxygen atom (O) Oxygen molecule (O2) Ozone molecule (O3) Ozone and Oxygen
