Vehicle exhaust pollution is an environmental pollution caused by exhaust emissions from automobiles. The main pollutants are hydrocarbons, nitrogen oxides, carbon monoxide, sulfur dioxide, lead compounds, benzopyrene and solid particles, which can cause photochemical smog. Harmful ingredients Carbon monoxide Carbon monoxide is an intermediate product of hydrocarbon fuel combustion, mainly in the case of local anoxic or low temperature conditions, due to the incomplete combustion of hydrocarbons, and is mixed in the exhaust gas of the internal combustion engine. When the car is under heavy load, slow running or running in neutral, the fuel cannot be fully burned, and the carbon monoxide content in the exhaust gas will increase significantly. Carbon monoxide is a colorless, odorless, suffocating toxic gas with a low chemical reactivity. Its relative density to air is 0.9670, and its solubility is small. When carbon monoxide enters the blood of the human body from the respiratory tract, it will combine with the hemoglobin Hb in the blood to form carboxyhemoglobin, which will lead to a decrease in oxygen carrying capacity and cause a reaction in the human body. For example, hearing may be damaged by the lack of oxygen in the cochlear nerve cells in the ear. . Inhalation of excess carbon monoxide can cause shortness of breath, purple lips, difficulty breathing, and even death. Studies have shown that people's ability to withstand carbon monoxide is quite high, and a healthy person can withstand 20% to 40% of carbon monoxide in the blood for a short time. Although the carbon monoxide threshold for no side effects on the human body has not been determined, long-term absorption of carbon monoxide is a potential threat to the health of urban residents. NOx Nitrogen oxides are produced in most of the gas in the cylinders of internal combustion engines. The emission of nitrogen oxides depends on factors such as combustion temperature, time and air-fuel ratio. The reason for the formation of nitrogen oxides is mainly the high temperature oxygen-rich environment, such as carbon deposits in the combustion chamber. From the combustion process, more than 95% of the emitted nitrogen oxides may be nitric oxide, and the rest is nitrogen dioxide. The case of human exposure to nitric oxide has not been found, but nitrogen dioxide is a reddish-brown respiratory irritant gas with an odor threshold of about 1.5 times the air quality, which has a great impact on the human body. Due to its low solubility in water, it is not easy to be absorbed into the upper respiratory tract and the lower respiratory tract and lungs, causing diseases such as bronchitis and pulmonary edema. Exposure to air at a concentration of 9.4 mg/m3 for 10 minutes can cause respiratory disorders. For the Nitrogen Oxide World Health Organization Environmental Health Assessment Group, it has been concluded that the concentration of nitrogen dioxide 0.94 mg/m-3 is the lowest level of harmful effects caused by short-term exposure, 0.19-0.32 mg/m-3 for up to 1 hour. It can't be more than two times a month to ensure public health. Hydrocarbons The hydrocarbons of automobile exhaust come from three sources. For a typical gasoline engine, about 60% of the hydrocarbons come from 20% to 25% of the exhaust emissions from the crankcase (PCV system), and the remaining 15% to 20% come from the evaporation of the fuel system (canister). Methane is a suffocating gas with an olfactory threshold of 142.8 mg, which is harmful to human health only at high concentrations. Ethylene, propylene and acetylene are mainly harmful to plants, so that trees on the roadside cannot grow normally. Benzene is a colorless gas-like gas that can cause loss of appetite, weight loss, fatigue, dizziness, headache, vomiting, insomnia, mucous membrane bleeding, etc. It can also cause blood changes, red blood cells, and poor Automobile exhaust pollution Automobile exhaust pollution Blood can also cause leukemia. Its olfactory threshold is 16.29 mg, which has a threshold of 34.8 mg which affects human health. Car exhaust also contains polycyclic aromatic hydrocarbons, although the content is very low, but because polycyclic aromatic hydrocarbons contain a variety of carcinogens (such as benzopyrene) and cause concern. HC and NOX produce a complex photochemical reaction in the atmosphere under intense ultraviolet light, which produces a new pollutant to form photochemical smog. In December 1952, the number of photochemical smog in London in 4 days was more than normal. In the same period, the deaths were more than 4,000, 45 years old and above, about three times the usual, and about one time below the age of one. During the week of the incident, deaths due to bronchitis, coronary heart disease, tuberculosis, and heart failure were 9.3 times, 2.4 times, 5.5 times, and 2.8 times, respectively, of the same number of deaths in the week prior to the event. Aldehyde Aldehydes are incomplete combustion of hydrocarbons, mainly emitted by exhaust gas from internal combustion engines. The aldehydes emitted from automobile exhausts are shown in the following table: other 0~10 The aldehydes emitted from automobile exhausts are mainly formaldehyde, accounting for 60% to 70%. Formaldehyde is an irritating gas that has an irritating effect on the eyes and also irritates the respiratory tract. The olfactory threshold is 0.06~1.2 mg. It can cause cough, chest pain, nausea and vomiting at high concentrations. Acetaldehyde is a low-toxic substance and has an anesthetic effect at high concentrations. Acrolein is a spicy irritating gas that is strongly irritating to the eyes and respiratory tract and can cause damage to bronchial cells. The olfactory threshold is 0.48~4.1 mg. Lead-containing substance Most of the lead-containing particles emitted by automobile exhausts come from exhaust emissions from internal combustion engines. Tetraethyl lead is added to gasoline as an antiknock agent. Generally, the lead content of gasoline is between 0.08% and 0.13%, and lead oxide is emitted after the combustion of tetraethyl lead. Lead mainly acts on the nervous system, hematopoietic system, digestive system and organs such as liver and kidney. Lead can inhibit the anabolic process of hemoglobin and can also act directly on mature red blood cells. Lead particles entering the body through the respiratory system, the larger particles can be adsorbed on the mucus of the respiratory tract, mixed in the sputum and spit out; the smaller particles, deposited in the deep tissue of the lungs, they are almost completely absorbed. Lead accumulates to a certain extent in various organs of the human body, causing damage to the human heart, lungs, etc., causing anemia, stupid behavior, decreased intelligence, inattention, and serious infertility and high blood pressure. According to the way of entering the body, up to 60% of the total lead intake can be permanently left in the human body, and 0.8 mg or more of the adult blood is called lead poisoning. After burning leaded gasoline, about 85% of the lead is discharged into the atmosphere, causing lead pollution. Lead oxide is not only harmful to the human body, it is also adsorbed on the catalyst surface of the automobile exhaust catalytic converter, which produces "poisonous" to the catalyst and significantly shortens the life of the catalytic catalytic purification device. It is a difficult problem to be solved by the automobile exhaust catalytic purification device. one. Since the 1940s, the amount of lead that has been emitted into the atmosphere through automobile combustion has reached millions of tons, making it a recognized global pollution. Exhaust gas destruction pollination Scientists' latest experiments on a pollinating moth show that their ability to detect flowers is affected by the exhaust emissions of vehicles, making it difficult to find plants and flowers for pollination. Automobile exhaust pollution Automobile exhaust pollution The picture shows a moth is pollinating flowers. The latest research shows that the pollution caused by vehicle exhaust can not be ignored, which will destroy the pollination ability of insects. According to foreign media reports, scientists have recently pointed out that pollutants such as exhaust emissions from cars can confuse insects and prevent them from pollinating plants. As the pollutants such as automobile exhausts are mixed into the air, the "nose" that is sensitive to moths and other insects will gradually become ineffective. The major problem caused by this effect is that insects such as bees cannot pollinate plants. The latest research report is published in the recently published issue of Science. The University of Washington scientist tobacco moth is placed in a laboratory wind tunnel for experimentation, exposing it to the mixed smell of cars, truck exhausts and plant fragrances, human activities. Environmental pollution has destroyed the ability of tobacco moths to discover flowers and changed the processing of floral odors in the brain olfactory nerves of tobacco moths. Professor Jeffrey Riffell of the University of Washington said: "Potatoes like bees, butterflies and moths use olfaction to locate flowers remotely, but we find that affected by the exhaust of traffic vehicles will destroy insect pollinators. The olfactory ability, even if there is a flower nearby, can't be detected. Now some moths fly long distances, and they can't fully smell the flowers and don't know where the flowers are." We need to go into more experiments to prove whether it will destroy the olfactory ability of other insect pollinators in the case of air pollution, such as bees, which will be very important for agriculture. Tobacco moth is a large nocturnal insect with a wingspan of 10 cm, mainly distributed from Canada to Central America. Their favorite flower is the mandala flower. In wind tunnel testing and computer-controlled scent stimulation systems, the researchers observed how tobacco moths differentiated the odors of different concentrations of mandala flowers, while they mixed vehicle exhaust in the odor, and the researchers tracked and placed them on the antennae of the tobacco moth. The electrode-activated nerve path, whose antennae correspond to the nose of the insect, is equivalent to part of the brain, and is capable of handling the odor of the tentacles. Exhaust pollutant The main pollutants of automobile exhaust are [2]: carbon monoxide, nitrogen oxides, hydrocarbons, lead, sulfides, etc. Their environmental pollution is mainly caused by the greenhouse effect, the destruction of the ozone layer, and the occurrence of acid rain and black rain. The harm to the human body is mainly caused by various diseases, severe damage to the respiratory system, and strong carcinogenicity. When the car is driving, harmful substances are discharged to damage the environment and human health. These harmful substances are very complex, mainly including carbon monoxide, nitrogen oxides, hydrocarbons and the like. Carbon monoxide is a product of incomplete combustion of fuel in the engine. Its binding to human hemoglobin is much stronger than the binding of oxygen to hemoglobin. Therefore, carbon monoxide weakens the ability of hemoglobin to transport oxygen to human tissues, affecting the central nervous system, and causing poisoning death in severe cases. Hydrocarbons are formed by incomplete combustion of fuel in the engine and volatilization of fuel. It includes a variety of hydrocarbon compounds, some of which are carcinogenic and cause chronic poisoning after entering the human body. Governance measures EU environmental experts believe that the most effective way to reduce the harm of automobile pollution to the urban environment is to adjust urban transport policies, significantly reduce the number of private cars, give priority to the development of public transport, and promote bicycle traffic. At the same time, it should accelerate development and popularize environmental protection. Cars, reducing dependence on fossil fuels. Control quantity In many large and medium cities, the number of cars has actually been "overloaded." The government can use macro-control methods to increase the price of automobiles, appropriately reduce the purchase of automobiles, promote the conversion of small-scale manufacturing vehicles, and control the number of vehicles within the scope of ecological balance. At the same time, public transport such as buses and subways should be developed rapidly. Bicycles, buses and subways should be promoted to the public. Civil servants should set an example by using public transport and less private cars to minimize vehicle emissions. quality improvement By the beginning of the 21st century, leaded gasoline has been banned in most cities around the world. It is necessary to improve the emission standards of automobile exhaust pollutants, strictly control, and not allow gasoline that does not meet the standard to flow into the market. Green technology Advanced automobile exhaust gas treatment technology to eliminate or modify vehicles that do not meet the exhaust emission standards. The three-way catalytic converter is cleaned regularly to maintain the exhaust gas purification performance of the vehicle. Promote natural gas-fueled gas vehicles, and transform gas vehicles to solve the problems of the engine power performance degradation and large space occupied by gas cylinders. Turning waste into treasure Solution A: The fuel and air in the cylinder are compressed to become a high-temperature and high-pressure gas, and the energy is still high after combustion. If these energy are used and converted into engine power, it saves fuel and reduces exhaust emissions. Option B: The automobile exhaust contains nitrogen oxides and sulfur oxides. If a collection and conversion device is installed on the exhaust pipe, it will be converted into industrial raw materials such as nitric acid and sulfuric acid. Although the collection amount may not be much, the accumulation is small. More, this is recycling resources while reducing pollution to the atmosphere. improve publicity Strengthen publicity on the importance of environmental protection, raise people's awareness of environmental protection, let the people consciously use public transport, do not buy cars with exhaust emissions, and resolutely do not buy or manufacture lead-containing or low-quality gasoline. Governance outcome "China's motor vehicle pollution prevention industry development prospects and investment forecast analysis report prospects" shows that the current local government measures have achieved some results, according to statistics, from 2000 to 2010, the total number of motor vehicles in China has tripled In many cases, pollutant emissions have only increased by 0.3 times, and all pollutants have been reduced by more than 50%. The control measures adopted have reduced 38 million tons of nitrogen oxides, 44.5 million tons of hydrocarbons, and 238.7 million. Emissions of tons of carbon monoxide and 7 million tons of particulate matter. Processing technology Fuel replacement (1) The use of unleaded petrol instead of leaded gasoline can reduce the emissions of toxic substances from gasoline tail gas. (2) Adding additives, changing fuel composition, improving fuel quality, etc., such as adding about one-thousandths of a thousand fuel partners. The incorporation of less than 15% methanol fuel in gasoline or the use of water-gasoline fuel containing 10% water can reduce or eliminate the pollution effects of CO, NOx, HC and lead dust to a certain extent. If "methanol fuel" is used, a fuel made by mixing methanol and other alcohols with gasoline is used. When methanol accounts for 30% to 40%, the pollutants emitted by automobile exhaust can be basically eliminated. (3) Select the appropriate lubricant additive - mechanical friction modifier. Add a certain amount (3% to 5%) of graphite, molybdenum disulfide, polytetrafluoroethylene powder and other solid additives to the engine oil, or use nanotechnology lubricant additives, such as copper medal oil companion, etc., added to the engine In the sump, engine fuel can be saved by about 5%. In addition, the use of the above solid lubricant can greatly improve the cylinder sealing performance of the automobile engine, increase the cylinder pressure, and complete the combustion. In the exhaust emissions, the CO and hydrocarbon contents are reduced, which can reduce the pollution to the atmospheric environment. (4) The use of green fuel can also reduce the emission of toxic gases from automobile exhaust. According to a research institute in Ohio, USA, soybean oil is mixed with methanol and caustic soda, and then the glycerin is removed to obtain "soybean diesel". It is blended into ordinary diesel oil in a ratio of 3:7 with "soybean diesel" for diesel vehicles. It greatly reduces the emissions of sulfides, hydrocarbons, carbon monoxide and soot during engine operation. It is known as green fuel. (5) Using multiple fuels as a source of fuel for automobiles. With the development of science and technology and the wide application of computers, we ensure the implementation of environmental protection regulations and energy-saving measures: new formula gasoline, electricity, compressed natural gas, solar energy and ecological fuel storage batteries can be widely used in automobiles. However, the computer is installed on this type of car, and the combination is continuously transferred in the driving to make the car perform at its best. The computer-controlled ignition system is used to quickly respond to different operating conditions of the engine to achieve optimum fuel economy and engine power performance, which can reduce the pollution of the exhaust gas to the atmosphere. (6) Energy conservation, environmental protection, and vigorous promotion of ethanol gasoline for vehicles. According to relevant experts, the development of ethanol instead of gasoline, which saves energy and digests the grain, reduces the harmful vapors emitted by automobiles, and is a new topic conducive to the protection of the environment and resources. Internal debugging (1) Reduce the injection advance angle. Reducing the fuel injection advance angle reduces the maximum operating temperature of the engine (1500 degrees Celsius) and reduces the amount of NOx produced. (2) Improve the quality of the injector, control the combustion conditions (fuel ratio, combustion temperature, combustion time), so that the fuel can be completely burned, thereby reducing CO, HC and soot. (3) Adjusting the fuel supply of the fuel injection pump can reduce the power of the engine, so that the atomized fuel has sufficient oxygen for complete combustion, thereby reducing the formation of CO, CH and soot. Exhaust gas purification That is, the automobile exhaust gas is changed from the original toxic gas to a non-toxic gas, and then discharged to the atmosphere. Thereby reducing pollution to the atmospheric environment. (1) Catalyst: CO is oxidized to CO2, HC is oxidized to CO2 and H2O, and NOx is reduced to N2. The catalysts used are manganese oxide, copper oxide, metal oxides such as chromium oxide, nickel oxide, and copper oxide, and noble metals such as white metal (platinum). They all purify CO and HC. The catalytic reactor is disposed between the exhaust manifold and the muffler in the exhaust system. (2) Washing: Through the water tank, the soot particles in the automobile exhaust gas are washed with water and filtered, and the steam is showered, and the toxic substances adhering to the carbon particles can be swollen and the carbon particles are swollen and removed. Internal purification (1) Design of the positive crankcase ventilation system: Recirculate the gas (mainly unburned gas) that has been pumped into the crankcase from the cylinder into the intake manifold, causing it to burn again, changing the direct discharge of the gas into the atmosphere. Pollution. The PCV system on the engine plays such a role. (2) Exhaust gas recirculation design: The engine exhaust port is connected to the intake manifold by a control valve, so that the exhausted gas is circulated again to reduce the emission of nitrogen oxides. (3) Design of evaporative emission control system (carbon canister): Introduce the gasoline vaporization vapor in the carburetor float chamber into the intake system, and introduce the vaporized vapor in the fuel tank into the storage system, which can greatly reduce the pollutant discharge. Strengthen management (1) Eliminate old cars and take retirement to welcome them. A new type of car that develops and uses a variety of fuels is the future direction of the car. Hydrogen-fueled battery electric vehicles, solar vehicles, electric vehicles, duplex vehicles, liquefied gas vehicles, and methanol vehicles. They are new cars with low pollution and the best future. At the same time, the car that can also be modified with a car engine is a diesel engine car. Although diesel fuel costs are high, CO production is small. If the NOx and dust emissions are relatively limited, then the diesel engine car is also the best car in the future. (2) Strictly implement national quality technical standards / control fuel standards. Related events In the 1940s, photochemical smog was first discovered in Los Angeles. Every autumn and winter, many people's eyes are slightly red and swollen, the throat is sore, and even the skin appears to have varying degrees of flushing, mound rash, etc.; people often have feelings of difficulty breathing and fatigue. In September 1955, severe automobile exhaust and high temperature, photochemical smog appeared again in Los Angeles, and the concentration was very high. Photochemical smog not only affected people's respiratory function, especially the damage of children's lung function; caused chest pain, nausea, Symptoms such as fatigue have caused thousands of people to suffer. In two days, more than 400 65-year-olds have died. The vegetables grown in the suburbs are all browned by green. No one dares to eat; fruits and crops are reduced, and a large number of trees are fallen. Yellowing, more than a quarter of the tens of thousands of hectares of forest have died. Following the world's first photochemical smog event in Los Angeles in 1943, the smog appeared in North America, the United Kingdom, Japan, Australia, and parts of Europe. National measures In Rome, Italy, since 1997, if a driver wants to travel in the area where the historical sites are located, he must pay a tax of about 200-332 euros a year. In addition, you need to prove that you are working in this area. As for the residents living here, as long as the symbolic exchange of 15 euros is enough. The funds pooled through the tax were originally planned to be used to build parking lots, but these parking lots were not built until 2006. Even so, these measures have reduced the number of vehicles passing through each day from 90,000 in 1997 to 70,000 in 2006. Singapore City has long adopted a policy aimed at restricting traffic in commercial centers. In 1975, the city first implemented the urban toll tax system, and drivers must pay this toll every day. By 1998, this method had changed and changed to an electronic tax collection system calculated on a time-period basis. This policy has reduced the traffic volume during peak hours (8:00-9 hours) because some people decided to take time periods when the toll tax is not too high (7:30-8:00 and 9:00-9:30) Drive through here. Corresponding regulations The Guangzhou Municipal Government promulgated the "Notice on the Basic Sale of Leaded Gasoline" and the "Regulations on the Prevention and Control of Motor Vehicle Exhaust Pollution in Guangzhou". The Beijing Municipal Government has successively issued the "Notice on Emergency Measures to Control Beijing's Air Pollution", "Resolution on Further Implementing Air Pollution Prevention and Control Measures, and Improving Environmental Quality", and the Municipal Environmental Protection Bureau organized "Implementation of Beijing Light Vehicle Exhaust Pollutants" standard". Most major cities in Norway require drivers to pay for the city, and this is also a direct reference to the practice of London, England. Since February 2003, London has installed 800 cameras and has to pay a £5 (about 7.5 Euro) pass to enter the 21-square-kilometer area from the Tower Bridge in the east to Hyde Park in the west. However, as the public transport system is outdated, the reform decided by the Mayor of London has been criticized by some citizens. The London municipality wants to reduce the city’s traffic by 10%-15% by implementing this anti-traffic congestion tax, and hopes to use the annual £130 million (about 195 million euros) toll tax for public development. Transportation. Germany is adopting a tax policy to deal with car pollution. Since January 2001, the annual tax amount of a car has been calculated based on the power of the car and the amount of polluting gas emitted by the car. In addition, a subsidy system has been introduced to subsidize cars that emit less polluting gas. With these two regulations, some drivers can pay a penny tax for several years. This policy has a positive effect on motivating automakers to produce more environmentally friendly cars. With the rapid development of the social economy, the car ownership has increased sharply, and car pollution has become the most important air pollution problem in the city. This article describes the main ways of car pollution to facilitate the study of effective control measures to control vehicle pollution.
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