What are the specific causes of heavy pollution weather?

Internal factors: high pollutant emission intensity

At present, fine particulate matter (PM2.5) is the pollutant that has the greatest impact on my country’s atmospheric environmental quality, whether it is from the number of cities that exceed standards, When analyzing the degree of exceeding the standards in each city or analyzing it from the perspective of its contribution to heavy pollution weather, the impact of PM2.5 is far greater than that of other pollutants. The sources of atmospheric PM2.5 pollution mainly include the direct contribution of primary particulate matter emissions, and the indirect contribution of secondary conversion of gaseous precursors such as sulfur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOCs) and ammonia (NH3). contribute.

Especially during the winter heating period, the contribution of coal-burning emissions to atmospheric PM2.5 pollution in Beijing-Tianjin-Hebei and surrounding areas is even more prominent. Organic carbon (OC), elemental carbon (EC), Major components such as sulfate are directly related to coal-burning emissions. Other major components such as nitrates and ammonium salts also partly come from coal-fired boilers and coal-burning. The primary task of preventing and controlling heavy air pollution in winter is to vigorously reduce Coal burning emissions.

Environmental monitoring data and related research have shown that since the implementation of the "Ten Atmospheric Measures" in 2013, air pollution prevention and control measures across the country and various regions have achieved results. The concentration of primary pollutants (SO2, NO2 and primary particulate matter, etc.) The decline is obvious. However, the decline of secondary components in particulate matter is significantly slower than that of primary pollutants. The explosive growth of atmospheric PM2.5 during periods of heavy pollution is often related to the rapid growth of secondary components such as sulfates and nitrates.

It is worth noting that in addition to the mechanism by which gaseous precursors such as SO2 and NOx are converted into secondary components such as sulfate and nitrate respectively, there is also the interaction between these chemical components, such as NO2 Promote the accelerated conversion of SO2 into sulfate, producing a "1+1>2" air pollution generation effect. The role of these mechanisms in the formation of heavy atmospheric pollution is critical to the formulation of heavy pollution forecasting and early warning and multi-pollutant collaborative control plans.

External factors: unfavorable meteorological conditions

Adverse meteorological conditions are the external factors causing heavy pollution weather, such as static conditions, light winds, high humidity and temperature inversion, etc., which will cause basically the same emissions when This will lead to more serious air pollution.

Research shows that since the implementation of the "Ten Atmospheric Measures", the pollution meteorological conditions in the Beijing-Tianjin-Hebei region have generally become unfavorable, which has also made pollution control more difficult. From the comparative analysis of pollution meteorological conditions in the Beijing-Tianjin-Hebei region, 2014 was 17% worse than 2013, and 2015 was 12% worse than 2013. In the autumn and winter of 2016, my country once again experienced very unfavorable pollution meteorological conditions, especially The cold air in the northern region is inactive, weak in intensity, low in wind speed, and obviously high in temperature. At the same time, there are interactions between air pollution processes and meteorological processes. When air pollution accumulates to a certain extent, the chemical components of particulate matter (such as sulfates, black carbon, and organic components) have a significant impact on radiation, which to a considerable extent weakens the atmospheric diffusion capacity of the boundary layer, further aggravating heavy pollution.

In addition, the formation of heavy pollution weather is also affected by global climate change. Climate change with global warming as the main feature makes the atmospheric stratification more stable, which has become international knowledge. For example, since the autumn and winter of last year, abnormal weather has generally occurred around the world. Many countries, including developed countries such as the United Kingdom, France, and South Korea that have basically solved the problem of heavy air pollution, have also experienced relatively high-intensity and large-scale heavy air pollution.