A short article describing sandstorms (200 words)

I want to sleep late on weekends, and my wife woke me up with a roar: "Look at the sandstorm." After getting up, I saw the sky in the west, gray, yellow and blue, which was a landscape. Volcanic ash poured in, Lan withdrew, and in a short time, the whole city was swallowed up by dust. Only the sun is struggling, pushed away by the dust for a while, and squeezed in for a while. In the gray-yellow sky, a bright spot is spinning. Sandstorms are nothing new in recent years. They come once or twice a year, and their initial fears have long since vanished. At this time, I just want to make a few complaints, but fortunately, it is getting less and less and weaker.

In fact, sandstorms are terrible and creepy. I remember in the early 1970s, my unit had a farm in a place called Shan in Gansu, which was a plain on a high mountain. When the car turned over a mountain ridge called Jiudaowan, the endless loess high slope came face to face, and a small river meandered into the distance. Where there is green grass, there are sheep scattered in it. When I got to my residence, I couldn't see the barracks. When I got off the bus, I saw that the house was semi-underground and the windows were next to the ground. Ask, why, say, and you will know soon. The company commander and several veterans all looked nervous. Give orders, unload the car, eat, enter the house, and give special instructions to prevent getting lost, lying down and standing by. As the saying goes, ignorance is fearless. After lunch, he took a walk near the barracks. After a while, he saw Huanglong soaring in the distance. It sounded like a cow growling and screaming and rolling like a muffled thunder. At first, there was a swaying yellow line, which rolled forward and became wider and wider, which was very spectacular. In an instant, before I could react, the yellow sand was swept away. Everything disappeared like magic. I can't see the house, the car or even my legs. I reached out and hit my face. It's okay. I have feelings. It took me a whole hour to find the hut. This is the first time I have seen a sandstorm.

However, sandstorms in Qinghai are not as chaotic as those in Gansu. If Gansu is a stew knife to cut meat, then Qinghai is to cut the gordian knot. Once in Golmud, Qinghai, a sandstorm was a sandstorm under the sun, and the sun shone and the sand danced. The wind screamed at the top of my lungs, and occasionally there were one or two screams. The flying gravel hit the car and made a "Dangdang" sound. A gust of wind can really blow stones all over the floor, which is also called a spectacle. The terrible thing is that the wind energy in Qinghai is killing people. I heard of a herder who was swept away by a gust of wind and thrown into a mountain a mile away.

Now, sandstorms have come to the city, just like high-end furniture should be matched with high-end houses. With more tall buildings and less forests, it is inevitable that dust will patronize. More wealth and a better life are social progress, but it is not a good thing for sandstorms to enter the city. This may be a joke played by human beings on nature, but the joke is really a bit big.

Beijing sandstorm and 2008 Olympic Games

Beijing has successfully won the right to host the 2008 International Olympic Games. When people are happy, they find that hosting the Olympic Games is not an easy task. Beijing has put forward the slogans of high-tech Olympics, green Olympics and cultural Olympics, which have been recognized by all walks of life. However, a series of preparations are needed to realize the high-tech Olympics, the green Olympics and the cultural Olympics. Comparatively speaking, it is much more difficult to realize the green Olympics than the high-tech Olympics and the cultural Olympics. There are two reasons for this. First, the international Olympic Committee and people in sports circles in various countries have very strong requirements for the environment. We have noticed that members of the Olympic Committee have raised environmental and traffic issues for Beijing's bid to host the Olympic Games, reflecting their high requirements in this regard; Second, there are indeed some problems in Beijing's present environment. In order to make Beijing's environment meet the requirements of the Olympic Games, a lot of environmental protection and construction are needed. Among them, sandstorm activity and sandstorm in Beijing are the most difficult environmental problems to deal with. Today, I will mainly talk about this issue and talk about my views.

Beijing is a high incidence area of sandstorm activities and sandstorms, and all residents in Beijing feel its threat. The so-called sandstorm activity is a series of physical phenomena caused by strong winds acting on the dry surface. Usually, fine dust flies into the atmosphere and is in suspension. With the help of airflow, it moves to dozens, hundreds, thousands and tens of thousands of kilometers away. Recently, an American friend told me that according to the results of satellite remote sensing monitoring, dust from the Asian continent can cross the Pacific Ocean and reach the central United States. Slightly larger sand grains jump on the ground, while coarse sand grains can't jump and can only roll on the ground. The movement of dust is simultaneous, which often gives people a feeling of darkness. In the words of the masses, it is called flying sand and walking stones. Gravel larger than coarse sand can't be moved by the wind, so it stays in its place. Due to sandstorm activities, the sand on the surface is constantly blown away, which leads to the coarsening of the surface. Finally, the Gobi was formed. On both sides of Lanzhou-Xinjiang Railway, you can see the vast Gobi Desert.

Sandstorm is only a form of sandstorm activity, but its harm is very extensive. Sandstorms make the air turbid. Visibility is greatly reduced, which affects the lift-off of aircraft and the normal operation of cars and trains. Dust is inhaled into the respiratory tract and becomes an important medium for the spread of germs. Dust flying into eyes will affect vision. At the same time, dust is an important factor that harms the environment and affects air quality. Inhalable particulate matter in the air of Beijing is still high. It is closely related to sandstorm activities and sandstorms. As the capital of China and an internationally renowned metropolis; Sandstorm activities and sandstorms have attracted the attention of the international community. As early as 1970s, the International Desertification Conference listed Beijing as one of the cities that suffered from sandstorms. In recent years, Newsweek published an article saying that the capital of China should leave Beijing. From these remarks, it is not difficult to see how much the international community attaches importance to Beijing's environment and sandstorm activities. In order to successfully host the Olympic Games in Beijing. We should make great efforts to control Beijing's environment and slow down sandstorms and sandstorms; Only in this way can we truly realize the green Olympics.

Sandstorm activity and sandstorm. It is the result of interaction between wind and sand. Wind and sand are the material basis and basic conditions of sandstorm activities, and they are indispensable.

Beijing belongs to the East Asian monsoon region, and the uneven heating between land and sea is the basic reason for the monsoon. Warm and humid air from the ocean blows to the mainland in summer, and dry and cold air from the mainland blows to the ocean in winter and spring. These are natural phenomena determined by atmospheric circulation and cannot be changed by human beings. Beijing is located in the southeast of Mongolia Plateau, where cold and high pressure fluctuate in winter and spring and spread to the southeast. So the main wind directions in Beijing in winter and spring are the north wind and the northwest wind. When the strong wind passes through the northern valley, it is strengthened by the narrow tube effect of the fluid and quickly enters the urban area of Beijing, thus causing sandstorm activities and sandstorms.

If there is no sand source in Beijing and there is a lot of forest vegetation on the surface, even if there is strong wind, it will not cause sandstorms. But there are sand sources in Beijing, which is an important condition for sandstorms and sandstorms to occur in Beijing. In the past, many old Beijingers thought that the dust in Beijing was a strong wind blowing from Bashang, Hebei and Inner Mongolia. This statement still exists today. For example, the "Mo Tian" in Huailai Basin was named after it. This sensory understanding is unreliable. After in-depth research by scientists, it is found that the sand in Beijing is very different from the desert in the surrounding areas in terms of morphology and heavy mineral content, especially the roundness (that is, smoothness) of the sand is poor, which belongs to local production and is not shipped from other places. Thus, the misunderstanding of sand gardens in other places was corrected. It should be pointed out that a considerable part of the dust in Beijing comes from other places, and some of it comes from local areas. The particle size (that is, the particle size) of dust is very different, so their transportation methods are essentially different and cannot be confused.

Where is the local sand source in Beijing? This is a problem that many people care about. There are two main local sand sources in Beijing, one is the underground sand source in Beijing, and the other is the sand source of Yongding River, Chaobai River and other rivers. There is sand in the river, which many people have seen. It is formed by alluvial rivers. In winter and spring, the river dries up and the river sand is exposed. People are familiar with this phenomenon, and many people may have seen this scene. I don't want to talk about it anymore.

People can't see the sand underground, and they often lack understanding. Beijing belongs to the piedmont alluvial fan. In the Quaternary geological period, the mountainous areas around Beijing were once covered with ice shells, and later the atmosphere became warmer due to the late ice age. The ice shell melted and burst, and huge ice cubes slid down the hillside under the action of running water. This is how the Quaternary glacial scratches in Moshikou, Shijingshan District and the glacial boulders in Barents Park were produced. Glacier flood at the foot of the mountain pushes a lot of sediment and gravel down the mountain, forming an alluvial fan, which is located in the urban and suburban areas of Beijing. According to the principle of sedimentology, relatively large individual gravels are deposited first, and then coarse sand, medium sand, fine sand, silt and soil are deposited. Because of this principle, gravel can often be seen at 8- 10 meters underground in Beijing. In places close to the mountains, such as Shijingshan District, you can see the gravel by peeling off the thin topsoil. Because the underground sand in the urban area is deeply buried, it can only be seen when the infrastructure is dug. Sand will be exposed to the ground in major constructions such as repairing subways and building tall buildings. The sand on the construction site will fly and spread under the action of strong wind. In recent years, Beijing has engaged in infrastructure construction with more than 1,000 construction sites, which is an important reason for the frequent sandstorm activities in Beijing in recent years.

In addition, cultivated land and garbage dumps in the suburbs of Beijing will also raise dust when the wind is strong in spring, which will become an important source of dust in Beijing. The number of cars in Beijing is increasing year by year, and the automobile exhaust contains carbon particles that are not completely burned. It will also increase the inhalable particles in the air. Industrial boilers and domestic coal burning will also produce coal ash, which will become a source of dust.

The above-mentioned dust, floating dust and floating dust are integrated under the action of strong wind and flutter with the wind, causing air pollution in Beijing and contributing to sandstorms.

Sandstorm activity and sandstorm are the common results of strong winds acting on the sand surface. Therefore, the basic principle of preventing and controlling sandstorms is to fix quicksand and reduce wind speed. The wind speed at which quicksand is blown off the surface is called sand-raising wind speed. The wind speed of blowing sand is related to the size of sand and the degree of dryness and wetness. As far as Beijing is concerned, when the wind speed reaches 4-5 m/s, there will be sandstorms. If there is forest vegetation on the surface, the roots of plants can fix quicksand and reduce sandstorm activities.

There are three main ways to prevent sandstorms. One is to plant trees and grass, which is called biological sand control. The second is to set up sand barriers, which are called engineering sand control. The third is spraying coagulant, which is called chemical sand control. Among them, biological sand control is the best sand control method, which is widely used in the world. Engineering sand control is an auxiliary means, and chemical sand control is rarely used in China.

Forest vegetation has many functions. Tall trees and low shrubs have good windproof effect. The so-called windproof function is not to prevent the occurrence of strong winds, but to reduce the wind speed. In the 1970s and 1980s, Beijing put forward the slogan of checking the air duct to block the air outlet, which was unscientific, because both the air duct and the air outlet could not be blocked, so we had to find ways to reduce the wind speed. When the strong wind passes through the forest, the sandstorm will be reduced because it is blocked, and the sand carried by the strong wind will land in front of and in the forest, thus slowing down the sandstorm activity. Over the forest, due to the action of airflow, the wind speed will also decrease. When the wind speed will be lower than the wind speed, the sandstorm activity will naturally weaken or stop.

Another function of the forest is to fix quicksand. When the forest is formed, shrubs and absinthe will grow under it. The roots of these vegetation are interlaced like a silk screen and covered with quicksand. Forest vegetation can store water and is called "green reservoir". When sand contains moisture, it is difficult to be blown up even in strong winds due to the surface tension of water.

Another important function of forest is often overlooked, that is, forest vegetation can affect rainfall. The fundamental cause of rainfall is atmospheric circulation. When water vapor from the ocean condenses into water droplets, it will fall from the sky. This is rain. Water vapor is foggy. Whether it can become raindrops depends on certain conditions. Only when water vapor adheres to a certain core can it easily become raindrops. The biological nucleus formed by the decay of forest vegetation floats over the forest and becomes the object of water vapor attachment, thus forming raindrops. Therefore, where there are many forests, there will be more rain. Where there are few forests, there is less rainfall, and it is difficult to rain where there are no forests. A large number of facts have proved that forest vegetation can affect rainfall in some areas. There is a folk saying in the northern countryside that it doesn't rain across the mountain, the river and the road, which is the phenomenon of uneven rainfall in the same area.

Planting trees and grass is the main way to prevent sandstorms. However, how to plant trees and grass is very knowledgeable, involving a lot of scientific knowledge, which can not be done by enthusiasm alone.

The first is the relationship between trees and grass. Ecological benefits of trees and shrubs. Much taller than grass. The lawn is delicate and needs sprinkler irrigation, fertilization and careful management. Lawn is easy to harden and needs to be perforated. So the cost of lawn is very high; In particular, lawns imported from other places and abroad are particularly difficult to manage. Beijing is a city short of water, and the lawn is a "water tiger", so it is impossible to do more. In airports and railway stations, some important squares can be done, but not too many. The ecological benefit of street flowers is lower, and there is no need to do it. For Beijing, a city with frequent sandstorms, priority should be given to ecological benefits.

Secondly, as far as planting trees is concerned, there is also the question of what kind of trees to plant. Trees are living things. According to its growth law, it can only grow slowly, but it is not enough to pull out the seedlings to encourage it. There is an idiom in China called "It takes ten years to plant trees, but it takes a hundred years to cultivate people". This is a fact. There are only seven years between now and the 2008 Olympic Games, so it is difficult to grow small saplings. In February this year, when I was interviewed by Global Times reporters Du Zengliang and Li Yuxia, I suggested that Beijing should plant big saplings. Survival will produce good ecological benefits. This opinion has attracted the attention of relevant parties in Beijing.

Whether to plant conifers or broad-leaved trees is also a problem that needs serious consideration. Beijing is a windy and dusty city. From the perspective of wind and sand prevention, there should be many kinds of conifers. The leaves of broad-leaved trees all fall off after late autumn, but in winter and spring, only the trunk has no leaves, and the bare branches lack the ability to resist wind and sand. Conifers are evergreen all year round. Even in winter and spring, they are still covered with leaves, which can effectively block sandstorms. Pine and cypress are barren-tolerant and long-lived. They are native trees in Beijing and are suitable for Beijing's natural conditions. Generally speaking, conifers live longer than broad-leaved trees, and poplars will be bald and hollow in thirty or fifty years, showing a state of decline. For thousands of years, pines and cypresses are still full of vitality. The life span of trees directly affects their ecological benefits. In addition, pine and cypress trees are used for urban greening. It gives people vitality and strength, which is more in line with the character and hobbies of China people.

In order to prevent farmland dust from flying into the urban area, we should plant a variety of trees in the urban-rural fringe and along the river to form a green circle, just like the second, third, fourth and fifth rings, which will surround the urban area. Forest belts and forest nets should be formed in cultivated land in suburbs, which can conserve water, prevent wind and sand, and birds in the forest can eliminate pests in the field, which has many benefits.

The valleys of Xishan, Du Jun and Yanshan are the main channels for strong winds from Bashang to Beijing. The construction of railways and highways destroyed the trees in the valley. In order to straighten the line, the mountains were cut and stones were cut. In this way, the valleys and valleys become open and unobstructed, which is more conducive to the entry of strong winds in spring. Therefore, it is necessary to plant a variety of trees in valleys and river valleys to form a green barrier, which can greatly slow down the wind speed. When the wind speed decreases, sandstorms and sandstorms can slow down. Trees in mountainous areas are easily cut down by residents. It is necessary to vigorously publicize scientific knowledge, let residents understand the great role of forests, and consciously care for trees.

Hosting the Olympic Games is a century-old dream of China people. How to run the Olympic Games well is the responsibility of Beijingers and the people of the whole country. Foreign countries, especially European and American countries, have a strong awareness of environmental protection and high requirements for the environment. We should have a clear understanding of this. The environment in Beijing is constantly improving and changing greatly, but we can't satisfy the present situation. This year's sandstorm has already appeared on New Year's Day. Some of them are unexpected. It gives us a wake-up call, and we must not be careless and take chances. Beijingers have some bad habits and don't care for flowers and trees. Is one of them. It is a very arduous task to arouse people's awareness of environmental protection. The students present here are all college students in the capital. I hope you can do more publicity about environmental knowledge and attack those behaviors that destroy the environment. Only when everyone is eager to be green and protect the environment from the bottom of his heart can the environment in Beijing be fundamentally changed. In order to host the Olympic Games and for our own survival, we should do a good job in Beijing's environment. Looking forward to the early realization of the new Beijing with green water and blue sky. Let's hold the Olympic Games under clear water and blue sky to show the beautiful style of the capital Beijing.