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
2024-04-17
49
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 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. [br] What is the main idea of the passage?
选项
A、Serious impact of air pollution.
B、What an air pollutant contains.
C、How much harm air pollutants can cause.
D、Results of compounds added to the atmosphere.
答案
B
解析
本文首先谈论空气污染物的定义及其定义随着时代不同而产生的变化。随后谈了空气污染物的构成成分及形成过程。故B)“空气污染物的构成”为正确答案。
转载请注明原文地址:https://tihaiku.com/zcyy/3559646.html
相关试题推荐
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
随机试题
Itissuggestedthatallgovernmentministersshould______informationtotheirf
Socialcontrolreferstosocialprocesses,plannedorunplanned,bywhichpe
[originaltext]M:Todaytimehasgonebysoquickly!Doyouestimatehowlonga
[originaltext]M:CanIhelpyou?W:Yes,Iamlookingforapairofgloves.Ith
Theresidents,______(他们所有的家园被洪水冲毁),weregivenhelpbytheRedCross.allofwhos
下列属于股权投资基金管理人的职责的是( )。A.依照规定开设基金资金账户 B
甲、乙、丙各出资5万元合伙开办一家餐馆,经营期间丙提出退伙,甲乙同意,三方约定丙
下列有关票据权利的表述,正确的有( )。A.票据权利的取得方式包括原始取得和继受
在民事诉讼中,可以适用留置送达的诉讼文书和法律文书包括哪些? A.人民法院的判
“前有悬崖,后有追兵”产生的动机冲突属于A.双趋冲突 B.双避冲突 C.趋避
最新回复
(
0
)