With the development of industry, cities are facing more and more serious environmental pollution. Do you know what environmental pollution is? What are the reasons for this? The following is my introduction to the causes of environmental pollution. I hope I can help you.
I. air pollution
Air pollution refers to the phenomenon that the concentration of pollutants in the air reaches a harmful level, which destroys the ecosystem and the conditions for the normal survival and development of human beings. It is called air pollution. The causes of air pollution include natural factors, such as volcanic eruption, forest fire, rock weathering, etc; There are also human factors, such as industrial exhaust, combustion exhaust, automobile exhaust and nuclear explosion. With the intensification of human economic activities and the rapid development of production, a large amount of waste gas and soot are discharged into the atmosphere while consuming a large amount of energy, which has seriously affected the quality of atmospheric environment. According to the regulations of the who, the definition of air pollution is: "if there are man-made pollutants in the outdoor atmosphere, their content, concentration and duration can cause discomfort to most residents, endanger public health in a large range, and hinder human, animal and plant life.
Cause of formation
A large amount of dust and sulfur dioxide gas emitted during volcanic eruption, and a large amount of carbon dioxide, hydrocarbons and thermal radiation produced by forest fire; Pollution caused by human production and life;
Caused by human production and life: 1. Waste gas discharged by industrial enterprises; Among the exhaust gases emitted, coal and oil are used as fuels, and dust, sulfur dioxide, nitrogen oxides, carbon monoxide and carbon dioxide are emitted during combustion. The other is a variety of organic and inorganic pollutants emitted in the process of industrial production. 2. Exhaust gas discharged by means of transportation; It is mainly the exhaust gas discharged by vehicles, ships and aircraft. Among them, the number of cars is large and concentrated in cities, so it has a great impact on urban air quality. It is a serious air pollution source. The main pollutants discharged are hydrocarbons, carbon monoxide, nitrogen oxides and black smoke.
II. Water pollution
Water pollution refers to the phenomenon that the chemical, physical, biological or radioactive characteristics of water body are changed due to the intervention of certain substances, which affects the effective utilization of water, endangers human health or destroys the ecological environment, resulting in the deterioration of water quality Water pollution sources are divided into natural pollution sources and man - made pollution sources Natural pollution source refers to the place where the geochemical anomaly of nature releases harmful substances or causes harmful effects Anthropogenic pollution source refers to the pollution of water body caused by pollutants produced by human activities Anthropogenic pollution sources include industrial pollution sources, domestic pollution sources and agricultural pollution sources
Cause of formation
Water pollutants come from many human activities. Industrial pollutants can flow out of the discharge pipes in the plant or from pipelines and underground storage tanks. Contaminated water may also flow out of the mine, and the water flowing through the mine may have been leached through mineral containing rocks, or may have been contaminated by chemicals processing ore. Most water pollution in cities and other residential areas comes from trace household chemicals mixed in sewers. Sometimes factories discharge pollutants into the urban sewage system, increasing all kinds of pollutants in the urban area. From like farmland. Pollutants from agricultural sources such as pastures, feedlots and farms include animal manure, agricultural chemicals and sediments produced in the process of corrosion.
III. soil pollution
Soil pollution is a phenomenon that pollutants produced by human activities enter the soil and accumulate to a certain extent, resulting in the deterioration of soil quality. Soil pollution can be roughly divided into two categories: inorganic pollutants and organic pollutants. Inorganic pollutants mainly include acids, alkalis, heavy metals, salts, compounds of radioactive elements cesium and strontium, compounds containing arsenic, selenium and fluorine, etc. Organic pollutants mainly include organic pesticides, phenols, cyanide, petroleum, synthetic detergent, benzopyrene and harmful microorganisms brought by municipal sewage, sludge and manure.
Cause of formation
(I) soil pollution caused by sewage irrigation
Domestic sewage and industrial wastewater contain nutrients needed by many plants, such as nitrogen, phosphorus and potassium. Therefore, reasonable use of sewage to irrigate farmland generally has the effect of increasing production However, sewage also contains many toxic and harmful substances such as heavy metals, phenols and cyanide. If sewage is directly used for farmland irrigation without necessary treatment, it will bring toxic and harmful substances in sewage to farmland and pollute soil
(II) soil pollution caused by air pollution
The harmful gas in the atmosphere is mainly the toxic waste gas discharged from industry. It has a large pollution surface and will cause serious pollution to the soil Industrial waste gas enters the soil through sedimentation or precipitation, causing pollution For example, the waste gas from non-ferrous metal smelters contains heavy metals such as chromium, lead, copper and cadmium, which pollutes the soil; Factories producing phosphate fertilizer and fluoride will cause dust pollution and fluorine pollution to the soil
(III) soil pollution caused by chemical fertilizer
Applying chemical fertilizer is an important measure to increase agricultural production, but unreasonable use will also cause soil pollution The long-term extensive use of nitrogen fertilizer will destroy the soil structure, cause soil hardening, deteriorate biological properties, and affect the yield and quality of crops.
(IV) impact of pesticides on Soil
Pesticides can prevent and control diseases, insects and weeds. If used properly, they can ensure the increase of crop yield, but they are a kind of harmful soil pollutants. Improper application will cause soil pollution
(V) soil pollution by solid waste
Industrial waste and municipal waste are solid pollutants in soil For example, all kinds of agricultural plastic films are widely used as greenhouses and mulch. If the management and recycling are poor, a large number of residual film fragments will be scattered in the field, which will cause "white pollution" of farmland.
1. Harm of acid rain to organisms
Acid rain acidifies soil and rivers and flows into lakes through rivers, resulting in Lake acidification. After acidification, the lake not only kills the plants growing in and near the lake, but also threatens the survival of fish, shrimp and shellfish in the lake, thus destroying the food chain in the lake and finally turning the lake into a "dead lake". Acid rain also directly endangers the leaves and buds of terrestrial plants and kills crops and trees.
Now, the harm caused by acid rain is becoming more and more serious, which has become one of the important problems of global environmental pollution. Sulfur dioxide is one of the main pollutants forming acid rain. With the development of economy, human beings will burn more coal, oil and natural gas and produce more pollutants such as sulfur dioxide. Therefore, the harm caused by acid rain may be more serious in the future. China is one of the countries that emit a large amount of sulfur dioxide in the world, and acid rain has appeared in some areas. For example, in a certain area in Southwest China, acid rain fell four times in three months in 1982, and the pH of the rain was 3.6 ~ 4.6, resulting in the damage of a large area of crops.
As early as the mid-19th century, it was noted that lichens and bryophytes could not survive in cities with serious air pollution, and plant leaves near chimneys often showed disease spots. After research, scientists found that these phenomena are related to the air pollution in the area, and some plants can be used to monitor the air pollution in a certain area. Different plants have different sensitivity to air pollutants such as sulfur dioxide. For example, when the content of sulfur dioxide in the atmosphere is relatively high, the leaves of alfalfa and sunflower will quickly fade green, or there are brown patches between leaf veins. In serious cases, the leaves will gradually necrosis. These plants are sensitive to air pollution and can be used to monitor the status of air pollution. They are called air pollution indicator plants.
2. Harm of harmful chemicals to organisms
Pesticides are a kind of common harmful chemicals. When people use pesticides to kill bacteria and pests, they will also cause environmental pollution and harm a variety of organisms, including humans.
Many pesticides are not easy to decompose compounds. After being absorbed by organisms, they will continue to accumulate in organisms, resulting in the content of such harmful substances in organisms far exceeding that in the external environment. This phenomenon is called bioconcentration. The bioconcentration increased with the extension of the food chain. For example, DDT, as a highly effective pesticide, was widely used to control pests decades ago. DDT was once used to control larvae in the lake in a certain place in the United States, so that DDT remained in the lake water, and the content of DDT in zooplankton reached more than 10000 times that of the lake water. Small fish eat zooplankton and big fish eat small fish. As a result, the content of DDT in these big fish is as high as more than 8 million times that of the lake water.
3. Harm of heavy metals to organisms
Some heavy metals such as Mn, Cu and Zn are essential trace elements for biological activities, but most heavy metals such as Hg and Pb are toxic to biological activities. Heavy metals such as Hg and Pb in the ecological environment can also be concentrated in organisms through bioaccumulation, resulting in serious harm
4. Effects of Hg on life activities of Daphnia
Through the demonstration experiment, it can be seen that Hg is toxic to Daphnia. Scientists have found that Hg in nature can be transformed into more toxic methylmercury through the action of microorganisms in water. In the sea water polluted by methylmercury, algae and plants change color, and a large number of marine fish die. Scientists also found that PbCl2 solution with a mass concentration of only 4mg / l could significantly inhibit the normal photosynthesis of spinach and tomato. It can be seen that heavy metals such as Hg and Pb are very harmful to the normal life activities of organisms.
5. Harm of eutrophication to organisms
Eutrophication refers to the deterioration of water quality due to the excessive content of mineral elements necessary for plants such as N and P in water. The water body contains an appropriate amount of mineral elements such as N and P, which is necessary for the growth and development of algae. However, if these mineral elements enter the water body in large quantities, algae and other plankton will multiply in large numbers. After these organisms die, they are first decomposed by aerobic microorganisms, which significantly reduces the content of dissolved oxygen in water. Then, the biological remains will be decomposed by anaerobic microorganisms to produce toxic substances such as hydrogen sulfide and methane, resulting in a large number of deaths of fish and other aquatic organisms. Lakes, bays and other slow-moving water bodies with eutrophication show blue, red and brown colors due to different types of plankton. Eutrophication in ponds and lakes is called "water bloom", and in seawater is called "red tide". Industrial wastewater, domestic sewage and water discharged from farmland contain many mineral elements necessary for plants such as N and P. these mineral elements are discharged into ponds and lakes in large quantities, which will lead to eutrophication of ponds and lakes. The eutrophication of ponds and lakes will not only affect the aquaculture industry, but also make the water contain carcinogens such as nitrite, which will seriously affect the safe drinking water of human and livestock.
Biological purification
Biological purification refers to the process that organisms reduce or disappear the concentration and toxicity of pollutants in the ecological environment through absorption, decomposition and transformation. In biological purification, green plants and microorganisms play an important role.
Purification of green plants
The purification effect of green plants is mainly reflected in the following three aspects: first, green plants can absorb harmful gases in the atmosphere within a certain concentration range. For example, 1 mm2 (hectare) Cryptomeria lanceolata forest can absorb 60 kg of sulfur dioxide per month. Second, green plants can block and absorb dust and radioactive pollutants in the atmosphere. For example, the amount of dust blocked and adsorbed by beech forest of 1hm2 in a year is 68T; For another example, planting trees with a certain width around factories and mines with radioactive pollution can reduce the pollution of radioactive pollutants to the surrounding environment. Third, many green plants, such as sycamore, orange and juniper, can secrete antibiotics and kill pathogens in the air. Therefore, the number of pathogenic bacteria in the air of forests and parks is significantly lower than that in downtown areas. In short, green plants can purify the atmosphere in many ways, especially forests. They are a green barrier to protect the ecological environment.
China is a country with vast territory and complex terrain. There are relatively superior conditions for the development of forestry. Many places in ancient China were covered with dense forests. However, for a long time, due to people's unreasonable use of forest resources, such as deforestation, deforestation and reclamation, there are fewer and fewer forests in China. In recent decades, China has vigorously carried out afforestation and made great achievements. However, at present, China's forest coverage is still very low. According to per capita calculation, China is one of the countries with the least forests in the world. Therefore, every citizen should start from me, take good care of every plant and tree around us, actively participate in afforestation activities and strive to improve China's forest coverage.
Since 1978, China has successively established ten major forestry ecosystem construction projects with the main goal of protecting and improving the ecological environment and realizing the sustainable utilization of resources. These ten forestry projects are: the construction project of shelter forest system in the three North (Western Northeast, northern North China and Northwest China); Protective forest system construction project in the middle and upper reaches of the Yangtze River; Coastal shelter forest system construction project; Plain farmland shelter forest system construction project; Taihang Mountain greening project; National desertification prevention and control project; Construction project of shelter forest system in Huaihe Taihu Lake Basin; Protective forest system construction project in the Pearl River Basin; A total of 120 million hectares of afforestation are planned for the construction project of protective forest system in Liaohe River Basin and the construction project of protective forest system in the middle reaches of the Yellow River. The implementation of the ten major forestry ecosystem construction projects has gradually improved the ecological environment in a considerable part of China.