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
40
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] 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://tihaiku.com/zcyy/3559650.html
相关试题推荐
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
[originaltext]W:Doyouthinkyoucangiveanexactdefinitionof"management",
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
Ausefuldefinitionofanairpollutantisacompoundaddeddirectlyorindi
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
WhyDepressionNeedsaNewDefinition[A]Manypsychiatristsbeli
随机试题
[originaltext]What’syourmother?[/originaltext][audioFiles]audio_ehbm_00280(#
I’vetoldyouthatI’mgoingtobuytheshirt,____________(无论它价值多少钱).howevermu
Underthecooperationofvarioussections,______(结果尽如我们所期望的那样).theresultturns
Mostpeoplehaveanintuitive【C1】______ofwhatintelligenceis,andmanywor
高中生物《生物膜的流动镶嵌模型》 一、考题回顾
患者女,11岁,面中1/3略突,面下1/3高度正常,上下前牙略唇倾,磨牙中性关系
急性心肌梗死时血清酶中升高最早的是A.AST B.肌红蛋白 C.LDH D
某管沟工程,设计管底垫层宽度为2000mm,开挖深度为2.00m,管径为1200
协助拍背的手法是()。A.五指握拳,用力叩打 B.五指并拢,稍向内合拳,由上
《带电设备红外诊断应用规范》要求要求,10kV浇筑式电压互感器当以本体为中心整体
最新回复
(
0
)