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
2016-01-05
52
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 materials 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 vapor might be considered an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulfur oxides(硫化物), 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 serve as an air purification scheme by allowing the compounds to move from the air to the water or soil. On a global basis, natures 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 effect appears 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, sulfur dioxide has detectable health effects at 0. 08 parts per million(ppm), which is about 400 times its natural level. Carbon monoxide, however, has natural level of 0. 1 ppm and is not usually a pollutant until its level reaches about 15 ppm.
The numerical value of the concentration level of a substance is only useful if______.
选项
A、it is in a localized area
B、it can be calculated quickly
C、the naturally occurring level is also known
D、the other substances in the area are known
答案
C
解析
由题干关键词The numerical value定位至第三段第四句,例如,硫氧化物在0.08ppm(百万分之0.08)时就会对健康有影响,这是它自然水平的400倍;然而一氧化碳的自然水平是0.1ppm,浓度只有达到15ppm才能成为污染物。因此可知C)“也知道其自然浓度的水平”为正确答案。
转载请注明原文地址:https://kaotiyun.com/show/8ZQ7777K
0
大学英语六级
相关试题推荐
A、Whyspeciesdon’tavoidextinctionbyadapting.B、Whyhumanswon’tbecomeextinctinthefuture.C、Whyspeciesbecomeextinct
A、Onlyanimaltearsaretobevalued.B、Onlyanimaltearscankillcertainbacteria.C、Onlyhumanscryforothers.D、Onlyhumans
Inthepushtocuttheamountofcarbonwereleaseintotheatmosphere,solutionsusuallyfocusonhowtoreduceourpoweruseo
Inthepushtocuttheamountofcarbonwereleaseintotheatmosphere,solutionsusuallyfocusonhowtoreduceourpoweruseo
Thehumannoseisanunderratedtool.Humansareoftenthoughttobeinsensitivesmellerscomparedwithanimals,butthisislar
Thehumannoseisanunderratedtool.Humansareoftenthoughttobeinsensitivesmellerscomparedwithanimals,butthisislar
Thehumannoseisanunderratedtool.Humansareoftenthoughttobeinsensitivesmellerscomparedwithanimals,butthisislar
Thehumannoseisanunderratedtool.Humansareoftenthoughttobeinsensitivesmellerscomparedwithanimals,butthisislar
随机试题
关于非票据结算方式,下列说法正确的有()。
中国各族人民都深深懂得国家分则弱、合则强的道理,反对分裂、反对战乱,希望国家统一、民族团结、人民安居乐业、经济繁荣发展。这体现了中华民族爱国主义传统中【】
某城市道路工程项目,施工承包商考虑到该工程受自然条件的影响较大,为了充分利用有限资金,以最快的速度、最少的消耗确保工程优质,创造最好的经济效益和社会效益,加强了对前期质量控制工作。具体控制工作如下:(1)对道路工程前期水文、地质进行实地调查。调查
在施工图设计阶段,根据施工图纸确定的工程量,套用有关预算定额单价、取费率和利税率等编制()。
由于撤销权的行使具有溯及力,被撤销的合同与无效合同一样,自始没有法律约束力。()
下列各项中,应列入利润表中“营业税金及附加”项目的有()。
社会工作者到一个新的社区,首先通过调查确定想要解决的全面性问题,其次详细列明具体问题及其形成的原因。这一认识和分析问题的方法是()。
项目采购管理是为完成项目工作从承担该项目的组织外部购买或获取项目所需的产品、服务或成果的过程。随着IT行业的快速发展和技术的不断进步,行业的分工更细,更加强调分工与合作。对本企业不能提供,或虽然能提供但不具备竞争力,同时市场已存在的高性价比的产品、服务和成
设x和y均为int型变量,则执行下面的循环后,y值为()。publicclassSun{publicstaticvoidmain(Stringargs[]){intx,y
GuiltyorNotGuiltyManyattemptshavebeenmadeinthepasttoassesstheeffectsofalcoholonroadsafety.Forseveral
最新回复
(
0
)