章节大纲

  • Lesson
    ::经验教训

     

    A skyline view of an urban area with haze suggesting high air pollution levels.
     

    What is a pollution advisory?
    ::什么是污染咨询?

    Urban areas in sunny locations have pollution advisories. This happens when  ozone  levels get high. On these days, you should stay indoors or exercise early or late in the  day . Drive less and avoid filling your tank. 
    ::阳光明媚的城市地区有污染警告,当臭氧含量升高时,就会发生这种情况。这些天,你应该留在室内,或者白天早晚锻炼,少开车,避免填满水箱。

    Air Pollutants
    ::空气污染物

    There are two main types of air pollutants: primary and secondary. Most air pollutants come from burning  fossil fuels . Some come from burning forests. Some are due to the  evaporation  of chemicals.
    ::空气污染物主要有两种类型:一级和二级,大多数空气污染物来自燃烧化石燃料,有些来自燃烧森林,有些是由于化学品蒸发。

    Types of Air Pollutants
    ::各类空气污染物的类型

    There are two basic types of pollutants in the air. They are known as  primary pollutants  and  secondary pollutants .  Primary pollutants  enter the air directly. Some are released by natural processes, like ash from  . Most are released by human activities.
    ::空气中有两种基本类型的污染物,称为主要污染物和次要污染物,主要污染物直接进入空气,有些是自然过程释放出来的,例如灰尘,大部分是人类活动释放出来的。

    • Carbon  oxides  are released when fossil fuels burn.
      ::化石燃料燃烧时释放出氧化碳。
    • Nitrogen oxides form when nitrogen and oxygen combine at high temperatures. This occurs in hot exhausts from vehicles, factories, and power plants.
      ::当氮和氧在高温时形成氮氧化物,这发生在汽车、工厂和发电厂的热排气管中。
    • Sulfur oxides are produced when sulfur and oxygen combine. This happens when  coal  that contains sulfur burns.
      ::硫氧化物在硫和氧合而为一时产生,在含硫的煤炭燃烧时产生。
    • Toxic heavy metals include mercury and lead. Mercury comes from smokestacks. Both metals have industrial uses.
      ::有毒重金属包括汞和铅,汞来自烟囱,两种金属都有工业用途。
    • Volatile  organic  compounds (VOCs) are carbon compounds, such as methane. VOCs are released by many human activities. Raising livestock, for example, produces a lot of methane.
      ::挥发性有机化合物(VOCs)是碳化合物,如甲烷,许多人类活动释放了挥发性有机化合物。
    • Particulates  are solid particles. These particles may be ash, dust, or even animal wastes. Many are released when fossil fuels burn.
      ::片段是固态颗粒。 这些颗粒可能是灰尘、尘埃,甚至动物废物。 许多颗粒是在化石燃料燃烧时释放出来的。

    Secondary pollutants  form from primary pollutants. Many occur as part of  photochemical smog . This type of smog is seen as a brown haze in the air. Photochemical smog forms when certain pollutants have a chemical reaction in the presence of sunlight. Photochemical smog consists mainly of  ozone  (O 3 ). Ozone near the ground is a pollutant ( Figure ). This ozone is harmful to humans and other living things. However, ozone in the   protects Earth from the Sun's harmful  ultraviolet radiation .
    ::从原始污染物中形成的次级污染物。许多是光化烟雾的一部分。这种烟雾被视为空气中的褐色烟雾。当某些污染物在阳光下发生化学反应时,光化烟雾的形式是光化学的。光化学烟雾主要由臭氧(O3)组成。地面附近的臭氧是一种污染物(图)。这种臭氧对人类和其他生物有害。然而,保护地球的臭氧免受太阳的有害紫外线辐射。

    Ground level ozone formation from sunlight, nitrogen oxides, and VOCs.
     
    Ozone forms near the ground as a secondary pollutant.

    Sources of Air Pollutants
    ::空气污染物的来源

    Most pollutants enter the air when fossil fuels burn. Some are released when forests burn. Others evaporate into the air.
    ::大多数污染物在矿物燃料燃烧时进入空气,有些在森林燃烧时释放,另一些在空气中蒸发。

    Burning Fossil Fuels
    ::燃烧化石燃料

    Burning fossil fuels releases many pollutants into the air. These pollutants include carbon monoxide, carbon dioxide, nitrogen dioxide, and sulfur dioxide.
    ::燃烧化石燃料将许多污染物释放到空气中,这些污染物包括一氧化碳、二氧化碳、二氧化氮和二氧化硫。

    • Motor vehicles account for almost half of fossil fuel use.
      ::机动车辆几乎占矿物燃料使用量的一半。
    • Power plants and factories account for more than a quarter of fossil fuel use ( Figure   ).
      ::发电厂和工厂占矿物燃料使用量的四分之一以上(图)。
    • Homes and other buildings burn fossil fuels.
      ::房屋和其他建筑燃烧化石燃料。
    Power plants with smokestacks releasing pollutants into the air, illustrating fossil fuel combustion.
     
    Smoke stacks release a lot of pollutants into the air.

    Burning Forests
    ::燃烧森林

    Millions of acres of forest have been cut and burned to make way for farming ( Figure  ). Burning trees produces most of the same pollutants as burning fossil fuels.
    ::数百万英亩的森林被砍伐和焚烧,以便耕种(图......),燃烧的树木产生的污染物与燃烧化石燃料的污染物大多相同。

    Cleared forest area with burnt trees, illustrating the impact of slash-and-burn agriculture.
     
    Cutting and burning trees to clear land for farming is called slash-and-burn agriculture. How does this affect the atmosphere?

    Evaporation of VOCs
    ::VOCs蒸发

    VOCs enter the air by evaporation. VOCs are found in many products, like paints and petroleum products. Methane is a VOC that evaporates from livestock waste and landfills.
    ::挥发性有机物通过蒸发进入空气中,许多产品中都发现了挥发性有机物,如油漆和石油产品,甲烷是一种挥发性有机物,从牲畜废物和垃圾填埋场中蒸发。

    Summary
    ::摘要

    • There are many types of primary pollutants, including carbon oxides, nitrogen oxides, sulfur oxides, particulates, lead, and volatile organic compounds.
      ::存在多种类型的主要污染物,包括氧化碳、氧化氮、氧化硫、微粒、铅和挥发性有机化合物。
    • Secondary pollutants form from chemical reactions that occur when pollution is exposed to sunlight.
      ::二次污染物来自污染暴露在阳光下的化学反应。
    • Most pollutants enter the atmosphere from fossil fuel burning. Burning forests and evaporation of some chemicals account for most of the rest.
      ::大多数污染物通过矿物燃料燃烧进入大气层,其余大部分是燃烧森林和蒸发某些化学品。

    Review
    ::回顾

    1. How are primary and secondary pollutants different?
      ::初级和二级污染物有何不同?
    1. Why do fossil fuels account for so much air pollution?
      ::为什么化石燃料造成如此之多的空气污染?
    1. What is ozone? Where is it harmful? Where is it beneficial?
      ::什么是臭氧?它在哪里有害?它在哪里有益?它在哪里有益?