An air pollutant is defined as 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 subtances known today. As ...
Nguyễn Thị Thương | Chat Online | |
02/09 17:16:05 (Tiếng Anh - Lớp 12) |
An air pollutant is defined as 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 subtances 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, carbon monoxide, and notrigen oxides, are found in nature. As the Earth developed, the concentration of these pollutants was 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, nature’s output of these compounds dwarfs that resulting from human activities.
However, human production usually occurs in a localized area, such as as city. In such a 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 subtance to be a pollutant; in fact, the numerial value tells us little until we know how much of an increase this represents over ther 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.
According to the passage, the numerical value of the concentration level of a substance is only useful if ________.
Lựa chọn một trả lời để xem Đáp án chính xác Báo sai đáp án hoặc câu hỏi |
A. the other substances in the area are known 0 % | 0 phiếu |
B. it is in a localized area 0 % | 0 phiếu |
C. the natural level is also known 0 % | 0 phiếu |
D. it can be calculated quickly 0 % | 0 phiếu |
Tổng cộng: | 0 trả lời |
Trắc nghiệm liên quan
- An air pollutant is defined as 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 ... (Tiếng Anh - Lớp 12)
- An air pollutant is defined as 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 ... (Tiếng Anh - Lớp 12)
- An air pollutant is defined as 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 ... (Tiếng Anh - Lớp 12)
- An air pollutnt is defined as 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 ... (Tiếng Anh - Lớp 12)
- An air pollutnt is defined as 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 ... (Tiếng Anh - Lớp 12)
- Read the following passage and mark the letter A,B,C or D on your answer sheet to indicate the correct answer to each of the questions. An air pollutnt is defined as a compound added directly or indirectly by humans to the atmosphere in such ... (Tiếng Anh - Lớp 12)
- Composers today use a wider variety of sounds than ever before, including many that were once considered undesirable noises. Composer Edgard Varese (1883-1965) called thus the “liberation of sound…the right to make music with any and all sounds.” ... (Tiếng Anh - Lớp 12)
- Composers today use a wider variety of sounds than ever before, including many that were once considered undesirable noises. Composer Edgard Varese (1883-1965) called thus the “liberation of sound…the right to make music with any and all sounds.” ... (Tiếng Anh - Lớp 12)
- Composers today use a wider variety of sounds than ever before, including many that were once considered undesirable noises. Composer Edgard Varese (1883-1965) called thus the “liberation of sound…the right to make music with any and all sounds.” ... (Tiếng Anh - Lớp 12)
- Composers today use a wider variety of sounds than ever before, including many that were once considered undesirable noises. Composer Edgard Varese (1883-1965) called thus the “liberation of sound…the right to make music with any and all sounds.” ... (Tiếng Anh - Lớp 12)
Trắc nghiệm mới nhất
- Theo GS. Trần Ngọc Thêm, ăn, mặc, ở, đi, lại là những yếu tố thuộc thành tố văn hóa nào? (Tổng hợp - Đại học)
- Xác định loại hình kinh tế - văn hóa dựa trên: (Tổng hợp - Đại học)
- Câu tục ngữ: “Giặc đến nhà đàn bà cũng đánh” là biểu hiện của: (Tổng hợp - Đại học)
- Schools are offering educational programs to have children _______ about the importance of conservation. (Tiếng Anh - Lớp 12)
- Bản chất của văn hóa được xem xét trong mối quan hệ: (Tổng hợp - Đại học)
- The more we understand the power of mass media, _______ we can use it for positive change. (Tiếng Anh - Lớp 12)
- Cách xác định các yếu tố cấu thành chỉnh thể văn hóa dựa trên nguyên tắc: (Tổng hợp - Đại học)
- Preserving natural habitats is key to protect biodiversity, _______ ultimately benefits all living things. (Tiếng Anh - Lớp 12)
- ASEAN is a growing and influential organisation that is playing _______ increasingly important role in the world. (Tiếng Anh - Lớp 12)
- Văn hóa thực hiện được chức năng của nó khi nó vận hành với tính cách là: (Tổng hợp - Đại học)