1. Status of Pollution
According to the Bulletin of China's Environmental Situation, in 1997, the air quality of China's cities was still at a relatively heavy pollution level, with the northern cities heavier than those in the south (see Figure 3-1). The average annual concentration of sulfur dioxide ranged from 3 to 248 micrograms/m3, with a national average of 66 micrograms/m3. More than half of the cities in the north and more than one third of the cities in the south had annual averages that exceeded the national second-grade standard (60 micrograms/m3). The annual average value for northern cities is 72 μg/m3; for southern cities, it is 60 μg/m3. Sulfur dioxide pollution is more serious in cities in the high-sulfur coal region of southwest China, represented by Yibin, Guiyang, and Chongqing, and in northern China's energy-consuming cities of Shanxi, Shandong, Hebei, Liaoning, Inner Mongolia, and parts of Henan and Shaanxi.
2. Sources of pollution
Energy use. With the rapid growth of China's economy and the improvement of people's living standards, the demand for energy is rising. Since 1980, China's consumption of raw coal has more than tripled. 1997 raw coal consumption has reached 1.39 billion tons, and is expected to increase to 1.45 billion tons by 2000. Energy consumption, mainly coal, bioenergy and petroleum products, is the main source of particulate matter in the atmosphere. Atmospheric fine particulate matter (less than 10 micrometers in diameter) and ultrafine particulate matter (less than 2.5 micrometers in diameter) are the most harmful to human health, and they come mainly from soot emitted from industrial boilers and domestic coal stoves. Most of the sulfur dioxide and nitrogen oxides in the atmosphere also come from these emission sources. Coal combustion in industrial boilers accounts for 33% of China's coal consumption, and because of their low combustion efficiency and low stack emissions, their share of near-surface air pollution exceeds their share of coal use. Although residential coal use accounts for only about 15% of total consumption, its share of air pollution is often 30%.
China's sulfur dioxide emissions have been a sharp increase in the trend of the early 1990s, China's sulfur dioxide emissions of more than 18 million tons, to 1997, has risen to 23 million tons, is expected to 2000 will increase to about 28 million tons. At present, China has become the world's number one country in sulfur dioxide emissions. Studies show that 87% of the sulfur dioxide in our atmosphere comes from burning coal. China's coal in the sulfur content is high, especially in the southwest, generally in 1% -2%, some as high as 6%. This is the main cause of acid rain pollution in the southwest region over the longest period of time, the most harmful main reason.
Motor vehicle exhaust. In recent years, the number of motor vehicles in China's major cities has grown substantially, motor vehicle exhaust has become an important source of urban air pollution. Especially in Beijing, Guangzhou, Shanghai and other major cities, the concentration of nitrogen oxides in the atmosphere seriously exceeds the standard, Beijing and Guangzhou nitrogen oxides air pollution index has reached level four, has become the primary pollution factor in the atmospheric environment, which is closely related to the sharp increase in the number of motor vehicles. Relevant research results show that the pollutants emitted by motor vehicles in Beijing, Shanghai and other big cities have accounted for more than 60% of the air pollution load, of which, the emission of carbon monoxide on the air pollution sharing rate of 80%, nitrogen oxides up to 40%, which shows that China's mega-cities of atmospheric pollution from the first generation of soot-type pollution to the second generation of automobile-type pollution change. 1985, the national motor vehicle fleet of only In 1985, the country's motor vehicle fleet was only 3 million, in 1990 it was 5 million, in 1997 it increased to 13 million, and it is expected that by 2000 it will reach 20 million, and in 2010 it will reach 45-50 million. At present, China's motor vehicle pollution control level is low, equivalent to the level of foreign countries in the mid-1970s, the level of pollution emissions from a single vehicle is 10-20 times that of Japan, the United States 1-8 times. For example, the number of motor vehicles in Beijing is only 1/10 of that of Los Alamos or Tokyo, but the pollution emissions from automobiles in these three cities are roughly at the same level.
In addition, automobile emissions of lead is also an important pollutant in the urban atmosphere. Since the 1980s, gasoline consumption has grown at an average annual rate of more than 70%, and the amount of tetraethyl lead added to gasoline has averaged 2,900 tons per year. After combustion of leaded gasoline, about 85% of the lead is emitted into the atmosphere causing lead pollution. The contribution of lead emissions from automobiles to air pollution reaches 80-90%. During the 10 years from 1986-1995, about 1500 tons of lead were discharged into the atmosphere, water bodies and other natural environments in China, and it was mainly concentrated in big cities, thus adversely affecting the health of children living in the cities, traffic policemen and cleaners.
3. Pollution Hazards
Because of the serious air pollution in China, resulting in a high incidence of respiratory diseases in China. Chronic obstructive respiratory diseases, including emphysema and chronic bronchitis, are the leading cause of death, with a disease burden more than twice the average for developing countries. Disease investigations have identified health consequences of exposure to certain concentrations of pollutants, such as airborne particulate matter and sulfur dioxide, such as declining respiratory function, chronic respiratory disease, premature death, and increased hospital outpatient and intake rates.In 1989, researchers studied the correlation between atmospheric pollution and daily mortality rates in two residential areas of Beijing. Very high concentrations of total suspended particulate matter (TSP) and sulfur dioxide (SO2) were monitored in both areas. Estimates showed an 11 per cent increase in total mortality for each doubling of atmospheric sulphur dioxide concentrations and a 4 per cent increase in total mortality for each doubling of total suspended particulate matter concentrations. The analysis of the causes of death shows that if the concentration of total suspended particulate matter increases by a factor of 1, the mortality rate of chronic obstructive respiratory disease increases by 38%, and the mortality rate of pulmonary heart disease increases by 8%. 1992, the researchers made a study on the relationship between atmospheric pollution and the daily mortality rate in Shenyang, and the results show that for every increase of 100 micrograms of sulphur dioxide and the concentration of total suspended particulate matter/meter 3, the total mortality rate increases by 2.4% and 1.7%, respectively. and 1.7%, respectively.
Other human health losses caused by urban air pollution are also significant. Analysis shows that air pollution caused by hospital respiratory disease outpatient rate rose 34,600 cases; severe air pollution also led to 6.8 million emergency cases each year; the annual loss of work due to excessive air pollution caused by the disease amounted to 4.5 million people.
Indoor air quality is sometimes worse than outdoor. Studies of indoor pollution in some parts of the country have shown that levels of particulate matter (from biomass and coal combustion) are typically higher indoors than outdoors (more than 500 μg/m3, with the highest concentrations of particulate matter in kitchens (more than 1,000 μg/m3.
Conservative assumptions have estimated that 110,000 premature deaths occur annually as a result of indoor air pollution. Carbon monoxide poisoning deaths occur year after year in northern China due to the use of coal stoves for indoor heating in tightly sealed rooms. The health problems caused by indoor coal and wood burning are almost equal to those caused by smoking in China. Women and children suffer most from indoor air pollution.
Acid rain, caused by acid-causing pollutants such as sulfur dioxide, is another important aspect of China's air pollution hazard. Acid rain is the product of a chemical reaction between atmospheric pollutants, such as sulfur compounds and nitrogen compounds, and water and oxygen in the air. Sulfur oxides and nitrogen oxides from the burning of fossil fuels are emitted into the atmosphere and form sulfuric and nitric acid substances with other chemicals. These emissions can remain in the air for days, with wells migrating hundreds or thousands of kilometers, before returning to the ground as acid rain.
Currently, acid rain in China is spreading rapidly and is the world's third largest heavy acid rain area after Europe and North America. 80's, acid rain in China mainly occurs in Chongqing, Guiyang and Liuzhou as the representative of the Sichuan-Guizhou-Two-Guangzhou area, the area of acid rain area of 1.7 million square kilometers. By the mid-1990s, acid rain had developed to the south of the Yangtze River, east of the Qinghai-Tibet Plateau and the vast area of the Sichuan Basin, and the acid rain area had expanded by more than 1 million square kilometers. Changsha, Ganzhou, Nanchang, Huaihua as the representative of the acid rain area in central China has now become the country's most seriously polluted areas of acid rain, the center of the annual precipitation pH value of its area is less than 4.0, the frequency of acid rain is higher than 90%, has reached the degree of every rain must be acid. Nanjing, Shanghai, Hangzhou, Fuzhou, Qingdao and Xiamen as the representative of the coastal areas of East China has also become China's main acid rain area. Acidic precipitation also occurs in localized areas of North China and Northeast China. Acid rain in our country a few of the prairie trend, the hazardous area has accounted for about 29% of the national area, its development rate is very alarming, and continue to be aggravated year by year trend.
Acid rain harm is multifaceted, including human health, ecosystems and building facilities have direct and potential harm. Acid rain can make children's immune function decline, the incidence of chronic pharyngitis, bronchial asthma increased, at the same time can make the elderly eye, respiratory disease increased. Acid rain can also make crops significantly reduce yields, especially wheat, in the PH value of 3.5 under the influence of acid rain, can reduce yields by 13.7%; PH value of 3.0 when the yield reduction of 21.6%, PH value of 2.5 when the yield reduction of 34%. Soybeans and vegetables are also susceptible to acid rain, resulting in a decrease in protein content and yield. Acid rain is also harmful to forests and plants, often making forests and plants withered leaves, pests and diseases aggravated, and ultimately causing widespread death.
According to a study of eight southern provinces, acid rain causes crop damage of 193 million mu per year, with an economic loss of 4.26 billion yuan, resulting in an economic loss of 1.8 billion yuan of timber. From a national perspective, the direct economic losses caused by acid rain 14 billion yuan a year.
Pollutants emitted by motor vehicles are very harmful. Due to motor vehicle exhaust emissions in the low air, just in the human breathing zone range, the impact on human health is very obvious. Such as emissions of carbon monoxide and nitrogen oxides can greatly impede the body's oxygen transfer function, lead can inhibit the intellectual development of children, resulting in liver dysfunction, particulate matter on the human body has a carcinogenic effect. Tailpipe emissions on the traffic police have a serious harmful effect, some data show that the life expectancy of traffic police is much lower than the average life expectancy of urban people. In addition, automobile emissions of carbon monoxide, nitrogen oxides and hydrocarbons in the sun's irradiation will be reacted in the atmosphere, the formation of photochemical smog, its pollution range is wider, more harmful to human health, ecological environment.