What's Up with the Ozone? Introduction It is practically impossible to watch the news, read a paper, or listen to the radio without hearing something about the ozone layer. "Don't use aerosol cans! Get your car in for a smog check! Major businesses must stop polluting! Don't use products with CFCs! The ozone hole is causing cancer!" To most of us, these quotes are simply generic messages that keep popping up in the weirdest places. However, not too many people know exactly what a CFC is, what the ozone layer is and what it means to us, and what the common person can do to help with the environment. The Ozone Layer - What is it? Ok, so what is the ozone layer made up of? More importantly, what is it? Why is it so important to us? Ozone (O3) is created when Oxygen (O2) absorbs ultraviolet radiation (hv) and is split into two separate oxygen atoms (O2 + hv -> 2O). The floating oxygen atoms quickly combine with a third oxygen atom to form ozone (O + O2 -> O3). Ozone does not randomly float around the earth's atmosphere, and it is not a very predominate gas in the earth's atmosphere. Most of it (90%) resides in the 15-40 km region of the earth's atmosphere, which falls in the stratosphere. Even in the middle of this specific range in the stratosphere, ozone is barely noticeable at 8 ppmv (parts per million by volume; i.e. If you have exactly one million particles, only eight of them would be ozone). - What does the ozone layer do? Ozone's main function is to absorb the harmful ultraviolet radiation from the sun to prevent it from reaching the earth in dangerous amounts. This is done through the absorption of ultraviolet radiation from ozone which splits up ozone into one Oxygen molecule and one atom of oxygen (O3 + hv -> O2 + O). Then, the O2 and the O recombine (in a process appropriately called "recombination") to go back and form ozone (O2 + O -> O3). Throughout this process, oxygen atoms and ozone molecules do not get consumed; they simply get used by being split up and recombined. Ozone absorbs UV-B radiation (lightwaves between 280 and 320 nm) and UV-C radiation (lightwaves less than 280 nm in length) while leaving UV-A (lightwaves longer than 320 nm) untouched. Specifically, ozone can absorb lightwaves from 240 to 320 nm. Another result of the ozone layer's work is the generation of heat. Through these small cycles, a lot of heat is formed. In the stratosphere, there is increasing heat as altitude increases (since the ozone on the top can absorb more UV radiation). This heat is good, but can be a problem when the "greenhouse effect" starts to work. UV Radiation and its Effects - Cancer Ultraviolet radiation, which is just beyond the human visual spectrum, is very harmful to organisms on earth. Although we do not know everything about UV radiation, we do know that it can cause skin cancer and cataracts. UV-B radiation is said to interrupt the DNA replication process by causing multiple, serious transcription errors in the replication process of this crucial genetic code. This can in turn lead to numerous genetic mutations which can be harmful and even fatal to an organism. UV-B is to blame for most of the skin carcinomas cases in the United States. UV-A radiation is thought to be the cause of some melanoma cases. - Cataracts In regards to causing cataracts, the eye is very sensitive to UV radiation. Because of this, most of UV radiation is filtered out through the lens of the eye causing the rest of the eye to continue functioning normally. However, extended exposure to UV radiation can burn the lens causing temporary "snowblindness." It is uncertain what extended UV exposure will do to the eye, but there is a high percentage of cataracts patients in comunities living in high UV environments. - Agriculture UV radiation can also dramatically affect plants. More than half of about 200 plants in one test were shown to be influenced by UV-B radiation. Rough estimates show that if the ozone layer is depleted by 10%, there could be drastic effects on agriculture, serious enough for global attention. It is also assumed that ozone depletion less than 10% will cause "a severe impact on local ecosystems." What's Depleting Our Ozone? - CFC Through extensive research, scientists have discovered that chlorofluorocarbons (CFCs) are the main causes of artifical ozone depletion. First of all, what is a CFC? CFCs are relatively harmless chemicals that were once used greatly for industral uses. CFCs are very stable by themselves; this is the reason why they were so appealing to companies to use. In fact, CFCs are so neutral that they are completely ignored by natural pollution-eliminating elements in the atmosphere. CFCs do have a weakness, however. They fall apart when exposed to UV radiation. CFCs do not, however, directly deplete the ozone layer. They are broken appart and release chlorine (Cl), a very harmful ozone depletion substance. The chlorine broken up by CFCs usually comes in the form of hydrogen chloride () or chlorine nitrate (ClONO2). These compounds eventually break up and form atomic chlorine (Cl) and chlorine monoxide (ClO), two very harmful chemicals to the ozone layer. There are many reactions that occur in ozone depletion, but the simplest involves these two substances. When chlorine comes into contact with ozone, chlorine monoxide and Oxygen are formed (Cl + O3 -> Cl0 + O2). The chlorine monoxide then finds an oxygen atom and ends up with chlorine and Oxygen (ClO + O -> Cl + O2). Each chlorine atom can destroy thousands of ozone molecules before being removed from the stratosphere. - Bromine Also affecting ozone depletion is bromine. Bromine (Br) is actually 10-100 times more harmful to ozone than chlorine, however bromine rarely does any serious damage due to its scarcity. They are 100 times as infrequent as CFCs (which are already very scarce). - Volcanic Eruptions Also, there are a few natural sources that contribute to ozone depletion. One of the most significant (even greater than human intervention) is a volcanic eruption. Recently, there have been steep record low global ozone levels throughout the world. Put to blame has been the 1991 erruption of Mt. Pinatubo "which led to a large increase in sulfate aerosol in the lower stratosphere throughout the globe" which, in turn, led to the promotion of ozone depletion. - CFCs: Friend or Foe? CFCs were first created in 1928 and were first used on a large-scale basis in the 1950s.. Since then, they have been used as refrigerants, aerosol propellants, foam blowing agents, and as solvents for electronics. (It should be noted here that after the 1970s, CFCs were discontinued in their use as aerosol propellants. Since then, safer alternatives have been found and are used.) CFCs do not dilute in water, and they are very stable by themselves. Industrial companies saw CFCs and recognized them as very cheap and safe to manufacture and work with. Up until the end of 1995, CFCs (mainly CFC-12; a.k.a. Freon) were used in air conditioners in cars and homes. When they were disposed of before 1990, they were not tightly controlled and were allowed to escape into the atmosphere, simply contributing to the problem. After the Clean Air Act of 1990, tight new regulations and requirements were put on service stations and car manufactures in an attempt to limit the amount of CFCs unnecessarily released. - CFC Alternatives Today, the air conditioning companies have found a reliable alternative, HFC-134a, which is harmless to the ozone layer since it does not contain chlorine. New alternatives such as HFC-134a have proven to be safer to the environment but are more expensive to manufacture. Also, one CFC alternative has been the using of HCFCs (hydrochlorofluorocarbons) and HFCs (hydrofluorocarbons). Since HCFCs still contain chlorine, they still have the potential of depleting ozone, yet not as seriously. HCFCs do not get past the troposphere, so they do not have much of a chance to do damage in the stratosphere. HFCs, however, do not contain chlorine. Because of this, they do not deplete the ozone, making them a good alternative. The "Ozone Hole" Everyone has heard about this notorious big "gap" in the earth's ozone layer over Antarctica. Although, most people do not know much about it. Questions about how it was found, how it was formed, how we measure it, and how we should repair it are often the most frequent ones asked by people. - How was it found? The Antarctic ozone hole was first discovered by scientists in 1985 by the British Antartic Survey (BAS). Because of the extremely low ozone level readings, the BAS scientists first thought that their instruments were not working, so they had new instruments built and shipped down. Eventually, they were able to confirm that the previous information was correct, and they were faced with an alarming drop in ozone thickness over Antartica. - Where did it come from? Many people often wonder why this big ozone hole is over the least populated continent. Most people tend to think that the heavy concentrations of harmful CFCs and similar compounds released by humans should cause ozone holes to appear over largely populated areas such as North America or Europe, yet this is not necessarily true. The facts behind this are the same ones that show where this Antartic hole came from. (By the way, there is ozone depletion over such populated regions, yet they are not nearly as bad as in Antartica.) The conditions in the Antartic are very supportive to ozone depletion. CFCs have to go through several processes before they are divided up and release the harmful chlorine atoms. Certain environmental conditions such as ice clouds, temperature, and early springtime sunshine greatly promote such ozone-destroying reactions. These conditions are all present in Antartica and thus trigger ozone depletion. - How is it measured? One accurate, however indirect, way of measuring ozone density is through the TOMS (Total Ozone Mapping Spectrometer) satellite system. TOMS detects and reports its information based upon the ammount of UV radiation reflected back into space. It specifically looks at the reflection from UV light with wavelengths of 312.5, 317.5, 331.3, and 339.9 nm, all of which are to greater or lesser extents absorbed by ozone. It uses reflections from 360.0 and 380.0 nm to calibrate its data (since these UV wavelengths are not absorbed by ozone). If ozone is dense in an area, TOMS will receive very little reflection from its "looks" at the 312.5-339.9 nm wavelengths. If ozone is very thin (i.e. there is a "hole" in the ozone layer), a lot of UV radiation will be reflected back into space. - How do we close it up? Quite simply, the best way to close up the ozone hole (and to prevent further ones) is through preventing, if not eliminating, the ammount of CFC and bromine released into the atmosphere. Greatly limiting these chemicals in the atmosphere will prevent the ozone-depleting reactions from taking place in the perfect Antartic environmental conditions. We can also help by controlling leaks from the current, limited uses of CFCs, HCFCs, and other similar compounds. We need to also realize and keep in mind that there is a 10-20 year "delay" between CFC emissions and ozone depletion. Currently, we are experiencing the effects of CFC emissions from the late '70s and early '80s. The laws and regulations that have been passed are to compensate and prepare for future increases in ozone depletion due to our recent past, present, and future actions concerning CFC emissions. What the World is Doing Naturally, the entire world population is concerned in some way by what is happening with the ozone layer. If ozone levels get too low, global agriculture production would theoretically be seriously hindered. Many global meetings and conventions have happened regarding this important topic. One such convention, the Vienna Convention for the Protection of the Ozone Layer, resulted in an agreement that started in 1988 to help protect the ozone layer. Canada has contributed much to this global concern. In the Montreal Protocol on Substances that Deplete the Ozone Layer agreement, countries agreed to follow a strict schedule that would lead to the eventually cycling out of CFCs in industrial use, starting in 1989. In 1990 and 1992, this time table was changed to adhere to the sooner deadline of January 1, 1996. The United States has also passed several new groups of laws, including the Clean Air Act of 1990. This also mandated a "phaseout" of ozone-depleting chemicals as well as better control and care of CFCs and similar harmful substances. The Moral Issues Many people find themselves faced with certain moral and ethical questions about contributing to ozone depletion. It is very important for man to be aware of his surroundings and to make all attempts to rebuild them when they are damaged. The ozone hole in Antartica is an excellent example. If the BAS team had not gone down there to do research and if they had not decided to get new instruments to recheck their readings, this rather large hole may not have been discovered for quite a while. Ozone depletion due to CFCs had not even been conceived of until they discovered the hard evidence. Since we found it when we did, we were able to study it, figure out what caused it, and find a way to close it. Thankfully, the availability of ozone-depleting substances has been strictly limited in recent years. This presents very few, if any, situations in which a person must decide between his or her moral values (concern for the environment) and simple whims or desires (the convenience of tossing something dangerous away without special care). In times like this, a person must seriously face innate beliefs that may have never been questioned before, which may be a tough thing to do. It takes a strong person to be able to stand up for what he or she knows is right and to support it all the way, despite obstacles along the way.