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
2023-08-21
54
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] From the first paragraph, we can infer that______.
选项
A、water vapor is an air pollutant in localized areas
B、today most air pollutants can be seen or smelled
C、the definition of air pollution will continue to change
D、a substance becomes an air pollutant only in cities
答案
C
解析
由题干提示定位至第一段。根据该段第二句可知,C)“空气污染的定义会继续改变”与此表述一致,而且在本文中也详细说明了这一变化情况,故为正确答案。
转载请注明原文地址:https://tihaiku.com/zcyy/2943383.html
相关试题推荐
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Althoughrecentyearshaveseensubstantialreductionsinnoxiouspollutants
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
随机试题
"TheHeredityVersusEnvironmentDebate"P1Thepastcen
Whatisthemainmessageofthenewsitem?[originaltext]Onein10youngpeo
TheStockholmConferenceunderminedrecognition【M1】______oftheenvironmen
Gettingagoodnight’ssleephaslongbeenknowntoconsolidatetheday’sme
A.慢性肥厚型念珠菌病 B.念珠菌性口角炎 C.急性萎缩型念珠菌病 D.慢
()不属于需满足以下规定的情形:经营机构通过营业网点向普通投资者进行告知、
现金结算的特点是()A、安全性高 B、直接便利 C、易于宏观控制和
4个月婴儿,昨日种了百白破混合疫苗,今日有轻度发热,稍哭吵不安,查:体温38.0
《国家中长期教育改革和发展规划纲要(2010--2020年)》指出,今后我国教育
下列符合支票管理规定的有()。A:现金支票可以提取现金B:支票金额必须在付款单
最新回复
(
0
)