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The main causes of ozone depletion and the ozone hole are manufactured chemicals, especially manufactured halocarbon refrigerants, solvents, propellants, and foam-blowing agents (chlorofluorocarbons (CFCs), HCFCs, halons), referred to as ozone-depleting
2024年4月25日 · Although ozone depleting substances, they are less potent at destroying stratospheric ozone than chlorofluorocarbons (CFCs). They have been introduced as temporary replacements for CFCs and are also greenhouse gases. See ozone depleting substance.
Chemical NameLifetime, In YearsOdp1 (montreal Protocol)Odp2 (wmo 2011)CFC-11 (CCl3F) Trichlorofluoromethane4511CFC-12 (CCl2F2) Dichlorodifluoromethane10010.82CFC-113 (C2F3Cl3) ...850.80.85CFC-114 (C2F4Cl2) ...19010.58另，我國自2006年起已不再生產任何破壞臭氧層物質（Ozone Depleting Substances，簡稱ODS）。 HCFCs與溴化甲烷為我國目前尚有輸入的物質，受到核配與許可制度的規範。 後續HCFCs消費量之階段削減目標為：自2030年起達到消費量為零的完全廢除目標。 此外，溴化甲烷僅限使用於檢疫與裝運前處理（Quarantine and Preshipment，簡稱QPS）用途。 臭氧層保護相關法規. 我國目前以107年8月1日修正發布之「空氣污染防制法」為準則，並依循108年2月15日修正發布之「蒙特婁議定書列管化學物質管理辦法」、108年2月18日修正發布之「氟氯烴消費量管理辦法」及108年2月18日發布之「溴化甲烷管理辦法」等辦法管制破壞臭氧層物質。
2011年7月6日 · 臭氧層破壞物質 (Ozone Depleting Substances，ODS) 破壞臭氧層的主要元兇氟氯碳化物（CFCs），顧名思義，即是含有氟 (F)、氯 (Cl)、碳 (C)的化合物，為美國Du Pont公司於1920年代末期所研發出來的一種化合物，其商品名稱為 “Freon”，日本人稱之為”Flon”。 CFCs由於化學性質安定、毒性低微，且具有選擇性溶解力、不自燃、不助燃等優異特性，而被廣泛使用做為塑膠發泡劑、噴霧產品推進劑、冷凍空調冷媒、電子零件及金屬之清洗溶劑等用途，與現代人的生活息息相關。 除了CFCs外，會破壞臭氧層的人造化學物質還包括氟氯烴（HCFCs）、海龍（Halon）、四氯化碳（CCl4）、1,1,1-三氯乙烷、氟溴烴（HBFC）和溴化甲烷。
- Overview
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- Antarctic ozone hole
ozone depletion, gradual thinning of Earth’s ozone layer in the upper atmosphere caused by the release of chemical compounds containing gaseous chlorine or bromine from industry and other human activities. The thinning is most pronounced in the polar regions, especially over Antarctica. Ozone depletion is a major environmental problem because it in...
In 1969 Dutch chemist Paul Crutzen published a paper that described the major nitrogen oxide catalytic cycle affecting ozone levels. Crutzen demonstrated that nitrogen oxides can react with free oxygen atoms, thus slowing the creation of ozone (O3), and can also decompose ozone into nitrogen dioxide (NO2) and oxygen gas (O2). Some scientists and environmentalists in the 1970s used Crutzen’s research to assist their argument against the creation of a fleet of American supersonic transports (SSTs). They feared that the potential emission of nitrogen oxides and water vapour from these aircraft would damage the ozone layer. (SSTs were designed to fly at altitudes coincident with the ozone layer, some 15 to 35 km [9 to 22 miles] above Earth’s surface.) In reality, the American SST program was canceled, and only a small number of French-British Concordes and Soviet Tu-144s went into service, so that the effects of SSTs on the ozone layer were found to be negligible for the number of aircraft in operation.
In 1974, however, American chemists Mario Molina and F. Sherwood Rowland of the University of California at Irvine recognized that human-produced chlorofluorocarbons (CFCs)—molecules containing only carbon, fluorine, and chlorine atoms—could be a major source of chlorine in the stratosphere. They also noted that chlorine could destroy extensive amounts of ozone after it was liberated from CFCs by UV radiation. Free chlorine atoms and chlorine-containing gases, such as chlorine monoxide (ClO), could then break ozone molecules apart by stripping away one of the three oxygen atoms. Later research revealed that bromine and certain bromine-containing compounds, such as bromine monoxide (BrO), were even more effective at destroying ozone than were chlorine and its reactive compounds. Subsequent laboratory measurements, atmospheric measurements, and atmospheric-modeling studies soon substantiated the importance of their findings. Crutzen, Molina, and Rowland received the Nobel Prize for Chemistry in 1995 for their efforts.
Human activities have had a significant effect on the global concentration and distribution of stratospheric ozone since before the 1980s. In addition, scientists have noted that large annual decreases in average ozone concentrations began to occur by at least 1980. Measurements from satellites, aircraft, ground-based sensors, and other instruments indicate that total integrated column levels of ozone (that is, the number of ozone molecules occurring per square metre in sampled columns of air) decreased globally by roughly 5 percent between 1970 and the mid-1990s, with little change afterward. The largest decreases in ozone took place in the high latitudes (toward the poles), and the smallest decreases occurred in the lower latitudes (the tropics). In addition, atmospheric measurements show that the depletion of the ozone layer increased the amount of UV radiation reaching Earth’s surface.
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This global decrease in stratospheric ozone is well correlated with rising levels of chlorine and bromine in the stratosphere from the manufacture and release of CFCs and other halocarbons. Halocarbons are produced by industry for a variety of uses, such as refrigerants (in refrigerators, air conditioners, and large chillers), propellants for aerosol cans, blowing agents for making plastic foams, firefighting agents, and solvents for dry cleaning and degreasing. Atmospheric measurements have clearly corroborated theoretical studies showing that chlorine and bromine released from halocarbons in the stratosphere react with and destroy ozone.
The most severe case of ozone depletion was first documented in 1985 in a paper by British Antarctic Survey (BAS) scientists Joseph C. Farman, Brian G. Gardiner, and Jonathan D. Shanklin. Beginning in the late 1970s, a large and rapid decrease in total ozone, often by more than 60 percent relative to the global average, has been observed in the springtime (September to November) over Antarctica. Farman and his colleagues first documented this phenomenon over their BAS station at Halley Bay, Antarctica. Their analyses attracted the attention of the scientific community, which found that these decreases in the total ozone column were greater than 50 percent compared with historical values observed by both ground-based and satellite techniques.
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As a result of the Farman paper, a number of hypotheses arose that attempted to explain the Antarctic “ozone hole.” It was initially proposed that the ozone decrease might be explained by the chlorine catalytic cycle, in which single chlorine atoms and their compounds strip single oxygen atoms from ozone molecules. Since more ozone loss occurred than could be explained by the supply of reactive chlorine available in the polar regions by known processes at that time, other hypotheses arose. A special measurement campaign conducted by the National Aeronautics and Space Administration (NASA) and the National Oceanic and Atmospheric Administration (NOAA) in 1987, as well as later measurements, proved that chlorine and bromine chemistry were indeed responsible for the ozone hole, but for another reason: the hole appeared to be the product of chemical reactions occurring on particles that make up polar stratospheric clouds (PSCs) in the lower stratosphere.
During the winter the air over the Antarctic becomes extremely cold as a result of the lack of sunlight and a reduced mixing of lower stratospheric air over Antarctica with air outside the region. This reduced mixing is caused by the circumpolar vortex, also called the polar winter vortex. Bounded by a stratospheric jet of wind circulating between approximately 50° and 65° S, the air over Antarctica and its adjacent seas is effectively isolated from air outside the region. The extremely cold temperatures inside the vortex lead to the formation of PSCs, which occur at altitudes of roughly 12 to 22 km (about 7 to 14 miles). Chemical reactions that take place on PSC particles convert less-reactive chlorine-containing molecules to more-reactive forms such as molecular chlorine (Cl2) that accumulate during the polar night. (Bromine compounds and nitrogen oxides can also react with these cloud particles.) When day returns to Antarctica in the early spring, sunlight breaks the molecular chlorine into single chlorine atoms that can react with and destroy ozone. Ozone destruction continues until the breakup of the polar vortex, which usually takes place in November.
A polar winter vortex also forms in the Northern Hemisphere. However, in general, it is neither as strong nor as cold as the one that forms in the Antarctic. Although polar stratospheric clouds can form in the Arctic, they rarely last long enough for extensive decreases in ozone. Arctic ozone decreases of as much as 40 percent have been measured. This thinning typically occurs during years when lower-stratospheric temperatures in the Arctic vortex have been sufficiently low to lead to ozone-destruction processes similar to those found in the Antarctic ozone hole. As with Antarctica, large increases in concentrations in reactive chlorine have been measured in Arctic regions where high levels of ozone destruction occur.
- Donald Wuebbles
2023年1月10日 · Climate 101: Ozone Depletion The ozone layer helps to protect life from harmful ultraviolet radiation. Find out what caused the ozone hole, and how the 1989 Montreal Protocol sought to put an...
In 1987, the world signed the Montreal Protocol: the first global agreement to reduce the use of substances that deplete the ozone layer, known as ‘ozone-depleting substances.’. These are substances such as chlorofluorocarbons (CFCs); hydrochlorofluorocarbons (HFCs); and halon gases used in refrigerators, deodorants, and other industrial ...
