甲烷排放可追溯至罗马时代-凯发k8官网

甲烷排放可追溯至罗马时代
文章来源:未知 文章作者:enread 发布时间:2012-10-09 06:47 字体: [ ] 
(单词翻译:双击或拖选)
1 of the greenhouse gas 3(甲烷) into the atmosphere can be traced back thousands of years in the greenland ice sheet. using special 4 methods, researchers from the niels bohr institute, among others, have 5 how much methane originates from natural sources and how much is due to human activity. the results go all the way back to roman times and up to the present, where more than half of the emissions are now human-made. the results are published in the scientific journal, nature.
 
methane is an important greenhouse gas, which today is partly emitted from natural sources and partly from human activities. the emissions from natural sources varies due to the climate variations. for example, bacteria in wetlands release methane and less is emitted in dry periods as the wetlands shrink.
 
emissions of methane into the atmosphere also come from human actions. for example, methane is emitted from rice fields, which are of course wetlands, and methane is emitted from biomass burning, either from burning of forest areas for 6 or the use of wood in furnaces. energy production through coal 7 also produces methane gases. but how can you determine where the methane gas comes from?
 
different sources can be traced 
 
"the different sources of methane have different 8 compositions. the methane produced by the burning of biomass, like wood, contains more of the heavier 9 (carbon-13) relative to the 10 isotope (carbon-12), than methane which is produced in wetlands," explains professor thomas blunier, centre for ice and climate at the niels bohr institute at the university of copenhagen. the researchers have measured the isotopic composition of the methane in ice cores that are drilled up from the greenland ice cap at the neem project in northwestern greenland. the ice cap is formed from snow that falls year after year and 11, gradually getting compressed into ice. the ice contains tiny air bubbles from the atmosphere in the snow that fell, and by analysing the composition of the air you can get a climate curve, which tells you about both the annual temperature and methane content.
 
the question is how far back in history man has had an impact on the methane concentration in the atmosphere?
 
methane emissions are peaking now 
 
"we have analysed the methane composition more than 2,000 years back in time. we can see that already 2,100 years ago during roman times, some cultures were spreading out and burning large amounts of wood for fuel in furnaces to work with metals that required intense heat to process. but the level was still low. the next significant increase was during the middle ages around 1,000 years ago. it was a warm period and it was dry so there were presumably many forest fires that emitted methane while the wetlands 12 and reduced methane emissions from that source. we also find emissions from natural forest fires and deforestation during the so-called 'little ice age' (between 1350 and 1850), which was a very cold and dry period, emissions of methane increased dramatically from around 1800, when the industrial revolution took off and where there occurred a large increase in population," explains thomas blunier.
 
the analyses show that from around the year 1800 there are large increases that are human-made. approximately half originates from the production of food -- especially rice fields and cattle. then a lot is emitted from the 13 of organic materials that are deposited and methane is emitted from burning coal for energy.
 
"the extent to which our ancestors were able to influence the emissions of methane with their activities is surprising. the general trend from 100 bce to the year 1600 shows a 14(相关) between the increase in the 15 of land for cultivation and the 2 of the biogenic methane. today, half of the methane emissions stem from human activities," says thomas blunier.


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1 1a87f8769eb755734e056efecb5e2da9     
排放物( emission的名词复数 ); 散发物(尤指气体)
参考例句:
  • most scientists accept that climate change is linked to carbon emissions. 大多数科学家都相信气候变化与排放的含碳气体有关。
  • dangerous emissions radiate from plutonium. 危险的辐射物从钚放散出来。
2 vjnz4     
n.发出物,散发物;发出,散发
参考例句:
  • rigorous measures will be taken to reduce the total pollutant emission.采取严格有力措施,降低污染物排放总量。
  • finally,the way to effectively control particulate emission is pointed out.最后,指出有效降低颗粒排放的方向。
3 t1eyx     
n.甲烷,沼气
参考例句:
  • the blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
  • methane may have extraterrestrial significance.甲烷具有星际意义。
4 llmys     
adj.分析的;用分析法的
参考例句:
  • i have an analytical approach to every survey.对每项调查我都采用分析方法。
  • as a result,analytical data obtained by analysts were often in disagreement.结果各个分析家所得的分析数据常常不一致。
5 duszmp     
adj.坚定的;有决心的
参考例句:
  • i have determined on going to tibet after graduation.我已决定毕业后去西藏。
  • he determined to view the rooms behind the office.他决定查看一下办公室后面的房间。
6 cnfzl     
n.耕作,培养,栽培(法),养成
参考例句:
  • the cultivation in good taste is our main objective.培养高雅情趣是我们的主要目标。
  • the land is not fertile enough to repay cultivation.这块土地不够肥沃,不值得耕种。
7 4qkzs     
n.燃烧;氧化;骚动
参考例句:
  • we might be tempted to think of combustion.我们也许会联想到氧化。
  • the smoke formed by their combustion is negligible.由它燃烧所生成的烟是可忽略的。
8 7ad2ece915960e8c295e01a4d04cc192     
adj.同位素的,合痕的
参考例句:
  • the isotopic signatures of most ancient limestones indicated the same process. 大多数古代石灰岩的同位素特征说明了同样的过程。 来自辞典例句
  • isotopic discrimination is not likely. 同位素甄别是不可能的。 来自辞典例句
9 isotope     
n.同位素
参考例句:
  • the isotope ratio is directly used for comparing oils or gases.同位素比率直接用于比较各种石油或天然气。
  • how to apply a radio isotope?如何运用放射性同位素?
10 5ppzpr     
n.打火机,点火器;驳船;v.用驳船运送;light的比较级
参考例句:
  • the portrait was touched up so as to make it lighter.这张画经过润色,色调明朗了一些。
  • the lighter works off the car battery.引燃器利用汽车蓄电池打火。
11 1kmzty     
n.剩余物,残留物;遗体,遗迹
参考例句:
  • he ate the remains of food hungrily.他狼吞虎咽地吃剩余的食物。
  • the remains of the meal were fed to the dog.残羹剩饭喂狗了。
12 b4a0c814a8e67ec80c5f9a6cf7853aab     
v.逐渐变少或变小( dwindle的过去式和过去分词 )
参考例句:
  • support for the party has dwindled away to nothing. 支持这个党派的人渐渐化为乌有。
  • his wealth dwindled to nothingness. 他的钱财化为乌有。 来自《简明英汉词典》
13 anfzt     
n. 分解, 腐烂, 崩溃
参考例句:
  • it is said that the magnetite was formed by a chemical process called thermal decomposition. 据说这枚陨星是在热分解的化学过程中形成的。
  • the dehydration process leads to fairly extensive decomposition of the product. 脱水过程会导致产物相当程度的分解。
14 rogzg     
n.相互关系,相关,关连
参考例句:
  • the second group of measurements had a high correlation with the first.第二组测量数据与第一组高度相关。
  • a high correlation exists in america between education and economic position.教育和经济地位在美国有极密切的关系。
15 on7ys     
n.拨款,批准支出
参考例句:
  • our government made an appropriation for the project.我们的政府为那个工程拨出一笔款项。
  • the council could note an annual appropriation for this service.议会可以为这项服务表决给他一笔常年经费。
tag标签: greenhouse roman methane
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