In the early 1980s, the pH value of precipitation in Europe was 4.0 ~ 5.0, and the sulfate content in rainwater increased obviously. 1972, the Organisation for Economic Co-operation and Development (OECD) formulated the Cooperative Research Plan for Long-distance Transport of Air Pollutants (LRTAP), which confirmed the existence of long-distance transport of sulfide in Europe. 1984 On March 6th, at the meeting of environment ministers held in Ottawa, 10 countries formed a "30% club", that is, these countries reached an agreement to reduce SO2 emissions by 30% at the latest by the end of 1993 (based on the emission level of 1980). From 65438 to 0984, IIASA developed a comprehensive acid rain model-Rains model, which integrated the research results of acid rain in Europe for more than 20 years. The model has played a great role in the negotiation of acid rain in Europe and the formulation of control countermeasures.
Acid rain was discovered later in North America than in Europe. 1978, then US President Carter approved the implementation of the Atmospheric Deposition Assessment Plan (NADP). In the same year, the United States and Canada set up an air pollution long-distance transmission advisory group and signed 1980 Memorandum on Transnational Air Pollution. Studies show that at least 50% of acid deposition in Canada comes from the United States. Under the pressure of Canada, the Reagan administration at that time spent $2.5 billion to develop clean coal technology (CCT), and Canada also spent huge sums of money to reduce its SO2 emissions. 1990, the us congress passed the clean air act amendment, which stipulated that by 20 10, the SO2 emission of power plants should be reduced by 1980, reaching 8.9 million tons.
In Asia, countries that pay more attention to acid rain are Japan, South Korea and China. Japan conducted two five-year national acid rain surveys. The results show that the pH value of precipitation is 4.5 ~ 5.2, which is high in the northeast and low in the southwest. South Korea began to monitor acid rain nationwide from 1983. The results show that acid rain is not serious in winter heating period, but the pH value of precipitation is lower than 5.0. At the end of 1970s, China conducted acid rain surveys in Beijing, Shanghai, Nanjing, Chongqing, Guiyang and other places, and found that acid rain pollution existed in these cities to varying degrees, especially in the southwest. 1985- 1986, acid rain monitoring was carried out nationwide. The results show that the areas with precipitation pH less than 5.0 are mainly concentrated in the southwest, south China and southeast coastal areas. During the "Seventh Five-Year Plan" and "Eighth Five-Year Plan", acid rain research was listed as a national key scientific and technological project for two consecutive times. The seventh five-year plan acid rain project mainly studies the formation mechanism, transmission and diffusion, control methods and ecological impact of acid rain in southwest and south China. The study of acid rain in the Eighth Five-Year Plan shows that acid rain pollution in China has been very serious, and large areas of acid rain have appeared in east China, south China and south of the Yangtze River in southwest China, accounting for about 40% of the country's land area. The eighth five-year plan acid rain project puts forward the countermeasures to control acid deposition in China, and develops a series of clean coal-burning technologies and desulfurization technologies. European and American countries began to take action to reduce SO2 emission in 1980s, and people began to pay attention to the impact of SO2 emission reduction on acid rain in the mid-1990s. Scientists are interested in the changes of chemical composition in atmospheric precipitation.
At the end of 1990s, JAMESALYNCH and others used the linear least squares trend analysis method to construct a model that can identify and quantify the chemical change trend of precipitation. The precipitation chemical data of NADP 1983 ~ 1994 are analyzed by using the model, and the precipitation chemical change trend in the United States is obtained, and the precipitation chemical data of 1995 ~ 1997 are estimated. By comparing the measured values of precipitation chemistry from 1995 to 1997 with the above estimated values, the following conclusions are drawn: the implementation of the fourth paragraph of the Clean Air Act Amendment 1 stage has reduced the emission of SO2-,which directly leads to the SO2-in precipitation in the eastern United States, especially in the Ohio Valley, the middle Atlantic coast and New England. The area where the concentration of SO _ 42- and H+ drops most significantly is the downwind area of the main stationary pollution sources stipulated in the fourth amendment to the Clean Air Law to reduce emissions. It can be seen that the implementation of Article 4 of the Clean Air Act Amendment has reduced acid rain in the eastern part of the United States, especially in the northeast [1].
In Europe and North America, the concentration of so42- decreased year by year, while the concentration of NO3- remained almost unchanged. Nitrogen oxides are not only the main precursors of acid rain, but also play an important role in atmospheric photochemical reactions, so nitrogen oxides in the air have attracted more and more attention from European and American scientists.
In recent years, scientists have measured the wet and dry deposition of nitrogen in different regions through a large number of field observations, and studied the chemical reaction mechanism of nitrogen oxides, CH and O3 in the atmosphere through simulation experiments, constantly improving and perfecting the chemical modules of regional acid deposition model and air quality model, and using these models to simulate the role of nitrogen oxides in the formation of acid deposition. During the three-year period from1August 1996 to1July 1999, NoreenPoor et al. observed the dry and wet deposition of nitrogen in the estuary of Tampa Bay. The measurement results show that the total amount of nitrogen oxides in the total amount of wet deposition in summer is concentrated in June, July and August, in which ammonia and ammonium salts account for 58%, and nitric acid and nitrate account for 42%[2]. HSievering et al. observed by flux gradient method that the average dry deposition rate of nitric acid in Crorado coniferous forest area is 7.6cm/s, and the higher dry deposition rate is mainly due to the high turbulence intensity and the small aerodynamic scale of coniferous forest leaves [3]. EdmundsHA et al. developed a city-scale atmospheric diffusion model (including a comprehensive chemical module, which can predict the concentrations of nitrogen oxides and O3 in the atmosphere), and predicted the concentrations of nitrogen oxides and NO2 in the air of London according to the emission list of nitrogen oxides, and compared the predicted results of the model with the measured concentrations at four measuring points [4]. At the same time, more and more people are devoted to the research of various nitrogen oxide reduction technologies, especially various catalytic purification technologies. BhattacharyyaS et al. developed an X zeolite catalyst by replacing cations in X zeolite with copper ions, and tested its purification effect on nitrogen oxides in automobile engine exhaust. The experimental results show that compared with precious metals, X zeolite catalyst has significant nitrogen oxide reduction ability in a wide air-fuel ratio range, and with the increase of air-fuel ratio, the nitrogen oxide reduction ability slowly decreases [5].
While people are keen to study the chemical composition changes of precipitation and NOX simulation control technology, other scientists in Europe and America continue to make efforts in traditional acid rain research fields such as acid precipitation model and critical load of acid precipitation, making acid rain research increasingly international. In the 1990s, researchers from the International Institute of Applied Systems Analysis (IIASA) absorbed the latest achievements of acid rain research and continuously developed a new version of RAINS model, which was developed from 65438 to RAINS8.0 in 0999. The current RAINS model not only analyzes and simulates SO2, but also considers nitrogen oxides, NH3 and O3. At the end of 1990s, OlendrzynskiK of Norwegian Institute of Meteorology developed a three-dimensional EMEP Euler grid model, which was mainly used to simulate the transport and deposition of acid pollutants in the European atmosphere with a resolution of 50km×50km. This model replaces the traditional EMEP Lagrangian trajectory model to calculate the transport of pollutants between European countries [6]. JonsonJE et al. used the above model to simulate the transmission and deposition of nitrogen in the European atmosphere by inputting the meteorological data output from the professional meteorological prediction model and the emission data of nitrogen oxides, NH3 and SO2 provided by various countries. The complex oxidation reactions of nitrogen oxides, NH3 and SO2 in the atmosphere and the dry and wet deposition of nitrogen were considered in the calculation, and the simulation results were compared with the monitoring results of 1992 [7]. In the mid-1990s, Stockholm Environmental Research Institute (SEI) in Sweden, with the support of Swedish International Development Cooperation Agency (SIDA), convened scientists from Japan, Russia, Australia, China, India, Brazil and other countries to carry out a research project called "Ecological Sensitivity Assessment of Global Acid Deposition". Based on the world soil map published by FAO 1995, this project puts forward a research method of ecological sensitivity of acid deposition based on global soil buffering capacity. On the basis of basic saturation and cation exchange capacity, the global ecological sensitivity map of acid deposition was obtained according to soil thickness and other parameters, and it was tested by the regional ecological sensitivity map of acid deposition and previous global research results [8]. In the 1990s, due to the implementation of various agreements signed by European and American countries for many years, SO2 emissions decreased, and the threat of acid rain and acid deposition tended to ease. However, due to the rapid economic development of Asian countries, the emission of pollutants has increased sharply, and acid rain pollution has become more and more serious. As a result, European and American countries have turned their attention to Asia, where acid rain is the most serious threat, and scientists from Asian countries have also actively devoted themselves to the study of acid rain. The study of acid rain in Asia is more active than before.
3. Study on1acid emission inventory
The discharge list of acid-causing substances is an important prerequisite for studying acid rain.
In the early 1990s, Akimoto et al. estimated that the grid emissions of SO2, NOX and CO2 in Asia were 1× 1, while the emissions of SO2, NOx and CO2 in China were 995 gg/a, 2,243 gg/a and 649 TG/a, respectively. 1997, RLArndt and GRCarmichael of the university of Iowa announced the anthropogenic and volcanic emissions of SO2 in Asia (1× 1) from 1987 to 65438, including 3 1.6 tons of anthropogenic emissions and 3.8 tons of volcanic emissions. Most emissions from Malaysia and Singapore come from power plants [10].
As a major emitter in Asia, the emission of acid-causing substances in China has become the focus of attention. In the mid-1990s, Professor Bai Naibin from the Center for Ecological Environment Research of Chinese Academy of Sciences estimated the emission data of CO2, SO2 and nitrogen oxides in Chinese mainland 1× 1 grid accuracy [1 1] by using specific domestic emission factors and emission source data published by national, departmental, provincial and municipal statistical yearbooks. Xue Zhigang and Yang Zhiming investigated the SO2 emissions from cities and power plants in China, and consulted the statistical data of SO2 emissions from different provinces in China. Based on the statistical data of energy consumption in various provinces and industries in China, and reasonably selecting relevant foreign emission factors, the emissions of nitrogen oxides in administrative units and provinces at the prefecture level in China in 1995 were calculated, and the emissions and emission intensity maps of SO 2 1× 1 grid in China and provinces with nitrogen oxides were drawn. Statistics and calculation results show that China is 1995.
3.2 Long-distance transmission and diffusion of acidic substances
In the middle and late 1990s, ArndtRL and CarmichaelGR of the University of Iowa in the United States used a three-layer Lagrangian acid deposition model to calculate the sulfur deposition in Asia from Pakistan in the west, Japan in the east and Mongolia in the south to Indonesia. The grid accuracy was 1 × 1. The results show that after the sulfur deposition in parts of central and southern China exceeds 10g/m2[65433], ArndtRL and CarmichaelGR estimate the seasonal sources and receiving points of sulfur deposition in Asian and Indian subcontinent countries on the basis of model calculation. According to these relations, the influence of long-distance transportation on sulfur deposition in various countries is analyzed. The analysis shows that there is a wide range of cross-border transportation of sulfur in this area: 35% of sulfur deposition in Vietnam comes from domestic emissions, 65,438+09% in Thailand and 39% in China; More than 60% of sulfur deposition in Nepal comes from India, and China's influence on Japan shows strong seasonality. The contribution of winter and spring is 2.5 times that of summer and autumn, and it is closely related to the wet removal rate. China and South Korea play an important role in sulfur deposition in southwest Japan, and sulfur deposition in northeast Japan mainly comes from volcanoes and domestic sources [14]. In 2000, scientists from the International Institute of Applied Systems Analysis (IIASA) developed the RAINSASIA model, which covers 24 countries in Southeast Asia and can provide decision-making basis for acid deposition control in this region.
Since 1990s, scientists in Asian countries have made unremitting efforts in the field of long-distance transportation of air pollutants. Wang Zifa, Huang et al. of lasg established a three-dimensional Euler pollutant transport model, studied the transport of acidic substances in China and East Asia, and obtained the sulfur transport matrix among China provinces [15]. Dr. Zhou of Tsinghua University and Wang Tijian of Nanjing University [16] also simulated the long-distance transport of acid-causing substances in China in the mid-1990s. IchikawaY of Japan Central Electric Power Research Institute established a smoke trajectory model to simulate wet sulfur deposition in East Asia. The results show that the proportion of sulfur deposition in Japan caused by man-made emissions in Japan and emissions from the Asian continent is 1: 2 [17]. KimJ and ChoSY of South Korea established a nested grid Euler model for sulfur transport, and used this model to simulate the acid rain in South Korea on June 1996+00. It is found that the concentrations of SO2 and O3 in the gas phase are in good agreement with the field monitoring values. The model calculates the concentration of sulfate and nitrate in rainwater, and further identifies the high concentration area of sulfate and nitrate in liquid phase [18].
3.3 Study on Critical Load of Acid Deposition
Since 1990s, European scientists and Asian scientists have done a lot of research on the critical load of acid precipitation. 1995, Dutch scientist HettelinghJP, Swedish scientist SverdrupH and Chinese Academy of Sciences Zhao Dianwu calculated the critical load in Southeast Asia, including China, South Korea, Japan, Philippines, Indonesia and Indian subcontinent, and drew the critical load distribution map. The critical load in Europe is calculated for forest soil and surface water. In Asia, the critical loads of 3 1 vegetation types such as forest, grassland, farmland and desert are calculated. This study gives the critical load distribution map of Asia 1× 1 power grid. The results show that the areas with low critical load in Asia mainly appear in Bangladesh, Indonesia and southern China. The geographical distribution of critical load in Asia obtained in this study provides a basis for regional risk assessment and emission distribution of acid-causing substances in this region [19].
At the end of 1990s, the research on the critical load of acid rain in China became more active. Dr. Duan Lei, Tsinghua University, adopted a semi-quantitative method based on mineral weathering rate and soil conditions, and corrected the effects of temperature, soil structure and land use, and obtained the critical load map of soil acid deposition in China. The most sensitive soil in China is the gray loam in the northeast, followed by latosol, dark brown soil, black soil and iron-aluminum soil in the south, and the least sensitive soil is the alpine soil in the Qinghai-Tibet Plateau and the arid soil in the northwest [20] Dr. Tao Fulu from China Academy of Agricultural Sciences and Professor Feng from China Academy of Sciences studied the acid deposition sensitivity of the terrestrial ecosystem in southern China with a sensitivity classification method suitable for subtropical ecosystems, and concluded that the sensitivity of the terrestrial ecosystem in southern China is zonal. Generally speaking, the sensitivity of ecosystem gradually increases from northwest to southeast, and the most sensitive areas are northwest and southeast Zhejiang, central Fujian, northeast Guangdong and Guangxi Zhuang Autonomous Region [2 1].
3.4 Study on comprehensive prevention and control countermeasures of acid rain and acid deposition
The increasingly serious acid rain in Asia has aroused great concern. Japan took the lead in adopting the method of redistribution, charging the fixed sources of SO2 emission, and using the collected funds to compensate the victims of air pollution [1]. In the mid-1990s, China began to take practical actions to prevent acid rain. 1In August, 1995, the National People's Congress Standing Committee (NPCSC) passed the newly revised Law on the Prevention and Control of Air Pollution in People's Republic of China (PRC), and proposed to delimit acid rain control zones and sulfur dioxide pollution control zones (hereinafter referred to as the two control zones) nationwide. According to the provisions of the Atmospheric Law, Tsinghua University and china environmental science Research Institute formed a joint research group to study the division of the two control areas under the leadership of the State Environmental Protection Bureau. The plan was approved and implemented by the State Council in June 5438+June 0998. 1In February, 1998, the State Environmental Protection Bureau held a national acid rain conference, and after the meeting, various localities compiled the Comprehensive Prevention and Control Plan for Acid Rain and Sulfur Dioxide Pollution. In 2000, china environmental science Research Institute undertook the preparation of the Tenth Five-Year Plan for the prevention and control of acid rain and sulfur dioxide pollution in two controlled areas. The plan puts forward the prevention and control targets of acid rain and sulfur dioxide pollution in the two control areas during the Tenth Five-Year Plan period, allocates the total sulfur dioxide emission targets in each province in 2005, puts forward control measures such as limiting sulfur content in coal, desulfurization in power plants and controlling other key sulfur dioxide emission sources, screens out the list of key sulfur dioxide pollution control projects, and puts forward management and economic policies such as sulfur dioxide pollution charges, pollution permits and pollution trading in the two control areas.
Future research trend of acid rain and acid deposition
Acid rain has become a global environmental pollution problem. In recent years, the joint research of European and American countries and Asian countries has promoted the internationalization of acid rain research. It can be predicted that the process of global networking will further strengthen the global cooperation trend of acid rain research in the future. With the rapid development of various basic disciplines, the research on the formation mechanism, transmission and diffusion, critical load and treatment technology of acid rain will be more in-depth. The future acid rain model will integrate many disciplines to study nitrogen oxides, which are very active in the atmosphere and play an important role in environmental problems such as acid rain, photochemical smog, ozone hole and greenhouse effect. Therefore, in the future research, the chemical reaction mechanism, transport and diffusion of nitrogen oxides in the atmosphere and the emission reduction technology of nitrogen oxides will still be the focus of research. In addition, in terms of the sensitivity of ecosystem to acid deposition, people will pay more and more attention to the response of biological characteristics of ecosystem to acid input, trying to link the sensitivity of ecosystem to acid deposition with the biological characteristics of ecosystem.