Haze weather knowledge

20 13 12, several cities in China suffered from severe haze. In order to popularize environmental protection knowledge, the related knowledge of smog is introduced as follows:

Haze is a mixture of fog and haze. When the humidity is high in the morning and evening, there are many components of fog. When the daytime humidity is low, haze is the main force, and the relative humidity is between 80% and 90%. Among them, fog is a natural weather phenomenon, and the water vapor in the air is dense. Although dust is the condensation core, it is generally non-toxic and harmless; The core substances of smog are substances suspended in the air such as smoke and dust. The relative humidity of the air is below 80% and the color is yellow. Gas can directly enter and attach to human lower respiratory tract and lung lobes, which is harmful to human health. The formation of haze weather is mainly man-made environmental pollution, and natural conditions such as low temperature and little wind make it difficult for pollutants to spread.

Smog is caused by automobile exhaust, factory exhaust and fireworks. Fog and haze weather

When the suspended water vapor in the atmosphere condenses and the visibility is lower than 1000 meters, it is called fog in meteorology.

When the water vapor contained in the air reaches the maximum, saturation will occur. If the water vapor exceeds saturation, the excess will condense out and combine with tiny dust particles in the air to form small water droplets or ice crystals, which will be suspended in the air layer near the ground and become fog. The lower the temperature, the less water vapor can be contained in the air, and the easier it is to form smog.

In view of the specific meteorological conditions in Beijing, North China and other places, under the influence of low temperature, when the warm and humid southerly wind near the ground moves horizontally, it gradually cools down after passing through the cold ground or water surface to form fog.

The main reasons for the haze weather are as follows:

First, the relative humidity of the air near the ground in these areas is relatively high, and the ground dust is relatively large, which is stirred by people and traffic on the ground;

Second, there is no obvious cold air activity, the wind is small and the atmosphere is relatively stable. Because the air does not flow, tiny particles in the air gather and float in the air;

Third, the sky is clear and partly cloudy, which is conducive to radiation cooling at night and makes the near-surface air with relatively high humidity saturate and condense to form fog.

Fourth, automobile exhaust is the main pollutant emission. In recent years, there are more and more cars in cities, and automobile exhaust is a factor of smog;

Five, secondary pollution produced by the factory;

Six, winter heating emissions of carbon dioxide and other pollutants.

Large-scale haze weather mainly appears in the situation of large-scale atmospheric circulation with weak cold air and good water vapor conditions, and the low altitude near the ground is still wind or breeze. Due to the high humidity and high water vapor in foggy days, fog droplets provide adsorption and reaction sites, which accelerate the transformation of reactive gaseous pollutants into liquid particulate components, and particulate matter is also easy to act as condensation nuclei to accelerate the formation of smog, and the interaction between them quickly forms pollution.

Non-diffusion folding of pollutants

Fog itself is not pollution, but the atmospheric environment that produces fog is in a relatively stable state, and pollutants in the air are not easy to spread outward, resulting in agglomeration effect, which will make pollution more and more serious. Similarly, under the conditions of low air pressure and low wind, the combination of urban pollutants and water vapor in the lower air will also aggravate the degree of smog. "

Meteorologists said that because the fog itself presents an uneven phenomenon. Therefore, there will be different degrees of smog in the same city.

The Central Meteorological Observatory predicts that the cold air activity in China will be weak in the next three to five days, and the central and eastern regions will still be in a foggy period.

But the foggy weather in these areas is intermittent. 14 ~ 15, there is a cold air activity in the north, and the haze weather in some areas will also be weakened. Throughout mid-June, there were relatively many foggy days in the central and eastern regions, with high incidence areas in North China Plain, Huanghuai area and Sichuan Basin.

PM2.5 folding

In foggy weather, PM2.5 is the "culprit". There are many main sources. One is automobile exhaust. In recent years, there are more and more cars in cities, and the emission of automobile exhaust is also increasing, which contributes about 60% to PM2.5 in urban air. The second is road dust and construction dust. According to research, road dust is the main source of PM2.5, accounting for about 20% of the source of PM2.5, and the third is the secondary pollution produced by factories. Fourth, the pollutants emitted by low-altitude coal burning during heating in winter. Fifth, the flue gas generated by the burning of biomass (straw and firewood) and garbage incineration is also an important source of PM2.5