章节大纲

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  • 碳循环与气候

    A diamond, symbolizing pure carbon, featured in a reflective setting with a purple background.
     

    What is a diamond?
    ::什么是钻石?

    Carbon takes all sorts of forms as an  element  and as a compound. A diamond is just carbon, pure carbon. A diamond is good for cutting things, but it's not good for breathing or building  proteins  out of, yet other forms of carbon are. Carbon is essential for life on Earth and, as carbon dioxide, it is an important atmospheric gas.
    ::碳作为一种元素和化合物有各种各样的形式。 钻石只是碳, 纯碳。 钻石对切割事物是有用的, 但对于呼吸或制造蛋白质是不好的, 而其他形式的碳是。 碳是地球上生命的关键, 而作为二氧化碳,它是一个重要的大气气体。

    The Carbon Cycle
    ::碳循环

    Carbon is a very important element to living things. As the second most common element in the human body, we know that human life without carbon would not be possible. Protein,  carbohydrates , and fats are all part of the body and all contain carbon. When your body breaks down food to produce  energy , you break down protein, carbohydrates, and fat, and you breathe out carbon dioxide.
    ::碳是生命中非常重要的因素。 作为人体第二大常见元素,我们知道没有碳的人类生命是不可能实现的。 蛋白质、碳水化合物和脂肪都是人体的一部分,并且都含有碳。 当你的身体为了生产能源而分解食物时,你会分解蛋白质、碳水化合物和脂肪,然后呼吸二氧化碳。

    Carbon occurs in many forms on Earth. The element moves through organisms and then returns to the environment. When all this happens in balance, the  ecosystem  remains in balance too.
    ::碳以多种形式存在于地球上,元素通过生物体流动,然后返回环境。当所有这一切都平衡地发生时,生态系统也保持平衡。

    Short Term Cycling of Carbon
    ::短期碳循环

    The short term cycling of carbon begins with carbon dioxide (CO 2 ) in the  atmosphere .
    ::碳的短期循环从大气中的二氧化碳(CO2)开始。

    Photosynthesis
    ::光合作用

    Through  photosynthesis , the  inorganic  carbon in carbon dioxide plus  water  and energy from sunlight is transformed into  organic  carbon (food) with oxygen given off as a waste product. The chemical equation for photosynthesis is:
    ::通过光合作用,二氧化碳中的无机碳加上阳光下的水和能量,转化成有机碳(食物),氧气作为废物产品被释放。

    Chemical equation of photosynthesis showing conversion of carbon dioxide and water into glucose and oxygen.
     

    Respiration
    ::呼吸呼吸

    Plants and animals engage in the reverse of photosynthesis, which is  respiration . In respiration, animals use oxygen to convert the organic carbon in sugar into food energy they can use. Plants also go through respiration and consume some of the sugars they produce.
    ::植物和动物使用光合作用,即呼吸。 在呼吸中,动物用氧把糖中的有机碳转化为他们可以使用的食品能量。 植物也通过呼吸和消耗他们生产的一些糖。

    The chemical reaction for respiration is:
    ::呼吸的化学反应是:

    C 6 H 12 O 6  + 6 O 2  → 6 CO 2  + 6 H 2 O + useable energy
    ::C6H12O6 + 6 O2 + 6 O2 + 6 CO2 + 6 H2O+ 6 H2O+ 可使用能源

    Photosynthesis and respiration are a gas exchange process. In photosynthesis, CO 2  is converted to O 2 ; in respiration, O 2  is converted to CO 2 .
    ::光合作用和呼吸是一种气体交换过程。在光合作用中,CO2被转换成O2;在呼吸中,O2被转换成CO2。

    Remember that plants do not create energy. They change the energy from sunlight into  chemical energy  that plants and animals can use as food.
    ::记住植物不会创造能源。它们会改变能量,从阳光变为植物和动物可以用作食物的化学能源。

    The carbon cycle showing reservoirs and carbon movement between them.
     
    The carbon cycle shows where a carbon atom might be found. The black numbers indicate how much carbon is stored in various reservoirs, in billions of tons ("GtC" stands for gigatons of carbon). The purple numbers indicate how much carbon moves between reservoirs each year. The sediments, as defined in this diagram, do not include the ~70 million GtC of carbonate rock and kerogen.

    Long-Term Carbon Cycling
    ::长期碳循环

    Carbon Sinks and Carbon Sources
    ::碳汇和碳源

    Places in the ecosystem that store carbon are  reservoirs . Places that supply and remove carbon are  carbon sources  and  carbon sinks , respectively ( Figure   ). If more carbon is provided than stored, the place is a carbon source. If more carbon dioxide is absorbed than is emitted, the reservoir is a carbon sink. What are some examples of carbon sources and sinks?
    ::储存碳的生态系统中的位置是碳库。供应和清除碳的地方分别是碳源和碳汇(图 )。如果提供的碳多于储存,那么碳源就是碳源。如果吸收的二氧化碳多于排放,碳库就是碳汇。碳源和碳汇的例子是什么?

    • Carbon sinks are reservoirs where carbon is stored. Healthy living forests and the oceans act as carbon sinks.
      ::碳汇是碳储存库,健康的活森林和海洋是碳汇。
    • Carbon sources are reservoirs from which carbon can enter the environment. Volcanic gases can be a  source  of carbon dioxide.
      ::碳源是碳可以进入环境的蓄碳库,火山气体可以成为二氧化碳的来源。

    A reservoir can change from a sink to a source and vice versa. A forest is a sink, but when the forest burns it becomes a source.
    ::水库可以从一个汇变成一个源,反之亦然。 森林是一个汇,但当森林燃烧时,它就会变成一个源。

    The amount of time that carbon stays, on average, in a reservoir is the  residence time  of carbon in that reservoir.
    ::碳在储油层中平均停留的时间是储油层中碳的停留时间。

    Atmospheric Carbon Dioxide
    ::大气中 二氧化二氧化碳

    Remember that the amount of CO 2  in the atmosphere is very low. This means that a small increase or decrease in the atmospheric CO 2  can have a large effect.
    ::记住大气中的二氧化碳含量非常低,这意味着大气中二氧化碳的少量增加或减少可以产生很大影响。

    By measuring the composition of air bubbles trapped in glacial ice, scientists can learn the amount of atmospheric CO 2  at times in the past. Of particular interest is the time just before the  Industrial Revolution , when society began to use  fossil fuels . That value is thought to be the natural content of CO 2  for this time period; that number was 280 parts per million (ppm).
    ::科学家们可以通过测量冰川冰层中的气泡构成,了解大气二氧化碳的含量。 尤其令人感兴趣的是工业革命前夕,即社会开始使用化石燃料的时候。 这一价值被认为是这一时期二氧化碳的自然含量;这个数字是百万分之280(ppm ) 。

    By 1958, when scientists began to directly measure CO 2  content from the atmosphere at Mauna Loa volcano in the Pacific Ocean, the amount was 316 ppm ( Figure ). In 2018, the atmospheric CO2content crossed over to 410 ppm.
    ::到1958年,当科学家开始直接测量太平洋Mauna Loa火山大气层的二氧化碳含量时,总量为316 ppm(图示),2018年,大气二氧化碳含量超过410 ppm。

    Graph showing atmospheric CO2 levels at Mauna Loa Observatory from 1960 to 2018.
     
    The amount of CO2 in the atmosphere has been measured at Mauna Loa Observatory since 1958. The blue line shows yearly averaged CO2. The red line shows seasonal variations in CO2.

    This is an increase in atmospheric CO 2  of 40% since the before the Industrial Revolution. About 65% of that increase has occurred since the first CO 2  measurements were made on Mauna Loa Volcano, Hawaii, in 1958.
    ::这是自工业革命前以来大气二氧化碳增加40%。 其中大约65%是自1958年在夏威夷莫纳洛亚火山(Mauna Loa Volcano)进行首次二氧化碳测量以来增加的。

    Human Actions Impact the Carbon Cycle
    ::人类行动对碳循环的影响

    Humans have changed the natural balance of the carbon cycle because we use  coal ,  oil , and  natural gas  to supply our energy demands. Fossil fuels are a sink for CO 2  when they form, but they are a source for CO 2  when they are burned.
    ::人类改变了碳循环的自然平衡,因为我们用煤炭、石油和天然气来供应能源需求。 化石燃料形成时是二氧化碳的吸收汇,但燃烧时却是二氧化碳的源头。

    The equation for combustion of propane, which is a simple  hydrocarbon  looks like this:
    ::丙烷燃烧的方程式, 这是一种简单的碳氢化合物, 看起来像这样:

    Chemical equation for the combustion of propane producing carbon dioxide and water.
     

    The equation shows that when propane burns, it uses oxygen and produces carbon dioxide and water. So when a car burns a tank of gas, the amount of CO 2  in the atmosphere increases just a little. Added over millions of tanks of gas and coal burned for electricity in power plants and all of the other sources of CO 2 , the result is the increase in atmospheric CO 2  seen in the  Figure .
    ::等式表明,当丙烷燃烧时,它会使用氧气,产生二氧化碳和水。因此,当一辆汽车燃烧一罐气体时,大气中的二氧化碳含量会略微增加。 发电厂和其他所有二氧化碳源中,为电力燃烧了数百万罐天然气和煤炭,结果造成大气二氧化碳的增加。

    The second largest source of atmospheric CO 2  is  deforestation  ( Figure ). Trees naturally absorb CO 2  while they are alive. Trees that are cut down lose their ability to absorb CO 2 . If the tree is burned or decomposes, it becomes a source of CO 2 . A forest can go from being a carbon sink to being a carbon source.
    ::大气中二氧化碳的第二大来源是砍伐森林(图 ) , 树木在活下来时自然吸收二氧化碳。 被砍伐的树木失去了吸收二氧化碳的能力。 如果树木被烧毁或分解,它就会成为二氧化碳的来源。 森林可以从碳汇变成碳源。

    A deforested area in Mexico, showing fallen trees and burned land for agriculture.
     
    This forest in Mexico has been cut down and burned to clear forested land for agriculture.

    Why the Carbon Cycle is Important
    ::为什么碳循环很重要

    Why is such a small amount of carbon dioxide in the atmosphere even important? Carbon dioxide is a  greenhouse gas . Greenhouse gases trap  heat  energy that would otherwise radiate out into space, which warms Earth. These gases were discussed in the chapter Atmospheric Processes.
    ::为什么大气中如此少量的二氧化碳更重要?二氧化碳是一种温室气体。温室气体会把热能困住,否则会辐射到地球温暖的太空。这些气体在《大气过程》的章节中讨论过。

    Summary
    ::摘要

    • Carbon is essential for life as part of proteins, carbohydrates, and fats.
      ::作为蛋白质、碳水化合物和脂肪的一部分,碳对生命至关重要。
    • The amount of carbon dioxide in the atmosphere is extremely low, but it is extremely important since carbon dioxide is a greenhouse gas, which helps to keep Earth's climate moderate.
      ::大气中的二氧化碳含量极低,但极为重要,因为二氧化碳是一种温室气体,有助于保持地球气候的温和。
    • The amount of carbon dioxide in the atmosphere is rising, a fact that has been documented on Mauna Loa volcano since 1958.
      ::大气中二氧化碳的含量正在上升,自1958年以来,Mauna Loa火山就记录了这一事实。

    Review
    ::回顾

    1. What does it mean to say that photosynthesis and respiration are gas exchange processes?
      ::光合作用和呼吸是气体交换过程,这是什么意思?
    1. How do scientists learn about carbon levels in the past?
      ::科学家如何了解过去碳水平?
    1. How do human activities affect the carbon cycle?
      ::人类活动如何影响碳循环?

    Explore More
    ::探索更多

    Use this resource to answer the questions that follow.
    ::使用此资源回答下面的问题 。

    1. What do greenhouse gases do?
      ::温室气体会做什么?
    1. Where did most of the carbon dioxide that was present in the early atmosphere go?
      ::早期大气中的二氧化碳大部分去了哪里?
    1. What did the early plants add to the atmosphere and why was that important? What else did they create?
      ::早期的植物给大气增加了什么?为什么如此重要?它们还创造了什么?
    1. What do organisms do with the organic carbon?
      ::生物对有机碳做什么?
    1. What are the two major things that carbon does?
      ::碳的两大作用是什么?
    1. What is the 30 second version of the carbon cycle?
      ::碳循环的30年第二版是什么?
    1. What does carbon fixation do with carbon dioxide?
      ::碳固碳对二氧化碳有何作用?
    1. How do organisms use the carbohydrates produced by carbon fixing reactions?
      ::生物如何使用碳固碳反应产生的碳水化合物?
    1. What is cellular respiration the reverse of?
      ::什么是细胞呼吸 反之?
    1. After the organisms metabolize carbohydrates, how is the carbon released back into the environment?
      ::在生物代谢碳水化合物后,碳是如何释放回环境中的?
    1. What happens when carbon dioxide mixes with water and what does it cause?
      ::当二氧化碳与水混合时会怎样呢?
    1. What happens to the carbonate ions in the marine environment?
      ::海洋环境中的碳酸盐离子会怎样?
    1. What happens when shell building organisms die? What happens if those organisms are buried deeply?
      ::当贝壳造生物体死亡时会怎样?如果这些生物体被埋得深埋,会怎样?
    1. How much carbon is wrapped up in fossil fuels compared to the total amount of carbon?
      ::与碳总量相比,化石燃料中有多少碳被包裹在碳中?
    1. Where does the carbon dioxide go that is released from fossil fuels? Where does the excess carbon dioxide go?
      ::化石燃料释放的二氧化碳流向何方? 过剩的二氧化碳流向何方?

    Resources
    ::资源