Views:26 Author:Xicheng Publish Time: 2021-07-11 Origin:Xicheng
At present, the main problems that plague the world's global air pollution are the greenhouse effect and the destruction of the ozone layer. The harm caused by this kind of pollution is no longer restricted by national borders, and it is enough to threaten whether human beings can continue to live on the earth. The consequences are very serious. It has become a matter of vital interest to all countries in the world and has aroused widespread concern. To solve this problem, all countries need to act in concert. In 1989, the United Nations adopted "Beware of Global Warming" as the theme of World Environment Day on June 5, to arouse the attention of all sectors of society on environmental pollution and the sense of crisis and responsibility of people all over the world for their own living environment.
The existence and harm of gases that cause global air pollution
Global air pollution has caused a series of problems worldwide. Certain chemical substances discharged into the atmosphere by human activities, such as CO2, CH4, N2O, and CFC (chlorofluoroalkanes), cause the greenhouse effect, which leads to global warming. In the past 100 years, the global average surface temperature has increased by 0.3-0.6°C. The global warming has caused the sea level to rise. The current world ocean temperature is rising at a rate of 0.1℃ per year. The global sea level has risen by 14.4cm in the past 100 years. The sea level along the coast of my country has also risen by an average of 11.5cm. It will seriously threaten the production, life and property safety of people in low-lying islands and coastal areas.
Chlorofluoroalkanes and N2O can not only produce the greenhouse effect, but also interact with the ozone in the stratosphere, leading to the depletion of the ozone layer. The results of the study show that the concentration of ozone in the stratosphere decreases by 1%, the amount of ultraviolet radiation will increase by 2%, the incidence of skin cancer will increase by 3%, and the incidence of cataracts will increase by 0.2-1.6%. Therefore, the depletion of the ozone layer has caused damage to the human body. The damage caused by the damage caused by crops, the production of forests, natural biosphere and marine ecological balance are seriously affected. To protect the ozone layer is to protect our own health and safety.
Various man-made greenhouse gases contribute to the global greenhouse effect in different proportions. Among them, CO2 accounts for 55%, CFC accounts for 4%, CH4 accounts for 5%, and N2O accounts for 6%. Therefore, the increase in CO2 is responsible for the global greenhouse effect. The main factor of warming.
The increase in the concentration of carbon dioxide in the atmosphere is mainly caused by the burning of fossil fuels such as coal, oil, and natural gas. The carbon dioxide is about 5 billion tons per year when converted into fuel. Secondly, due to the logging and burning of forests, the amount of carbon dioxide used as fuel is about 1 billion to 1.6 billion tons per year. The carbon dioxide absorbed by forests through photosynthesis, large areas of forests are destroyed, and the ability to absorb carbon dioxide is greatly reduced. In addition, in recent years, scientists have discovered that the frozen ground along the Arctic Ocean also releases a large amount of carbon dioxide in autumn. Of the carbon dioxide emitted from fossil combustion, 80% is produced in developed countries, while the carbon dioxide emitted from forest destruction mainly occurs in developing countries.
Sources of methane include fermentation in the stomach of livestock, wet areas such as fields and swamps, and natural gas leakage. Bacteria in the intestines and stomach of cattle can turn 3%-10% of plant fiber material into biogas. It is estimated that 54 million to 100 million tons of biogas are released into the atmosphere by cattle each year. Scientists have discovered that the bubbles in the permafrost along the Arctic Ocean in Eastern Siberia are also rich in methane, whose concentration is thousands or even tens of thousands of times the current air content.
The main source of N2O in the atmosphere is soil. In the case of sufficient nitrogen supply sources such as NH4+ and NO3-, N2O can be produced from moist soil. Nitrogen removal also exists in the ocean. Man-made sources are mainly fertilizers. According to relevant research results, when chemical fertilizers are used, nearly 1/3 of nitrogen fertilizers denitrify into the atmosphere within a short period of time, and about 5-20% of them become N2O; burning trees and crops Residual roots and minerals, as well as the flight of stratospheric supersonic aircraft, also produce N2O.
The main reason for the destruction of the ozone layer is that human activities increase the concentration of certain compounds in the atmosphere, which makes the production and disappearance of stratospheric ozone out of balance. These compounds are mainly chlorofluoroalkanes, halons, carbon tetrachloride and methyl. Chloroform, etc., which are manufactured and diffused by humans in the industrial production process, such as refrigerants for refrigeration devices, smoke sprays, solvents for plastics, foam generators, cleaning agents for precision instruments and electronic devices, etc. They are not active in the lower atmosphere and transferred to the stratosphere. The strong solar ultraviolet radiation caused them to decompose chlorine atoms, thereby destroying the ozone layer.