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
2023-07-07
55
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(有害地). 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(悬殊的差别)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(水蒸气)might be considered an air pollutant under certain conditions.
Many of the more important air pollutants, such as sulfur oxides, carbon monoxide, and nitrogen oxides, are found in nature. As the Earth developed, the concentrations(浓度)of these pollutants were altered by various chemical reactions; they became components in biogeochemical(生物地球化学的)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, 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(有害的)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, 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 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 vapor is an air pollutant in localized areas
B、the definition of air pollution 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
第一段主要介绍的是关于空气污染物的定义,A项“水蒸气在局部区域是一种空气污染物”与文中表述有出入,文中说的是“In the future…under certain conditions(在将来……在特定的条件下)”;B项“空气污染物的定义还会继续变化”,正确,原文提到:“空气污染需要灵活定义,从而可以不断变更”;C项“一种物质只有在城市才成为空气污染物”,在文中找不到依据;D项“如今的大部分空气污染物都能被看到或闻到”不正确,第一段提到,“能看到或能闻到”这种定义已经和如今对污染物的定义有很悬殊的差别了,可以推知现在的extensive list包含了许多看不见、闻不到的物质。故选B。
转载请注明原文地址:https://tihaiku.com/zcyy/2817421.html
相关试题推荐
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Howusefularetheviewsofpublicschoolstudentsabouttheirteachers?
Howusefularetheviewsofpublicschoolstudentsabouttheirteachers?
Howusefularetheviewsofpublicschoolstudentsabouttheirteachers?
[originaltext]Fearanditscompanionpainaretwoofthemostusefulthings
DefinitionsofObesityA)Howdoesonedefinewhenapers
DefinitionsofObesityA)Howdoesonedefinewhenapers
DefinitionsofObesityA)Howdoesonedefinewhenapers
随机试题
MothersuseTVasababysitterto______.[br]Theword"nag"(Line5,Para.3)
Whatisthesourceofthisextremeself-confidencefoundinalmostalloptim
[originaltext]M:No.11PoliceStation.CanIhelpyou?W:Yes.It’saboutmys
下述哪一项是审计小组用于评价一个公司面临的一般风险的最佳证据来源?A.问题清单或
根据所给图表,文字资料回答81~85题。 2008年,全国民政事业基本建设完
根据下面的文字资料回答86~90题 2003年,武汉市农村居民8大类消费支出
某交通管理局从国外租来一部设备,每年支付1000美元租金,年利率8%,租期五年。
下列投标情形中,评标委员会应在评标中否决其投标的是()。A.投标人的综合评分最低
甲、乙、丙设立某普通合伙企业,从事餐饮服务。2017年6月5日,甲退伙。6月10
某大型水电站建于干热河谷,为跟踪监测电站建成后对干热河谷陆生生态的影响,监测计划
最新回复
(
0
)