课程教案(中)
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  • 时间:2012-10-01 14:27:43
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7.6.3 EFFECTS ON WATER RESOURCE

The negative impacts of climate change on freshwater systems outweigh the benefits. All of the regions assessed in the IPCC Fourth Assessment Report (Africa, Asia, Australia and New Zealand, Europe, Latin America, North America, Polar regions (Arctic and Antarctic), and small islands) showed an overall net negative impact of climate change on water resources and freshwater ecosystems.

Semi-arid and arid areas are particularly exposed to the impacts of climate change on freshwater. With very high confidence, it was judged that many of these areas, e.g., the Mediterranean basin, western USA, southern Africa, and north-eastern Brazil, would suffer a decrease in water resources due to climate change.

7.6.3 EFFECTS ON HUMAN HEALTH

Climate change had:

²       altered the distribution of some infectious disease vectors

²       increased heatwave-related deaths

Human beings are exposed to climate change through changing weather patterns (temperature, precipitation, sea-level rise and more frequent extreme events) and indirectly through changes in water, air and food quality and changes in ecosystems, agriculture, industry and settlements and the economy.

Millions of people would be affected through, for example, increases in malnutrition; increased deaths, diseases and injury due to extreme weather events; increased burden of diarrhoeal diseases; increased frequency of cardio-respiratory diseases due to high concentrations of ground-level ozone in urban areas related to climate change; and altered spatial distribution of some infectious diseases.

7.7 LOW CARBON SOCIETY

 

7.7.1 LOW CARBON ECONOMY

 

A Low-Carbon Economy (LCE) or Low-Fossil-Fuel Economy (LFFE) is a concept that refers to an economy which has a minimal output of greenhouse gas (GHG) emissions into the biosphere, but specifically refers to the greenhouse gas carbon dioxide.

 

7.7.2 TOWARD A LOW CARBON SOCIETY

 

In order to avoid climate change at any point in the future, all nations considered carbon intensive societies and societies which are heavily populated, should become zero-carbon societies and economies. Several of these countries have pledged to become 'low carbon' but not entirely zero carbon, and claim that emissions will be cut by 100% by offsetting emissions rather than ceasing all emissions - carbon neutrality. In other words, some emitting will continue which will be offset.

二、教学要求

1.温室效应概念与作用(definition of Greenhouse effects and its effect on ecosystem)

板书:to illustrate the mechanism of Greenhouse effects。(Sun radiation,

2.温室气体识别与排放(Greenhouse gases: CO2, Vapor, N2O, CH4, CFCsSF6),引出碳当量概念和计算方法。

3.全球变暖后果(consequence of Global Warming: Rise of sea level, melting of polar ice cap, climate change……

4. 需要简单介绍的内容有:气候模型      

5. 重点介绍:碳减排 全球合作

6. 低碳经济与低碳社会  http://www.ditan360.com/ 

三、教学方法

讲授,采用问题导入法

四、教学过程

1. 说明本章学习目的(Learning Objectives

When you are finished with this session you should be able to:

& #8226;           Define green house effect, climate change and global warming.

& #8226;           Describe the major effects of global warming on human health and other living things.

& #8226;           Describe the major causes of global warming and types of sources.

& #8226;           Name and summarize the principal mechanism of greenhouse effect and CO2-caused global warming.

& #8226;           Describe the general idea of Low-Carbon Economy (LCE) and how to realize it.

2. 导入问题:

Questions:

1What is greenhouse effect and it’s mechanism ? Illustrate it.

2What are the greenhouse gases? And where are they from? How is the concentration of these gases in atmosphere? How is the estimated emission in the future?

3) What is CERTAINTY ?

4What is LIKELY BUT NOT CERTAIN?

3. 要学生思考5分钟,后根据以上问题展开讲授。

4. 介绍低碳经济和低碳社会:概念,涉及的领域

      1)理念

A Low-Carbon Economy (LCE) or Low-Fossil-Fuel Economy (LFFE) is a concept that refers to an economy which has a minimal output of greenhouse gas (GHG) emissions into the biosphere, but specifically refers to the greenhouse gas carbon dioxide.

低碳经济是以低能耗、低污染、低排放为基础的经济模式,是人类社会继农业文明、工业文明之后的又一次重大进步。低碳经济实质是能源高效利用、清洁能源开发、追求绿色GDP的问题,核心是能源技术和减排技术创新、产业结构和制度创新以及人类生存发展观念的根本性转变。

2低碳经济提出的大背景

全球气候变暖对人类生存和发展的严峻挑战。随着全球人口和经济规模的不断增长,能源使用带来的环境问题及其诱因不断地为人们所认识,不止是烟雾、光化学烟雾和酸雨等的危害,大气中二氧化碳(CO2)浓度升高带来的全球气候变化也已被确认为不争的事实。

3)新概念、新政策

   碳足迹低碳经济低碳技术低碳发展低碳生活方式低碳社会低碳城市低碳世界等。

4低碳经济涉及的产业领域和管理领域、个人生活方式(学生自由发言)。

5. 安排课后小组合作学习活动:观看Al Gore 制作的影片《An Inconvenient Truth》和对全球变暖原因持异议的另外一部影片《The Great Global Warming Swindle》,下一节课谈自己的看法。


第八章  臭氧层破坏(OZONE DEPLETION

2学时)

 

一、教学内容

CHAPTER 8 OZONE DEPLETION

 

8.1 ATMOSPHERE: COMPOSITION & STRUCTURE

8.1.2 ATMOSPHERE STRUCTURE

1.Troposphere

The troposphere starts at the Earth's surface and extends 8 to 14.5 kilometers high (5 to 9 miles). This part of the atmosphere is the most dense. As you climb higher in this layer, the temperature drops from about 17 to -52 degrees Celsius. Almost all weather is in this region. The tropopause separates the troposphere from the next layer. The tropopause and the troposphere are known as the lower atmosphere.

2.Stratosphere

The stratosphere starts just above the troposphere and extends to 50 kilometers (31 miles) high. Compared to the troposphere, this part of the atmosphere is dry and less dense. The temperature in this region increases gradually to -3 degrees Celsius, due to the absorbtion of ultraviolet radiation. The ozone layer, which absorbs and scatters the solar ultraviolet radiation, is in this layer. Ninety-nine percent of "air" is located in the troposphere and stratosphere. The stratopause separates the stratosphere from the next layer.

3.Mesosphere

The mesosphere starts just above the stratosphere and extends to 85 kilometers (53 miles) high. In this region, the temperatures again fall as low as -93 degrees Celsius as you increase in altitude. The chemicals are in an excited state, as they absorb energy from the Sun. The mesopause separates the mesophere from the thermosphere.

4.Thermosphere

The thermosphere starts just above the mesosphere and extends to 600 kilometers (372 miles) high. The temperatures go up as you increase in altitude due to the Sun's energy. Temperatures in this region can go as high as 1,727 degrees Celsius. Chemical reactions occur much faster here than on the surface of the Earth. This layer is known as the upper atmosphere.

8. 2   THE OZONE DEPLETION

8.2.1 THE OZONE LAYER

The Earth's atmosphere is divided into several layers. The lowest region, the troposphere, extends from the Earth's surface up to about 10 kilometers (km) in altitude. Virtually all human activities occur in the troposphere. Mt. Everest, the tallest mountain on the planet, is only about 9 km high. The next layer, the stratosphere, continues from 10 km to about 50 km. Most commercial airline traffic occurs in the lower part of the stratosphere.

As shown in the graph, most atmospheric ozone is concentrated in a layer in the stratosphere, about 15-30 kilometers above the Earth's surface (graph courtesy of World Meteorological Organization, Scientific Assessment of Ozone Depletion: 1998, WMO Global Ozone Research and Monitoring Project - Report No. 44, Geneva, 1998). Ozone is a molecule containing three oxygen atoms. It is blue in color and has a strong odor. Normal oxygen, which we breathe, has two oxygen atoms and is colorless and odorless. Ozone is much less common than normal oxygen. Out of each 10 million air molecules, about 2 million are normal oxygen, but only 3 are ozone.

However, even the small amount of ozone plays a key role in the atmosphere. The ozone layer absorbs a portion of the radiation from the sun, preventing it from reaching the planet's surface. Most importantly, it absorbs the portion of ultraviolet light called UVB. UVB has been linked to many harmful effects, including various types of skin cancer, cataracts, and harm to some crops, certain materials, and some forms of marine life.

8.2.2 THE ANTARCTIC OZONE HOLE

Antarctic Ozone Levels in Fall 2003

The ozone hole is represented by the purple, red, burgundy, and gray areas that appeared over Antarctica in the fall of 2003. The ozone hole is defined as the area having less than 220 Dobson units (DU) of ozone in the overhead column (i.e., between the ground and space).

The ozone hole is a well-defined, large-scale destruction of the ozone layer over Antarctica that occurs each Antarctic spring. The word "hole" is a misnomer; the hole is really a significant thinning, or reduction in ozone concentrations, which results in the destruction of up to 70% of the ozone normally found over Antarctica.

8.2.3 THE PROCESS OF OZONE DEPLETION

The ozone depletion process begins when CFCs and other ozone-depleting substances (ODS) are emitted into the atmosphere(1). Winds efficiently mix the troposphere and evenly distribute the gases. CFCs are extremely stable, and they do not dissolve in rain. After a period of several years, ODS molecules reach the stratosphere, about 10 kilometers above the Earth's surface (2).

Strong UV light breaks apart the ODS molecule. CFCs, HCFCs, carbon tetrachloride, methyl chloroform, and other gases release chlorine atoms, and halons and methyl bromide release bromine atoms (3). It is these atoms that actually destroy ozone, not the intact ODS molecule. It is estimated that one chlorine atom can destroy over 100,000 ozone molecules before it is removed from the stratosphere (4). Ozone is constantly produced and destroyed in a natural cycle, as shown in the above picture, courtesy of NASA GSFC. However, the overall amount of ozone is essentially stable. This balance can be thought of as a stream's depth at a particular location. Although individual water molecules are moving past the observer, the total depeth remains constant. Similarly, while ozone production and destruction are balanced, ozone levels remain stable. This was the situation until the past several decades.

Large increases in stratospheric chlorine and bromine, however, have upset that balance. In effect, they have added a siphon downstream, removing ozone faster than natural ozone creation reactions can keep up. Therefore, ozone levels fall.

Since ozone filters out harmful UVB radiation, less ozone means higher UVB levels at the surface. The more the depletion, the larger the increase in incoming UVB. UVB has been linked to skin cancer, cataracts, damage to materials like plastics, and harm to certain crops and marine organisms. Although some UVB reaches the surface even without ozone depletion, its harmful effects will increase as a result of this problem.

8.2.4 THE EFFECTS OF OZONE DEPLETION

The Connection Between Ozone Depletion and UVB Radiation

Reductions in ozone levels will lead to higher levels of UVB reaching the Earth's surface. The sun's output of UVB does not change; rather, less ozone means less protection, and hence more UVB reaches the Earth. Studies have shown that in the Antarctic, the amount of UVB measured at the surface can double during the annual ozone hole. Another study confirmed the relationship between reduced ozone and increased UVB levels in Canada during the past several years.

Effects on Human Health

Laboratory and epidemiological studies demonstrate that UVB causes nonmelanoma skin cancer and plays a major role in malignant melanoma development. In addition, UVB has been linked to cataracts. All sunlight contains some UVB, even with normal ozone levels. It is always important to limit exposure to the sun. However, ozone depletion will increase the amount of UVB and the risk of health effects.

Effects on Plants

Physiological and developmental processes of plants are affected by UVB radiation, even by the amount of UVB in present-day sunlight. Despite mechanisms to reduce or repair these effects and a limited ability to adapt to increased levels of UVB, plant growth can be directly affected by UVB radiation.

Indirect changes caused by UVB (such as changes in plant form, how nutrients are distributed within the plant, timing of developmental phases and secondary metabolism) may be equally, or sometimes more, important than damaging effects of UVB. These changes can have important implications for plant competitive balance, herbivory, plant diseases, and biogeochemical cycles.

Effects on Marine Ecosystems

Phytoplankton form the foundation of aquatic food webs. Phytoplankton productivity is limited to the euphotic zone, the upper layer of the water column in which there is sufficient sunlight to support net productivity. The position of the organisms in the euphotic zone is influenced by the action of wind and waves. In addition, many phytoplankton are capable of active movements that enhance their productivity and, therefore, their survival. Exposure to solar UVB radiation has been shown to affect both orientation mechanisms and motility in phytoplankton, resulting in reduced survival rates for these organisms. Scientists have demonstrated a direct reduction in phytoplankton production due to ozone depletion-related increases in UVB. One study has indicated a 6-12% reduction in the marginal ice zone.

Effects on Biogeochemical Cycles

Increases in solar UV radiation could affect terrestrial and aquatic biogeochemical cycles, thus altering both sources and sinks of greenhouse and chemically-important trace gases e.g., carbon dioxide (CO2), carbon monoxide (CO), carbonyl sulfide (COS) and possibly other gases, including ozone. These potential changes would contribute to biosphere-atmosphere feedbacks that attenuate or reinforce the atmospheric buildup of these gases.

Effects on Materials

 

Synthetic polymers, naturally occurring biopolymers, as well as some other materials of commercial interest are adversely affected by solar UV radiation. Today's materials are somewhat protected from UVB by special additives. Therefore, any increase in solar UVB levels will therefore accelerate their breakdown, limiting the length of time for which they are useful outdoors.

 

二、教学要求

1. 要求深刻理解与熟练掌握的重点内容有:1、臭氧层作用;2、臭氧层破坏机理。

2. 要求一般性理解与掌握内容有:臭氧层破坏的后果

3. 难点:臭氧层破坏机理与消耗臭氧层物质。

4. 教学过程:观看视频:臭氧层消耗机理

三、教学方法

   讲授,穿插课堂讨论。

四、教学过程

1. 说明本章学习目的(Learning Objectives

When you are finished with this session you should be able to:

& #8226;  Define ozone layer and ozone depletion.

& #8226;  Describe the major effects of ozone depletion on human health and other living things.

& #8226;  Describe the major causes of ozone depletion and types of sources.

& #8226;           Name and summarize the Substitutes of ozone depletion substances .

2. 通过以下教学素材讲授紫外线对生命体的影响机制和后果:

ultraviolet light

UVA

UVB

UVC

200-290 nm

290-320 nm

320-400nm

harmful to the skin

is most strongly associated with skin cancer formation

is the range used for tanning

Definitions of UVA and UVB with diagrams

 

 

 

UVC radiation has a wavelength of 200-290 nanometers.

UVB radiation (290-320 nanometers) is the wavelength that is most strongly associated with skin cancer formation.

UVA radiation (320-400nm) is the range used for tanning. It is important to remember that there is actual great variation in the biologic effects of different wavelengths within each of these subdivisions.

 3. 通过动画片解说臭氧层消耗机理和控制策略

    4. 介绍国际合作取得的成果


第九章 酸沉降(ACID DEPOSITION

2学时)

 

一、教学内容

CHAPTER 9 ACID DEPOSITION

9. 1   THE DEFINITION OF ACID RAIN

"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.

Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including how acidic the water is, the chemistry and buffering capacity of the soils involved, and the types of fish, trees, and other living things that rely on the water.

Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.

Prevailing winds blow the compounds that cause both wet and dry acid deposition across state and national borders, and sometimes over hundreds of miles.

Scientists discovered, and have confirmed, that sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal.

Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid.

9. 2   THE MEASURE OF ACID RAIN

Acid rain is measured using a scale called "pH." The lower a substance's pH, the more acidic it is. Pure water has a pH of 7.0. Normal rain is slightly acidic because carbon dioxide dissolves into it, so it has a pH of about 5.5. As of the year 2000, the most acidic rain falling in the US has a pH of about 4.3.

Acid rain's pH, and the chemicals that cause acid rain, are monitored by two networks, both supported by EPA. The National Atmospheric Deposition Program measures wet deposition, and features maps of rainfall pH (follow the link to the isopleth maps) and other important precipitation chemistry measurements.

9. 3   THE EFFECTS OF ACID RAIN

Acid rain causes acidification of lakes and streams and contributes to damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage. Prior to falling to the earth, SO2 and NOx gases and their particulate matter derivatives, sulfates and nitrates, contribute to visibility degradation and harm public health.

9.3.1 EFFECTS OF ACID RAIN: LAKES & STREAMS

The ecological effects of acid rain are most clearly seen in the aquatic, or water, environments, such as streams, lakes, and marshes. Acid rain flows to streams, lakes, and marshes after falling on forests, fields, buildings, and roads. Acid rain also falls directly onF aquatic habitats. Most lakes and streams have a pH between 6 and 8, although some lakes are naturally acidic even without the effects of acid rain. Acid rain primarily affects sensitive bodies of water, which are located in watersheds whose soils have a limited ability to neutralize acidic compounds (called "buffering capacity"). Lakes and streams become acidic (pH value goes down) when the water itself and its surrounding soil cannot buffer the acid rain enough to neutralize it. In areas where buffering capacity is low, acid rain also releases aluminum from soils into lakes and streams; aluminum is highly toxic to many species of aquatic organisms.

9.3.1.1 Acid Rain Affect Fish and Other Aquatic Organisms

Acid rain causes a cascade of effects that harm or kill individual fish, reduce fish population numbers, completely eliminate fish species from a waterbody, and decrease biodiversity. As acid rain flows through soils in a watershed, aluminum is released from soils into the lakes and streams located in that watershed. So, as pH in a lake or stream decreases, aluminum levels increase. Both low pH and increased aluminum levels are directly toxic to fish. In addition, low pH and increased aluminum levels cause chronic stress that may not kill individual fish, but leads to lower body weight and smaller size and makes fish less able to compete for food and habitat.

Some types of plants and animals are able to tolerate acidic waters. Others, however, are acid-sensitive and will be lost as the pH declines. Generally, the young of most species are more sensitive to environmental conditions than adults. At pH 5, most fish eggs cannot hatch. At lower pH levels, some adult fish die. Some acid lakes have no fish. The chart below shows that not all fish, shellfish, or the insects that they eat can tolerate the same amount of acid; for example, frogs can tolerate water that is more acidic (has lower pH) than trout.

   Together, biological organisms and the environment in which they live are called an ecosystem. The plants and animals living within an ecosystem are highly interdependent. For example, frogs may tolerate relatively high levels of acidity, but if they eat insects like the mayfly, they may be affected because part of their food supply may disappear. Because of the connections between the many fish, plants, and other organisms living in an aquatic ecosystem, changes in pH or aluminum levels affect biodiversity as well. Thus, as lakes and streams become more acidic, the numbers and types of fish and other aquatic plants and animals that live in these waters decrease.

9.3.1.2 The Role of Nitrogen in Acid Rain and other Environmental Problems

The impact of nitrogen on surface waters is also critical. Nitrogen plays a significant role in episodic acidification and new research recognizes the importance of nitrogen in long-term chronic acidification as well. Furthermore, the adverse impact of atmospheric nitrogen deposition on estuaries and near-coastal water bodies is significant. Scientists estimate that from 10-45 percent of the nitrogen produced by various human activities that reaches estuaries and coastal ecosystems is transported and deposited via the atmosphere. For example, about 30 percent of the nitrogen in the Chesapeake Bay comes from atmospheric deposition. Nitrogen is an important factor in causing eutrophication (oxygen depletion) of water bodies. The symptoms of eutrophication include blooms of algae (both toxic and non-toxic), declines in the health of fish and shellfish, loss of seagrass beds and coral reefs, and ecological changes in food webs.

9.3.2 EFFECTS OF ACID RAIN: FORESTS

Over the years, scientists, foresters, and others have watched some forests grow more slowly without knowing why. The trees in these forests do not grow as quickly at a healthy pace. Leaves and needles turn brown and fall off when they should be green and healthy. In extreme cases, individual trees or entire areas of the forest simply die off without an obvious reason.

9.3.2.1 Acid Rain on the Forest Floor

A spring shower in the forest washes leaves and falls through the trees to the forest floor below. Some trickles over the ground and runs into a stream, river, or lake, and some of the water soaks into the soil. That soil may neutralize some or all of the acidity of the acid rainwater. This ability is called buffering capacity, and without it, soils become more acidic. Differences in soil buffering capacity are an important reason why some areas that receive acid rain show a lot of damage, while other areas that receive about the same amount of acid rain do not appear to be harmed at all. The ability of forest soils to resist, or buffer, acidity depends on the thickness and composition of the soil, as well as the type of bedrock beneath the forest floor. Midwestern states like Nebraska and Indiana have soils that are well buffered. Places in the mountainous northeast, like New York's Adirondack and Catskill Mountains, have thin soils with low buffering capacity.

9.3.2.2 How Acid Rain Harms Trees

Acid rain does not usually kill trees directly. Instead, it is more likely to weaken trees by damaging their leaves, limiting the nutrients available to them, or exposing them to toxic substances slowly released from the soil. Quite often, injury or death of trees is a result of these effects of acid rain in combination with one or more additional threats.

9.3.2.3 How Acid Rain Affects Other Plants

Acid rain can harm other plants in the same way it harms trees. Although damaged by other air pollutants such as ground level ozone, food crops are not usually seriously affected because farmers frequently add fertilizers to the soil to replace nutrients that have washed away. They may also add crushed limestone to the soil. Limestone is an alkaline material and increases the ability of the soil to act as a buffer against acidity.

9.3.3 THE EFFECTS OF ACID RAIN ON AUTOMOTIVE COATINGS

Over the past two decades, there have been numerous reports of damage to automotive paints and other coatings. The reported damage typically occurs on horizontal surfaces and appears as irregularly shaped, permanently etched areas. The damage can best be detected under fluorescent lamps, can be most easily observed on dark colored vehicles, and appears to occur after evaporation of a moisture droplet. In addition, some evidence suggests damage occurs most frequently on freshly painted vehicles. Usually the damage is permanent; once it has occurred, the only solution is to repaint.

9.3.4 EFFECTS OF ACID RAINMATERIALS

Acid rain and the dry deposition of acidic particles contribute to the corrosion of metals (such as bronze) and the deterioration of paint and stone (such as marble and limestone). These effects seriously reduce the value to society of buildings, bridges, cultural objects (such as statues, monuments, and tombstones), and cars.

Dry deposition of acidic compounds can also dirty buildings and other structures, leading to increased maintenance costs. To reduce damage to automotive paint caused by acid rain and acidic dry deposition, some manufacturers use acid-resistant paints, at an average cost of $5 for each new vehicle (or a total of $61 million per year for all new cars and trucks sold in the U.S.) The Acid Rain Program will reduce damage to materials by limiting SO2 emissions. The benefits of the Acid Rain Program are measured, in part, by the costs now paid to repair or prevent damage--the costs of repairing buildings and bridges, using acid-resistant paints on new vehicles, plus the value that society places on the details of a statue lost forever to acid rain.

9.3.5 EFFECTS OF ACID RAINVISIBILITY REDUCTION

Sulfates and nitrates that form in the atmosphere from sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions contribute to visibility impairment, meaning we can't see as far or as clearly through the air. Sulfate particles account for 50 to 70 percent of the visibility reduction in the eastern part of the United States, affecting our enjoyment of national parks, such as the Shenandoah and the Great Smoky Mountains. The Acid Rain Program is expected to improve the visual range in the eastern U.S. by 30 percent. Based on a study of the value national park visitors place on visibility, the visual range improvements expected at national parks of the eastern United States due to the Acid Rain Program's SO2 reductions will be worth over a billion dollars annually by the year 2010. In the western part of the United States, nitrates and carbon also play roles, but sulfates have been implicated as an important source of visibility impairment in many of the Colorado River Plateau national parks, including the Grand Canyon, Canyonlands, and Bryce Canyon.

9.3.6 EFFECTS OF ACID RAINHUMAN HEALTH

Acid rain looks, feels, and tastes just like clean rain. The harm to people from acid rain is not direct. Walking in acid rain, or even swimming in an acid lake, is no more dangerous than walking or swimming in clean water. However, the pollutants that cause acid rain (sulfur dioxide (SO2) and nitrogen oxides (NOx)) also damage human health. These gases interact in the atmosphere to form fine sulfate and nitrate particles that can be transported long distances by winds and inhaled deep into people's lungs. Fine particles can also penetrate indoors. Many scientific studies have identified a relationship between elevated levels of fine particles and increased illness and premature death from heart and lung disorders, such as asthma and bronchitis.

二、教学要求

1. 要求深刻理解与熟练掌握的内容有:

1)酸沉降概念;

2)酸雨控制对策      

2. 要求一般性理解与掌握的内容有:酸沉降后果
    3.  
难点:二氧化硫、氮氧化物控制技术。

三、教学方法

案例教学法

四、教学过程

1. 说明本章学习目的(Learning Objectives

When you are finished with this session you should be able to:

& #8226;  Defineacid rain.

& #8226;  Describe the major effects of acid rain on human health and other living things.

& #8226;  Describe the major causes of acid deposition and types of sources.

& #8226;  Describe the situation of acid deposition in China.

& #8226; Name and summarize the methods of acid deposition control.

  2. Case study 柳州市的酸雨控制(收集柳州市历年的酸雨形势,采取的控制方法,效果)


 

PART III    ENVIRONMENTAL POLLUTION
      

第十章 大气污染(AIR POLLUTION

3学时)

一、教学内容

CHAPTER 10 AIR POLLUTION

10. 1 AIR POLLUTION

We all breathe in air, we can feel, and even smell the air and say whether it is fresh or stale. Air Pollution is the presence in the air of substances put there by the acts of man in concentrations sufficient to interfere with health, comfort, or safety, or with full use and enjoyment of property.

10. 1 AIR POLLUTANTS

An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made.

Pollutants can be classified as either primary or secondary. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.

Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone— one of the many secondary pollutants that make up photochemical smog.

Major primary pollutants produced by human activity include:

·           Sulfur oxides (SOx) - especially sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.

·           Nitrogen oxides (NOx) - especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities.Nitrogen dioxide is the chemical compound with the formula NO2. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.

·           Carbon monoxide - is a colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.

·           Carbon dioxide (CO2) - a greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere.

·           Volatile organic compounds - VOCs are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane (CH4) and non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hydrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toluene and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.

·           Particulate matter - Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be manmade or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.

·           Toxic metals, such as lead, cadmium and copper.

·           Chlorofluorocarbons (CFCs) - harmful to the ozone layer emitted from products currently banned from use.

·           Ammonia (NH3) - emitted from agricultural processes. Ammonia is a compound with the formula NH3. It is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs and fertilizers. Ammonia, either directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.

·           Odors— such as from garbage, sewage, and industrial processes

·           Radioactive pollutants - produced by nuclear explosions, war explosives, and natural processes such as the radioactive decay of radon.

Secondary pollutants include:

·           Particulate matter formed from gaseous primary pollutants and compounds in photochemical smog .Smog is a kind of air pollution; the word "smog" is a portmanteau of smoke and fog. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by sunlight to form secondary pollutants that also combine with the primary emissions to form photochemical smog.

·  Ground level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere (it is also an important constituent of certain regions of the stratosphere commonly known as the Ozone layer). Photochemical and chemical reactions involving it drive many of the chemical processes that occur in the atmosphere by day and by night. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.

·  Peroxyacetyl nitrate (PAN) - similarly formed from NOx and VOCs.

Minor air pollutants include:

·      A large number of minor hazardous air pollutants. Some of these are regulated in USA under the Clean Air Act and in Europe under the Air Framework Directive.

·      A variety of persistent organic pollutants, which can attach to particulate matter.

Persistent organic pollutants (POPs) are organic compounds that are resistant to environmental degradation through chemical, biological, and photolytic processes. Because of this, they have been observed to persist in the environment, to be capable of long-range transport, bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential significant impacts on human health and the environment.

10.2 AIR POLLUTANTS AND THERE EFFECTS

10.2.1 NITROGEN OXIDES

10.2.1.1 SOURCES

Nitrogen oxides, or NOx, is the generic term for a group of highly reactive gases, all of which contain nitrogen and oxygen in varying amounts. Many of the nitrogen oxides are colorless and odorless. However, one common pollutant, nitrogen dioxide (NO2) along with particles in the air can often be seen as a reddish-brown layer over many urban areas.

Nitrogen oxides form when fuel is burned at high temperatures, as in a combustion process. The primary manmade sources of NOx are motor vehicles, electric utilities, and other industrial, commercial, and residential sources that burn fuels. NOx can also be formed naturally.

10.2.1.2 CHIEF CAUSES FOR CONCERN

NOx

·       is one of the main ingredients involved in the formation of ground-level ozone, which can trigger serious respiratory problems.

·       reacts to form nitrate particles, acid aerosols, as well as NO2, which also cause respiratory problems.

·       contributes to formation of acid rain.

·       contributes to nutrient overload that deteriorates water quality.

·       contributes to atmospheric particles, that cause visibility impairment most noticeable in national parks.

·       reacts to form toxic chemicals.

·       contributes to global warming.

NOx and the pollutants formed from NOx can be transported over long distances, following the pattern of prevailing winds in the world. This means that problems associated with NOx are not confined to areas where NOx are emitted. Therefore, controlling NOx is often most effective if done from a regional perspective, rather than focusing on sources in one local area.

10.2.1.2 HEALTH AND ENVIRONMENTAL IMPACTS OF NOx

NOx causes a wide variety of health and environmental impacts because of various compounds and derivatives in the family of nitrogen oxides, including nitrogen dioxide, nitric acid, nitrous oxide, nitrates, and nitric oxide.

 

Ground-level Ozone (Smog) - is formed when NOx and volatile organic compounds (VOCs) react in the presence of sunlight. Children, people with lung diseases such as asthma, and people who work or exercise outside are susceptible to adverse effects such as damage to lung tissue and reduction in lung function. Ozone can be transported by wind currents and cause health impacts far from original sources. Millions of Americans live in areas that do not meet the health standards for ozone. Other impacts from ozone include damaged vegetation and reduced crop yields

 

Acid Rain - NOx and sulfur dioxide react with other substances in the air to form acids which fall to earth as rain, fog, snow or dry particles. Some may be carried by wind for hundreds of miles. Acid rain damages; causes deterioration of cars, buildings and historical monuments; and causes lakes and streams to become acidic and unsuitable for many fish.

 

Particles - NOx reacts with ammonia, moisture, and other compounds to form nitric acid and related particles. Human health concerns include effects on breathing and the respiratory system, damage to lung tissue, and premature death. Small particles penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory disease such as emphysema and bronchitis, and aggravate existing heart disease.

 

Water Quality Deterioration - Increased nitrogen loading in water bodies, particularly coastal estuaries, upsets the chemical balance of nutrients used by aquatic plants and animals. Additional nitrogen accelerates "eutrophication," which leads to oxygen depletion and reduces fish and shellfish populations. NOx emissions in the air are one of the largest sources of nitrogen pollution in the Chesapeake Bay.

 

Global Warming - One member of the NOx, nitrous oxide, is a greenhouse gas. It accumulates in the atmosphere with other greenhouse gasses causing a gradual rise in the earth's temperature. This will lead to increased risks to human health, a rise in the sea level, and other adverse changes to plant and animal habitat.

 

Toxic Chemicals - In the air, NOx reacts readily with common organic chemicals and even ozone, to form a wide variety of toxic products, some of which may cause biological mutations. Examples of these chemicals include the nitrate radical, nitroarenes, and nitrosamines.

 

Visibility Impairment - Nitrate particles and nitrogen dioxide can block the transmission of light, reducing visibility in urban areas and on a regional scale in our national parks.

10.2.2 SULFUR DIOXIDE

10.2.2.1 SOURCES

Sulfur dioxide, or SO2, belongs to the family of sulfur oxide gases (SOx).  These gases dissolve easily in water.  Sulfur is prevalent in all raw materials, including crude oil, coal, and ore that contains common metals like aluminum, copper, zinc, lead, and iron.  SOx gases are formed when fuel containing sulfur, such as coal and oil, is burned, and when gasoline is extracted from oil, or metals are extracted from ore.  SO2 dissolves in water vapor to form acid, and interacts with other gases and particles in the air to form sulfates and other products that can be harmful to people and their environment.

10.2.2.2 CHIEF CAUSES FOR CONCERN

SO2 contributes to respiratory illness, particularly in children and the elderly, and aggravates existing heart and lung diseases.

SO2 contributes to the formation of acid rain, which:

  • damages trees, crops, historic buildings, and monuments; and
  • makes soils, lakes, and streams acidic.

SO2 contributes to the formation of atmospheric particles that cause visibility impairment, most noticeably in national parks.

SO2 can be transported over long distances.
SO2 and the pollutants formed from SO2, such as sulfate particles, can be transported over long distances and deposited far from the point of origin.  This means that problems with SO2 are not confined to areas where it is emitted.

10.2.2.3 HEALTH AND ENVIRONMENTAL IMPACTS OF SO2

SO2 causes a wide variety of health and environmental impacts because of the way it reacts with other substances in the air.  Particularly sensitive groups include people with asthma who are active outdoors and children, the elderly, and people with heart or lung disease.

 

Respiratory Effects from Gaseous SO2
Peak levels of SO2 in the air can cause temporary breathing difficulty for people with asthma who are active outdoors.  Longer-term exposures to high levels of SO2 gas and particles cause respiratory illness and aggravate existing heart disease.
Respiratory Effects from Sulfate Particles
SO2 reacts with other chemicals in the air to form tiny sulfate particles.  When these are breathed, they gather in the lungs and are associated with increased respiratory symptoms and disease, difficulty in breathing, and premature death.

 

Visibility Impairment
Haze occurs when light is scattered or absorbed by particles and gases in the air.  Sulfate particles are the major cause of reduced visibility in many parts of the U.S., including our national parks.

 

Acid Rain
SO2  and nitrogen oxides react with other substances in the air to form acids, which fall to earth as rain, fog, snow, or dry particles.  Some may be carried by the wind for hundreds of miles.

 

Plant and Water Damage
Acid rain damages forests and crops, changes the makeup of soil, and makes lakes and streams acidic and unsuitable for fish.  Continued exposure over a long time changes the natural variety of plants and animals in an ecosystem.

 

Aesthetic Damage
SO2 accelerates the decay of building materials and paints, including irreplaceable monuments, statues, and sculptures that are part of our nation's cultural heritage.

10.2.3 PARTICULATE MATTER

10.2.3.1 SOURCES

“Particulate matter," also known as particle pollution or PM, is a complex mixture of extremely small particles and liquid droplets. Particle pollution is made up of a number of components, including acids (such as nitrates and sulfates), organic chemicals, metals, and soil or dust particles.

The size of particles is directly linked to their potential for causing health problems. EPA is concerned about particles that are 10 micrometers in diameter or smaller because those are the particles that generally pass through the throat and nose and enter the lungs. Once inhaled, these particles can affect the heart and lungs and cause serious health effects. EPA groups particle pollution into two categories:

  • "Coarse particles," such as those found near roadways and dusty industries, range in size from 2.5 to 10 micrometers in diameter.
  • "Fine particles," such as those found in smoke and haze, have diameters smaller than 2.5 micrometers. These particles can be directly emitted from sources such as forest fires, or they can form when gases emitted from power plants, industries and automobiles react in the air.

10.2.3.1 EFFECTS OF PARTICLE POLLUTION

The size of particles is directly linked to their potential for causing health problems. Small particles less than10 micrometers in diameter pose the greatest problems, because they can get deep into your lungs, and some may even get into your bloodstream.

Health Effects

Particle pollution - especially fine particles - contains microscopic solids or liquid droplets that are so small that they can get deep into the lungs and cause serious health problems. Numerous scientific studies have linked particle pollution exposure to a variety of problems, including:

*      increased respiratory symptoms, such as irritation of the airways, coughing, or difficulty breathing, for example;

*      decreased lung function;

*      aggravated asthma;

*      development of chronic bronchitis;

*      irregular heartbeat;

*      nonfatal heart attacks; and

*      premature death in people with heart or lung disease.

Welfare Effects

Visibility reduction
Fine particles (PM 2.5) are the major cause of reduced visibility (haze) in parts of the United States, including many of our treasured national parks and wilderness areas. 

Environmental damage

Particles can be carried over long distances by wind and then settle on ground or water.  The effects of this settling include: making lakes and streams acidic; changing the nutrient balance in coastal waters and large river basins; depleting the nutrients in soil; damaging sensitive forests and farm crops; and affecting the diversity of ecosystems.

 Aesthetic damage

Particle pollution can stain and damage stone and other materials, including culturally important objects such as statues and monuments.

10.2.4 GROUND-LEVEL OZONE

10.2.4.1 SOURCES

Ozone (O3) is a gas composed of three oxygen atoms.  It is not usually emitted directly into the air, but at ground level is created by a chemical reaction between oxides of nitrogen (NOx) and volatile organic compounds (VOC) in the presence of sunlight.  Ozone has the same chemical structure whether it occurs miles above the earth or at ground level and can be "good" or "bad," depending on its location in the atmosphere.  "Good" ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the earth's surface and forms a layer that protects life on earth from the sun's harmful rays.  In the earth's lower atmosphere, ground-level ozone is considered "bad."     VOC + NOx + Sunlight = Ozone

10.2.4.2 CHIEF CAUSES FOR CONCERN

Ground-level Ozone

*      Triggers a variety of health problems even at very low levels

*      May cause permanent lung damage after long-term exposure

*      Damages plants and ecosystems

The summertime pollutant

Peak ozone levels typically occur during hot, dry, stagnant summertime conditions.  The length of the ozone season varies from one area of the United States to another.  Southern and Southwestern states may have an ozone season that lasts nearly the entire year.

Ozone can be transported over long distances

Ozone and the chemicals that react to form it can be carried hundreds of miles from their origins, causing air pollution over wide regions. Millions of Americans live in areas where ozone levels exceed EPA's health-based air quality standards, primarily in parts of the Northeast, the Lake Michigan area, parts of the Southeast, southeastern Texas, and parts of California.

Ozone and the pollutants that form it can cause air quality problems hundreds of miles away

10.2.4.3 HEALTH AND ENVIRONMENTAL IMPACTS

Ground-level ozone even at low levels can adversely affect everyone.  It can also have detrimental effects on plants and ecosystems.

10.2.5 CARBON MONOXIDE

10.2.5.1 SOURCES

Carbon monoxide, or CO, is a colorless, odorless gas that is formed when carbon in fuel is not burned completely.  It is a component of motor vehicle exhaust, which contributes about 56 percent of all CO emissions nationwide.  Other non-road engines and vehicles (such as construction equipment and boats) contribute about 22 percent of all CO emissions nationwide.   Higher levels of CO generally occur in areas with heavy traffic congestion.  In cities, 85 to 95 percent of all CO emissions may come from motor vehicle exhaust.   Other sources of CO emissions include industrial processes (such as metals processing and chemical manufacturing), residential wood burning, and natural sources such as forest fires.  Woodstoves, gas stoves, cigarette smoke, and unvented gas and kerosene space heaters are sources of CO indoors.  The highest levels of CO in the outside air typically occur during the colder months of the year when inversion conditions are more frequent.  The air pollution becomes trapped near the ground beneath a layer of warm air.
 10.2.5.2 CHIEF CAUSES FOR CONCERN

co

*      is poisonous even to healthy people at high levels in the air.

*      can affect people with heart disease.

*      can affect the central nervous system.

10.2.5.3 HEALTH AND ENVIRONMENTAL IMPACTS

Carbon monoxide can cause harmful health effects by reducing oxygen delivery to the body's organs (like the heart and brain) and tissues.  

 

Cardiovascular Effects.  The health threat from lower levels of CO is most serious for those who suffer from heart disease, like angina, clogged arteries, or congestive heart failure.  For a person with heart disease, a single exposure to CO at low levels may cause chest pain and reduce that person's ability to exercise; repeated exposures may contribute to other cardiovascular effects.

 

Central Nervous System Effects.  Even healthy people can be affected by high levels of CO.   People who breathe high levels of CO can develop vision problems, reduced ability to work or learn, reduced manual dexterity, and difficulty performing complex tasks.   At extremely high levels, CO is poisonous and can cause death.

 

Smog.  CO contributes to the formation of smog ground-level ozone, which can trigger serious respiratory problems.  

10.2.6 LEAD

10.2.6.1 SOURCES

 

Lead is a metal found naturally in the environment as well as in manufactured products.  The major sources of lead emissions have historically been motor vehicles (such as cars and trucks) and industrial sources.  Due to the phase out of leaded gasoline, metals processing is the major source of lead emissions to the air today. The

highest levels of lead in air are generally found near lead smelters. Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers.

10.2.6.2 CHIEF CAUSES FOR CONCERN

Lead. . .

*      particularly affects young children and infants

*      is still found at high levels in urban and industrial areas

*      deposits on soil and water and harms animals and fish

Children are at greatest risk
Although overall blood lead levels have decreased since 1976, infants and young children still have the highest blood lead levels.  Children and others can be exposed to lead not only through the air, but also through accidentally or intentionally eating soil or paint chips, as well as food or water contaminated with lead.

High levels of lead are still of concern in localized areas.
Urban areas with high levels of traffic, trash incinerators, or other industry, as well as areas near lead smelters, battery plants, or industrial facilities that burn fuel, may still have high lead levels in air.  In 1999, ten areas of the country did not meet the national health-based air quality standards for lead.

10.2.6.3 HEALTH AND ENVIRONMENTAL IMPACTS

People, animals, and fish are mainly exposed to lead by breathing and ingesting it in food, water, soil, or dust. Lead accumulates in the blood, bones, muscles, and fat.  Infants and young children are especially sensitive to even low levels of lead.

 

Damages organs - Lead causes damage to the kidneys, liver, brain and nerves, and other organs.  Exposure to lead may also lead to osteoporosis (brittle bone disease) and reproductive disorders. 

 

Affects the brain and nerves - Excessive exposure to lead causes seizures, mental retardation, behavioral disorders, memory problems, and mood changes. Low levels of lead damage the brain and nerves in fetuses and young children, resulting in learning deficits and lowered IQ.

 

Affects the heart and blood - Lead exposure causes high blood pressure and increases heart disease, especially in men.  Lead exposure may also lead to anemia, or weak blood. 

 

Affects animals and plants - Wild and domestic animals can ingest lead while grazing.  They experience the same kind of effects as people who are exposed to lead.  Low concentrations of lead can slow down vegetation growth near industrial facilities. 

 

Affects fish - Lead can enter water systems through runoff and from sewage and industrial waste streams. Elevated levels of lead in the water can cause reproductive damage in some aquatic life and cause blood and neurological changes in fish and other animals that live there.

10.4 A BRIFE INTRODUCTION TO POLLUTION METEOROLOGY

Meteorology is the scientific study of weather and climate.

  • Weather is the day-to-day variation in temperature, humidity, wind, light and precipitation.
  • Climate is the long-term weather pattern of a given region.

We can use our knowledge of weather and climate to

  • understand how they both influence the behaviour and transportation of pollutants
  • assess the impact of air pollutants on humans, our economy, ecosystems and the climate itself.

Pollutants can be transported from a few metres to thousands of kilometres away from their source, depending on their distance above the Earth's surface.Weather conditions directly influence the distance pollutants travel and how they react and interact. Several factors effect and influence the behaviour and transportation of air pollutants

  • warm versus cool temperatures
  • the presence or absence of sunlight
  • windy versus calm conditions
  • warm fronts and cold fronts, and when they occur and interact
  • precipitation or lack of it
  • the change in temperature with increasing altitude

10.4.1 TEMPERATURE

Temperature affects both the speed at which molecules move and the rate at which they react. At higher temperatures, since molecules move faster, the likelihood of them colliding increases. Higher temperatures also increase the effectiveness of the collisions. In other words, increased temperatures speed up the reactions of air pollutants.

10.4.2 SUNLIGHT

Sunlight is an energy source that drives the reactions of certain pollutants in the atmosphere. Sunlight causes nitrogen oxides (NOx) and volatile organic compound (VOCs) to react.

²       Nitrogen dioxide (NO2) absorbs light energy and splits to form nitric oxide (NO) and atomic oxygen (O).

²       The atomic oxygen quickly combines with the oxygen gas (O2) present in the atmosphere to form ozone (O3).

The reactions are represented as follows:

Sunlight 1) NO2 → NO + O
and
Sunlight 2) O + O2 → O3

Both of these reactions produce unstable products. If other factors are not present, the ozone (O3), nitric oxide (NO) and atomic oxygen (O) react to form nitrogen dioxide (NO2) and oxygen gas (O2) and a chemical equilibrium (balanced concentration) of ozone results. In other words, there is no significant increase in ozone. In the warm weather months, concentrations of ozone in   unpolluted air range from 20 to 50 ppb (parts per billion).

When VOCs are present, the nitric oxide and atomic oxygen react with them, instead of with the ozone, to create harmful and reactive compounds. Since the nitric oxide and atomic oxygen are tied up in reactions with the VOCs, ozone accumulates. For this reason, ozone is the leading component of smog in Ontario.

Since sunlight must be present for the chemical reactions that produce smog to occur, the proper name for the phenomenon is photochemical smog. The products of photochemical reactions, such as ozone, are called secondary pollutants because they are produced by reaction between primary pollutants (originating directly from a source).

10.4.3 WIND

Air near the Earth's surface is heated by solar radiation. The air rises as it is heated, creating high pressure up in the atmosphere and leaving behind an area of lower pressure. As the air continues to rise, it expands and cools and any water vapour condenses and falls to the Earth as precipitation. Once the rising, cooling air has reached the temperature of the surrounding air, it flows horizontally toward low pressure areas of sinking cool, dry air.

10.4.4 MOISTURE

To some degree, rain, snow, sleet and hail "rinse" pollutants from the atmosphere. Many of us are familiar with the term acid precipitation or deposition. SOx and NOX are typical air pollutants. They react in the atmosphere to produce oxy-acids of sulphur and nitrogen. These acids dissolve readily in water present in the air or attach to particulate matter and are brought to earth in precipitation.

When storms with strong winds accompany precipitation, little rinsing of pollutants occurs. Much of the pollution is carried away by winds and is diluted by the mixing of surrounding air. Therefore, the greatest threat in terms of acid deposition occurs during periods of light rain or snow fall or when fog is present.

10.4.5 VERTICAL TEMPERATURE DISTRIBUTION

Under normal atmospheric conditions, the temperature in the troposphere becomes progressively cooler as the altitude increases. This decrease or lapse in temperature with altitude is called the "lapse rate".

Air pollutants that are released as a by-product of some thermal process, rise until the warm parcel of air that contains them reaches a temperature equal to the surrounding air. Consider emissions from a gasoline-powered car - as the warm air rises (expands), it begins to cool. Eventually it cools to a point where its temperature is the same as the air around it. Once the parcel of air reaches an equal temperature with the surrounding air, it levels off.

When temperature increases with altitude, it is referred to as a temperature or thermal inversion. In other words, the normal conditions are inverted or reversed

    In a thermal inversion, cool air is trapped under a warm air mass or inversion layer. During an inversion, pollutants are held under a ceiling of warm air. In warm weather months, when photochemical pollution is often at its worst, a thermal inversion can intensify smog levels.

10.4.6 LAPSE RATES

In the troposphere, temperature decreases with height up to an elevation of approximately 10 km. This decrease is due to the reduction of heating processes with height and radiative cooling of air, and reaches its maximum in the upper levels of the troposphere. Temperature decrease with height is described by the lapse rate. On the average, temperature decreases -0.65°C/ 100 m or -6.5°C/km. This is the normal lapse rate.

If a parcel of warm dry air were lifted in a dry environment, it would undergo adiabatic expansion and cool. This adiabatic cooling would result in a lapse rate of -1°C/l00 m or -10°C/km, the dry adiabatic lapse rate.

The relationship of environmental lapse rate to stability is illustrated in Figure 3.4. When there are no sources or sinks of thermal energy the temperature of arising air parcel will decrease at a rate of -1°C/100 m, or the dry adiabatic lapse rate. If a parcel of warm air is released into an environment where the temperature decrease with height is greater than the adiabatic lapse rate, say -2°C/100 m, the parcel will rise rapidly. The atmosphere will be unstable and conditions for the vertical dispersion of pollutants will be excellent. This is a superadiabatic lapse rate.

10.4.7 THERMAL INVERSION

An inversion occurs where the temperature is inverted. Temperature increases with height, Therefore dispersion potential is very poor, and suppresses the vertical motion of gaseous pollutants.

10.4.8 THE FORMATION OF PHOTOCHEMICAL SMOG

Photochemical smog is a type of air pollution produced when sunlight acts upon motor vehicle exhaust gases to form harmful substances such as ozone (O3), aldehydes and peroxyacetylnitrate (PAN).

Photochemical smog formation requires the following conditions:

*       a still, sunny day

*       temperature inversion (pollutants accumulate in the lower inversion layer)

Ozone causes breathing difficulties, headaches, fatigue and can aggrevate respiratory problems.

The peroxyacetylnitrate (CH3CO-OO-NO2) in photochemical smog can irritate the eyes, causing them to water and sting.

Ozone Production

Motor vehicles produce exhaust gases containing oxides of nitrogen such as nitrogen dioxide (NO2) and nitric oxide (NO).

At the high temperatures of the car's combustion chamber (cylinder), nitrogen and oxygen from the air react to form nitric oxide (NO):

N2(g) + O2(g) 2NO(g)

Some of the nitric oxide (NO) reacts with oxygen to form nitrogen dioxide (NO2):

2NO(g) + O2(g) 2NO2(g)

The mixture of nitric oxide (NO) and nitrogen dioxide (NO2) is sometimes referred to as NOx.

When the nitrogen dioxide (NO2) concentration is well above clean air levels and there is plenty of sunlight, then an oxygen atom splits off from the nitrogen dioxide molecule:

NO2(g)

sunlight
---------->

NO(g)

+

O(g)

This oxygen atom (O) can react with oxygen molecules (O2) in the air to form ozone (O3):

O + O2   O3

Nitric oxide can remove ozone by reacting with it to form nitrogen dioxide (NO2) and oxygen (O2):

NO(g) + O3(g) NO2(g) + O2(g)

When the ratio of NO2 to NO is greater than 3, the formation of ozone is the dominant reaction. If the ratio is less than 0.3, then the nitric oxide reaction destroys the ozone at about the same rate as it is formed, keeping the ozone concentration below harmful levels.

The reaction of hydrocarbons (unburnt petrol) with nitric oxide and oxygen produce nitrogen dioxide also in the presence of sunlight, increasing the ratio of nitrogen dioxide to nitric oxide.

Peroxyacetylnitrate Production

Nitrogen dioxide (NO2), oxygen (O2) and hydrocarbons (unburnt petrol) react in the presence of sunlight to produce peroxyacetylnitrate (CH3CO-OO-NO2):

NO2(g) + O2(g) + hydrocarbons 

sunlight

CH3CO-OO-NO2(g)

Catalytic Converters

Catalytic converters on motor vehicle exhausts are a way of trying to reduce the carbon monoxide and nitrogen oxide emissions.

The catalyst used is either platinum or a combination of platinum and rhodium.

The platinum catalyses the reaction of unburnt hydrocarbon (such as pentane) and oxygen (O2) to produce carbon dioxide (CO2) and water vapour (H2O):

C5H12
(pentane)

+

8O2

platinum catalyst
------------------->

5CO2

+

6H2O

The rhodium catalyses the reaction of carbon monoxide (CO) and nitric oxide (NO) to form carbon dioxide (CO2) and nitrogen gas (N2):

2CO + 2NO

rhodium catalyst
------------------->

2CO2 + N2

The reduction of nitric oxide (NO) to nitrogen gas (N2) must proceed more quickly than the oxidation of carbon monoxide (CO) to carbon dioxide (CO2) or else all the carbon monoxide will be oxidised to carbon dioxide before it can be used to reduce the nitric oxide.

Motor vehicles can only use catalytic converters if they use unleaded petrol since the lead in petrol renders the catalyst inactive.

二、教学要求

1. 要求深刻理解与熟练掌握的重点内容有:

1)大气污染分类与特征;

2)主要大气污染物及其来源;

3)污染气象学原理。
    2.  
要求一般性理解与掌握的内容有:大气污染控制技术
     3.
难点:1)空气污染指数(API: Air pollution index)计算; 2)光化学烟雾形成机理与产物。

三、教学方法

讲授,采用问题导入法(Question- based learning),穿插课堂讨论。

四、教学过程

1. 说明本章学习目的(Learning Objectives

Learning  Objectives

When you are finished with this session you should be able to:

& #8226;      Define air  pollutants  and  air pollution water pollution.

& #8226;      Describe the major effects of air pollution on human health and other living things.

& #8226;      Describe the major causes of air pollution and types of sources.

& #8226;      Name and summarize the methods of air pollution control. i.e. Cyclonic separator, fabric filter, wet scrubber and electrostatic precipitator.

  2. 展示大气污染图片,说明其严重性(穿插学生讲述周围大气污染现象)

3. 布置小组学习课外作业:4个小组,每个小组学习一种常规的颗粒物污染控制技术(Cyclonic separator, fabric filter, wet scrubber and electrostatic precipitator),制作PPT,下一节课在课堂做陈述(presentation


第十一章 水污染(WATER POLLUTION

4学时)

 

一、教学内容

CHAPTER 11 WATER POLLUTION

11.1 INTRODUCTION

11.1.1 WATER RESOURCES

Water is generally classified into two groups: Surface Water and Ground Water.

Surface water is just what the name implies; it is water found in a river, lake or other surface impoundment. This water is usually not very high in mineral content, and many times is called "soft water" even though it usually is not. Surface water is exposed to many different contaminants, such as animal wastes, pesticides, insecticides, industrial wastes, algae and many other organic materials. Even surface water found in a pristine mountain stream possibly contains Giardia or Coliform Bacteria from the feces of wild animals, and should be boiled or disinfected by some means prior to drinking.

Ground Water is that which is trapped beneath the ground. Rain that soaks into the ground, rivers that disappear beneath the earth, melting snow are but a few of the sources that recharge the supply of underground water. Because of the many sources of recharge, ground water may contain any or all of the contaminants found in surface water as well as the dissolved minerals it picks up during it's long stay underground. Waters that contains dissolved minerals, such as calcium and magnesium above certain levels are considered "hard water" Because water is considered a "solvent", ie, over time it can break down the ionic bonds that hold most substances together, it tends to dissolve and 'gather up' small amounts of whatever it comes in contact with. For instance, in areas of the world where rock such as limestone, gypsum, fluorspar, magnetite, pyrite and magnesite are common, well water is usually very high in calcium content, and therefore considered "hard".

Due to the different characteristics of these two types of water, it is important that you know the source of your water -- Surface or Ground. Of the 326 million cubic miles of water on earth, only about 3% of it is fresh water; and 3/4 of that is frozen. Only 1/2 of 1% of all water is underground; about 1/50th of 1% of all water is found in lakes and streams. The average human is about 70% water. You can only survive 5 or less days without water.