Haze generated real reason by Academician
Tang Xiaoyan: Chinese Academy of engineering, environmental science experts, former vice chairman of the China Environmental Society, director of the Center for2018-08-15 19:38:12
Tang Xiaoyan: Chinese Academy of engineering, environmental science experts, former vice chairman of the China Environmental Society, director of the Center for Environmental Sciences at Peking University, won the National Science and Technology Progress Award 1, National Science and Technology Progress Award three times, "Ho Leung Ho Lee" Science and Technology Progress Award 1 time. As the Environmental Chemistry founder of the atmosphere, she has done many system work with a pioneering and creative attitude in the field of environmental chemistry frontier atmospheric ozone, acid rain and airborne fine particulate matter (aerosols) chemistry. Fog & haze are meteorology term. Fog & haze is not the only one factor to cause pollution. Haze exists in ancient times. There are many fine air particulate matter, such as dust, foam waves brought up, pollen, etc., in particular winding up with soil particles, it is as it exists in nature. When these tiny particles float in the atmosphere, the surface will absorb some moisture, and the gravity is not big and is easy to settle, it will float to the sky after absorbing large amounts of water to become cloud or fog condensation nuclei. There are some fine particles gather near the ground and after being affected by ground humidity, they absorb, refract or reflect sunlight to cause reduced visibility. In this way these fine particles are involved in the formation of haze. When there are a large number of sulfur dioxide, nitrogen oxides and volatile organic compounds and other pollutants in the atmosphere, they form sulfuric acid and sulfates, nitrates and nitric acid and organic matter etc.. Their light effect results in a visual range of obstacles to make haze and to increase the degree of harmfulness. Except the humidity problems, Fog and haze difference might seem small. But their boundary issues has caused a period of academic discussion and controversy among meteorological communities. Briefly speaking, according to the current definition of the meteorological department, when the atmospheric humidity is below 80 percent of particulate matter, the light effect visibility will be dropped to 10 kilometers, resulting in a gray haze phenomenon which is called visual range obstacles, but when the humidity is high more than 90 percent , then it becomes mist, vapor becomes larger and the fog forces. Fog is easier to disperse, but haze is difficult. Because large foggy moisture content is affected relatively more by changes in the weather. Then the sun comes out and encountering dry air, it is easy to disperse the fog, it is generally not foggy all day. But the haze is more troublesome, because it contains much water vapor, the humidity is eighty percent or less, plus the the haze space is generally below 3,000 meters, if and when the inversion layer exists over, there will be no wind and the horizontal direction or the wind is very small. When the upper and lower convection air flow or level is not clear, haze can not be dispersed. Haze pollution is causing serious internal & external weather conditions. Haze is with related to emissions from energy use. As we know, sulfur dioxide, nitrogen oxides, ammonia and volatile organic compounds and other pollutants are gases. Why particulate matter affects the atmosphere and ultimately forces haze? Because the atmosphere has an oxidizing gas pollutant emissions, combustion energy can be said to be a contaminant, after entering the atmosphere, it results in a very complex chemical reaction to produce secondary pollutants. Due to a low valence pollutants, such as sulfur dioxide, nitric oxide and a large number of free radicals exist in the atmosphere, the gas valence stays easy reaction with oxidized free radically to form high valence sulfuric acid, nitric acid, nitrate and sulfate as well as organic substances. Currently, the causes of haze in the importance of VOC (volatile organic compounds) we study is not enough. VOC emissions coming into the atmosphere and nitrogen oxides in the atmosphere are the key to enhance oxidative substances, because of their non-linear relationship between the ratio of the different areas of action is different. For example, there have been studies indicating that the atmospheric oxidation of Beijing urban areas enhances, VOC's role is even greater than the nitrogen oxide and opposite for the suburbs . VOC is a combination of hydrocarbon, a substantial part of its production and combustion-related, you can say that any combustion will produce VOC, so closely associated with the use of energy, coal, oil, natural gas, which are presented in organic matter, oil refining. Chemicals are discharged largely, even straw combustion and paints as well as catering also produce VOC. Coal combustion has been regarded as the main cause to haze formation for a long time, ignored polluting chemical produced, the focus is mainly on soot and sulfur dioxide, nitrogen oxides and ignoring VOC, clear up if recognized, natural gas can not be considered clean energy. Boiler and automobile combustion process will produce fine particulate matter & PM2.5 emissions and have a secondary emission points, a particulate matter emission is produced by direct combustion of secondary emission gas and nuclear chemical reaction in the atmosphere particles produced after the reaction. The plant currently existing dust removal device can only get rid of more than PM1 particles, PM1 following also can not be removed. Cars will discharge a lot VOC, VOC's and combustion of oil and how much the adequacy of a great relationship, the best conversion of organic matter comes into carbon dioxide and water, but the combustion process is completed on time to be fully discharged, especially car driving in urban areas at low speeds or when idling. In some countries, there is a special law- cars must turn off at red lights. Some people think that the city is with a lot of car emissions of nitrogen oxides which is in fact incomplete.When largest cars traveling in the city , the speed is not too fast. Accordingly NOx relationship between combustion temperature and the engine combustion temperature is not too high, nitrogen and reactive oxygen conversion is relatively small. Nitrogen oxides is more on the highway, coz the car travels quickly, the engine temperature is very high at highway speeds. As a result, more nitrogen oxides are produced. And diesel vehicles emit more. A method of controlling automobile exhaust fumes is to install "catalytic converters" in the car, the car is now generally installed inside, but with a long time it will be aging, the role will be weakened, so that nitrogen oxide emissions by new cars is lower than used cars. Hong Kong now requires car "three-way catalytic converter" must be replaced once every two years, but the majority of our provinces do not have this requirement. Sometimes I go to the North Fifth Ring in Beijing , on 2 side of the road, there are a lot of people holding a sign of vehicle inspection agency, and now this thing has become an industry, regardless of your car fail the test, they can help you to be qualified. Now there are leased "three-way catalytic converter" phenomenon, the owner can pay to lease a new car specifically dealing with the subject, and then return to the people after the test finished. Behind this phenomenon is the management problems, and now management is extensive, but not fine. Do not underestimate a street food, VOC and more sulfur dioxide is high, the nitrogen oxides are also high, so that the energy issue is very complex. Particularly for northern cities, burning coal for winter heating problems, how much bulk coal piepe spent each year for heating suburb area in winter ? Some governments ignore these small issues, they just pay attention on large boiler plant these key sources as well as metallurgy. Bulk coal combustion dispersed pollution is very serious. So I think the energy revolution should include production and consumption, and the small things that were not previously noted should be paid with high attention. I particularly like a city in Brazil. At the beginning of their urban planning the mayor designed a special road channel which width allows only a bus to a bus to go and is with two-way street. Financial institutions, government agencies, businesses headquarters are only allowed to be constructed on this main road and Voeux Road. Only buses are allowed to pass through this road, all light vehicles must stop only in the suburbs or along the roadside, and then people change the bus into the city. In addition, to make sure good air circulation, the houses on both sides of the main road are relatively low, tall buildings were built in the back, not in the places where cars are concentrated. The city has 2.2 million inhabitants, more than 70 use public transport, this status has been performed for decades from the 1960s to now. The urban environment is also cleaner than the Rio and Sao Paulo etc..