Iceland and China, volcanic ash and acid rain, previously unrelated words, were linked by a volcanic eruption. On April 14, a volcano erupted near the Eyjafjallajokull ice sheet in Iceland, and the dust formed by volcanic ash rushed to the altitude of 1 1000 meters.
On April 22nd, Beijing ushered in a spring rain. With the humid air, a message was widely circulated on the Internet and mobile phones of users in China: "Please don't get wet from today to the 28th. Acid rain once in 750 years has a high probability of getting skin cancer after getting wet. Because of the eruption of a volcano in Europe, a large amount of sulfide sprayed into the sky, forming a thick and highly acidic volcanic ash layer at the height of 7000m to10000m in the atmosphere. Please pay attention and forward this information to people around you. "
Will volcanic ash really bring acid rain? Can you really get skin cancer in the rain? With the spread of rumors, the serenity and comfort brought by light rain have been replaced by fear and panic.
"In the past, the rainfall at the turn of spring and summer in Beijing was really weak, but the pH value of this rainfall on the 22 nd was 6.23, not acid rain." Zhang Mingying, a senior engineer of Beijing Meteorological Observatory, clearly told reporters that this kind of worry is unnecessary. "The Beijing Meteorological Observatory has set up an acid rain monitoring station in Cheng Nan to monitor the pH value of rainwater all the year round."
But as we all know, the pH value of acid and alkali is measured by 7, and those with pH less than 7 are acidic and those with pH greater than 7 are alkaline. Why is the pH value of this rainfall 6.23, but it is not acid rain?
In the face of a reporter's question, Zhang Mingying told reporters that this is because the air contains carbon dioxide, and the combination of water and carbon dioxide will be acidic. So when we test the pH of rain in nature, the pH value is 5.6. The pH value of the rain on the 22nd is 6.23, which is greater than 5.6, so it is not acid rain.
■ The volcanic ash floating over China is a micron-sized substance, which will only stay in the stratosphere and will not cause acid rain.
"People are worried that volcanic ash will cause acid rain, mainly because of its composition and drift route." Lasg researcher Wang told reporters frankly.
He told reporters that when a volcano erupts, it will spew a lot of dust at an altitude of 7000 meters to 20000 meters. The main components of these volcanic ash are iron oxide, silicon dioxide and sulfur dioxide. Due to different geological structures, the contents of various substances in volcanic ash components are also different. The combination of sulfur dioxide and water will produce acid rain. When the Icelandic volcano erupted this time, the substances with larger particles in the volcanic ash have settled in the volcanic eruption area due to their heavy weight and short transportation distance, forming a thick volcanic ash covering the surface, and these substances cannot float to China. The micron-sized substances with smaller particles in volcanic ash will continue to rise and reach the higher stratosphere because of their light weight. The wind, frost, rain and snow that people usually feel are produced in the lower troposphere, and the materials in the stratosphere will only drift with the atmospheric circulation and will not settle. Because China is thousands of kilometers away from Iceland, even if there is volcanic ash floating over China with the atmospheric circulation, it is a micron-sized substance, which will only stay in the stratosphere and will not cause acid rain. In addition, there are several paths of volcanic ash diffusion, which will continue to spread during transportation, so that with the extension of transportation distance, the larger the diffusion range, the lower the concentration.
Shao Min, a professor at Peking University Institute of Environmental Science and Engineering, believes that the maximum troposphere can reach10000m. When volcanic ash floats at this height, sulfur-containing particles in it may combine with water to produce acid rain. However, this will only have a certain impact on the volcanic eruption site. In China, far away from the volcanic eruption site, the impact is not significant because the concentration of volcanic ash has been greatly reduced. Moreover, the height of most cumulonimbus clouds is very low, so the possibility of acid rain in China due to volcanic ash is very small.
Zhang Mingying, a senior engineer of Beijing Meteorological Observatory, also told the reporter that three days after the eruption of Iceland volcano, that is, 17, it began to rain in many European countries, but even in these countries which are much closer to Iceland than China, there was no acid rain. In his view, volcanic ash from Iceland volcano is distributed at an altitude of 3000 meters to 10000 meters. Among them, the larger particles drift south and settle not far away under the influence of low-level airflow, while the smaller particles drift north under the influence of high-level airflow, which can be said to have little impact on China.
■ Once the volcanic ash containing iron oxide and silicon dioxide is inhaled into the aircraft engine, the consequences will be unimaginable.
So besides acid rain, what impact will volcanic ash have on human life?
"In fact, after the eruption of Iceland volcano, the field that affected human life before acid rain was mainly aviation." Cao, an academician of the China Academy of Sciences, a member of the Expert Advisory Committee of the Commission of Science, Technology and Industry for National Defense and a researcher at the Beijing Institute of Aeronautical Materials, told the reporter.
Some experts said that even after the "9. 1 1" terrorist attack, the aviation industry was only affected for three days, and this aviation paralysis was the most serious aviation chaos in Europe since World War II in terms of scale and time, and the detention of a large number of passengers also made local rooms overcrowded. In addition, the domino effect brought by aviation chaos has spread to the global logistics industry, and there is a shortage of food, medicine and other commodities in Europe.
Why does volcanic eruption paralyze the European aviation industry? Cao told reporters that after the eruption of Iceland volcano, volcanic ash was mainly distributed in the air between 7000m and 10000m in Europe, which is the normal flight altitude of most civil aviation aircraft. The attachment of volcanic ash to the plane surface has little effect. Crucially, once the volcanic ash containing iron oxide and silicon dioxide is inhaled into the aircraft engine, the consequences will be unimaginable. There are blades, gears and steel plates in the aircraft engine. If some volcanic ash particles with low melting point but large volume enter the engine, they will stick to the blades and gears, leading to engine failure.
In addition, if the concentration of volcanic ash is too high, it will also affect the pilot's sight. Although modern aircraft are equipped with computer-controlled blind flying equipment, pilots can't rely entirely on instruments when taking off and landing, but rely on visual operation.
■ Volcanic eruption will lead to an increase in temperature, covering the atmosphere with volcanic ash and thinning the ozone layer.
Apart from acid rain, aviation ban, paralysis of logistics industry and damage to tourism, this Icelandic volcanic eruption will also have some indirect effects.
Wang told reporters that although the volcanic eruption in Iceland has weakened, it has not completely stopped. This volcanic eruption lasted for a long time, and a large amount of volcanic ash continued to enter the atmosphere. Volcanic ash will first weaken the solar radiation, thus reducing the solar energy obtained by the earth. In some places, it will heat up and in some places it will cool down. Shao Min, a professor at Peking University Institute of Environmental Science and Engineering, also supports this view. He believes that the direct impact of volcanic ash on solar radiation is that the global temperature will be lower than normal years.
Will this affect agricultural production? When interviewed, Zhang, representative of the World Food Organization in China, and China, spokesman of the United Nations Food Program, both said that there was no impact for the time being.
Wang believes that the impact of volcanic ash on crops should be distinguished between the north and the south, because this time Icelandic volcanic ash will enter the northern part of China first, so the impact on the north is greater than that on the south without changing the drift direction. However, the atmospheric circulation is constantly moving, and the volcanic ash in the stratosphere will continue to move eastward with the atmospheric circulation, so even if it has an impact, it is temporary.
At the same time, both Wang and Wang believe that volcanic eruption will lead to an increase in temperature, thus covering the atmosphere with volcanic ash and thinning the ozone layer.
As to whether people are worried that volcanic ash will increase the incidence of respiratory diseases, Shao Min thinks that Iceland, where the volcano erupted, is far from our country. In addition, the volcanic ash floating over China is very thin, and it is all micron-sized substances that stay in the stratosphere above 10000 meters. With the circulation of the atmosphere, these volcanic ash will soon drift away, so it will not increase the probability of people suffering from respiratory diseases.