This should start with plastics. Plastic is a polymer material. Ethylene, propylene, vinyl chloride, styrene, etc. It can be made of petroleum, and the molecules of these substances can react with each other under certain conditions to produce compounds with high molecular weight (i.e. polymers): polyethylene, polypropylene, polyvinyl chloride and polystyrene. The plastics we usually use are materials composed of the above four polymers (polyethylene and polypropylene films are fragile when shaking, while PVC films are soft and have no brittle sound when shaking; Foam plastic is generally polystyrene, which has smoke when burning). Since the 1960s, plastics have entered a stage of wide application. Because plastic has many advantages: easy to obtain materials, low price, convenient processing and light texture, it was welcomed by the world as soon as it came out and quickly penetrated into all aspects of social life. Plastic is made into bowls, cups, bags, cans, barrels, pipes and so on. Plastic is listed as one of the greatest inventions in the 20th century, and its popularity is called the White Revolution.
With the continuous increase of plastic production and the continuous reduction of cost, a large number of agricultural films, plastic bags for packaging and disposable plastic tableware we use are abandoned in the environment after use, which has brought great damage to the landscape and environment. Because most plastic packages are white, the environmental pollution they cause is called white pollution.
Second, the harm of white pollution
White pollution has two kinds of hazards: visual pollution and potential hazards.
Visual pollution refers to plastic bags, boxes, cups and bowls scattered in the environment, which bring bad stimulation to people's vision and affect the aesthetic feeling of the environment. A few years ago, someone joked that there are two Great Walls in Wan Li, one is the ancient Great Wall and the other is the White Great Wall. White lunch boxes and plastic bags are everywhere along the China Railway, which is visual pollution. In our school, disposable lunch boxes and plastic bags of various colors can be seen everywhere. When the wind blows, plastic bags fly all over the sky, which seriously affects the beauty of the campus.
The potential harm of white pollution is various.
1, disposable foamed plastic lunch boxes and plastic bags for food seriously affect our health. On March 20th, Beijing Consumers Association issued a consumer warning. 1 (200 1): When the temperature reaches 65℃, harmful substances in disposable foamed plastic tableware will penetrate into food, causing damage to human liver, kidney and central nervous system. Therefore, on April 23rd, 20001year, the State Economic and Trade Commission issued the Emergency Notice on Immediately Stopping the Production of Disposable Foamed Plastic Tableware, demanding that the production of disposable foamed plastic lunch boxes be stopped.
The ultra-thin plastic bags we use to hold food now are generally PVC plastic. As early as forty years ago, it was found that vinyl chloride monomer remained in PVC plastics. When people are exposed to vinyl chloride, there will be symptoms such as wrist and finger edema and skin sclerosis, and spleen enlargement and liver damage may also occur. 1975, the United States prohibits the packaging of food and beverages with PVC plastics. In China, what is more serious is that almost all the ultra-thin plastic bags we use come from the reuse of waste plastics, which are produced by small enterprises or family workshops. CCTV's "News Investigation" program group has visited plastic bag factories, and the raw materials used in these factories are discarded plastic barrels, pots, disposable syringes and so on. In production, the raw materials are crushed into plastic particles by machinery, then the plastic particles are put into a pool for cleaning (called disinfection), taken out and dried, and then pressed into films by machinery to make various plastic bags. The reporter asked the boss, is this kind of plastic bag used to hold food harmful to the human body? The boss publicly admitted that this kind of film is definitely harmful to the health if it is not disinfected. He never uses this kind of plastic bag for food himself. Every time I have a meal, many students pack their meals in plastic bags. They don't know that this kind of behavior not only harms the environment, but also harms their own health.
2. Deteriorating the soil environment and seriously affecting the growth of crops. The plastic products currently used in China are generally non-degradable, and the molecular weight is above 20,000. Only when the molecular weight drops below 2000 can it be used by microorganisms in nature, which takes at least 200 years. Waste agricultural film and plastic bags remain in farmland for a long time, which will affect the permeability of soil and hinder the flow of water, thus affecting the absorption of water and nutrients by crops, inhibiting the growth and development of crops and causing crop yield reduction. If livestock eat plastic film, it will cause digestive tract diseases and even death.
3. Landfill is still the main way to deal with municipal waste in China. Due to the low density and large volume of plastic film, it can quickly fill the site and reduce the ability of landfill to treat garbage; Moreover, due to the soft foundation of the landfill, harmful substances such as bacteria and viruses in the garbage can easily penetrate into the ground, pollute the groundwater and endanger the surrounding environment.
4. If waste plastics are burned directly, it will cause serious secondary pollution to the environment. When plastics are burned, it will not only produce a lot of black smoke, but also produce dioxin, which is by far the most toxic substance. It takes at least 15 months for dioxins to decompose gradually after entering the soil, which is harmful to plants and crops. Dioxin has serious damage to the liver and brain of animals. The environmental pollution caused by dioxins produced by garbage incineration has become a sensitive issue of concern all over the world.
Third, the prevention and control of white pollution.
1. Stop using disposable tableware and ultra-thin plastic bags. Because disposable plastic tableware is difficult to degrade, many cities are now promoting the use of green tableware-paper tableware, because cellulose can be degraded by microorganisms. However, many environmental experts believe that it is unwise to replace foamed plastic tableware with paper tableware. First of all, paper tableware will also bring visual pollution, because their degradation speed is not fast, and often it will not be completely degraded for dozens of days or even months. Secondly, when making paper and tableware, in addition to straw pulp and rice pulp, wood pulp of about 1/3 should be added. If it is fully promoted, it will inevitably lead to the consumption of a large number of wood and the intensification of deforestation. It is worth noting that the forest coverage rate in China is only 13.92%, the per capita forest area is only 17.2% of the world average, and the world ranking is 1 12. Thirdly, pulping has always been a big consumer of water, energy and sewage. The pulping process needs a lot of water. The per capita water resources in China ranks 88th in the world, and it has been listed in the world 12 list of water-deficient countries. If the sewage is directly discharged into the river without treatment, it will cause water pollution; Paper tableware needs to be dried immediately after forming, which consumes a lot of energy. China's energy structure is dominated by burning coal, which will increase the content of SO2 in the air and cause acid rain. Therefore, it is a good thing not to use disposable plastic tableware and paper tableware from the perspective of environmental protection or resource conservation. Any disposable tableware is not only not conducive to environmental protection, but also the biggest waste of resources. In daily life, we should refuse to use ultra-thin plastic bags to buy food or hold food. We can use vegetable baskets or thick plastic bags to avoid disposable use, thus reducing the pollution of plastic bags to the environment.
2. Recycling waste plastics is the fundamental way to solve white pollution. In fact, compared with other materials, plastics have a significant advantage: they can be easily recycled. Plastics can be recycled, sorted, cleaned, and then heated and melted to make products again. In terms of composition, polyethylene, polypropylene and polystyrene are all composed of hydrocarbon elements, while fuels such as gasoline and diesel oil are also composed of hydrocarbon elements, but their molecular weights are small. Therefore, in the absence of air, these kinds of plastics can be heated to high temperature, cracked and fractionated to obtain gasoline and diesel oil.
In recent years, some countries have vigorously carried out the "3R" campaign, that is, demanding the reduction, reuse and recovery of waste plastics. At present, in Germany, Japan, the United States and other countries, due to the emphasis on the recycling of packaging materials, a virtuous cycle of plastic production, use, recycling and reuse has been realized, and white pollution has been fundamentally eliminated.
3. Develop degradable plastics. Degradable plastics have the same use function as ordinary plastics, but after being discarded after completing the use function, its chemical structure can change under certain conditions, so that the polymer can be decomposed into molecules with smaller molecular weight and finally assimilated by the natural environment. There are three kinds of degradable plastics: photodegradable plastics, biodegradable plastics and biodegradable plastics. But now many degradable plastics are not 100% degraded, but only become plastic fragments. It is reported that Yangling District, Shaanxi Province, China has successfully developed 100% degradable plastics. Starch and non-degradable plastics are physically combined after being crushed to nanometer level by special equipment, and then the ratio of the two is controlled within a certain range. The agricultural plastic film produced by this new technology has been tested in the field for four to five years. The results showed that starch was completely degraded into H2O and CO2 within 70 to 90 days, and plastic became fine particles harmless to soil and air, and it was also completely degraded into H2O and CO2 within 17 months. Now this kind of plastic has been put into mass production. At present, degradable plastics are far from being widely used in the world. The development and use of degradable plastics can only be used as an auxiliary measure to solve white pollution.
4. Strengthening environmental protection propaganda, raising citizens' awareness of environmental protection and forming a good environmental protection atmosphere in society are the prerequisites for solving white pollution and other forms of pollution. For example, to recycle waste plastics, it is necessary to implement the garbage recycling and sub-packaging system and put different kinds of garbage in different trash cans, which requires us to have a high degree of conscious awareness of environmental protection.
Let's set up the idea of being proud of caring for the environment and ashamed of destroying it, eliminate white pollution and other pollution on campus with practical actions, and build No.4 Middle School into a green campus and a civilized campus.