Love and hate talk about ozone
The protective effect of the ozone layer in the atmosphere on life on earth is now widely known-it absorbs most of the ultraviolet rays released by the sun and protects animals and plants from such rays. In order to make up for the increasingly thin ozone layer and even the hole in the ozone layer, people try their best, such as promoting the use of fluorine-free refrigerants and reducing the damage of substances such as freon to ozone. The world has also set up an international day to protect the ozone layer. This gives people the impression that the more ozone you protect, the better. Actually, it's not. If there is too much ozone accumulated in the atmosphere, especially near the ground, the high ozone concentration will be a disaster for human beings.
Ozone is a trace gas in the earth's atmosphere, which is formed by the decomposition of oxygen molecules in the atmosphere into oxygen atoms by solar radiation, and then the oxygen atoms combine with the surrounding oxygen molecules, containing three oxygen atoms. More than 90% of ozone in the atmosphere exists in the upper atmosphere or stratosphere, which is 50 kilometers away from the ground 10 ~ 50. This is the atmospheric ozone layer that needs human protection. There are still a few ozone molecules hovering near the ground, which can still play a certain role in blocking ultraviolet rays. However, in recent years, it has been found that the ozone concentration in the near-surface atmosphere is increasing rapidly, which is not good.
Where does ozone come from? Like lead pollution and sulfide, it also comes from human activities. Cars, fuels and petrochemicals are important sources of ozone pollution. Walking in the busy streets, we often see the air is slightly light brown and has a pungent smell, which is commonly known as photochemical smog. Ozone is the main component of photochemical smog. It is not directly launched, but converted. For example, nitrogen oxides emitted by automobiles can produce ozone under suitable meteorological conditions as long as they are exposed to sunlight. With the increase of automobile and industrial emissions, ground ozone pollution has become a common phenomenon in many cities in Europe, North America, Japan and China. According to the data currently available to experts, it is predicted that by 2005, the ozone layer in the near-surface atmosphere will become the main pollutant affecting the air quality in North China.
Research shows that when the ozone concentration in the air is at the level of 0.0 12ppm, which is also a typical level in many cities, it will cause people's skin itching, eyes, nasopharynx and respiratory tract irritation, and lung function will be affected, causing symptoms such as cough, shortness of breath and chest pain. The ozone level in the air rose to 0.05ppm, and the number of inpatients increased by 7% ~ 10% on average. The reason is that as a strong oxidant, ozone can react with almost any biological tissue. When ozone is inhaled into the respiratory tract, it will quickly react with cells, liquids and tissues in the respiratory tract, resulting in weakened lung function and tissue damage. For people with asthma, emphysema and chronic bronchitis, the harm of ozone is more obvious.
From the nature of ozone, it can not only help people, but also harm people. It is not only an umbrella from heaven and human beings, but sometimes it is like a fierce poison. At present, people have a * * * understanding of the positive role of ozone and what measures humans should take to protect the ozone layer, and have done a lot of work. However, although people have known the negative effects of the ozone layer, there is no really feasible way to solve it except atmospheric monitoring and air pollution prediction.
The principle of ozone disinfection can be considered as an oxidation reaction.
Inactivation mechanism of (1) ozone on bacteria;
Ozone always inactivates bacteria quickly. Different from other fungicides, ozone can react with the lipid double bond of bacterial cell wall, penetrate into bacteria, act on protein and lipopolysaccharide, change the permeability of cells, and lead to bacterial death. Ozone also acts on nuclear substances in cells, such as purines and pyrimidines in nucleic acids, to destroy DNA.
(2) Inactivation mechanism of ozone on virus:
The effect of ozone on virus is firstly that the four polypeptide chains of virus capsid protein are destroyed, especially the protein which forms it. After the bacteriophage was oxidized by ozone, it was observed by electron microscope that its epidermis was broken into many fragments, from which many ribonucleic acids were released, which interfered with its adsorption on sediments.
There is no doubt about the thoroughness of ozone sterilization.
Destroy the ozone layer and endanger all of us.
Ultraviolet rays affect human health in many ways. Sunburn, eye diseases, immune system changes, light changes and skin diseases (including skin cancer) can occur in human body. Skin cancer is a stubborn disease, and the increase of ultraviolet rays will increase the risk of this disease. Ultraviolet photons have enough energy to break the double bond. Short-and medium-wave ultraviolet rays can penetrate deep into human skin, causing skin inflammation, destroying human genetic material DNA (deoxyribonucleic acid), transforming normal growth cells into cancer cells and continuing to grow into a whole skin cancer. Others say that sunlight penetrates the surface of the skin. Ultraviolet radiation bombards the basic unit of DNA in the skin nucleus, melting many units into useless fragments. The repair process of these defects may be abnormal, which may lead to cancer. Epidemiology has confirmed that the incidence of non-melanoma skin cancer in factories is closely related to sun exposure. People with all skin types are likely to suffer from non-melanoma skin cancer, but people with light skin have a higher incidence. Animal experiments have found that ultraviolet B wavelength region is the wavelength region with the strongest carcinogenic effect.
It is estimated that the total ozone will be reduced by 1% (that is, ultraviolet B will be enhanced by 2%), and the canceration rate of basic cells will be increased by about 4%. Recent studies have found that ultraviolet B can change the function of the immune system. Some experimental results show that infectious skin diseases may also be related to the enhancement of ultraviolet B caused by ozone reduction. It is estimated that the total ozone will decrease 1%, the incidence of skin cancer will increase by 5%-7%, and cataract patients will increase by 0.2%-0.6%. Since 1983, the incidence of skin cancer in Canada has increased by 235%, and the number of patients with skin diseases in 199 1 year has reached 47,000. The director of the US Environmental Protection Agency said that the number of people who died of skin cancer in the United States in the next 50 years will increase by 200,000 compared with the previous forecast. Australians like sunbathing and tanning their skin. Although scientists have repeatedly warned that more sunlight will lead to skin cancer, they still like dark skin. Results People didn't wake up until the incidence of skin cancer in Australia was 1 times higher than that in other parts of the world. People suffering from skin cancer have accounted for 1/3 of the total number of cancer patients in the world.
The United Nations Environment Programme warned that if the ozone layer of the earth continues to decrease and thin at the current rate, the proportion of skin cancer in the world will increase by 26% to 300,000 by the year 2000. If the ozone layer decreases by 10% at the beginning of the next century, the number of people suffering from cataracts in the world may reach 1.6 million-1.75 million every year.
Exposure to ultraviolet light may also induce measles, chickenpox, malaria, scab, mycosis, tuberculosis, leprosy and lymphoma.
The increase of ultraviolet rays will also lead to the death of marine plankton, shrimp and crab larvae and shellfish, leading to the extinction of some organisms. As a result of ultraviolet radiation, groups of rabbits will suffer from myopia and thousands of sheep will be blind.
Ultraviolet B weakens the function of light platform. According to experiments in coastal areas of Africa, it is speculated that the photosynthesis of plankton is weakened by about 5% under enhanced ultraviolet B irradiation. Enhanced ultraviolet B can also change the freshwater ecosystem by destroying microorganisms in water, thus weakening the self-purification ability of water. Enhanced ultraviolet B can also kill young fish, shrimps and crabs. If the original plankton in the Antarctic ocean drops extremely, the whole marine life will change greatly. However, some plankton are sensitive to ultraviolet rays, while others are not. The damage degree of ultraviolet rays to DNA of different organisms is different 100 times.
It has seriously hindered the normal growth of various crops and trees. Some plants, such as peanuts and wheat, are very resistant to ultraviolet B, while others, such as lettuce, tomatoes, soybeans and cotton, are very sensitive. Trenmora of the Agricultural Biotechnology Center of the University of Maryland observed six soybean varieties with solar lights. The results showed that three soybean varieties were extremely sensitive to ultraviolet radiation. Specifically, the photosynthetic intensity of soybean leaves decreased, resulting in a decrease in yield, while soybean was planted in protein and its oil content decreased. The loss of atmospheric ozone layer 1% will also reduce soybean production 1%.
Tremola also spent four years observing the effects of high-dose ultraviolet radiation on the growth of trees. The results showed that the accumulation of wood decreased obviously, and the growth of root system was also hindered.
Adverse effects on global climate: A large reduction in ozone in the upper stratosphere and a corresponding increase in ozone in the lower stratosphere and upper troposphere may have adverse effects on global climate. The vertical redistribution of ozone may warm the lower atmosphere and aggravate the greenhouse effect caused by the increase of carbon dioxide.