What is the vacuuming function of plants?

Green plants purify air pollutants. Green plants are the pillars of ecological balance. Green plants can not only beautify the city and absorb carbon dioxide to produce oxygen, but also play a long-term and comprehensive role in absorbing harmful gases, adsorbing dust particles, sterilizing, improving microclimate, preventing vibration and noise, and monitoring air pollution. 1. Absorption of harmful gases by green plants: The absorption of harmful gases by green plants mainly depends on leaves. According to experiments, the leaf area of a tall forest of 10 thousand square meters can reach 750 thousand square meters; A lawn of 10,000 square meters has a leaf area of 220,000-280,000 square meters. The huge leaf area plays an important role in purifying the atmosphere. But the harmful gas in the atmosphere exceeds the concentration that green plants can bear, and the plants themselves will suffer or even die. Only those green plants with strong resistance to harmful gases and great absorption capacity can grow tenaciously in areas with serious air pollution and play their purification role. Here is a brief introduction to the purification effect of green plants on harmful gases in the atmosphere. (1) absorption of sulfur dioxide The sulfur dioxide in the atmosphere mainly comes from the waste gas produced by fuel combustion, fertilizer, sulfuric acid and other industries. When the concentration of sulfur dioxide in the atmosphere reaches 0.2-0.3ppm for a certain period of time, some sensitive plants may be harmed. When it reaches 1ppm, some trees will have symptoms, especially conifers. When the concentration reaches 2- 10ppm, ordinary trees will suffer acute damage. According to the experiments of relevant departments, it is considered that the plants with strong resistance mainly include nearly 80 kinds of plants with strong resistance to sulfur dioxide, such as Platycladus orientalis, Pinus bungeana, Picea crassifolia, Cedar, Ailanthus altissima and Elm. There are mainly more than 20 species of moderately resistant plants, such as Pinus armandii, Populus euphratica, Populus euphratica, Pterocarya stenoptera and Mulberry. The plants with weak resistance are Albizia Albizia, Huang Jinshu and Gynostemma pentaphyllum. Sulfur is one of the nutrient elements needed by plants. In non-polluted areas, the sulfur content in leaves is about 0. 1-0.3% (dry weight). There are more than 5 species/kloc-0 with strong sulfur dioxide absorption capacity, such as weeping willow, Populus euphratica, hawthorn, acacia, spruce and peach tree. There are more than 10 species of Platycladus orientalis, Sabina vulgaris, Amorpha fruticosa and Lonicera maackii, which have moderate absorption capacity for sulfur dioxide. (2) The absorption of hydrogen fluoride mainly comes from the waste gas produced by chemical fertilizer, metallurgy, electroplating and other industries. The concentration of hydrogen fluoride harmful to plants is shown in Table 7-9. The main reason why hydrogen fluoride harms plants is cumulative poisoning, and the length of contact time is an important factor to harm plants. There are more than 40 kinds of plants with strong resistance to hydrogen fluoride, such as Pinus bungeana, conifer, Platycladus orientalis, Ginkgo biloba and Evodia rutaecarpa. Obviously, plants absorb hydrogen fluoride to purify the atmosphere. The maximum fluorine absorption capacity of plants for hydrogen fluoride can reach more than 1000ppm, and the maximum fluorine absorption capacity of different plants is generally 2-3 times different. See table 7- 10 for the fluorine content per hectare of different tree species. Because leaves, vegetables, flowers and plants can absorb a lot of fluorine, people will be poisoned if they eat foods and vegetables with high fluorine content, livestock will be poisoned if they eat feed with high fluorine content, and silkworms will be poisoned if they eat mulberry leaves with high fluorine content. Therefore, in areas with serious hydrogen fluoride pollution, it is not suitable to plant edible plants, but suitable to plant various non-edible trees, flowers and other plants. (3) Chlorine absorption Chlorine gas is a yellow-green gas with a strong smell, which mainly comes from chemical plants, pharmaceutical factories and pesticide plant. According to related experiments, when the chlorine concentration was 2ppm for 6 hours, 25% of the leaf area of Lonicera rubra and 30% of Ligustrum lucidum were damaged, while Platycladus orientalis, Sabina vulgaris, Buxus macrophylla and Iris were not damaged. Some people abroad use 0. 1ppm chlorine to do experiments, which can harm plants with weak resistance such as radish and some cruciferous plants. Peach trees were fumigated with 0.56ppm chlorine for 3 hours, and pine trees were fumigated with 1ppm for 3 hours, and the needles showed obvious symptoms. There are nearly 30 species of plants with strong chlorine tolerance, such as Sabina vulgaris, Platycladus orientalis, Pinus bungeana, Gleditsia sinensis, Robinia pseudoacacia and Ginkgo biloba. The plants with moderate resistance mainly include Pinus armandii, weeping willow, Fraxinus mandshurica, Fraxinus mandshurica, Paulownia, mulberry and so on. The plants with weak resistance mainly include Pinus tabulaeformis, Wei Zi, Torch Tree, Snow Willow and Apple. Plants have a certain ability to absorb and accumulate chlorine. The chlorine content in the leaves of plants growing in chlorine-polluted areas is often several times to dozens of times higher than that in non-polluted areas. The chlorine absorption capacity of plants per 10,000 square meters is: Tamarix ramosissima 140 kg, Gleditsia sinensis 80 kg, Robinia pseudoacacia 42 kg, Betula platyphylla 35 kg, Eucalyptus globulus 32.5 kg, Pinus armandii 30 kg, Cinnamomum cassia 26 kg, Broussonetia papyrifera 20 kg and weeping willow 9 kg. (4) Absorption of other harmful gases by plants The relevant units have determined the mercury content in a batch of plant leaves near the mercury vapor source. The mercury content per gram of dry weight leaves is: 96 nanograms of oleander, 84 nanograms of palm, 60 nanograms of cherry blossoms and mulberry trees, 52 nanograms of Euonymus japonicus, 65,438+09.2 nanograms of canna, 6.8 nanograms of Magnolia grandiflora and laurel ... It has also been reported in foreign countries that the absorption of mercury by tobacco leaves can be as high as 0.47%, and even if such a large amount of mercury is absorbed, only slight symptoms will appear. This is an excellent plant for purifying mercury vapor, but the tobacco after absorbing mercury is not suitable for human consumption. The relevant experimental units determined the lead content in plant leaves under the lead smoke environment. The lead content in leaves per gram dry weight is 42.6 ng, that in Ligustrum lucidum and Ulmus pumila is 36. 1 ng, that in pomegranate and citrus is 34.7 ng, and that in Robinia pseudoacacia is 35.6 ng. None of these plants showed any symptoms of injury after reaching the above lead content. Experiments also show that most plants can absorb ozone, among which Ginkgo biloba, Cryptomeria fortunei, Cinnamomum camphora, Cyclobalanopsis glauca, Nerium oleander, Robinia pseudoacacia, etc. 10 have a great purification effect on ozone. 2. Dust suppression function of green plants: all green plants have dust retention function, and the dust retention amount is closely related to tree species, forest belt, lawn area, planting situation and meteorological conditions. (1) Dust retention of trees and green spaces There are three ways for trees to retain dust: stagnation, adhesion and stickiness. For trees with smooth leaves, the way of dust collection is mostly to stop; For trees with rough and fluffy leaves, the dust collection method is mostly adhesion; Leaves or branches secrete resin, mucus, etc. , and its dust collection method is adhesion. According to the investigation and determination near the cement dust source in Nanjing, China, the dust retention per unit area of various leaves is shown in Table 7- 1 1. The dust suppression effect of green trees is very obvious. Generally speaking, the amount of floating dust in green tree areas is much lower than that in non-green open spaces. According to the determination in Beijing area, the dustfall rate of green belt is 2 1-39%, and that in Nanjing area is 37-60%. So some people say that the forest is a natural vacuum cleaner. And because the trees are tall and dense, the wind speed can be reduced and the dust can be reduced. Green space can also play the role of dust suppression and lush turf growth, and its leaf area is more than 20 times its area. At the same time, its roots are closely combined with the soil surface to form a ground cover, which is not easy to cause secondary dust when there is wind, and has a special dust suppression function. According to the measurement in Beijing, the concentration of particulate matter in the air with turf in the breeze is about 0.20mg/m3, and it is about 0.88mg/m3 in the football field with turf during the competition. However, in the children's playground with bare ground, the concentration of particulate matter in the atmosphere is as high as 2.67mg/m3, and it can be as high as 9mg/m3 when there is 4-5 gale. (2) Selection of Dust-proof Tree Species Trees with large total leaf area, rough and fluffy leaves and capable of secreting viscous oil or juice are all good dust-proof tree species, such as walnut, Populus tomentosa, Broussonetia papyrifera, chestnut, Ailanthus altissima, Platycladus orientalis, Pinus armandii, Kalopanax spinosa, Pu Shu, Chongyang, Robinia pseudoacacia, Platanus acerifolia, Ligustrum lucidum and Paulownia. 3. Sterilization of green plants: There are all kinds of bacteria scattered in the atmosphere, and usually many bacteria are attached to dust particles. Reduce bacteria in the air through dust suppression of green plants. At the same time, green plants themselves also have bactericidal effect. See table 7- 12 for tree species with strong bactericidal ability. According to the determination of relevant research departments, the amount of bacteria in the air is generally1000-5,000 /m3 in green spaces and parks with few people, but it can be as high as 20,000-50,000 /m3 in public places or busy streets. In the downtown area without greening, the amount of bacteria in the air is about 0.8 times higher than that in the downtown area with dense branches and leaves of street trees. 4. The role of green plants in absorbing carbon dioxide and releasing oxygen: Green plants are naturally processed plants that absorb carbon dioxide and release oxygen. Generally, a broad-leaved forest of 10,000 square meters can consume one ton of carbon dioxide and release 0.73 ton of oxygen in the growing season. If an adult breathes 0.75 kg of oxygen and discharges 0.9 kg of carbon dioxide every day, then everyone needs 10 square meter of forest area to consume the carbon dioxide discharged by breathing and supply the required oxygen. According to relevant data, a well-grown lawn can absorb carbon dioxide 1.5g per square meter per hour during photosynthesis, so a 25-square-meter lawn can absorb all the carbon dioxide exhaled by a person during the day. It can be seen that green plants, especially trees, can absorb and utilize a lot of carbon dioxide and release oxygen, which has a great influence on the survival of global organisms and the stability of climate. In addition, green plants can also reduce noise and absorb radioactive substances. Relevant tests show that the 40-meter-wide forest belt can reduce the noise 10- 15 decibels; Forest belts in urban parks can reduce the noise to 26-43dB, making it almost harmless to people. Tree species with good sound insulation include: cedar, juniper, cypress, Metasequoia glyptostroboides, Platanus acerifolia, weeping willow, spruce, hickory, cypress, Ailanthus altissima, camphor tree, banyan tree, Cryptomeria fortunei, oak tree, osmanthus fragrans and Ligustrum lucidum. According to the experimental measurement in Nanjing, China, it is considered that the noise reduction effect of green plants used for greening is closely related to the width, height, location, configuration and tree species of sound-proof forest belts: the width of forest belts is 6- 15 m in cities and 15-30 m in suburbs, and the effect is better if multiple narrow forest belts can be established. The height of the center of the forest belt is preferably above10m. The forest belt should be close to the sound source, not to the sound receiving area. Generally, the edge of the forest belt is 6- 15 meters away from the sound source, and the effect is the best. The forest belt will combine trees, shrubs and grasslands to form a continuous and dense obstacle zone, and the effect will be better. Green plants also have the function of absorbing radioactive substances. According to relevant experiments, setting a certain structure of green forest belt around factories and mines with radioactive pollution can obviously prevent and reduce the harm of radioactive substances; An Ericaceae plant can still grow normally when the neutron-γ mixed radiation dose exceeds 15000 rad, which shows that green plants have strong radiation resistance. 5. The role of forests in the prevention and control of air pollution: At present, the global forest area is about 2.8 billion hectares, accounting for only 22% of the land area. Because the forest is renewable, it can rebuild and recover itself without being completely destroyed. The annual fixed solar energy of the forest is about 123 1mj, carbon dioxide is absorbed116.25 million tons, water content is 2212.5 million tons, and oxygen is released 73.75 billion tons. Forests can also turn a lot of soil liquid water into water vapor and discharge it into the atmosphere. All these functions of forests regulate the composition of the atmosphere. Therefore, the forest is the regulator of the natural environment and plays a vital role in the prevention and control of air pollution. China is a country with scarce forests, deteriorating ecological environment and frequent natural disasters. To this end, China also attaches great importance to forest protection and greening. Since the founding of New China, sand-fixing forests, farmland shelterbelts and soil and water conservation forests have been built successively from north to south, and various benefits such as improving ecological environment, protecting farmland and increasing yield have been achieved in key areas. In particular, the five shelterbelt systems under construction will play an important role in improving the ecological environment. These five shelterbelt systems include: northwest, northern North China and western Northeast China (referred to as "Three North") shelterbelt system projects; Shelterbelt system project in the middle and upper reaches of the Yangtze River; Coastal shelterbelt system engineering; Taihang Mountain Greening Project; Plain greening project. The five shelterbelt systems are composed of many types of shelterbelts; Shelterbelt is combined with firewood forest, timber forest and economic forest; Combination of arbor, shrub and grass; Protecting natural forests is combined with artificial afforestation, closing hillsides to facilitate afforestation and sowing by plane; In form, it is a combination of sheet, net and belt, mainly woody plant community. The construction scope of the above five protection systems is 5.78 million square kilometers, accounting for 60.2% of the land area, including the main soil erosion areas, sandstorm areas and disaster-stricken areas in China. Therefore, after the completion of the five shelterbelts, about 900 million mu of farmland can be protected, soil erosion in the loess plateau and the middle and upper reaches of the Yangtze River, which are the most serious in the world, can be eradicated, and the ecological environment can be fundamentally improved. Xiang Jian /wsfw/kxg/ Wu Sheng/web1/res/senior bio/teach/bio _ 2/9 _ 03/015.htm Resources: /wsfw/