The evaluation of ambient air quality is not subjective, but describes, evaluates and predicts the air quality in a specific area at a certain time or period in strict accordance with established standards and methods. As a measure, the evaluation criteria and methods will have a decisive impact on the air evaluation results. By studying the changes of environmental standards at home and abroad vertically and horizontally, it can be found that not only the environmental standards of different countries in the same period are not completely the same, but even the environmental standards of the same country in different historical periods are dynamic. The former is different because different countries are at different stages of economic and social development, and the air pollution situation and air quality management ability are different; The latter is different because with the development of economy and society, not only the types of pollutants and their effects on human health will change, but also the ability to monitor and control specific pollutants economically and effectively will change. Therefore, according to the requirements of economic and social development and environmental protection, timely adjustment of environmental standards, monitoring indicators, evaluation weights and environmental quality classification is the embodiment of people-oriented and advancing with the times.

The first ambient air quality standard in China was issued in 1982. Although 1996 and 2000 were revised twice, its last revision was more than 10, which is obviously out of date. It is not only criticized by the theoretical circle, but also questioned by the public in practice. In recent years, great changes have taken place in the characteristics of environmental air pollution and atmospheric environment in China. Air pollution changed from soot type to compound type, and acid deposition changed from sulfuric acid type to nitric acid-sulfuric acid compound type. According to the old standard, the evaluation and prediction results of air environmental quality are quite different from people's feelings, which leads to the phenomenon of "talking to yourself" between monitoring data and air quality evaluation. In this context, 20 12 has finally been revised for the third time. 20 12 On February 29th, the executive meeting of the State Council agreed to issue a new standard for ambient air quality. The main contents of this revision are as follows: first, the classification of ambient air functional zones has been adjusted, and the three types of zones have been merged into the second type, which has expanded the scope of protection for people; Second, the concentration limit of PM2.5 and the 8-hour average concentration limit of ozone are increased, and PM 1Q, carbon dioxide, lead and benzo [? ] The concentration limits of pollutants such as pyrene meet the first-stage target values of the World Health Organization; Thirdly, the validity of data statistics is adjusted. For example, it is clearly stated that all valid data should participate in statistics and evaluation, and data and human intervention that are unfavorable to monitoring and evaluation results cannot be selectively discarded.

The new standard stipulates the implementation time in stages. 20 12 carried out monitoring projects such as PM2.5 and ozone in key areas such as Beijing-Tianjin-Hebei, Yangtze River Delta and Pearl River Delta, as well as municipalities directly under the central government and provincial capital cities. 20 13 years, 1 13 years key environmental protection cities and national environmental protection model cities; 20 15, all cities above the prefecture level; In 2006, 2065438+65438+ 10/month, and the new standard was implemented nationwide. Compared with the current ambient air quality standard, the new standard emphasizes the protection of human health as the primary goal. The new standard adjusts the classification expression by adding the pollutant items participating in the evaluation, and releases the main pollutant concentration, AQI and the corresponding air quality evaluation results at each monitoring point every hour, which provides reference for the public to understand the environmental quality and arrange their lives and trips reasonably. The new standard is an important measure of China's macro-strategy of atmospheric environmental protection. Responding to the public's concern about air quality, especially PM2.5, it bears the new expectations of the whole society for air quality improvement and is the unity of the will of the state and the will of the people. The new standard also reflects the change of our country's environmental air quality management ideas from primary pollutant control to secondary pollutant-based composite pollution control, and from local control to regional joint prevention and control.