首页
登录
职称英语
A useful definition of an air pollutant is a compound added directly or indi
A useful definition of an air pollutant is a compound added directly or indi
游客
2023-08-23
15
管理
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. [br] It can be inferred from the first paragraph that______.
选项
A、water vapour is an air pollutant in localized areas
B、the definition of an air pollutant will continue to change
C、a substance becomes an air pollutant only in cities
D、most air pollutants today can be seen or smelled
答案
B
解析
细节题。根据文章第一段Air poilution requires a very flexible definition thatpermits continuous change.“空气污染物的定义要求具有灵活性以适应不断的变化”和B选项“空气污染物的定义会继续发生变化”的表达一致。所以答案选B。
转载请注明原文地址:https://tihaiku.com/zcyy/2950918.html
相关试题推荐
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
[originaltext]M:I’vejustfoundthemostusefuldeviceatthenewoutdoorstor
[originaltext]M:I’vejustfoundthemostusefuldeviceatthenewoutdoorstor
[originaltext]M:I’vejustfoundthemostusefuldeviceatthenewoutdoorstor
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
随机试题
Conservationistsmaybemiscalculatingthenumbersofthethreatenedanimals
MostAmericanstudentsare______tospend180daysayearatschool.A、intendedB、
当无法获得历史数据时,不可能使用的预测方法是:A.线性回归法 B.德尔菲法
患者男性,45岁。因食欲不振、恶心呕吐,伴乏力及尿黄近10天就诊。10年前因外伤
(2021年真题)客户的退休最终都要以一定的收入来源为基础,退休的收入来源主要有
关于沉入桩准备工作,说法错误的是()。A、沉桩前应掌握工程地质钻探资料、水文资
患者,男,30岁,口角歪向右侧,左眼不能闭合2天,左侧额纹消失。治疗应选取何经穴
下列各项中,属于数据采集过程工作内容的是()A、数据转换 B、数据清理 C、
按CIFLanded贸易术语成交,买卖双方的风险划分界限为( )。A.货
项目经理部计量管理员对施工使用的计量器具进行现场跟踪管理,工作内容包括( )。
最新回复
(
0
)