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1, Mas Valley Smoke Event 1930

Mas Valley Industrial Zone, Belgium. There are many factories in this narrow valley, such as oil refinery, metal factory and glass factory. From February to 5th, 65438+/kloc-0, a strong inversion layer appeared over the valley, which prevented the smoke and dust emitted by the 1 3 chimney from spreading, and a large number of harmful gases accumulated in the near-earth atmosphere, causing serious harm to human body. More than 60 people died in a week, among which the death rate of patients with heart disease and lung disease was the highest, and many livestock died. This is the earliest recorded public hazard event in this century.

2. Los Angeles photochemical smog incident 1943

In summer, Los Angeles on the west coast of the United States. 2.5 million cars in this city burn 1 100 tons of gasoline every day. The hydrocarbons produced by gasoline combustion react chemically under the irradiation of ultraviolet rays from the sun, forming light blue smoke, which makes most citizens in the city envious and have a headache. Later, people called this pollution photochemical smog. There were two photochemical smog incidents in Los Angeles at 1955 and 1970. In the former, more than 400 people died of five senses poisoning and respiratory failure, while in the latter, three quarters of the people in the city were sick.

3. Donola Smoke Incident 1948

There are many large ironmaking plants, zinc smelting plants and sulfuric acid plants in Donola, Pennsylvania, USA. 1948101In the early morning of October 26th, the air was filled with fog, which was controlled by anticyclone and inversion temperature, so the harmful gas emitted by the factory could not spread out. Among 0/4000 people in the city/KLOC-6,000 people have symptoms such as eye pain, sore throat, headache, chest tightness, vomiting and diarrhea. 17 people died.

4. London Fog and Haze Event 1952

Since 1952, there have been 12 major smog events in London, and the main culprits are dust and sulfur dioxide emitted from coal combustion. Smoke forced all planes to stop flying, cars turned on their lights during the day, pedestrians had difficulty walking, and smoke incidents led to a sharp increase in respiratory diseases. 1952 65438+ During that period in February, more than 4,000 people died in five days and more than 8,000 people died in two months.

5. Minamata disease incident 1953 1956.

The wastewater discharged by a nitrogenous fertilizer company in Minamata Town, Kumamoto Prefecture, Japan contains mercury, which is converted into methylmercury by some organisms after being discharged into the bay. These mercury are concentrated in seawater, sediments and fish, and they are poisoned through the food chain. At that time, the most sick cat was the one who loved fish. The poisoned cat went crazy and twitched and committed suicide by jumping into the sea. In a few years, even cats disappeared in Minamata. 1956 patients with symptoms similar to those of cats appeared. Because the reason was not clear at first, it was named after the local place name. 199 1 year, there are still 2248 poisoned patients announced by the Japanese Environment Agency, of which 1004 died.

6. Bone pain incident 1955 1972

Cadmium is an element that the human body does not need. Some lead-zinc mines in Toyama Prefecture, Japan discharge wastewater during mining and smelting, and the wastewater accumulates heavy metal "cadmium" in rivers. People who drink such river water for a long time and eat rice irrigated with cadmium-containing river water will suffer from severe bone deformation, severe pain, shortened body length and brittle bones.

7. Japan rice bran oil incident 1968.

First, hundreds of thousands of chickens died after eating poisonous feed. People didn't delve into the source of the poison, and then 13000 people in Kitakyushu suffered. These chickens and people got sick from eating rice bran oil containing PCBs. The patient began to have eyelid edema, sweaty palms and red papules all over his body. Then liver function drops, muscles ache and cough. This incident once put the whole western Japan into a panic.

9. Chernobyl nuclear accident 1986

On April 26th, the Chernobyl nuclear power plant in the suburb of Kiev, Ukraine caught fire in the explosion of No.4 reactor due to mismanagement and operational errors, resulting in a large amount of radioactive materials leaking. Radioactive materials leaked from nuclear power plants have been detected in western European countries and most parts of the world. 3 1 person died and 237 people were seriously injured by radiation. Moreover, within 20 years, there may be 30 thousand people suffering from cancer. Primary and secondary school students in Kiev and Kiev all evacuated to the seaside, all crops around the nuclear power plant were buried, 20 million tons of grain was lost, and all trees within 7 kilometers of the power station died. In the next half century, farming and grazing can't be carried out within 10 km, and milk can't be produced within 100 km ... This nuclear pollution and flying dust have also brought serious disasters to neighboring countries. This is the most serious nuclear pollution in the world.

10. The Rhine River is polluted by highly toxic substances 1986.

1 65438+1October1day, the warehouse of Sandoz chemical plant in Basel, Switzerland caught fire, and nearly 30 tons of highly toxic sulfides, phosphides and mercury-containing chemical products flowed into the Rhine with fire extinguishing agent and water. In the downstream 150km range, more than 600,000 fish were poisoned, and the well water on both sides of the river bank was not drinkable within 500km. The waterworks along the river bank closed and the brewery stopped production. Poisons deposited at the bottom of the river will make the Rhine "extinct" for 20 years. ▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲

I. Air pollution

Definition of air pollution

In a clean atmosphere, the composition of trace gases can be ignored. However, in a certain range of the atmosphere, trace substances have appeared, and their quantity and duration may have adverse effects and harm on people, animals, plants, articles and materials. When the concentration of pollutants in the atmosphere reaches a harmful level, even destroying the ecological system and the conditions for the normal survival and development of human beings, the phenomenon that harms people or things is called air pollution. The causes of air pollution are both natural factors and human factors, especially human factors, such as industrial waste gas, combustion, automobile exhaust and nuclear explosion. With the rapid development of human economic activities and production, while consuming a lot of energy, a lot of waste gas and smoke are discharged into the atmosphere, which seriously affects the quality of the atmospheric environment, especially in densely populated cities and industrial areas. The so-called dry and clean air refers to the air (composed of mixed gas, water vapor and impurities) in a natural state without water vapor and impurities, and its main component is nitrogen, accounting for 78.09%; Oxygen, accounting for 20.94%; Argon, accounting for 0.93%; Other trace gases (such as neon, helium, carbon dioxide and krypton) with the content less than 0. 1%.

Classification of air pollutants

Air pollutants can be mainly divided into two categories, namely natural pollutants and man-made pollutants, which often cause public hazards, mainly from fuel combustion and large industrial and mining enterprises.

Particulate matter: refers to liquid and solid substances in the atmosphere, also known as dust.

Sulfur oxide: it is the general term for sulfur oxides, including sulfur dioxide, sulfur trioxide, sulfur trioxide, sulfur monoxide, etc.

Oxides of carbon: mainly including carbon dioxide and carbon monoxide.

Nitrogen oxides: it is the general term for nitrogen oxides, including nitrous oxide, nitric oxide, nitrogen dioxide and nitrogen trioxide.

Hydrocarbons: Compounds formed by carbon and hydrogen, such as methane, ethane and other hydrocarbon gases.

Other harmful substances: such as heavy metals, fluorine-containing gases and chlorine-containing gases.

The harm of air pollution

Air pollution has a great influence on the climate. The pollutants discharged by air pollution will have a certain impact on the local and global climate, especially on the global climate. In the long run, this effect will be very serious.

First, the content of carbon dioxide in the atmosphere is increasing, and the fuel contains various complex components, which will produce various harmful substances after combustion. Even if the fuel without impurities is completely burned, water and carbon dioxide will be produced. It is precisely because of fuel combustion that the concentration of carbon dioxide in the atmosphere is increasing, which destroys the balance of carbon dioxide in nature and may even lead to the "greenhouse effect" and the rise of the earth's temperature. Second, the ozone layer is destroyed.

After air pollution, due to the different sources, nature and duration of pollutants, the differences in meteorological conditions, geographical environment and other factors in polluted areas, as well as the differences in people's age and health status, the harm to human body is not the same. Harmful substances in the atmosphere invade the human body mainly through the following three ways:

(1) enters the human body through direct breathing;

(2) adhering to food or dissolving in water, so that it can invade the human body with diet;

(3) Entering the human body by contacting or stimulating the skin. Among them, invading the human body through breathing is the main way and the most harmful.

The harm of air pollution to people can be roughly divided into three types: acute poisoning, chronic poisoning and carcinogenesis.

Atmospheric protection

Many environmental problems are transnational or even global, such as the greenhouse effect, ozone layer destruction and other air pollution problems, which need the concerted efforts of all countries in the world and Qi Xin to be solved step by step. People began to realize that HCFCs may be harmful to the environment in the early 1970s, and began to look for alternatives. By the middle of1980s, the evidence of ozone layer destruction became more and more obvious, and the call for concerted action became louder and louder. 1987, representatives from many countries gathered in Montreal, Canada's second largest city, and signed the Montreal Protocol on Substances that Deplete the Ozone Layer. The agreement is a pioneering international agreement to deal with environmental pollution in the world, aiming at controlling the consumption of HCFCs and other substances that destroy the ozone layer, protecting the "coat" of the earth and protecting human beings themselves.

The revised Montreal Protocol is a binding international agreement. According to this regulation, industrialized countries must immediately reduce the emissions of HCFCs and other restricted substances and completely stop using these substances before 2000. Developing countries can continue to increase the consumption of these substances to a limited extent before 1996, and then gradually reduce it. By 20 10, they must completely stop using these harmful substances. In addition to the time concession, this agreement also contains two clauses in favor of developing countries: first, the establishment of a temporary multilateral fund to help developing countries adopt technologies to replace HCFCs; The other is the technology transfer clause, which requires the signatory countries to transfer the best technology according to "fair and most favorable conditions".

China has joined the revised Montreal Protocol, and formulated a national action plan to fulfill its international obligations, including the establishment of ozone layer protection organizations and management institutions, the formulation of relevant industry management norms, the active research on substitutes and alternative technologies, and the arrangement of matching funds for enterprises' alternative technological transformation.

Second, acid rain.

Some people think that acid rain is a silent crisis, the most serious environmental threat that has ever attacked us, and an invisible enemy. This is not an alarmist.

With the increase of industrialization and energy consumption, acid emissions are also increasing. They enter the air and form acid rain after a series of actions.

People have controlled the discharge of acid, but there is still acid rain. Atmospheric dust may be another cause of acid rain.

Acid discharge

The condensation of water vapor is due to the existence of condensation nuclei in the range of 0. 1 ~ 10 micron in the free atmosphere, and then it grows further through the processes of collision and coalescence, forming clouds and raindrops. In the cloud, cloud droplets collide with each other or with aerosol particles, and at the same time absorb gas pollutants in the atmosphere, and chemical reactions occur inside the cloud droplets. This process is called the removal of pollutants in the cloud or the removal of rainwater. In the process of raindrops falling, raindrops will wash away gases and aerosols in the passing air, and chemical reactions will also occur inside raindrops. This process is called the removal or washing of pollutants under the cloud. These processes are also the processes of removing particulate matter from gaseous substances in the atmosphere by precipitation, and acidification is formed in these processes.

Atmospheric dust

Recent discoveries show that acid rain is a much more complicated phenomenon than previously thought. The results show that the basic compounds in the atmosphere unexpectedly play a key role. Alkali counteracts the influence of acid rain by neutralizing acidic pollutants. We find that people focus all their attention on acidic substances in the atmosphere, which masks the fact that alkali emissions have also decreased. It seems that many factors are reducing the content of these alkalis in the atmosphere, thus aggravating the ecological impact of acid rain. Ironically, some of these factors are the measures taken by the government to improve air quality.

Most of the alkali in the atmosphere can be found in air particles called atmospheric dust. These dust particles are rich in minerals such as calcium carbonate and magnesium carbonate, which can act as alkali when dissolved in water. Atmospheric dust particles are formed from many sources. The combustion of fuel and industrial activities such as cement production, mining and metal smelting will produce alkaline particles. Vehicles driving on construction sites, farms and unpaved roads can also produce dust particles.

Three. ozone depletion

The ozone layer is the best umbrella for the earth, which absorbs most of the ultraviolet rays from the sun. However, in recent twenty years, scientific research and atmospheric observation have found that the ozone layer in the Antarctic atmosphere is thinning every spring. In fact, there is an ozone hole in the polar atmosphere.

This phenomenon of ozone depletion is an abnormal phenomenon. Does this indicate that this ultraviolet absorption layer is in a global disaster? Through continuous scientific research, people have found that substances released by human social activities have seriously damaged the ozone layer. Of course, this phenomenon is also influenced by the unique meteorological conditions in this area (polar vortex, cold stratospheric temperature, polar stratospheric clouds).

Discovery process

Atmospheric scientists from the British Antarctic Survey conducted a research project in Antarctica, which was conducted on the ground and in the air. Ball-borne instruments generally detect the composition and chemical properties of the atmosphere in which the instruments travel. Land-based detectors and space-borne detectors perform telemetry tasks. These research activities take the form of international cooperation. For example, in 1987, about 150 scientists and auxiliary personnel representing 19 organization and four countries gathered in punta arenas, Chile, and conducted an unprecedented research, namely the aerial Antarctic ozone experiment. This experiment shows that the size of ozone hole reached the largest in history in 1987. This discovery shocked the scientific community.

Formation mechanism

At present, the cause of the Antarctic "ozone hole" is still inconclusive, and the most convincing is the pollutant theory. In addition, Calis and others of Hampton Zhili Center of NASA proposed that the destruction of Antarctic ozone layer is related to strong solar activity; Tung of Massachusetts Institute of Technology and others believe that the unique atmospheric environment in Antarctica causes ozone loss in late winter and early spring. According to the theory of atmospheric dynamics, it is pointed out that a large number of oxygen atoms are produced by the large use of chlorofluorocarbons and the lack of sunshine in early spring in Antarctica, and therefore the circulation mechanism of oxygen-free atoms is put forward.

Through the analysis, it seems that we can draw the following main points: (1) Antarctic "ozone hole" is a special phenomenon caused by the participation of polar stratospheric clouds and heterogeneous chemical reactions under the special temperature and circulation conditions in Antarctic spring. (2) The influence of polar vortex and other factors on the transport of gas components is not the decisive factor for the formation of Antarctic "ozone hole", but only affects the intensity of ozone hole. (3) The influence of solar cycle change on the intensity of Antarctic ozone hole through photochemical reaction can be ignored.

Fourth, water pollution.

Human activities will cause a large number of industrial, agricultural and domestic wastes to be discharged into water bodies and pollute them. Definition of "water pollution": The phenomenon that the chemical, physical, biological or radioactive characteristics of a water body change due to the intervention of a substance, thus affecting the effective utilization of water, endangering human health or destroying the ecological environment, and causing the deterioration of water quality is called water pollution.

There are two kinds of water pollution: one is natural pollution; The other is man-made pollution. At present, man-made pollution is the most harmful to water bodies. Water pollution can be divided into three categories: chemical pollution, physical contamination and biological pollution.

1, seawater pollution

Sewage, waste residue, waste oil and chemicals keep flowing into the sea. In many sea areas, it is illegal to dump sewage mixed with oil pollution, but this kind of thing still happens from time to time. The real oil disaster occurs when a giant oil tanker leaks or sinks. Now, we try to use chemicals to precipitate oil in water to remove it.

Dumping chemical and radioactive wastes into the sea has been going on for many years. The container will corrode one day and harmful substances will enter the sea water. We don't know much about the circulation of deep water and surface water, and the process may be faster than we thought before. Therefore, harmful substances will spread to the water layer of biological activities.

2. Ground water pollution

More than 500 years ago, people thought it was dangerous to drink river water flowing through big cities, but industrialization, population growth and new toxic chemicals made the situation worse and worse.

With the laying of drainage system and the increasing use of cleaning agents, the phosphate content in our waterways and lakes is increasing day by day. This overnutrition leads to the rapid proliferation of algae. Consume oxygen in water, kill fish and worsen ecosystem. Due to improper treatment of mercury compounds and other heavy metals in industry, serious water pollution has also been caused. Mercury gradually concentrates through the food chain, eventually causing serious nerve damage to fish-eating birds or humans.

3. Groundwater pollution

Like surface water, groundwater is also threatened by pollution, which mainly comes from the infiltration of surface water or soil water. Oil and phenol in agricultural nitrogen fertilizer and garbage pollute groundwater. Once the nitrate in nitrogen fertilizer enters the ground, it will be transformed into nitrite, which can be transformed into carcinogen in human body. The destruction of ground vegetation and the drainage of wetlands reduce the infiltration of surface water, thus reducing the groundwater level. Due to the excessive demand of cities and industries, fresh water is continuously pumped out as domestic and industrial water, and then discharged as surface sewage again, which will further reduce the groundwater level. On the other hand, a large number of frequent irrigation can enhance infiltration and make the groundwater level rise to the surface. In arid areas, the land infiltrated by water will precipitate salt from underground water due to abnormal evaporation, and it will become uncultivated saline-alkali land sooner or later.

water resources protection

There seems to be an inexhaustible supply of water on the earth. In fact, according to the current situation of human use, only fresh water is the main water resource, and only a small part of fresh water is available for people to use. Fresh water is a renewable resource, and its renewability depends on the water cycle of the earth. With the development of industry and the increase of population, a large number of water bodies are polluted; In order to extract river water, many countries have built dams in the upper reaches of rivers, which have changed the flow situation and seriously affected the circulation and self-purification of water.

Verb (abbreviation for verb) solid waste

All solid or semi-solid substances produced in the process of human activities that are no longer of use value to the owner and are discarded are collectively referred to as solid waste. Solid waste produced in various production activities is commonly known as waste residue; Solid waste produced in daily life activities is called garbage. "Solid waste" is actually only aimed at the original owner. In any production or life process, owners often only use some effective ingredients in raw materials, commodities or consumer goods, while most solid wastes that are no longer of use value to the original owners still contain ingredients needed by other production industries. After a certain technical link, it can be transformed into raw materials for production in relevant departments and industries, and can even be used directly. It can be seen that the concept of solid waste changes with time and space and is relative.

Method for producing solid waste

The substance that maintains all activities in human society is in a dynamic equilibrium process, which follows the law of conservation of mass and can be described by social material flow.

1. Compared with the external environment, all human activities are just the development and utilization of materials, and finally return to the environment in the form of waste. The "utilization and return" of this material is often in a cross state. In the process of production and product consumption, various forms of waste will be produced, and some of these wastes will be recovered and reused for production and consumption. The other part, just like the raw materials developed in the environment, returns to the environment as waste, forming a closed circulation system.

2. In modern society, every link of human activities will produce all kinds of wastes, from the development of raw materials in the environment to the utilization of products, without exception. Therefore, the only way to reduce waste production is to reduce the development of raw materials and reduce the consumption of raw materials for products.

Classification of solid waste

The classification of solid waste depends on the way and nature of its production. In economically developed countries, solid waste is divided into four categories: industrial, mining, agricultural solid waste and municipal waste. In the "Solid Waste Management Law" formulated by China, solid waste is divided into industrial solid waste (waste residue) and municipal waste. Among them, toxic and harmful components are listed separately.

Harm of solid waste

Garbage is becoming a major problem that plagues human society. The world produces more than 654.38 billion tons of garbage every year. Due to the lack of treatment system, a large number of domestic and industrial wastes are piled up in the open air. The phenomenon of garbage siege is becoming more and more serious. Piles of garbage stink, germs breed, and toxic substances pollute the surface and groundwater, which seriously harms human health. If this phenomenon is not contained, human beings will be buried by their own garbage.

Six, land subsidence

Land subsidence refers to the phenomenon that the height of the ground decreases within a certain surface area. The phenomenon of subsidence has long been recorded in history books. As a natural disaster, land subsidence has certain geological reasons. However, with the development of human society and economy and the expansion of population, the phenomenon of land subsidence has become more and more frequent and the subsidence area has become larger and larger. In densely populated cities, land subsidence is particularly serious. Now we study the causes of land subsidence, and it is not difficult to find that human factors have greatly exceeded natural factors. The present land subsidence phenomenon is not so much a natural disaster as a man-made disaster.

Geological causes of land subsidence

Judging from geological factors, there are three reasons for land subsidence in nature:

1, loose layer or semi-loose layer on the surface, etc. Under the action of gravity, when the loose stratum becomes dense, hard or semi-hard stratum, the ground will settle due to the decrease of stratum thickness.

2. Ground subsidence caused by geological structure.

3. The earthquake caused the ground subsidence.

Man-made causes of land subsidence

Land subsidence is closely related to human activities. Especially in recent decades, the over-exploitation of oil, natural gas, solid minerals and groundwater by human beings has directly led to the global land subsidence today. Due to the great population pressure in large and medium-sized cities, over-pumping of groundwater is more serious, which leads to land subsidence in most cities and seawater intrusion in coastal areas.

Seven. Changes in biodiversity

Biological communities are diverse, and people can divide them into several types from different angles. The meaning of biodiversity is very broad, including the diversity of biological species, ecological adaptability, morphology, physiological and ecological diversity and so on.

Different geographical and climatic environments have different biological communities. With the development of industrial civilization, human society has gradually expanded, which has changed the biological environment in vast areas and seriously affected biodiversity. Species are decreasing from the earth at an unprecedented rate.

It is estimated that thousands of species of animals and plants are extinct all over the world every year.

disafforestation

The biggest threat to animals and plants in the world is the destruction of the ecological environment. It is difficult for most living things to leave their adapted environment. One of the richest places in the world is the tropical rain forest, but now it is being destroyed faster and faster. In fact, all the natural forests in the world are seriously threatened. The lightest thing is that the rainforest has been replaced by a single economic forest, and the most serious place has become a barren shrub land due to erosion.

According to the estimate of WWF, the global forests are disappearing at the rate of 2% every year. At this rate, people will not see natural forests in 50 years.

Reclaim grassland

Many grasslands in North America have more or less disappeared. In Africa, in order to solve the food problem of the growing population, people are burning a large number of savannahs rich in animal resources. It is unreliable and dangerous to adopt traditional agricultural methods in arid areas. The efforts to recover the inland grasslands in Central Asia have suffered many unfortunate setbacks.

Dry and wet land

Swamp wetland is not only the living environment of organisms, but also plays an important role in hydrological cycle. It can adjust the flow rate of rivers and improve the recharge of groundwater. But in order to develop industry and build houses, many wetlands are either drained or filled with water. Trying to turn wetlands into cultivated land often leads to poor soil and low yield.

Urbanization development

Towns develop in areas with good agriculture, and urbanization often means sacrificing cultivated land to build houses, streets and parking lots. In this way, cultivated land becomes a wasteland, and no living things can be produced. From a natural or economic point of view, it is difficult to restore such land to farmland.

Animal extinction

Many animal species are on the verge of extinction, and the number of endangered vertebrates alone is amazing. The nature of the threat is varied: European raptors are threatened by egg gatherers, while tigers are in danger of being cut down in dense forests. Many endangered animals are difficult to save, while others can survive if they can be protected.

Eight, red tide

Red tide is the sudden proliferation and aggregation of some tiny phytoplankton, protozoa or bacteria in the water body under certain environmental conditions, which causes the water body to change color for a certain period of time. Usually, due to the number and species of red tide organisms, the colors of water bodies are red, yellow, green and brown.

Although red tide has existed since ancient times, with the rapid development of industrial and agricultural production, water pollution is becoming more and more serious.

The cause of red tide

Whether red tide is caused by existing natural phenomena or man-made pollution is still inconclusive. However, according to a large number of investigations and studies, the occurrence of red tide must meet the following conditions:

① Hypertrophy of seawater;

② Some special substances are involved as inducing factors, including vitamin B 1, B 12, iron, manganese and deoxyribonucleic acid.

(3) Environmental conditions such as water temperature and salinity also determine the biological types of red tide. At present, there are 63 species of plankton, 24 species of diatoms, 32 species of dinoflagellates, 3 species of cyanobacteria, 2 species of Chrysophytes 1 species, 2 species of Cryptophytes and 0 species of protozoans 1 species.

Harm of red tide

Red tide not only causes serious harm to marine environment, marine fishery and mariculture, but also affects human health and even life. It mainly includes two aspects:

(1) caused marine anomalies, partially interrupted the marine food chain, and made the sea area once a dead sea;

② Some red tide organisms secrete toxins and are ingested by some organisms in the food chain. If humans eat these creatures again, it will lead to poisoning and even death.

Nine, soil erosion

Land resource is one of the three major geological resources (mineral resources, water resources and land resources), and it is the most basic resource and labor object of human production activities. The use of land by human beings reflects the development of human civilization, but it also causes direct damage to land resources, mainly manifested in soil erosion, land desertification, secondary salinization of land and soil pollution caused by unreasonable farming, among which soil erosion is particularly serious, which is another serious crisis facing the world today.

Overview of soil erosion

Soil erosion refers to the whole process of soil erosion, migration and precipitation under the action of water flow. In the natural state, the process of surface erosion caused by natural factors is very slow, and it is often in a relatively balanced state with the process of soil formation. Therefore, the slope can remain intact. This kind of erosion is called natural erosion, also known as geological erosion. Under the influence of human activities, especially after human beings have seriously damaged the vegetation on sloping land, the process of surface soil destruction and land material movement caused by natural factors is accelerated, that is, soil erosion occurs.

Soil erosion is the most common geological disaster that destroys land resources in China, especially in the Loess Plateau. At present, the overall situation of soil erosion in China is that it is controlled in point and expanded in surface, and the control can't keep up with the destruction. The area of soil erosion in China was 65.438+0.74 billion mu at the beginning of liberation, and about 600 million mu was controlled by 654.38+0.980. Due to the failure of control, the area of soil erosion has expanded to 2.25 billion mu, accounting for about 1/6 of the total land area, involving nearly 1,000 counties. There are about 400 million mu of sloping farmland in mountainous and hilly areas of China, including 654.38 billion mu of terraced fields, and another 300 million mu of sloping farmland is suffering from soil erosion.

Harm of soil erosion

When soil fertility declines, soil erosion will cause a lot of fertile topsoil to lose.

Reservoir siltation, river bed elevation, navigation capacity reduction, flood disaster.

Threaten the safety of industrial and mining traffic facilities. In high mountains and deep valleys, soil erosion often leads to debris flow disasters, endangering the safety of industrial and mining traffic facilities.

Deteriorate the ecological environment. In 1930s-1960s, people's understanding of soil and water loss disasters remained on the direct economic loss of land, but after 1960s, it began to involve the impact on the whole human environment, including sediment pollution and ecological environment deterioration.

Causes of soil erosion

Geological and geomorphological conditions and climatic conditions that are prone to soil erosion are the main reasons for soil erosion.

With a large population, the demand for food and civil fuel is under great pressure. Under the condition of low productivity, land is plundered, grain output is emphasized unilaterally, and the comprehensive development of agriculture, forestry and animal husbandry according to local conditions is neglected, and the land suitable for forestry and animal husbandry is also turned into farmland. A large number of steep slopes have been reclaimed, which makes the steep slopes poorer and poorer, and the ecosystem is vicious circle; Deforestation, even indiscriminate digging of roots and lawns, sharply reduced trees, exposed surface, aggravated soil erosion. In addition, some capital construction does not meet the requirements of soil and water conservation, such as unreasonable construction of roads, factories, coal mining and quarrying, which destroys vegetation and reduces slope stability, resulting in more serious geological disasters such as landslides, landslides and mudslides.

Prevention and control of soil erosion

Soil erosion is caused by the movement of slope surface runoff. The basic principles of various prevention and control measures are: reducing slope runoff, slowing down runoff speed, improving soil water absorption capacity and slope erosion resistance, and raising erosion datum as much as possible. When taking prevention measures, we should start from the area where surface runoff forms, follow the runoff movement route, adjust measures to local conditions, strengthen and control step by step, combine prevention with prevention, and give priority to prevention; Slope control is combined with gully control, mainly slope control; Engineering measures are combined with biological measures, mainly biological measures. Only by taking various measures to carry out comprehensive centralized management,

References:

I looked up a lot in Baidu.