China News Agency, Beijing, June 2 (Reporter Ruan Yulin) Bai Qiuyong, director of the Department of Ecological Environment Monitoring of the Ministry of Ecology and Environment, told reporters in Beijing on the 2nd that in recent years, China's ozone (O3) pollution has gradually emerged, and the concentration has increased year by year .

  Bai Qiuyong said that in recent years, China's ozone pollution problem has gradually emerged, and the concentration has increased year by year. In 2019, the number of days exceeding the standard with ozone as the main pollutant accounted for 41.8% of the total number of days exceeding the standard, second only to PM2.5 (fine particulate matter) which accounted for 45%. Ozone pollution in summer has become an important "blocking tiger" to win the blue sky defense battle, and PM2.5 pollution in autumn and winter has become the "two mountains" in front of us.

  Bai Qiuyong said that in recent years, the global ozone background concentration has been increasing, with an average annual increase of about 1 microgram. This is mainly related to global warming, anthropogenic pollution emissions, and large-scale regional transmission.

  In 2019, Beijing-Tianjin-Hebei and surrounding areas and the Fenwei Plain are both heavily polluted by PM2.5 and high in O3 concentration. The spatial distribution of ozone pollution in China is more consistent with PM2.5. Analysing the reason, Bai Qiuyong said that mainly volatile organic compounds and nitrogen oxides are both precursors for the photochemical reaction to generate ozone, and also the main precursors for the secondary components in PM2.5. At the same time, when the concentration of PM2.5 in the atmosphere drops significantly, it will lead to enhanced optical radiation, which is conducive to ozone generation. The monitoring results show that the interannual changes of PM2.5 and ozone are generally inversely correlated.

  According to reports, ozone has become the primary pollutant affecting summer air quality. Among them, Beijing-Tianjin-Hebei and surrounding “2+26” cities and Fenwei Plain were the most polluted months of O3 from June to July, the most polluted months were from June to September in the Yangtze River Delta, and the pollution was from September to November in the Pearl River Delta The heaviest month. From northern China to southern China, the peak time of O3 gradually showed a backward trend.

  Bai Qiuyong believes that at this stage, the fundamental cause of ozone pollution in China is that ozone precursors such as volatile organic compounds and nitrogen oxides are still maintained at a relatively high concentration level. Under adverse weather conditions such as strong sunshine, high temperature, less cloud cover, weak wind force, and less rainfall, the photochemical reaction will be accelerated, resulting in ozone concentration exceeding the standard.

  In 2019, the average concentration of O3 in 337 cities across the country is 148 micrograms per cubic meter. Bai Qiuyong said that according to research, the average concentration of O3 exceeds 160 micrograms per cubic meter, it will affect the human body, so do not talk about "oxygen" color change. Ozone pollution is more subtle than PM2.5 pollution. Normally, ozone exceeding the standard is generally concentrated in the period of high afternoon temperature and strong sunshine. During this period, as long as possible to minimize going out and outdoor activities, the impact of ozone on human health can be Anti-controllable". (Finish)