The automobile is a symbol of modern civilization, but the emergence of which is only 100 years old. At the beginning of the 20th century, there was no antipathy to cars coming and going on the road because there were not many cars then. After the end of the World War II, the public hazards of automobile pollution began to appear in some big cities as the number of cars increased.
Automobile pollution, first of all, refers to the pollution of automobile exhaust. It is common to see clouds of white smoke billowing from the tailpipes of small cars, black smoke billowing from diesel cars and three-wheeled motorcycles, and the bad smell and the noise of the horn and the cylinder vibration are even more annoying. When a ton of gasoline is burned by an automobile engine to generate power, it emits 10-70 kilograms of exhaust gas. In addition, there is the leakage of gasoline and gas from the fuel and combustion system, which is about 20kg to 40kg. The exhaust gas contains 150 to 200 different compounds, as well as lead dust, carbon black, and other particulate matter.
The most serious hazard of automobile exhaust pollution is the "photochemical smog", which is the nitrogen oxides that are emitted or leaked by cars, and photochemical decomposition occurs in the intense sunlight and generates free oxygen atoms. Free oxygen atoms are highly active and are catalyzed in the atmosphere to form ozone with ordinary oxygen molecules. Ozone is highly oxidized and can oxidize hydrocarbons in automobile exhaust into formaldehyde, acetaldehyde, and ketones, and it can further react with nitrogen oxides and produce a series of strong oxidizing agents such as oxalyl nitrate.
Photochemical smog is not only harmful to the health of residents but also harmful to plants. During the smog in Los Angeles, suburban vegetables changed from green to brown, and no one wanted to eat them; large numbers of trees, including pine trees and evergreen trees, have withered. Besides that, photochemical smog also causes diseases in domestic animals, cracks in rubber products, and corrosion and damage to buildings.
Besides the photochemical smog, sulfur dioxide, carbon monoxide and lead compounds in automobile exhaust are also highly toxic. The noise, vibration, and dust raised by cars are also important factors to pollute the urban environment. The automobile is a modern means of transportation, which not only represents a high level of comfortable life but also represents an important source of pollution in modern society.