Unit8整理

Unit 8Unit Goals:Describing pollutants in air pollutionGiving profiles of major primary pollutants produced by human activityVocabulary building: words and terms of air pollutantsAir pollution ⅡAir pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment, into the atmosphere. The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratosphericozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth's ecosystems.PollutantsAn air pollutant is known as a substance in the air that can cause harm to humans and the environment is known as an air pollutant. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made. Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog.Some pollutants may be both primary and secondary: that is, they are both emitted directly and formed from other primary pollutants. About 4 percent of deaths in the United States can be attributed to air pollution, according to the Environmental Science Engineering Program at the Harvard School of Public Health.Major primary pollutants produced by human activity Sulfur oxides (SOx) - especially sulphur dioxide, a chemical compound with the formula SO2. SO2is produced by volcanoes and in various industrial空气污染Ⅱ空气污染是化学物质、微粒物质或生物材料的引入，这些物质对人类或其他生物造成伤害或不适，或对自然环境造成破坏，进入大气。

大气是一种复杂的动态自然气体系统，且是维持地球生命所必需的。

由于空气污染而导致的平流层臭氧损耗长期以来被认为是对人类健康和地球生态系统的威胁。

污染物空气污染物被认为是空气中的一种物质，它会对人类造成危害，环境也被称为空气污染物。

污染物可以以固体颗粒、液滴或气体的形式存在。

此外，它们可能是天然的或人造的。

污染物可分为一次污染物和二次污染物。

通常，一次污染物是直接从某些过程当中直接排放出来，比如火山喷发的火山灰，汽车尾气中的一氧化碳气体或者工厂排放的二氧化硫。

二次污染物不是直接排放的。

相反，是一次污染物发生反应或相互作用时在空气中所形成的。

二次污染物的一个重要的例子是地面臭氧，它是构成光化学烟雾的许多次生污染物之一。

一些污染物可能同时是一次污染物和二次污染物：也就是说，它们都是直接排放并且由其他一次污染物直接形成的。

根据哈佛大学公共健康学院的环境科学工程项目，美国大约4%的死亡可以归咎于空气污染。

人类活动产生的主要主要污染物硫氧化物(SOx) -特别是二氧化硫，一种含有SO2的化合物。

SO2是由火山和各种工业过程产生的。

由于煤和石油通常含有硫磺化合物，它们的燃烧产生二氧化processes. Since coal and petroleum often contain sulphur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.Nitrogen oxides (NOx) - especially nitrogen dioxide are emitted from high temperature combustion. It can be seen as the brown haze dome above or plume downwind of cities. Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.Carbon monoxide - is a colourless, odorless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.Carbon dioxide(CO2), a greenhouse gas emitted from combustion.Volatile organic compounds (VOCs) are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our 硫。