天造还是人为？

○沙尘暴发生的三要素是大风、不稳定的大气层结状态和地面的沙尘源，所以常常发生在春季

The three factors of sandstorm are strong wind, unstable atmospheric stratification and dust source on the ground, so it often occurs in spring

○沙尘暴产生的年代已很久远，但近期有加剧的趋势

The sandstorm has been produced for a long time, but there is a trend of aggravation in the near future

○沙尘暴的发生与沙漠化有关，自然成因和人为因素都起作用

The occurrence of sandstorm is related to desertification, and both natural and human factors play a role

春天终于来了，北方人在感受花红柳绿、燕舞莺歌之前，总是躲不开几次沙尘的“洗礼”。你知道如何确定沙尘暴天气吗？当你站在户外混浊的空气中看不到离你一公里远的地方时，这便是沙尘暴天气了。沙尘暴一来遮天蔽日，户外的人们苦不堪言。狂暴的风沙阻断交通，摧毁通讯线路甚至建筑，毁伤人命。我们平常所说的沙尘暴，实际上是沙暴和尘暴两者的总称。一般说来，沙暴是就地起沙(扬沙)，它携带的沙物质搬运的距离不远，而尘暴(浮尘)却能在高空中飘移几千公里之外，甚至更远。去年夏天，法国波尔多大学地质学家弗朗西斯与他的同事竟然在欧洲阿尔卑斯山的积雪中发现了来自中国的这些“不速之客”。近年来媒体对沙尘暴的关注很多，体现了社会各界对此问题的焦虑及治理的重视。要想找到治理的正确途径必须先把它的形成机理搞清楚。那么沙尘暴是几个简单原因造成还是多个系统复合作用的结果？沙源是短期形成、发生的，还是长期形成、发生的，甚至是一个地质变化过程？沙尘暴是自然成因为主还是人为的结果？本文试着就这些问题作一探讨。

Spring has finally come. Before the northern people feel the red flowers and the green willows and the song of the dancing warblers, they can't avoid the "baptism" of the dust several times. Do you know how to determine the sandstorm weather? When you stand outside in the turbid air and can't see the place one kilometer away from you, this is the sandstorm weather. As soon as the sandstorm came to block out the sun, the outdoor people were suffering. Violent sandstorms block traffic, destroy communication lines and even buildings, and damage human lives. What we usually call sandstorm is actually the general term of sandstorm and dust storm. Generally speaking, sandstorm is to raise sand on the spot (blowing sand). The distance of carrying sand material is not far, but the dust storm (floating dust) can move thousands of kilometers or even farther in the air. Last summer, Francis, a geologist at the University of Bordeaux in France, and his colleagues found these "unexpected visitors" from China in the snow of the European Alps. In recent years, the media has paid a lot of attention to sandstorm, which reflects the anxiety of all walks of life and the importance of governance. In order to find the right way of governance, we must first make clear its formation mechanism. So are sandstorms caused by several simple causes or by multiple systems? Is the source of sand formed and occurred in a short time, or in a long time, or even a geological change process? Is sandstorm a natural or man-made result? This paper tries to discuss these problems.

沙尘暴的空间和时间分布

Spatial and temporal distribution of sandstorm

中国北方沙尘暴发生的特点是西北多于东北、平原(或盆地)多于山区、沙漠多于其他地区。我国北方干旱半干旱地区有五大沙尘暴中心：一是新疆的塔里木盆地，主要包括塔克拉玛干沙漠和罗布泊地区，二是内蒙西部、甘肃、宁夏的阿拉善高原，包括巴丹吉林沙漠、腾格里沙漠、乌兰布和沙漠和河西走廊。三是内蒙中部的鄂尔多斯高原，包括毛乌素沙地和北部黄土高原。四是内蒙古东南部，包括后山地区、浑善达克沙地和科尔沁沙地。五是华北平原，范围可至北京以南。这些地区的地面物质在强劲偏北风作用下影响我国北方地区甚至长江流域。

The occurrence of sandstorms in northern China is characterized by more sandstorms in Northwest China than in Northeast China, more sandstorms in plain (or basin) than in mountain area, more sandstorms in desert than in other areas. There are five sandstorm centers in the arid and semi-arid areas of northern China: the Tarim Basin in Xinjiang, mainly including Taklimakan Desert and Lop Nur area; the Alxa Plateau in western Inner Mongolia, Gansu and Ningxia, including Badain Jaran Desert, Tengger Desert, Ulan Buh Desert and Hexi corridor. The third is the Ordos Plateau in the central part of Inner Mongolia, including the Mu Us sandy land and the northern Loess Plateau. Fourth, the southeast of Inner Mongolia, including Houshan area, Hunshandak sand land and Horqin Sand Land. Fifth, the North China plain extends to the south of Beijing. Under the strong northerly wind, the surface materials in these areas affect the northern China and even the Yangtze River Basin.

科学研究证明，沙源的形成是一个相当长的过成，其中自然力起的作用是主要的。据对深海岩心和冰盖沉积物的测定，早在白垩纪末(距今7000万年)就有风沙尘暴出现，我国最早的记录可以追溯到公元前205年。在漫长的地质历史中沙尘暴显示出周期性变化，它与地质时期气候变化和地面沙尘物质的消长有关，遇气候暖湿时期地面植被生长茂密，生态环境条件好，沙尘暴发生频率低；反之，在冷干气候时期，则沙尘暴发生频率高。我国从公元前205年以来有85%以上的沙尘暴都发生在3～5月份，而且多出现于春季的午后。这是由于春季是全年中空气冷暖变化最剧烈的季节，午后到傍晚之前又是一天中气温最高的时段，更容易造成空气层结的不稳定。沙尘的肆虐，就在于对流层低层存在着强烈的垂直方向的不稳定和强对流。另外，春季北方地区气温陡然回升，大地解冻，同时干旱少雨，地表干燥松软，不论是耕地还是荒漠草原，均无植被覆盖而裸露无遗，为沙尘暴的发生提供了丰富的沙尘源。

Scientific research has proved that the formation of sand source is a long-term over formation, in which natural forces play a major role. According to the determination of deep-sea cores and ice sheet sediments, sandstorms appeared as early as the end of Cretaceous (70 million years ago), and the earliest record in China can be traced back to 205 BC. In the long geological history, sandstorm shows periodic change, which is related to the climate change in geological period and the fluctuation of ground dust material. In the warm and humid climate period, the ground vegetation grows luxuriantly, the ecological environment conditions are good, and the frequency of sandstorm is low; on the contrary, in the cold and dry climate period, the frequency of sandstorm is high. Since 205 BC, more than 85% of sandstorms in China have occurred in March to may, and most of them occur in the afternoon of spring. This is because spring is the season with the most violent change of air temperature in the whole year. From afternoon to evening, it is the period with the highest temperature in the day, which is more likely to cause the instability of air stratification. The rampant of dust lies in the strong vertical instability and strong convection in the lower troposphere. In addition, in spring, the temperature in the northern region rises sharply, the land thaws, and the surface is dry and soft with little rain. No matter in cultivated land or desert grassland, there is no vegetation coverage and bare, which provides a rich source of sand and dust for the occurrence of dust storms.

沙尘暴产生的三个条件

Three conditions of sandstorm

沙尘暴形成需要三个条件：大风、不稳定的大气层结状态和地面上的沙尘。沙尘暴天气的发生一般需要有足够强劲持久的风力，平均风速在每秒12米以上。光有大风是不够的，只有在低层空气不稳定的情况下，沙尘才会被卷扬得很高，被风吹到很远的地方。当然还要有充足的沙源。

The formation of sandstorm requires three conditions: strong wind, unstable atmospheric stratification and dust on the ground. The occurrence of sandstorm generally requires strong and lasting wind, with an average wind speed of more than 12 meters per second. It's not enough to have strong winds. Only when the air in the lower layer is unstable, the dust will be blown high and far away. Of course, there should be sufficient sand sources.

从天气学角度看，大风的形成，一是强冷空气入侵，即冷锋过境，穿越锋面的次级环流促使锋前强烈上升、锋后动量下传，由此产生变压风，这是造成近地面大风的主要因素；二是冷锋前地面热低压发展使锋区气压梯度增大而形成梯度风。强冷空气是形成沙尘天气的驱动力，只有足够的冷空气方有可能形成强的气压差，推动大气的水平流动。又由于此时低空不同高度水平风速的不同，以及低层的强烈辐合，迫使空气产生垂直方向的流动，从而产生强烈的水平和垂直运动。瞬时最大风速为每秒17米，短时七、八级以上，即可出现沙尘暴。形成沙尘暴的冷空气强度要比一般大风的冷空气更猛烈。

From the synoptic point of view, the formation of gale is mainly caused by the strong cold air invasion, i.e. the cold front transit, the secondary circulation passing through the front, which causes the strong rise in front of the front and the momentum passing down behind the front, resulting in the variable pressure wind, which is the main factor causing the gale near the ground; the second is that the development of the surface hot low pressure before the cold front increases the pressure gradient in front of the front to form the gradient wind. Strong cold air is the driving force for the formation of dust weather. Only enough cold air can form a strong pressure difference and promote the horizontal flow of the atmosphere. At the same time, due to the different horizontal wind speed at different altitude and the strong convergence of the lower layer, the air is forced to flow in the vertical direction, resulting in strong horizontal and vertical movement. The maximum instantaneous wind speed is 17 meters per second, and the sandstorm can occur if the wind speed is above seven or eight levels in a short time. The intensity of cold air is stronger than that of normal gale.

大气层结是否稳定是形成沙尘暴的另一决定性因素。以最常出现区域性强沙尘暴的甘肃省河西地区为例，这里处在冷空气东南下的西北通道上，一般来说，冬春两季特别是春季经常有势力强大的冷空气入侵，而且春季植物稀少，沙漠和裸露的地表温度上升得很快，只要连续晴好两三天，地面气温可以升得很高。如果这时遇上强大的冷空气在中午前后过境，可形成上冷下暖的不稳定的温度层结，沙尘暴常常在此时发生。

The stability of atmospheric stratification is another decisive factor for the formation of dust storms. Taking Hexi area of Gansu Province, where the most frequent regional strong sandstorm occurs, as an example, it is located on the northwest passage under the southeast of cold air. Generally speaking, in winter and spring, especially in spring, there are often strong cold air intrusions, and there are few plants in spring. The temperature of desert and bare surface rises rapidly. As long as it is sunny for two or three days, the temperature of ground can rise very high. If the strong cold air passes through the area around noon, the unstable temperature stratification of upper cold and lower warm can be formed. Sandstorm often occurs at this time.

沙源都是些什么东西呢？它们是怎么来的呢？我们能“消灭”或封闭这些物质吗？下面我们就从沙尘源的形成来寻找答案。

What is Shayuan? How do they come from? Can we "eliminate" or seal off these substances? Let's look for the answer from the formation of dust sources.

从我国北方地区沙尘源的形成看，一类是自然形成的第四纪沉积、堆积物；另一类是人类生产活动堆积物。前者有风成沙、沙砾戈壁、风蚀劣地、沙质粘土、第三纪红色沙岩、现代流水冲积物、湖积物、黄土等。这些沙尘源物质量大且分布面积广，为强沙尘暴的形成提供了丰富的物质基础。后者有尾矿砂、废弃物、炉灰等堆积物和开垦耕地的裸露地面等，比如退化的森林草地、没有植被覆盖的干松土地和城乡建筑工地的沙土堆。近年发生的沙尘暴中，沙质草地和旱作耕地是主要沙源。从自然成因上看，人类无法消除沙尘暴。但从人类自身活动来看，乱砍滥伐和对土地、水资源的不合理利用而加速沙尘暴发生的负面作用是可以消减的，可以在一定程度上消减沙尘暴发生的频率和强度。

In terms of the formation of dust sources in northern China, one is naturally formed Quaternary deposits and accumulations; the other is accumulations of human production activities. The former includes eolian sand, gravel gobi, wind eroded bad land, sandy clay, Tertiary red sandstone, modern fluvial alluvium, lacustrine deposit, loess, etc. These dust sources have a large mass and wide distribution area, which provide a rich material basis for the formation of strong dust storms. The latter includes tailings, wastes, ashes and other deposits, as well as the bare ground of cultivated land, such as degraded forest grassland, dry pine land without vegetation cover and sand piles of urban and rural construction sites. In recent years, sandy grassland and dry cultivated land are the main sources of sand. In terms of natural causes, human beings cannot eliminate sandstorms. However, from the perspective of human activities, the negative effects of deforestation and unreasonable use of land and water resources to accelerate the occurrence of sandstorm can be reduced, and the frequency and intensity of sandstorm can be reduced to a certain extent.

沙源物质颗粒的大小也影响沙尘飞行的距离。如科尔沁沙地组成物质主要是中细砂粉砂层和粉细砂。鄂尔多斯等地含细砂、粉砂高达80%。松散沉积环境加上合适的环流条件，使这些地区成为沙尘暴的高发区和物源区。沙尘发生地区辽阔坦荡的地貌也是成因之一。

The size of sand particles also affects the distance of dust flight. For example, the components of Horqin sandy land are mainly medium and fine sand and silty sand. Ordos and other places contain 80% fine sand and silt. The loose sedimentary environment and suitable circulation conditions make these areas the high incidence area and source area of sandstorm. It is also one of the causes of the formation of the vast and flat landform in the dust producing area.

荒漠化扩大了沙尘源，增加了沙尘暴天气的发生，近年来气候干暖化和人为活动强度加大，造成荒漠化速度加快。荒漠化与经济活动强度及人口数量增加成正相关。人口的增加加大了对土地资源和水资源的压力，低素质的人群中便出现乱砍滥伐、过牧和水资源利用不当的现象，从而加速了荒漠化的蔓延，形成恶性循环。

In recent years, the intensity of dry and warm climate and human activities has increased, resulting in the acceleration of desertification. Desertification is positively related to the intensity of economic activities and the increase of population. The increase of population has increased the pressure on land resources and water resources, and the phenomenon of deforestation, overgrazing and improper use of water resources has appeared among the low-quality population, thus accelerating the spread of desertification and forming a vicious circle.

沙漠以外地区的沙尘源也是一个不容忽视的因素。我国北方春季气候干燥，风力较强，土壤墒情差，植被疏矮，每遇大风天气，表层干燥土壤容易被风刮起，形成扬尘。而城郊地带由于破土施工、建材堆积、垃圾堆放不合理等也是扬沙的来源之一。

The source of dust outside the desert is also a factor that can not be ignored. In the north of China, the climate is dry in spring, the wind is strong, the soil moisture is poor, and the vegetation is sparse. In case of windy weather, the surface dry soil is easy to be blown by the wind, forming dust. The suburban area is also one of the sources of sand lifting due to the construction of broken soil, the accumulation of building materials and the unreasonable stacking of garbage.

有关防治对策的探讨

Discussion on prevention and control measures

我们要树立的一个信心是，人类现有的科学技术可以遏制或减轻沙尘暴对人类的危害。防御沙尘暴的长远对策是从根本上改善生态环境，人为改变荒漠和半荒漠地表现状以及恶劣的生态环境。下面就介绍几种防风固沙工程：

We should establish a confidence that the existing science and technology of human beings can contain or reduce the harm of Sandstorm to human beings. The long-term countermeasures to prevent sandstorm are to fundamentally improve the ecological environment, artificially change the surface status of deserts and semi deserts and the poor ecological environment. Here are some wind and sand control projects:

一是机械沙障，主要用杂草、树枝以及其他材料，在流沙上设置阻滞风沙流和固定沙面的障碍物。例如，草方格沙障是用稻草、麦秆和芦苇等柔性材料，将其直接插入沙层内，直立于沙丘上，扎设成方格状，粘土沙障是有粘土碎块堆成小土埂而成。如果你乘火车经过宁夏回族自治区的沙坡头，就会看到很多的这种机械沙障的景观。

One is mechanical sand barrier, which is mainly made of weeds, branches and other materials. Obstacles are set on quicksand to block sand flow and fix sand surface. For example, straw, wheat straw, reed and other flexible materials are directly inserted into the sand layer, standing on the sand dune, and tied into a grid. Clay sand barrier is made of clay fragments piled into small ridges. If you take a train through Shapotou, Ningxia Hui Autonomous Region, you will see a lot of this mechanical sand barrier landscape.

二是化学固沙，它是在流动沙地上喷洒化学粘结材料，使其在沙地表面形成一层有一定强度的防护壳，让沙尘吹不起来。例如美国的赌城拉斯韦加斯，周围除了沙漠就是盐碱地，加上严重缺水，树难栽活。当地用科学技术手段，开发出一种像发胶的材料，喷洒在沙尘上，形成沙壳。这种材料总体上分为三大类：一类是将植物纤维和旧报纸纸浆与粘性物质搅拌在一起，喷洒在沙尘的表面。在喷洒时还可以将这些材料添加绿色染料，远看上去像一层茵茵绿草。这类纤维粘料喷在沙尘表面不深，浅浅地结成块，由于比较薄，人不能在上面走。另一类粘性胶质材料喷洒在沙漠上，渗进沙漠要深一些，板块层厚硬，人可以行走，但汽车等机动车辆上不去。第三类粘性胶质材料叫做“锁定沙尘”。这种材料喷洒在沙漠上，渗透沙漠半英寸，表层粘结厚而坚硬，可以行人和各种车辆，它不怕压，不起灰，是最结实的一种。如果没有人为破坏或雨水流失，每喷洒一次一般可以锁定沙尘一到两年。这三类粘性物质的成本一般在每英亩500美元到2000美元之间，比种植树木花草成本要低得多。

The second is chemical sand fixation, which is to spray chemical bonding materials on the flowing sand, so that it forms a protective shell with certain strength on the surface of the sand, so that the sand dust can not be blown up. For example, Las Vegas, the gambling city of the United States, is surrounded by salt and alkali land except for deserts. With severe water shortage, it is difficult to plant trees. By means of science and technology, a hair gel like material was developed and sprayed on the sand dust to form a sand shell. The materials are generally divided into three categories: one is to mix plant fibers and old newspaper pulp with viscous substances and spray them on the surface of dust. When spraying, these materials can also be added with green dye, which looks like a layer of grass. This kind of fiber cement is not deep on the surface of sand dust, and it forms a block in a shallow way. Because it is relatively thin, people can't walk on it. Another kind of sticky gum material is sprayed on the desert. It needs to penetrate deeper into the desert. The plate layer is thick and hard, so people can walk, but cars and other motor vehicles can't. The third type of sticky gum material is called "sand dust locking". This kind of material is sprayed on the desert. It penetrates the desert for half an inch. The surface layer is thick and hard. It can be used by pedestrians and various vehicles. It is not afraid of pressure and ash. It is the strongest one. If there is no man-made damage or rainwater loss, the dust can be locked for one to two years after each spraying. The cost of these three types of viscous substances is generally between $500 and $2000 per acre, which is much lower than the cost of planting trees, flowers and plants.

植物固沙当然是长远大计。在水资源允许的条件下，在沙源地栽种植物，草、灌木和乔木，不仅能够长久固定流沙，还可以从根本上遏制沙漠发展。在我国，每年的植树节前后，大家都去义务植树并设法把树种活是很重要的。旱地节水技术、防护林工程以及水资源利用和调控工程等也是比较成熟的技术和治理模式。

Fixing sand with plants is certainly a long-term plan. With the permission of water resources, planting plants, grass, shrubs and trees in the sand source can not only fix the quicksand for a long time, but also fundamentally curb the development of the desert. In our country, it is very important for everyone to plant trees voluntarily and try to make them live before and after the tree planting festival every year. Dry land water-saving technology, shelterbelt project and water resource utilization and regulation project are also relatively mature technologies and governance models.

当然，防治沙尘暴的办法不光是靠这些防治工程技术以及植树造林，我们更要加强科技教育和法制教育，将生态环境的保护治理、自然资源的开发利用等纳入科技教育和法制教育的内容，唤起公众的忧患意识，加强全民生态伦理、道德和法制观念，增强全社会对自然灾害的防护意识。

Of course, the way to prevent and control sandstorm is not only based on these prevention and control engineering technologies and afforestation, but also on strengthening science and technology education and legal education, including the protection and management of ecological environment, the development and utilization of natural resources, etc., in science and technology education and legal education, arousing the public's sense of suffering, strengthening the ecological ethics, morality and legal concept of the whole people, and enhancing the whole society's self-respect However, the awareness of disaster protection.

在这里我们再来看看美国拉斯韦加斯对沙尘暴的防治。制度管理是当地根治沙尘的一个重要办法。人为因素是该县沙尘问题产生的一个重要原因。比如：有些人喜欢在沙漠上开车，弄得沙尘飞扬；再如：随着拉斯韦加斯的扩建，在沙漠上建房、施工、修路也都可能会引起沙尘问题，如果遇到刮风就更糟了。政府采取宣传加惩罚的措施，一是通过媒体、路牌告示及发放宣传品，告诉人们不要人为制造沙尘。二是对沙漠土地拥有者实行承包责任制。如果沙漠土地拥有者和居住在那里的屋主，不能很好地控制沙尘，将会受重罚，每天罚款500美元，再不执行，每天增罚2000美元。三是对人为制造沙尘者进行电话举报，有举报必处理。四是限制施工单位制造沙尘。对在沙漠中施工的承包单位负责人和职工在开工前至少上4个小时的环境课，让他们在施工中尽量减少灰尘，要求他们一边施工一边用水消尘。如果达不到要求，空气质检部门将勒令其停工或给予罚款。

Let's take a look at the prevention and control of sandstorms in Las Vegas, USA. System management is an important way to eradicate dust. Human factor is an important reason for the dust problem in the county. For example, some people like to drive in the desert and make the dust fly; for example, with the expansion of Las Vegas, building houses, construction and road construction in the desert may also cause dust problems, even worse in case of wind. The government adopts measures of publicity and punishment. First, it tells people not to create dust artificially through media, road signs and distribution of propaganda materials. The second is to implement the contract responsibility system for the owners of desert land. If the owner of desert land and the owner of the house who lives there can't control the dust well, they will be fined $500 a day. If they don't implement it, they will be fined $2000 a day. The third is to report the man-made dust by telephone. If there is a report, it must be handled. Fourth, the construction unit shall be limited to produce dust. The person in charge of the contractor and the staff who construct in the desert shall have an environmental class at least 4 hours before the commencement of construction, so that they can reduce the dust as much as possible during the construction and require them to use water to eliminate the dust while constructing. If it fails to meet the requirements, the air quality inspection department will order it to stop work or impose a fine.

这对我们国家防治沙尘暴是一个很好的启发，我们每一位公民都要增强对沙尘暴的防护意识，保护环境从自身做起。

This is a good inspiration for our country to prevent and control sandstorm. Every citizen of our country should enhance the awareness of sandstorm protection and protect the environment from their own.