有机氯氟烃

G. Rusch
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The first were the hydrochlorofluorocarbons (HCFCs) and the second were the hydrofluorocarbons (HFCs). Both contain hydrogen and are susceptible to attack by hydroxyl radicals present in the atmosphere. Therefore, they have a shorter atmospheric lifetime and either are not transported to the stratosphere or are transported there only in small amounts. The HCFCs contain chlorine and are still capable of causing ozone depletion, although, since their atmospheric lifetimes are short, their ozone-depleting potential (ODP) is lower than those associated with the CFCs. The HFCs do not contain chlorine (or bromine, also associated with ozone depletion). They, therefore, do not cause ozone depletion. A ranking scale has been developed using CFC11 as the reference compound, with an assigned value of 1. These values are also presented. \n \n \n \nA second concern, regarding both CFCs and their replacements, is that they are greenhouse warming gases. They, along with other substances such as carbon dioxide, trap the sun's infrared radiation and convert it to heat. However, they are also good insulating materials, and frequently their use as foam blowing agents in refrigeration equipment can lead to considerable energy savings, reducing carbon dioxide emissions. The greenhouse warming potentials (GWPs) for many of the CFCs, HCFCs, and HFCs are given. \n \n \n \nMany methods have been developed for atmospheric monitoring of these substances. Because of their widespread use and concerns about their environmental effects and health effects, several reviews have been written on these materials. \n \n \n \nFrom the reviews as well as the data presented later in this chapter, it can be seen that many of these chemicals are not highly toxic. Some, in fact, do not show significant signs of toxicity at air exposure levels up to a few percent or even over 5 or 10%. 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引用次数: 2

摘要

20世纪30年代,氯氟烃作为二氧化硫、氨、四氯化碳和氯仿等制冷剂的“安全”替代品问世。在第二次世界大战中,它们被用来生产杀虫剂气雾剂,以保护热带地区的部队免受疟疾和其他虫媒疾病的侵害。在接下来的40-50年里,应用的数量和类型扩大到包括泡沫吹制、精密清洁、医药、化妆品和通用气雾剂的推进剂、空调和制冷。这些用途最终导致氟氯化碳排放到大气中。由于它们的化学反应性低,它们通常在大气中停留时间长,因此它们分布在全球。1974年,莫利纳和罗兰假设,一旦氟氯化碳到达平流层,它们将发生分解,释放氯原子。氯原子随后会与平流层的臭氧发生反应,将其分解成氧气。由于平流层臭氧吸收了大部分太阳的紫外线β辐射(UVB),臭氧水平的降低将导致地面UVB的增加。这可能会影响作物生长,导致白内障和非黑色素瘤皮肤癌的增加。在南极冬季出现南极上空臭氧柱明显下降(即“臭氧空洞”)的报告后,1987年,世界上大多数国家起草并签署了一项协议,呼吁逐步淘汰氟氯化碳。这项协议被称为《蒙特利尔议定书》。开发了两种“实物”替代品。第一种是氢氯氟烃(HCFCs),第二种是氢氟烃(hfc)。两者都含有氢,容易受到大气中羟基自由基的攻击。因此,它们在大气中的寿命较短,要么不被输送到平流层,要么只少量输送到平流层。氟氯烃含有氯,仍然能够造成臭氧消耗,但由于其在大气中的寿命较短,其臭氧消耗潜能值(ODP)低于与氟氯烃相关的潜能值。氢氟碳化物不含氯(或溴,也与臭氧消耗有关)。因此,它们不会造成臭氧消耗。以CFC11为参比化合物,编制了排序量表,赋值为1。还给出了这些值。关于氟氯化碳及其替代品的第二个担忧是,它们是温室气体。它们与二氧化碳等其他物质一起捕获太阳的红外辐射并将其转化为热量。然而,它们也是良好的绝缘材料,并且经常将它们用作制冷设备中的泡沫发泡剂,可以节省大量能源,减少二氧化碳排放。给出了许多CFCs、HCFCs和hfc的温室增温潜能值(GWPs)。已经开发了许多方法对这些物质进行大气监测。由于它们的广泛使用以及对其环境影响和健康影响的关注,已经对这些材料进行了一些评论。从评论以及本章后面提供的数据可以看出,这些化学品中的许多都不是剧毒的。事实上,在空气暴露水平高达几个百分点甚至超过5%或10%的情况下,有些没有显示出明显的毒性迹象。过度接触后最典型的反应是与这些化学物质的麻醉特性有关的中枢神经系统抑制。此外,有些还会引起肝毒性,偶尔还会对生殖产生影响。每个化合物都单独讨论。它们大致分为三大类:氯氟烃、氢氯氟烃和氢氟烃。关键词:CFC 11-13;氯氟化碳112 - 115;HFC 21、22、123、124、132、133a、141b、142b, HFC 32、125、1344a、152a、245fa;臭氧消耗潜力;Chlorofluorcarbons;温室效应;全球变暖;大气一生
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Organic Chlorofluoro Hydrocarbons
The chlorofluorocarbons (CFCs) were introduced in the 1930s as “safe” replacements for refrigerants such as sulfur dioxide, ammonia, carbon tetrachloride, and chloroform. In World War II, they were used to produce insecticide aerosols to protect the troops in tropical areas against malaria and other insectborne diseases. During the next 40–50 years, the number and type of applications expanded to include foam blowing, precision cleaning, and propellants for medicinal, cosmetic, and general-purpose aerosols, air conditioning, and refrigeration. These uses eventually resulted in emission of the CFCs into the atmosphere. Because of their low chemical reactivity, they typically have long atmospheric residence times, and as a consequence, they are distributed globally. In 1974 Molina and Rowland hypothesized that, once the CFCs reach the stratosphere, they will undergo breakdown to release chlorine atoms. The chlorine atoms could then react with the stratospheric ozone breaking it down into oxygen. Since the stratospheric ozone absorbed much of the sun's ultraviolet β radiation (UVB), decreased ozone levels would lead to increases in ground-level UVB. This could affect crop growth and lead to increases in cataracts and nonmelanoma skin cancers. Following reports of a marked drop in column ozone over Antarctica (the “ozone hole”) during the Antarctic winter, in 1987 most of the nations of the world drafted and signed an agreement calling for the phaseout of CFCs. This agreement is known as the Montreal Protocol. Development was initiated on two types of “in-kind” replacements. The first were the hydrochlorofluorocarbons (HCFCs) and the second were the hydrofluorocarbons (HFCs). Both contain hydrogen and are susceptible to attack by hydroxyl radicals present in the atmosphere. Therefore, they have a shorter atmospheric lifetime and either are not transported to the stratosphere or are transported there only in small amounts. The HCFCs contain chlorine and are still capable of causing ozone depletion, although, since their atmospheric lifetimes are short, their ozone-depleting potential (ODP) is lower than those associated with the CFCs. The HFCs do not contain chlorine (or bromine, also associated with ozone depletion). They, therefore, do not cause ozone depletion. A ranking scale has been developed using CFC11 as the reference compound, with an assigned value of 1. These values are also presented. A second concern, regarding both CFCs and their replacements, is that they are greenhouse warming gases. They, along with other substances such as carbon dioxide, trap the sun's infrared radiation and convert it to heat. However, they are also good insulating materials, and frequently their use as foam blowing agents in refrigeration equipment can lead to considerable energy savings, reducing carbon dioxide emissions. The greenhouse warming potentials (GWPs) for many of the CFCs, HCFCs, and HFCs are given. Many methods have been developed for atmospheric monitoring of these substances. Because of their widespread use and concerns about their environmental effects and health effects, several reviews have been written on these materials. From the reviews as well as the data presented later in this chapter, it can be seen that many of these chemicals are not highly toxic. Some, in fact, do not show significant signs of toxicity at air exposure levels up to a few percent or even over 5 or 10%. The most typical response seen following overexposure is CNS depression related to the anesthetic properties of many of these chemicals. Also, some have caused hepatotoxicity and occasionally reproductive effects. Each compound is discussed individually. They have been divided into three general areas: chlorofluorocarbons, hydrochlorofluorocarbons, and hydrofluorocarbons. Keywords: CFC 11-13; CFC 112-115; HCFC 21, 22, 123, 124, 132, 133a, 141b, 142b, HFC 32, 125, 1344a, 152a, 245fa; Ozone depletion potential; Chlorofluorcarbons; Greenhouse effect; Global warming; Atmospheric lifetime
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