首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantitie
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantitie
admin
2015-01-31
51
问题
A useful definition of an air pollutant is a compound added directly or indirectly by humans to the atmosphere in such quantities as to affect humans, animals, vegetation, or material adversely. Air pollution requires a very flexible definition that permits continuous change. When the first air pollution laws were established in England in the fourteenth century, air pollutants were limited to compounds that could be seen or smelled—a far cry from the extensive list of harmful substances known today. As technology has developed and knowledge of the health aspects of various chemicals has increased, the list of air pollutants has lengthened. In the future, even water vapour might be considered an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulphur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the earth developed, the concentrations of these pollutants were altered by various chemical reactions; they became components in biogeochemical cycles. These reactions serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, nature’ s output of these compounds dwarfs that resulting from human activities. However, human production usually occurs in a localized area, such as a city.
In this localized region, human output may be dominant and may temporarily overload the natural purification scheme of the cycles. The result is an increased concentration of noxious chemicals in the air. The concentrations at which the adverse effects appear will be greater than the concentrations that the pollutants would have in the absence of human activities. The actual concentration need not be large for a substance to be a pollutant; in fact the numerical value tells us little until we know how much of an increase this represents over the concentration that would occur naturally in the area. For example, sulphur dioxide has detectable health effects at 0.08 parts per million(ppm), which is about 400 times its natural level. Carbon monoxide, however, has a natural level of 0.1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
What effect did the development of earth have on the air pollutants such as carbon monoxide?
选项
A、Their harm to human activities became more serious.
B、Their ability to purify air was improved a lot.
C、Their concentrations were changed by chemical reactions.
D、Their quantities in the air were mainly from human activities.
答案
C
解析
细节题。根据carbon monoxide可定位到第二段As the earth developed,theconcentrations of these pollutants were altered by various chemical reactions;theybecame components in biogeochemical cycles.These serve as an air purification schemeby allowing the compounds to move from the air to the water or soil.“随着地球的发展,这些污染物的浓度会随着各种化学反应而发生改变:他们成为了生物地球化学循环的组成部分。这些循环使得这些化合物从空气中转移到水中或土壤中,从而达到净化空气的作用。”和C选项内容一致,其中changed和原文altered为同义转换,所以答案选C。
转载请注明原文地址:https://kaotiyun.com/show/LWh7777K
0
大学英语六级
相关试题推荐
A、Financialaid.B、Freejobtraining.C、Advancedtechnology.D、Commontaxsystems.A细节题。文中提到,一些国家想知道如果他们减少或停止种植烟草能否获得经济援助(financ
NewtechnologylinkstheworldasneverbeforeOurplanethas【B1】______.It’snowa"globalvillage"wherecountriesareonlyse
NewtechnologylinkstheworldasneverbeforeOurplanethas【B1】______.It’snowa"globalvillage"wherecountriesareonlyse
Thetrendtowardsmallerfamiliesmaynotbeasmodernaswethink.Althoughwomengatherershadfourorfivechildren,onlytwo
DoestheWorldFaceaFutureofWaterWars?[A]Throughouthistory,peoplehavefoughtbitterwarsoverpoliticalideology,natio
Whentelevisionisgood,nothing—notthetheater,notthemagazinesornewspapers—isbetter.Butwhentelevisionisbad,not
A、Bothencyclopediasanddictionariesareinteresting.B、Dictionariesaremostusefulthanencyclopedias.C、Sheusesavarietyo
A、Factorsthataffecttheabilitytomemorise.B、Theinfluenceofchildhoodmemoriesonadulthood.C、Aproposalforfuturepsych
A、Tohelppeopleunderstandhorsesbetter.B、Tohelppeopleenjoyafamilyatmosphere.C、Tohelppeoplehavefunaboveotherthi
Knowledgemaybeacquiredthroughconversation,watchingtelevisionortravelling,butthedeepestandmostconsistentwayisth
随机试题
可反映左心室收缩功能的指标是
判定肺结核临床类型的主要依据是
中标人、竞得人支付的投标、竞买保证金,抵作国有土地使用权出让金,其他投标人、竞买入支付的标、竟买保证金,出让人必须在招标拍卖挂牌活动结束后()个工作日内予以退还,不计利息。
电梯轿厢组装后的工序是()等相关附件。
1954年4月5日,中国国际旅行社在北京西交民巷4号诞生。()
下列说法正确的是()。
小李:如果在视觉上不能辨别艺术复制品和真品之间的差异,那么复制品就应该和真品的价值一样。因为如果两件艺术品在视觉上无差异,那么它们就有相同的品质。要是它们有相同的品质,它们的价格就应该相等。小王:你对艺术了解得太少啦!即使某人做了一件精致的复制品
假设两变量为线性关系,这两变量为等距或等比的数据,但总体不呈正态分布,计算它们的相关系数时应选用()。
设置TCP/IP属性的备用DNS服务器地址202.112.88.31。
Nosooner______thanastudentcametovisither.
最新回复
(
0
)