Unit 2 I think life is better today
Class Type
Reading and writing
Objectives
Enable students to read and understand the passage” Life in the past.” Enable student to write a composition about the
advantages and disadvantages of life today including the main points and the examples.
Key structure
The comparative degree and the superlative degree of adjectives.
Difficulties
How to write an argument using the main points and the examples.
Vocabulary
eldest, married, couple, diet
fall off, get married
Periods
1
Procedure
Lead-in
Review. Translate the phrases in Unit 1 into English.
Step 1
Look at these Beijing’s pictures. Say what life was like in the past and what life is like today.
Step 2
Get the students look at the photos and talk about the changes.
Step 3
Skim the passage and answer the questions.
Step 4
Read and take notes on Mrs. Li says about the points in Activity 1.
Step 5
Talk about the changes of life for Mrs. Li.
Step 6
Work in groups and talk about the changes in your hometown. Then report it to the class.
Step 7
Complete the passage with the words and expression in the box.
Step 8
Ask Ss to Write a passage about the advantages and disadvantages of life today.
Step 11
Language points: explain the key words and phrases in Unit 2.
课件64张PPT。Unit 2 I think life is better today Module 31、天就要黑了。
2、就要完成了！
3、你觉得今天的生活比过去更好吗?
4、人们比过去活得长。
5、懂得更多的医学Revision It’s getting late.Nearly finished!Do you think that life is better today than in the past?They live longer than they did in the past. know more about medicine6、如何处理平常的疾病
7、不像过去锻炼那么多
8、我认为…
9、更少地骑自行车
10、更多的财富有时候意味着更少的健康。how to deal with the ordinary diseasesdon’t take as much exercise as they used toI suppose that …use one’s bikes lessMore health sometimes means less health.11、污染加倍。
12 、象50年前他们那样艰苦地工作
13、很少有人说他们有足够的空闲时间。
14、你为什么不去问问?
The pollution is doubled.work as hard as they did 50 years ago.People seldom say they have enough spare time. Why don’t you go and ask?
= Why not go and ask?15、记得讲话要大声点
16、耳朵有点聋
Remember to speak up!a bit deafLook at these Beijing’s pictures. Say what life was like in the past and what life is like today.roads --- narrowhouses --- small, crowdedring roads --- widebuildings --- tall, brightliving conditions --- hardliving conditions --- comfortablecommunications --- simple, slowin the pastat presentcommunications --- various, quick, easyLook at the woman in the photo. How do you think she feels? Think about what she will talk about. family
health
work
educationFamily: bigger, five children
Food:
Work:
Education:Read and take notes on what Mrs. Li says about the points in Activity 1. Then complete the notes and more points of your own.Life in the pastsimple, meat only once or twice a yearhard and difficult work, long hoursexpensive, often only for boysFamily: smaller; one child
Life nowFood: more food and netter food
Work: interesting jobs for boys and girls
Education: good schools for everyoneRead the passage again and answer the questions.What kind of article is it?
Where does Mrs Li live?
An interview.Mrs. Li lives in Beijing.3. How often could Mrs Li eat meat in the past?
4. Why does Mrs Li feel lonely sometimes?
Once or twice a year.Because her daughter can’t come to see her often.Work in pairs and talk about the advantages and disadvantages of life now for Mrs Li.Talk about the changes in your hometown. Then report it to the class.What was / were … like in the past?
What has happened to … nowadays?
What will … be like in the future?live in low houseslive in tall buildingsplant crops with the
help of farm animalsplant crops with the
help of farm machinesstudy in a modern schoolstudy in an old schoolComplete the passage with the words and expression in the box. candles cold generally speaking
postman tiny traffic Mrs. Li’s father was a _______________. He often worked outside for twelve hours a day in the summer heat or in the winter ____________. They lived in a __________
house and used _________________ for light. postman cold tinycandlesMrs. Li says that _______________, life is better today. But not everything is satisfying. There are some things that she is not happy with, for example, the _________________.generally speaking trafficWrite a passage about the advantages
and disadvantages of life today.Write a composition.First, consider it carefully.Next, draw up an outline.Then, write the composition.Finally, check over the composition.● Choose two or three points from the notes in Activity 2 to write about:
Families are smaller …
● Give examples or reasons to support those points.
Most people only have one child today.● For each of the points you choose, write about an advantage and / or a disadvantage. Use the words however, but, although or used to where appropriate.
Families are smaller because most people only have one child today. As a result, families have more money to spend on their child. However, an only child may feel lonely…
● Finish the passage with your conclusion.
Generally speaking, I think ...The Advantages and Disadvantages of Life TodaySample Although transport is easier than it used to be, we now have much more traffic, which means it is harder to cross the road. There are more kinds of food now than before, but many people eat too much and don’t take enough exercise. Education and work for girls are much better than they used to be. Generally speaking, I think life is better, but it is nosier and busier.请以“city life and country life”为题，根据以下提示写一篇不少于80词的英语短文。 提示：1.城市生活的优缺点； ????? 2.乡村生活的优缺点； ????? 3.自己的观点。 I have lived in this city for two years, but before that I lived with my family in a village about a hundred miles away from here. Life is very different in two places, but there are things that I like about each of them.
In the country it is quiet and beautiful because there are not many people. The air is clean, and there is beautiful scenery all around. The people who live in the country seem friendly and helpful to their neighbors. The cost of living is low there because food is usually cheap. I like living in the city, too. In the city there are interesting things to do all the time. People have a big choice of activities. There are latest?movies, and most of the theatres are good. Everything is convenient here, because in the city you usually live close to grocery stores and schools. Traffic is efficient, so it is easy to get from one place to another.
Every coin has two sides. You can decide where to live.1. … looking after us was more than a full - time job.Language points “more than +名词”表示“不只是，不仅仅是”
He is more than a father to her.
他待她胜过父亲。
Kate?was?more?than?a?teacher.?She?also?did?what?she?could?to?take?care?of?her?pupils.?
凯特不仅仅是位教师，她还尽其所能照顾她的学生。?more?than与数词连用，意思是“多于，大于，超过”。例如：?
I?have?known?him?for?more?than?twenty?years.
我认识他已超过二十年了。?
?
?more?than与形容词连用，表示“非常、十分”。例如：?
They?were?more?than?happy?to?see?us?come?back?from?the?holiday.?
看到我们度假归来，他们异常高兴。?知识链接 afford v. 担负得起(……的费用、损失、后果等), 常用在can和be able to之后; 通常构成短语afford sth.或afford to do sth.。
The boy wants to see a movie, but he can’t afford a ticket.
那个男孩想看场电影, 但却买不起票。
She can’t afford to go abroad.
她没有足够的钱去国外。2. … because my family couldn’t afford it.答案：can't afford to do sth. “负担不起”是固定搭配，故答案选Ｂ。句意：我们不能再浪费时间了。There’s a lot to do. We can’t ________ to waste any time. (2011年江苏省无锡市中考) A. wait B. afford
C. want D. have根据句意和所给解释补全句中的单词。
The house is too dear. I can’t ______ it. (be able to meet the cost of)
The man had enough money and he could afford ______ the famous car.
A. to buy ???????? B. buying ?????????
C. buy ???? D. bought
affordAprovide 是“提供”之意, 通常构成provide sb. with sth.或provide sth. for sb.
The school provided the students with many books.
= The school provided many books for the students.
学校向学生提供了很多书。知识链接supply意为“供给；供应”, 通常构成supply sth. to sb.或supply sb. with sth.。supply还可以作名词。如:
Water is in short supply in this area.
这个地区水供应不足。
The government supplies some food and clothes to the poor.
政府给贫困群众提供了一些食物和衣服。 用afford, supply 或provide的适当形式填空。
Last weekend, we held a food festival. I
_________ noodles and dumplings for it.
2. In this area, food is in short _______.
3. When I saw the information about homeless
children on the Internet, I decided to
_________________ them with help.
4. My brother needs a computer, but he can’t
_________ to buy one. providedsupplyprovide / supplyafford education n. (各人的)教育；学业
More money should be spent on?education.??
应当在教育方面投入更多的资金。
She received a medical?education?in Japan. ??
她在日本受过医学教育。
He gave his son a first-rate?education. ??
他让他的儿子接受了一流的教育。
educational adj. 教育的；有教育意义的3. She has a good education.education一般用作不可数名词，但
表示一段或一种“教育”时, 其前可
加不定冠词; 在有形容词修饰时, 则
一定要加不定冠词。--- What are you reading, Jane?
--- Some books on _______ education. I’m
now interested in _______ education of
young people.
A. an; the B. /; the
C. the; an D. an; /
解析: 第一个 education 意为“教育; 教育学”，为不可数名词，因此不用冠词; 而第二个 education 表示特指，意为“年轻人的教育”，因此用定冠词，故答案为 B。
B? get married 意思是“结婚”，表示动作。如：
We had known each other for years before we got married.
They have had a happy life since they got married.
be married强调结婚了的状态, 可与表示一段时间的状语连用; 而get married只能跟表示某一时间点的状语连用。4. … even after getting married. be busy doing sth. 忙于做某事
He is busy preparing for the examination.
他忙着准备考试。
He is busy writing a letter.
他正忙着写信。
萨莉现在忙着照顾婴儿。
Sally is now busy _____________ the baby.5. … she is busy working every day.taking care of 【2013山东枣庄】汉译英
这些学生现在忙于观看中国和美国的篮球赛。（be?busy?doing）These?pupils / students?are?busy?watching?
the?basketball?game / competition?between?
China?and?the?U.S.?now.? be busy with … 忙于做某事
He is busy with some important work.
他正忙于处理一些重要的事情。
busy用于too ... to结构时可接动词不定式。
She is too busy to look after her child.
她太忙，没有时间照料孩子。知识拓展6. It’s so difficult to cross the road. It’s … (for sb.) to do sth. 这是一个很常用的句型, 意思是“(对某人来说) 做某事是…….”。例如：
It’s normal (for you) to feel nervous before an exam.
It wasn’t easy (for me) to work out the maths problem.
It’s important (for him) to know the truth.7. I really enjoy watching … enjoy v. 享受；喜欢
enjoy后可接名词、代词、反身代词或动名词，但不能接不定式。
Now that I am free, I can enjoy music for a while.
既然有空，我可以享受一下音乐。
I enjoy reading the Chinese classics.
我喜欢读中国名著。【2013 上海】48. The retired couple enjoy _______ photos. They always go out with their cameras
A. take B. took
C. to take D. taking
【2013 湖南衡阳】25. —Laura enjoys ________ story books.
—Me, too.
A. reading B. read C. to readfinish, practise, imagine, worth,
forgive, mind, miss, enjoy, suggest,
avoid, escape, stand, keep …只接动名词的动词：只接不定式的动词：want, hope, fail, manage, offer, refuse, appear, wish, expect, decide, agree, promise, happen, determine …知识链接【2013湖南娄底】26. —Would you mind ________ the window? It's very hot.
— No, not at all.
A. open B. to open C. opening
【答案】C
【解析】考查固定用法, mind + doing表示介意做某事。故答案为C。【2013天津】30. He promised ______his old friend during his stay in Tianjin.
A. see B. seeing C. saw D. to see
【答案】D
【解析】promise to do sth.意为“许诺做某事”。故选D。【2013河北】39. The children decide _____
their school yard this Friday afternoon.
A. clean B. to clean
C. cleaning D. cleaned
【答案】B
【解析】decide后接动词不定式，表示决定去做某事，故答案应选B。【2013四川雅安】8. — Can you finish ________ these books before 10 o'clock?
— Yes, I can.
A. to read B. read
C. reads D. reading
【答案】D
【解析】finish后面要跟名词或动名词作宾语，所以选择答案D。8. Generally speaking, I think life is better today. generally speaking 一般来说，大致说
常位于句首，与in general 同义。
Generally speaking, we enjoyed the trip.
总的来说，我们这次旅行很愉快。
Generally speaking, the parks are full on holidays.
一般来说，假日里公园都挤满人。类似结构还有 :
exactly speaking 准确地说；确切地说
strictly speaking 严格来说；?严格说来
frankly?speaking 坦白说, 老实说
honestly?speaking 老实说知识链接Pollution
Air pollution from World War II production.
Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i.e. physical systems or living organisms .[1] Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy. Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels. Pollution is often classed as point source or nonpoint source pollution. The Blacksmith Institute issues annually a list of the world's worst polluted places. In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine and Zambia.21·cn·jy·com
History
Throughout history from Ancient Greece to Andalusia, Ancient China, central Europe during the Renaissance until today, philosophers ranging from Aristotle, Al-Farabi, Al-Ghazali, Averroes, Buddha, Confucius, Dante, Hegel, Avicenna, Lao Tse, Maimonedes, Montesquieu, Nussbaum, Plato, Socrates and Sun Tzu wrote about the pollution of the body as well as the mind and soul.2-1-c-n-j-y
Prehistory
Humankind has had some effect upon the environment since the Paleolithic era during which the ability to generate fire was acquired. In the Iron Age, the use of tooling led to the practice of metal grinding on a small scale and resulted in minor accumulations of discarded material probably easily dispersed without too much impact. Human wastes would have polluted rivers or water sources to some degree. However, these effects could be expected predominantly to be dwarfed by the natural world.
Ancient cultures
The first advanced civilizations of Mesopotamia, Egypt, India, China, Persia, Greece and Rome increased the use of water for their manufacture of goods, increasingly forged metal and created fires of wood and peat for more elaborate purposes (for example, bathing, heating). The forging of metals appears to be a key turning point in the creation of significant air pollution levels. Core samples of glaciers in Greenland indicate increases in air pollution associated with Greek, Roman and Chinese metal production[2]. Still, at this time the scale of higher activity probably did not disrupt ecosystems.【出处：21教育名师】
Middle Ages
The European Dark Ages during the early Middle Ages probably saw a reprieve in widespread pollution, in that industrial activity fell, and population levels did not grow rapidly. Toward the end of the Middle Ages populations grew and concentrated more within cities, creating pockets of readily evident contamination. In certain places air pollution levels were recognizable as health issues, and water pollution in population centers was a serious medium for disease transmission from untreated human waste.
Since travel and widespread information were less common, there did not exist a more general context than that of local consequences in which to consider pollution. Air pollution was largely from wood burning which must be properly ventilated. Septic contamination or poisoning of a clean drinking water source was very easily fatal, and contamination was not well understood. Bad septic contamination and pollution contributed greatly to the Bubonic plague.21*cnjy*com
Official acknowledgement
But gradually increasing populations and the proliferation of basic industrial processes saw the emergence of a civilization that began to have a much greater collective impact on its surroundings. It was to be expected that the beginnings of environmental awareness would occur in the more developed cultures, particularly in the densest urban centers. The first medium warranting official policy measures in the emerging western world would be the most basic: the air we breathe.
The earliest known writings concerned with pollution were Arabic medical treatises written between the 9th and 13th centuries, by physicians such as al-Kindi (Alkindus), Qusta ibn Luqa (Costa ben Luca), Muhammad ibn Zakarīya Rāzi (Rhazes), Ibn Al-Jazzar, al-Tamimi, al-Masihi, Ibn Sina (Avicenna), Ali ibn Ridwan, Ibn Jumay, Isaac Israeli ben Solomon, Abd-el-latif, Ibn al-Quff, and Ibn al-Nafis. Their works covered a number of subjects related to pollution such as air contamination, water contamination, soil contamination, solid waste mishandling, and environmental assessments of certain localities.[3]
King Edward I of England banned the burning of sea-coal by proclamation in London in 1272, after its smoke had become a problem.[4][5] But the fuel was so common in England that this earliest of names for it was acquired because it could be carted away from some shores by the wheelbarrow. Air pollution would continue to be a problem in England, especially later during the industrial revolution, and extending into the recent past with the Great Smog of 1952. This same city also recorded one of the earlier extreme cases of water quality problems with the Great Stink on the Thames of 1858, which led to construction of the London sewerage system soon afterward.
It was the industrial revolution that gave birth to environmental pollution as we know it today. The emergence of great factories and consumption of immense quantities of coal and other fossil fuels gave rise to unprecedented air pollution and the large volume of industrial chemical discharges added to the growing load of untreated human waste. Chicago and Cincinnati were the first two American cities to enact laws ensuring cleaner air in 1881. Other cities followed around the country until early in the 20th century, when the short lived Office of Air Pollution was created under the Department of the Interior. Extreme smog events were experienced by the cities of Los Angeles and Donora, Pennsylvania in the late 1940s, serving as another public reminder.[6]
Modern awareness
Early Soviet poster, before the modern awareness: "The smoke of chimneys is the breath of Soviet Russia"
Pollution became a popular issue after WW2, when the aftermath of atomic warfare and testing made evident the perils of radioactive fallout. Then a conventional catastrophic event The Great Smog of 1952 in London killed at least 8000 people. This massive event prompted some of the first major modern environmental legislation, The Clean Air Act of 1956.
Pollution began to draw major public attention in the United States between the mid-1950s and early 1970s, when Congress passed the Noise Control Act, the Clean Air Act, the Clean Water Act and the National Environmental Policy Act.
Bad bouts of local pollution helped increase consciousness. PCB dumping in the Hudson River resulted in a ban by the EPA on consumption of its fish in 1974. Long-term dioxin contamination at Love Canal starting in 1947 became a national news story in 1978 and led to the Superfund legislation of 1980. Legal proceedings in the 1990s helped bring to light Chromium-6 releases in California--the champions of whose victims became famous. The pollution of industrial land gave rise to the name brownfield, a term now common in city planning. DDT was banned in most of the developed world after the publication of Rachel Carson's Silent Spring.
The development of nuclear science introduced radioactive contamination, which can remain lethally radioactive for hundreds of thousands of years. Lake Karachay, named by the Worldwatch Institute as the "most polluted spot" on earth, served as a disposal site for the Soviet Union thoroughout the 1950s and 1960s. Second place may go to the to the area of Chelyabinsk U.S.S.R. (see reference below) as the "Most polluted place on the planet".
Nuclear weapons continued to be tested in the Cold War, sometimes near inhabited areas, especially in the earlier stages of their development. The toll on the worst-affected populations and the growth since then in understanding about the critical threat to human health posed by radioactivity has also been a prohibitive complication associated with nuclear power. Though extreme care is practiced in that industry, the potential for disaster suggested by incidents such as those at Three Mile Island and Chernobyl pose a lingering specter of public mistrust. One legacy of nuclear testing before most forms were banned has been significantly raised levels of background radiation.
International catastrophes such as the wreck of the Amoco Cadiz oil tanker off the coast of Brittany in 1978 and the Bhopal disaster in 1984 have demonstrated the universality of such events and the scale on which efforts to address them needed to engage. The borderless nature of atmosphere and oceans inevitably resulted in the implication of pollution on a planetary level with the issue of global warming. Most recently the term persistent organic pollutant (POP) has come to describe a group of chemicals such as PBDEs and PFCs among others. Though their effects remain somewhat less well understood owing to a lack of experimental data, they have been detected in various ecological habitats far removed from industrial activity such as the Arctic, demonstrating diffusion and bioaccumulation after only a relatively brief period of widespread use.
Growing evidence of local and global pollution and an increasingly informed public over time have given rise to environmentalism and the environmental movement, which generally seek to limit human impact on the environment.【来源：21·世纪·教育·网】
Forms of pollution
The major forms of pollution are listed below along with the particular pollutants relevant to each of them:
Air pollution, the release of chemicals and particulates into the atmosphere. Common gaseous air pollutants include carbon monoxide, sulfur dioxide, chlorofluorocarbons (CFCs) and nitrogen oxides produced by industry and motor vehicles. Photochemical ozone and smog are created as nitrogen oxides and hydrocarbons react to sunlight. Particulate matter, or fine dust is characterized by their micrometre size PM10 to PM2.5.
Water pollution, by the release of waste products and contaminants into surface runoff into river drainage systems, leaching into groundwater, liquid spills, wastewater discharges, eutrophication and littering.
Soil contamination occurs when chemicals are released by spill or underground leakage. Among the most significant soil contaminants are hydrocarbons, heavy metals, MTBE[7], herbicides, pesticides and chlorinated hydrocarbons.
Littering
Radioactive contamination, resulting from 20th century activities in atomic physics, such as nuclear power generation and nuclear weapons research, manufacture and deployment. (See alpha emitters and actinides in the environment.) 【版权所有：21教育】
Noise pollution, which encompasses roadway noise, aircraft noise, industrial noise as well as high-intensity sonar.
Light pollution, includes light trespass, over-illumination and astronomical interference.
Visual pollution, which can refer to the presence of overhead power lines, motorway billboards, scarred landforms (as from strip mining), open storage of trash or municipal solid waste.
Thermal pollution, is a temperature change in natural water bodies caused by human influence, such as use of water as coolant in a power plant.
Pollutants
Main article: Pollutant
A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence
Sources and causes
Air pollution comes from both natural and manmade sources. Though globally manmade pollutants from combustion, construction, mining, agriculture and warfare are increasingly significant in the air pollution equation.[8]
Motor vehicle emissions are one of the leading causes of air pollution.[9][10][11] China, United States, Russia, Mexico, and Japan are the world leaders in air pollution emissions. Principal stationary pollution sources include chemical plants, coal-fired power plants, oil refineries,[12] petrochemical plants, nuclear waste disposal activity, incinerators, large livestock farms (dairy cows, pigs, poultry, etc.), PVC factories, metals production factories, plastics factories, and other heavy industry. Agricultural air pollution comes from contemporary practices which include clear felling and burning of natural vegetation as well as spraying of pesticides and herbicides[13]
Some of the more common soil contaminants are chlorinated hydrocarbons (CFH), heavy metals (such as chromium, cadmium--found in rechargeable batteries, and lead--found in lead paint, aviation fuel and still in some countries, gasoline), MTBE, zinc, arsenic and benzene. In 2001 a series of press reports culminating in a book called Fateful Harvest unveiled a widespread practice of recycling industrial byproducts into fertilizer, resulting in the contamination of the soil with various metals. Ordinary municipal landfills are the source of many chemical substances entering the soil environment (and often groundwater), emanating from the wide variety of refuse accepted, especially substances illegally discarded there, or from pre-1970 landfills that may have been subject to little control in the U.S. or EU. There have also been some unusual releases of polychlorinated dibenzodioxins, commonly called dioxins for simplicity, such as TCDD.[14]
Pollution can also be the consequence of a natural disaster. For example, hurricanes often involve water contamination from sewage, and petrochemical spills from ruptured boats or automobiles. Larger scale and environmental damage is not uncommon when coastal oil rigs or refineries are involved. Some sources of pollution, such as nuclear power plants or oil tankers, can produce widespread and potentially hazardous releases when accidents occur.21·世纪*教育网
In the case of noise pollution the dominant source class is the motor vehicle, producing about ninety percent of all unwanted noise worldwide.
Effects
Human health
Overview of main health effects on humans from some common types of pollution. [15] [16] [17]
Adverse air quality can kill many organisms including humans. Ozone pollution can cause respiratory disease, cardiovascular disease, throat inflammation, chest pain, and congestion. Water pollution causes approximately 14,000 deaths per day, mostly due to contamination of drinking water by untreated sewage in developing countries. Oil spills can cause skin irritations and rashes. Noise pollution induces hearing loss, high blood pressure, stress, and sleep disturbance. Mercury has been linked to developmental deficits in children and neurologic symptoms. Lead and other heavy metals have been shown to cause neurological problems. Chemical and radioactive substances can cause cancer and as well as birth defects.www-2-1-cnjy-com
Ecosystems
Sulphur dioxide and nitrogen oxides can cause acid rain which lowers the pH value of soil.
Nitrogen oxides are removed from the air by rain and fertilise land which can change the species composition of ecosystems.
Soil can become infertile and unsuitable for plants. This will affect other organisms in the food web. 21世纪教育网版权所有
Smog and haze can reduce the amount of sunlight received by plants to carry out photosynthesis and leads to the production of tropospheric ozone which damages plants. www.21-cn-jy.com
Invasive species can out compete native species and reduce biodiversity. Invasive plants can contribute debris and biomolecules (allelopathy) that can alter soil and chemical compositions of an environment, often reducing native species competitiveness. 【来源：21cnj*y.co*m】
Biomagnification describes situations where toxins (such as heavy metals) may pass through trophic levels, becoming exponentially more concentrated in the process.
Carbon dioxide emissions cause ocean acidification, the ongoing decrease in the pH of the Earth's oceans as CO2 becomes dissolved.
The emission of greenhouse gases leads to global warming which affects ecosystems in many ways.
Regulation and monitoring
Main article: Regulation and monitoring of pollution
To protect the environment from the adverse effects of pollution, many nations worldwide have enacted legislation to regulate various types of pollution as well as to mitigate the adverse effects of pollution.
Pollution control
Pollution control is a term used in environmental management. It means the control of emissions and effluents into air, water or soil. Without pollution control, the waste products from consumption, heating, agriculture, mining, manufacturing, transportation and other human activities, whether they accumulate or disperse, will degrade the environment. In the hierarchy of controls, pollution prevention and waste minimization are more desirable than pollution control.
Pollution control devices
Dust collection systems
Cyclones
Electrostatic precipitators
Baghouses
Scrubbers
Baffle spray scrubber
Cyclonic spray scrubber
Ejector venturi scrubber
Mechanically aided scrubber
Spray tower
Wet scrubber
Sewage treatment
API oil-water separators[18][12]
Sedimentation (water treatment)
Dissolved air flotation (DAF)
Activated sludge biotreaters
Biofilters
Powdered activated carbon treatment
Vapor recovery systems
Perspectives
The earliest precursor of pollution generated by life forms would have been a natural fun_ction of their existence. The attendant consequences on viability and population levels fell within the sphere of natural selection. These would have included the demise of a population locally or ultimately, species extinction. Processes that were untenable would have resulted in a new balance brought about by changes and adaptations. At the extremes, for any form of life, consideration of pollution is superseded by that of survival.21教育网
For humankind, the factor of technology is a distinguishing and critical consideration, both as an enabler and an additional source of byproducts. Short of survival, human concerns include the range from quality of life to health hazards. Since science holds experimental demonstration to be definitive, modern treatment of toxicity or environmental harm involves defining a level at which an effect is observable. Common examples of fields where practical measurement is crucial include automobile emissions control, industrial exposure (eg Occupational Safety and Health Administration (OSHA) PELs), toxicology (eg LD50), and medicine (eg medication and radiation doses).21cnjy.com
"The solution to pollution is dilution", is a dictum which summarizes a traditional approach to pollution management whereby sufficiently diluted pollution is not harmful.[19][20] It is well-suited to some other modern, locally-scoped applications such as laboratory safety procedure and hazardous material release emergency management. But it assumes that the dilutant is in virtually unlimited supply for the application or that resulting dilutions are acceptable in all cases.2·1·c·n·j·y
Such simple treatment for environmental pollution on a wider scale might have had greater merit in earlier centuries when physical survival was often the highest imperative, human population and densities were lower, technologies were simpler and their byproducts more benign. But these are often no longer the case. Furthermore, advances have enabled measurement of concentrations not possible before. The use of statistical methods in evaluating outcomes has given currency to the principle of probable harm in cases where assessment is warranted but resorting to deterministic models is impractical or unfeasible. In addition, consideration of the environment beyond direct impact on human beings has gained prominence.
Yet in the absence of a superseding principle, this older approach predominates practices throughout the world. It is the basis by which to gauge concentrations of effluent for legal release, exceeding which penalties are assessed or restrictions applied. The regressive cases are those where a controlled level of release is too high or, if enforceable, is neglected. Migration from pollution dilution to elimination in many cases is confronted by challenging economical and technological barriers.
Greenhouse gases and global warming
Main article: Global warming
Historical and projected CO2 emissions by country. Source: Energy Information Administration.[21][22] 21*cnjy*com
Carbon dioxide, while vital for photosynthesis, is sometimes referred to as pollution, because raised levels of the gas in the atmosphere are affecting the Earth's climate. Disruption of the environment can also highlight the connection between areas of pollution that would normally be classified separately, such as those of water and air. Recent studies have investigated the potential for long-term rising levels of atmospheric carbon dioxide to cause slight but critical increases in the acidity of ocean waters, and the possible effects of this on marine ecosystems.21教育名师原创作品
