environmental problems

If you have a good memory, recite it to scare the teacher.

I. Concept of environment

The so-called environment always exists as the opposite of a central thing. It changes with different central things, and changes with the change of central things. The surrounding things related to a central thing are the environment of this central thing.

The environment studied by environmental science, the central thing of which is human beings, is the external world with human beings as the main body, that is, the environment necessary for human survival and reproduction, or the synthesis of material conditions, which can be divided into natural environment and artificial environment (see the right picture).

The structure of human environment

The natural environment existed before the appearance of human beings, and it is the general name of natural conditions and natural resources necessary for human survival, life and production, that is, the sum of natural factors such as sunlight, temperature, climate, geomagnetism, air, water, rocks, soil, animals and plants, microorganisms and crustal stability, which can be summarized in one sentence? Quot The sum of all natural substances, energy and natural phenomena that directly or indirectly affect human beings is sometimes called the environment.

In addition to the natural environment, the environmental factors formed by human activities, including artificial buildings (such as cities and villages), artificial products (such as various chemicals), energy, and the relationship between people formed in human activities, constitute the artificial environment in environmental science.

According to the Environmental Law of People's Republic of China (PRC), "environment refers to the sum of natural and artificially modified natural factors that affect human survival and development, including atmosphere, water, ocean, land, mineral deposits, forests, grasslands, wildlife, natural relics, cultural relics, nature reserves, scenic spots, cities and villages."

ISO 1400 1 standard defines the environment as the external existence of organization operation, including air, water, land, natural resources, plants, animals, people and their relationships.

Note: In this sense, external existence extends from the organization to the global system.

Second, what is the environmental problem?

Human understanding of what is an environmental problem has gone through a development process. In the sixties and seventies of this century, people's understanding of environmental pollution was still limited to this, equating environmental pollution with environmental problems. However, floods, droughts, insect disasters, earthquakes and storms are all considered natural disasters. However, with the rapid economic development in recent decades, natural disasters have become increasingly frequent, and the number of people affected and losses have surged. People have come to realize that the main causes of flood and drought disasters are cutting down trees, destroying vegetation and other behaviors that seriously endanger the ecological balance due to population growth and blind development of agricultural production. China 1998 Yangtze River flood is largely the result of long-term deforestation and soil erosion in its upper reaches. Natural disasters caused by human destruction of the ecological environment also belong to the category of environmental problems.

Therefore, environmental problems, in terms of their scope, can be understood in a broad sense and a narrow sense.

Broadly speaking, all objective problems that directly or indirectly affect the survival and development of human beings due to the destruction of ecological balance by natural forces or manpower are environmental problems.

Narrow sense: all the problems that make the natural ecosystem out of balance just because of human production and life activities, and then affect human survival and development, are all environmental problems in a narrow sense.

If we consider the root causes of environmental problems, environmental problems can be divided into two categories:

First environmental problems: environmental problems caused by natural forces mainly refer to natural disasters such as earthquakes, volcanoes, tsunamis, floods and droughts.

Eco-environmental problems (second environmental problems): Environmental problems caused by human activities can be divided into two categories: environmental pollution and ecological destruction.

The environmental problems involved in ISO 14000 series standards are mainly environmental pollution and ecological destruction.

Environmental pollution generally means that harmful substances or factors enter the environment, and spread, migrate and transform in the environment, changing the structure and function of the environmental system and adversely affecting the survival and development of human beings and other organisms.

The classification of environmental pollution is as follows:

The destruction of ecological environment is the destruction of natural ecological system, and it is the harm caused by human activities directly acting on nature. Human plunders resources from nature, resulting in resource shortage and ecological destruction, thus causing a serious ecological crisis.

Third, the emergence and development of environmental problems.

(A) environmental problems caused by the agricultural revolution

For a long time after its birth, human beings were only gatherers and predators of natural food and had little impact on the environment. At that time, "production" was very dependent on the natural environment. Humans mainly use life activities, physiological metabolic processes and the environment to transform matter and energy, mainly using the environment, and rarely consciously transforming the environment. What if it was also sent at that time? Quot "Environmental problems", which are mainly due to the natural growth of population, indiscriminate logging and abuse of resources, resulting in the lack of means of subsistence and famine.

Therefore, before the agricultural revolution, the environment basically changed according to the laws of nature, and people were still attached to the natural environment to a large extent.

Subsequently, human beings learned to cultivate and domesticate animals and plants, and started agriculture and animal husbandry, which was a great revolution in the history of production and development. With the development of agriculture and animal husbandry, the role of human beings in improving the environment has become more and more obvious, but at the same time, corresponding environmental problems have emerged, such as massive deforestation, grassland destruction, slash-and-burn cultivation, blind land reclamation, etc., which often lead to serious soil erosion, frequent floods and droughts, and land desertification; Another example is the construction of water conservancy and unreasonable irrigation, which often leads to soil salinization and swamp, resulting in the prevalence of some infectious diseases.

The ecological damage caused by the emergence of agricultural civilization has reached a considerable scale in some areas, and has produced serious social consequences. Historically, the improper development of agricultural civilization has brought about the deterioration of the ecological environment and led to the decline of civilization.

The ancient Egyptian civilization born in the Nile Valley can be said to be "the gift of the Nile". Historically, every summer, silt rich in inorganic minerals and organic matter in the upper reaches of rivers will flood, leaving Egypt with a thin layer of sediment. The amount will not block the irrigation canal and affect irrigation and flood discharge, but it is enough to supplement the inorganic mineral nutrients absorbed by crops harvested from the field, which almost perfectly meets the demand for organic matter in farmland, so that this land can produce a large amount of food to raise a large number of people born on it. Historians believe that it is this unparalleled natural condition that has created Egypt's long and splendid civilization. However, due to the continuous logging, overgrazing and reclamation in the upper reaches of the Nile, soil erosion is becoming more and more serious, and the sediment of the Nile is increasing year by year, so Egypt can no longer get that precious fertile soil. Quot Mediterranean granary has lost its former glory, and now it has become one of the poorest areas on earth.

Mesopotamia, located between the Euphrates and Tigris rivers (present-day Iraq), is the birthplace of the famous Babylonian civilization. Before BC, it used to be lush forests and fertile fields, and the rich natural environment gave birth to splendid Babylonian culture-"cuneiform", "code of hammurabi" and 60-decimal timekeeping ... The city of Babylon was the largest city in the world at that time, and it was also a famous commercial center in West Asia. The "hanging garden" built by the king of Babylon for the imperial concubine was regarded as one of the seven wonders of the world. However, while creating splendid culture and developing agriculture, Babylonians destroyed the virtuous circle of ecological environment due to endless farming, overgrazing and wanton logging, and finally turned this fertile land into a barren land ravaged by sandstorms. The long yellow sand made the kingdom of Babylon disappear from the earth 2000 years ago. Today, the population supported by this land is less than that of14 in Hammurabi's time, and the splendid city of Babylon was not excavated by archaeologists until modern times and reappeared in front of the world.

The Yellow River Basin is the birthplace of ancient civilization in China. More than 4,000 years ago, there were lush forests, abundant aquatic plants, mild climate and fertile land. According to records, in the Zhou Dynasty, the forest coverage rate of the Loess Plateau reached 53%, and a good ecological environment provided superior conditions for agricultural development. However, since the Qin and Han Dynasties, the forests in the Yellow River basin have been cut down on a large scale, which has aggravated soil erosion and increased the sediment concentration of the Yellow River. The sediment concentration of the Yellow River reached 50% in the Song Dynasty, increased to 60% in the Ming Dynasty and further reached 70% in the Qing Dynasty, which made the riverbed of the Yellow River higher and higher, and some sections were much higher than the ground, forming a "suspended river". During the rainstorm season, the river burst its banks and flooded, making the Yellow River a veritable "river disaster". At the same time, the desert area in this area is expanding day by day, and the ecological environment is deteriorating sharply.

As can be seen from the above examples, in agricultural society, ecological destruction has reached a considerable scale and has produced serious social consequences.

But generally speaking, in the era of agricultural civilization, the main environmental problem is ecological destruction. Because the human population is still very small, the scope of activities on the earth is still very limited, and the scale and influence of environmental problems are not very prominent.

(B) environmental problems brought about by the industrial revolution

With the development of productive forces, another great revolution-industrial revolution appeared in the history of production development from11960s to19th century. It makes small-scale production based on individual talents, technology and experience be replaced by large-scale production based on scientific and technological achievements, which greatly improves labor productivity, enhances human ability to use and transform the environment, and changes the composition and structure of the environment on a large scale, thus changing the material circulation system in the environment and expanding the field of human activities, but it also brings new environmental problems. Some industrialized cities and industrial enterprises in industrial and mining areas discharge a lot of waste to pollute the environment, which makes pollution incidents happen constantly. Among them, 8 incidents attracted attention.

Mas Valley incident. The temperature in Maas Valley 1930 65438+65438 in Belgium reversed from 0 to 5 days in February, and harmful gases and soot dust emitted by factories accumulated in the near-earth atmosphere. Three days later, people began to get sick. Within a week, more than 60 people died and many livestock died. This incident was mainly caused by the combined action of several harmful gases and soot dust pollution. At that time, the concentration of sulfur dioxide in the atmosphere was as high as 25 ~ 100 mg/m3.

-The Donora incident. During the period of 1948, 10,126 to 3 1 day, heavy fog continued in most parts of Donora town, Pennsylvania, USA, causing 43% of the population (59 1 1) to get sick one after another, among which This event was caused by the interaction of sulfur dioxide with metal elements and metal compounds. At that time, the concentration of sulfur dioxide in the atmosphere was as high as 0.5 ~ 2.0 mg/m3, and there were dust particles.

London smog incident. 1952 65438+from February 5 to 8, London, England, which is known as the "foggy city", suddenly many people suffered from respiratory diseases and more than 4,000 people died one after another. In the next two months, more than 8000 people died. The reason for this incident was that the concentration of dust particles in the atmosphere at that time was as high as 4.46 mg/m3, which was 0/0 times that of normal, and the concentration of sulfur dioxide was as high as 1.34mg/m3, which was 6 times that of normal.

-photochemical smog incident in Los Angeles. The oil production in Los Angeles from 65438 to 0936 stimulated the development of the local automobile industry. By the early 1940s, there were 2.5 million cars in Los Angeles, consuming about160,000 liters of gasoline every day. However, due to the low vaporization rate of automobiles, a large amount of hydrocarbons are discharged into the atmosphere every day, which forms light blue photochemical smog under the action of sunlight, making this coastal city with beautiful scenery and mild climate "the fog capital of the United States". This kind of smoke irritates people's eyes, throat and nose, causing symptoms such as eye diseases, laryngitis and headache, leading to an increase in local mortality. At the same time, it also reduced the output of oranges and pine trees hundreds of miles away.

-Minamata incident. A Japanese factory producing nitrogen fertilizer has set up a factory in Minamata City, southern Kyushu, Japan since 1908, and methylmercury compounds produced in the production process of this factory are directly discharged into Minamata Bay. From 1950, a "suicide cat" was first discovered, and then a strange disease appeared in life, which was called "Minamata disease" because doctors could not diagnose it. After years of investigation, it was found that this disease was caused by eating fish in Minamata Bay. A large number of methylmercury compounds are discharged into Minamata Bay, forming high concentration accumulation in fish. Cats and people will be poisoned and sick if they eat this polluted fish.

Toyama incident. In 1950s, Mitsui Metal Mining Company of Japan opened a zinc smelting plant in the upper reaches of Toyama Plain. The wastewater discharged from this factory contains cadmium, and this cadmium-containing water is used to irrigate farmland and make rice contain cadmium. Many people eat cadmium-containing rice and drink cadmium-containing water poisoning, and their whole body aches. So? Quot bone pain. " According to statistics, from May 1963 to May 1968, 258 patients were diagnosed and 28 died/kloc-0.

-A four-day event. In 1950s and 1960s, many petrochemical plants were established in Shikoku, a coastal city in the east of Japan. The exhaust gas from these factories containing sulfur dioxide and metal dust caused many residents to suffer from respiratory diseases such as asthma and die. 1967, a patient committed suicide because of unbearable pain. By 1970, there were more than 500 patients.

-The rice bran oil incident. 1968, in the process of producing rice bran oil in Aichi Prefecture, Kyushu, Japan, due to production errors, PCBs were mixed in rice bran oil, resulting in poisoning of more than 1400 people after eating it. Four months later, the number of poisoned people soared to more than 5,000, and 16 people died. At the same time, the use of black oil, a by-product of rice bran oil, as poultry feed caused hundreds of thousands of chickens to die.

The characteristics of environmental pollution in this period are: from industrial pollution to urban pollution and agricultural pollution; From point source pollution to non-point source pollution (rivers, lakes and oceans); Local pollution is moving towards regional and global pollution, which constitutes the first climax of global environmental problems. Since then, people have begun to face up to protecting the environment. Although the pollution problem in developed countries has been partially solved and the environmental situation has improved after nearly two decades of efforts, the environmental problems have not been completely solved. At the same time, with the development of new technological revolution, it will bring new environmental problems. Many developing countries are following the old path of developed countries. While developing economy, environmental pollution is becoming more and more serious. 1The "Bhopal Massacre" in India in February 1984 is an obvious example.

(c) Contemporary human environmental problems

As mentioned earlier, since the industrial revolution, especially since the 20th century, with the rapid progress of science and technology, the power of human beings to interfere with and transform nature has never been stronger, and the economy has developed rapidly, creating more than/kloc-0.5 trillion dollars of wealth every year. At the same time, the environment has also paid a huge price. Environmental problems have increased in frequency, intensity and scope. Generally speaking, whether it is environmental pollution or ecological destruction, the environmental quality of the contemporary world is further deteriorating.

The stage of contemporary human environmental problems began in 1984, when British scientists discovered it, and in 1985, the United States confirmed that there was an ozone hole over Antarctica, which constituted the second climax of environmental problems. At present, the core of environmental problems is the three global atmospheric environmental problems, which are closely related to human survival, such as global warming, ozone layer destruction and acid deposition, which have attracted great attention from governments and all mankind.

1, acid rain

Acid rain, also known as acid precipitation, refers to natural precipitation (wet precipitation) and precipitation of acid gases and particles (dry precipitation) with PH less than 5.6. Environmental acidification caused by acid rain is one of the biggest environmental problems in this century.

With the rapid growth of population and the development of production, the consumption of fossil fuels is increasing, and the seriousness of acid rain problem is gradually revealed. Before 1950s and 1960s, acid rain only appeared in some areas. In 1950s and 1960s, acid rain appeared in Northern Europe due to the influence of acid waste gas from industrial zones in Central Europe. From the late 1960s to the early 1980s, the harm of acid rain showed that the scope of acid rain expanded from northern Europe to central Europe, and a large area of acid rain area appeared in North America. Since 1980s, acid rain has appeared all over the world, such as China, Japan, South Korea and Southeast Asian countries in Asia, Brazil and Venezuela in South America, Nigeria and C? te d 'Ivoire in Africa.

At present, the most concentrated and largest areas of acid rain are Europe, North America and China. The regions with the highest sulfur deposition in global precipitation are Europe, the central United States and the southwest of China, and the loads are all greater than1.0g (s)/(m2 a). Other areas with high sulfur deposition are North America, the former Soviet Union and Asia-Pacific region, with a load of 0.3g (s)/(m2 a).

The harm scope of acid rain is expanding, and the harm degree is deepening. Soil acidification in Central and Northern Europe, the United States and Canada is very obvious. The acidification of water bodies affected by acid rain in the United States, Canada and northern Europe is becoming more and more serious. By the end of this century, nearly 50,000 species in Canada's 300,000 lakes will be completely extinct. The harm of acid rain to forests is common in many countries. Of the 6.5438+6.5438 billion hectares of forests in Europe, 50 million hectares are fragile and withered by acid rain. As for the phenomenon of acid rain, it exists all over the world.

In China, a large area of acid rain still exists, mainly distributed in the south of Yangtze River, east of Qinghai-Tibet Plateau and Sichuan Basin. According to the statistics of 77 cities in 1994, the average annual precipitation PH value is below 5.6, accounting for 48. 1% (Environmental Bulletin 1995).

Acid rain contains mainly sulfuric acid and nitric acid, which are converted from SO2 and NOX produced by burning fossil fuels and discharged into the atmosphere. Sulfur dioxide, in particular, is the main pollutant that forms acid rain. The development of acid rain is related to fuel consumption, energy structure, technical level and population growth. According to this analysis, although the population and economy in Europe and North America, where acid rain is most concentrated at present, will continue to grow in the future, the problem of acid rain will not be significantly aggravated. However, in developing countries, acid rain may become more and more serious due to the sharp increase in acid pollutant emissions.

2. Greenhouse effect and climate change

L) greenhouse effect and greenhouse gases

Some trace components in the atmosphere can make the short-wave radiation of the sun penetrate and heat the ground, but the thermal radiation released after the ground warms is absorbed by these components, which makes the atmosphere warm. This phenomenon is called the greenhouse effect. These trace components that can warm the earth's atmosphere are called greenhouse gases. The main greenhouse gases are CO2, CH4, N2O and CFC. The research results in the 1980s show that various man-made greenhouse gases have different effects on the global greenhouse effect, including CO2 accounting for 55%, CFC accounting for 24%, CH4 accounting for 65,438+05% and N2O accounting for 6%, so the increase of CO2 is the main reason for global warming.

2) The influence of greenhouse effect

There is a greenhouse effect in the earth's atmosphere, which keeps the earth in a normal temperature environment suitable for human survival. It is only because of the increasing scale of human activities that excessive greenhouse gases are discharged into the atmosphere, which enhances the greenhouse effect, thus causing a series of problems on a global scale.

The first problem is global warming. In the past century, the global average ground temperature has increased by 0.3℃ ~ 0.6℃. The 1980s became the hottest year in this century: 10. The global average temperature 1988 is 0.34℃ higher than the multi-year average 1949 ~ 1979 and 0.59℃ higher than that at the beginning of this century. All these prove that the earth is really warming.

Climate warming leads to sea level rise. At present, the world ocean temperature is rising at the rate of 0. 1℃ every year. In the past century, the global sea level has risen by 14.4cm on average, and the coastal sea level in China has also risen by 1 1.5cm on average, which will seriously threaten the lives and property of people in low-lying islands and coastal areas.

3) Global climate change trend

It is an established fact that the concentration of greenhouse gases in the atmosphere is rising, and it has been accepted by most people that the greenhouse effect leads to global warming. However, there are many factors that affect the global climate, and there are still different views on the comprehensive effect of these factors on the future climate. In addition to the theory of global warming, there are also the theories of "cooling" and "fluctuation" of the earth. In addition, there is still scientific uncertainty about whether global warming is caused by greenhouse effect, natural climate fluctuation or both. Therefore, it is difficult to judge the influence trend of greenhouse effect completely and accurately.

It is predicted that if the concentration of CO2 in the atmosphere increases by 1 time, the global temperature will rise by 5℃, and the concentration of CO2 in the atmosphere can completely double by the next century. According to the judgment of the Intergovernmental Panel on Climate Change (IPCC) on global climate change, the global temperature will rise by 0.3℃ every 10 year in the next century, and by 2050, it will rise by 1℃. The sea level will rise by 6cm every year, and by 2070, it will rise by 65cm, but there are great differences in different sea areas. It can be seen that with the increase of greenhouse gas emissions, the trend of global warming still exists, and the resulting impact will continue to increase. Therefore, the issue of greenhouse gas emissions still needs to be taken seriously.

3. Ozone layer destruction

1) ozone layer destruction

1985, the British scientist Farmen and others summarized their observation results at Haley Bay Observatory in Antarctica, and found that the total ozone concentration there has decreased by more than 30% every year in early spring (Antarctic 10) since 1975. This discovery has been confirmed by the observation results of Antarctic scientific stations in many other countries. The amazing reduction of ozone has caused a great shock all over the world. Since then, the problem of ozone layer destruction has been widely concerned not only by the scientific community, but also by governments, enterprises and all walks of life all over the world.

Since the mid-1980s, it has been reported that the concentration of ozone layer over Antarctica dropped significantly in spring (10). Further measurements show that in the past 10- 15 years, stratospheric ozone over Antarctica was consumed rapidly and massively every spring, and nearly 95% of the ozone in the ozone layer center over the polar regions was destroyed. Looking up from the ground, the ozone layer at high altitude is extremely thin. Compared with the surrounding area, it looks like a "hole" with a diameter of thousands of kilometers, hence the name "ozone hole". Satellite observation shows that the coverage area of ozone hole is sometimes even larger than that of the United States.

The following two pictures show the downward trend of ozone concentration in the Antarctic ozone hole and over Antarctica respectively.

Further research and observation also found that ozone depletion occurred not only in the Antarctic, but also in the Arctic and other mid-latitude regions to varying degrees. In fact, although no ozone loss similar to that of Antarctic caves was found in the Arctic, scientific research found that the ozone loss at the height of 16-20km was about 10% of the normal concentration in the Arctic1-February, and the damage of ozone column concentration was about 5%-8% in the range of 60o-70o north latitude. Therefore, compared with the ozone damage in the Antarctic, the ozone loss in the Arctic is much lighter and the duration is relatively short.

In fact, the reduction of total ozone concentration occurred on a global scale. Using ground observation and satellite data, Zhou Xiuji of the Chinese Academy of Meteorology reported that there is an ozone low value center on the Qinghai-Tibet Plateau. The center appears in June every year, and the annual decline rate of total ozone concentration in the center reaches 0.345%, which is very abnormal in the northern hemisphere. It is also found that since 1979, the total amount of atmospheric ozone in China has been declining year by year, with an average annual decline rate of 0.077%-0.75%.

2) Causes and mechanisms of ozone layer destruction

Ozone is a trace gas in the earth's atmosphere, which is composed of three oxygen atoms and is called oxygen allotrope. Ozone is usually distributed in two layers in the atmosphere, namely the troposphere and the stratosphere. The height of the atmosphere around the earth's surface is 8- 16 km, which is called the troposphere. This layer of ozone is harmful to human beings and ecological environment, and it is also the main substance of photochemical smog pollution in urban air at present. The troposphere is about 50 kilometers high, commonly known as stratosphere. In fact, the stratosphere preserves 90% of the ozone in the atmosphere, and this high level of ozone can effectively absorb ultraviolet rays harmful to human health (UV-B segment), thus protecting life on earth.

Generally speaking, ultraviolet radiation from the sun is divided into three regions according to wavelength. Ultraviolet light with a wavelength of 315-400 nm (1nm =10-9m) is called UV-A region. The ultraviolet rays in this area can't be effectively absorbed by ozone, but it won't damage the biosphere on the surface. In fact, a small amount of ultraviolet light in this band is also necessary for surface organisms, which can promote the transformation of human sterols into vitamin D. If it is lacking, it will cause rickets, especially for children's development. Ultraviolet light with the wavelength of 280-3 15 nm is called UV-B region, which is the part that may reach the surface and is the most harmful to human beings and ecosystems. Ultraviolet light with a wavelength of 200-280 nm is called UV-C region, with short wavelength and high energy. But the ultraviolet light in this area can be completely absorbed by oxygen and ozone in the atmosphere. Even if stratospheric ozone is exhausted, UV-C ultraviolet rays will not reach the surface, causing adverse effects.

In the stratosphere, intense ultraviolet radiation decomposes CFC and halon molecules, releasing highly active chlorine and bromine atoms, which are also free radicals. Chlorine radical and bromine radical are the main substances that destroy the ozone layer, and their destruction of ozone is carried out in a catalytic way:

Cl + O3 →ClO + O2

ClO+oxygen → chlorine+oxygen

The end result is:

O3 + O → 2O2

In the above reaction, Cl destroyed one ozone molecule, but Cl itself was not consumed, and it could continue to destroy another ozone molecule. Substances that play this role in chemical reactions are called catalysts. The above reaction is called catalytic reaction.

Bromine radical destroys ozone in the same process, so it is also a catalyst. It is estimated that a chlorine atom group can destroy 104- 105 ozone molecules, and the bromine atom group released by halons is 30-60 times more destructive to ozone than chlorine atom. Moreover, there is a synergistic effect between chlorine and bromine, that is, when they exist at the same time, the ability to destroy ozone is greater than their simple addition.

What worries scientists and all walks of life is that the atmospheric lifetime of chlorofluorocarbons and halons is long, and once they enter the atmosphere, it is difficult to remove them, which means that their damage to the ozone layer will last for a long time, and the ozone layer is greatly threatened by human activities.

In order to evaluate the relative ability of various ozone-depleting substances to destroy global ozone, the parameter "ozone depletion potential (ODP)" was adopted scientifically. Ozone depletion potential refers to the ratio of the global ozone loss caused by a substance to the ozone loss caused by CFC- 1 1 with the same mass during the atmospheric lifetime period. In atmospheric chemical model calculation, the ODP value of substance X can be expressed as:

ODP= global ozone reduction per unit substance X/global ozone reduction per unit mass CFC- 1 1.

The atmospheric concentration distribution of ozone-depleting substances and the atmospheric chemical processes involved are the main factors affecting their ODP values. Due to the different treatment methods of these factors, the ODP values of ozone-depleting substances obtained by different researchers are different to some extent, but the order of ODP values of various ozone-depleting substances is basically the same: the ODP values of hydrogen-containing chlorofluorocarbons are much lower than those of Freon, and the destruction ability of many halons to stratosphere is much higher than that of Freon. These studies provide a powerful scientific basis for decision makers to formulate elimination strategies and substitutes for ozone-depleting substances.

3) Harm caused by ozone layer destruction

After the depletion of the ozone layer, its ability to absorb ultraviolet radiation is greatly weakened, resulting in an obvious increase in ultraviolet B reaching the earth's surface, which brings many hazards to human health and ecological environment. At present, people have paid extensive attention to the impact on human health, terrestrial plants, aquatic ecosystems, biochemical cycles, substances, tropospheric atmospheric components and air quality.

(1) on human health

The increase of UV-B in sunlight is harmful to human health. Experiments show that ultraviolet rays can damage cornea and lens, such as cataract and lens deformation. According to analysis, stratospheric ozone will decrease by 1%, global cataract incidence will increase by 0.6-0.8%, and the number of people who are blind due to cataract will increase by 1 10,000, reaching10.5 million. If no measures are taken to increase ultraviolet rays, the increase of UV-B radiation will lead to about180,000 cataract cases from now until 2075. The increase of UV-B segment can obviously induce three common skin diseases. Among these three kinds of skin diseases, basal mesothelioma and squamous mesothelioma are non-malignant. Another malignant melanoma is a very dangerous skin disease. The latest research results obtained from animal experiments and human epidemiological data show that if the ozone concentration decreases 10%, the incidence of non-malignant melanoma will increase by 26%. Scientific research also reveals the internal relationship between UV-B ultraviolet rays and malignant melanoma, especially for people with light skin color, especially in childhood.

(2) Effects on terrestrial plants

At present, the harm mechanism of ozone layer depletion to plants is not as clear as its impact on human health, but research shows that more than 50% of the plants that have been studied are negatively affected by UV-B, such as beans, melons and other crops, and the quality of other crops such as potatoes, tomatoes and beets will decline;

(3) Impact on aquatic ecosystem

The researchers measured the increase of UV-B radiation and the amount of UV-B radiation penetrating the water body in Antarctica, and there was sufficient evidence to prove that the natural phytoplankton community was directly related to the change of ozone. The comparison of phytoplankton productivity inside and outside the ozone hole shows that the decline of phytoplankton productivity is directly related to the increase of UV-B radiation caused by ozone reduction. A study shows that the productivity of the glacier edge has decreased by 6- 12%. As plankton is the basis of marine food chain, the decrease of species and quantity of plankton will also affect the output of fish and shellfish. According to the results of another scientific study, if stratospheric ozone is reduced by 25%, the primary productivity of plankton will be reduced by 10%, which will lead to a decrease of 35% of the organisms near the water surface.

(4) Influence on materials

The increase of solar ultraviolet radiation caused by stratospheric ozone depletion will accelerate the degradation and aging of materials used in construction, spraying, packaging, wires and cables, especially polymer materials. Especially in tropical areas with high temperature and abundant sunshine, this kind of harm is more serious. It is estimated that the global losses caused by this destructive influence are as high as billions of dollars every year.

Compared with previous environmental problems, this climax is very different:

First, the scope of influence is different. The first climax mainly appeared in industrialized countries, focusing on local and small-scale environmental pollution problems, such as cities, rivers and farmland. The second climax is large-scale and even global environmental pollution and large-scale ecological destruction. These environmental problems not only endanger a certain country or region, but also endanger the whole earth environment on which human beings depend.