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
2014-12-26
24
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.
The author puts forward the examples of sulphur dioxide and carbon monoxide at last to show that______.
选项
A、sulphur dioxide is more dangerous than carbon monoxide
B、sulphur dioxide is less dangerous than carbon monoxide
C、the numerical value of noxious chemicals in the air is not the key in defining pollution
D、it needs a great increase in concentration for noxious chemicals in the air to be pollutants
答案
C
解析
细节题。根据原文第三段最后三句“实际上,浓度值并不能告诉我们什么,除非我们能知道这个浓度值相对于这种物质在该地区自然状态下的浓度的增长幅度。比如.当每百万个气体分子中含有0.08个二氧化硫气体分子时,人体就会明显感到不适。这个浓度大约是正常浓度的400倍。而一氧化碳的正常浓度是百万分之零点一.在不超过百万分之十五时就不算污染物。”可知化学物质的浓度值不是界定污染物的关键.和选项C的表述一致。所以答案选C。
转载请注明原文地址:https://kaotiyun.com/show/EOm7777K
0
大学英语六级
相关试题推荐
A、Itwasbetterthanthepreviousone.B、Itdistortedthemayor’sspeech.C、Itexaggeratedthecity’seconomicproblems.D、Itre
A、Heisbotheredbythepaininhisneck.B、Hecannotdohisreportwithoutacomputer.C、Hecannotaffordtohaveacoffeebrea
A、Theyarethemysteriesinthesea.B、Theyarethetreasuredlandmarks.C、TheymeanlittlefortheAmericanpeople.D、Theyare
A、Smith’sstoriesaremostlyforyoungsters.B、Youngpeoplelacklogicthinking.C、Themandoesn’tthinkmuchofSmith’snovels.
A、Thehouseswithinhispricerangearesoldout.B、Mostpeopleinthiscitywanttoownahome.C、Hehasdifficultyfindingaff
A、In1776.B、In1783.C、In1808.D、In1828.D细节题。文中明确提到,TheAmericanDictionaryoftheEnglishLanguage(《美国英语词典》)是在1828年出版的,故答案为
A、Takeaphysicalexaminationregularly.B、Nevertakedifferentmedicinesatthesametime.C、Nevertakemedicineswithoutdocto
A、Bysendingwaterdirectlybacktotheseawithgreatforce.B、Byreducingwaveenergy.C、Byreducingbeachwidth.D、Bystabili
A、Itshouldbereplacedbywarninglabels.B、Itisnecessaryduetoitsusefulinformation.C、Itcanaffectalotofpeoplewhen
Inasense,thenewprotectionismisnotprotectionismatall,atleastnotinthe【C1】______senseoftheterm.Theoldprotectio
随机试题
在编制合并报表时,强调单一管理机构对一个经济实体控制的理论是()
根据《电离辐射防护与辐射源安全基本标准》,从事放射性工作的特殊人员应做到
下列属于真性肿瘤的是
下图所示的工程双代号时标网络计划执行到第4周末和第10周末时,检查其实际进度如下图前锋线所示,检查结果表明()。
关于政府和社会资本合作(PPP)项目及其决策程序的说法,正确的是()
沥青混凝土路面初压紧跟摊铺机后进行,宜采用()静压1~2遍。
主板上市的甲上市公司拟于2017年8月向原股东配售股份,下列情形中不构成配股障碍的是()。
结合实际论述教育中三种典型的师生关系模式对学生的影响。
[*]
假设现在是2018年10月1日的下午2时20分7秒,则下面程序的输出结果为()。importtimeprint(time.strftime(”%y-%m-%d@%H-%M-%S”,time.gmtime()))
最新回复
(
0
)