Air quality in winter
Why is it worse than summer?
After entering the winter season
You can clearly feel that the haze is starting to increase
Why after entering the winter
We can feel the air visibility dropping
What about the significant increase in the number of smog days?
This issue of environmental science popularization
David shares the reasons why
Causes of haze weather
Let's start with the conclusion: there are two main reasons for the impact of haze weather: pollutant emissions and meteorological conditions.
Affected by these two conditions, there are obvious seasonal variation characteristics of pollutant concentration. In other words, winter meteorological conditions are not conducive to the dispersion of pollutants, resulting in poor air quality in winter. Of course, this is still a conclusive reason, without analyzing the root cause of the problem, and David will analyze it in depth for you below.
Pollutant emissions
One
Coal-fired heating during the heating period
In winter, the temperature in the northern region is low, and coal is mostly used for heating, and the amount of coal burned increases significantly, and the emission of coal soot and dust is an important factor causing poor air quality in winter.
Many cities have already switched from coal-fired boilers to combined heat and power and gas-fired boilers to reduce pollution, and we expect cleaner energy sources to be available for winter heating in the future.
Two
Motor vehicle exhaust emissions are increasing
Compared with summer, due to the decrease in temperature in winter, the gas pressure and temperature of the automobile engine working cycle are not high, the combustion rate of mixed gas slows down, the engine combustion is not sufficient, and the exhaust emissions of motor vehicles increase, resulting in an increase in PM2.5 and other pollutants (sulfur dioxide, nitrogen oxides, VOCs, etc.). Of course, the cold weather in winter also increases the number of people driving, which in turn increases exhaust emissions.
In recent years, new energy vehicles have become rapidly popularized, and many people have purchased new energy vehicles, which has reduced some vehicle exhaust emissions. Yutong new energy sanitation vehicles all use pure electric power, operating in the city, not increasing the burden on the environment, but also reducing pollution emissions in winter.
Meteorological conditions
Inversion plays a key role in the influence of meteorological conditions on PM2.5 concentrations. Normally, the air temperature decreases with altitude, with the lower air being hotter and the upper air being colder. Cold air is heavy and will sink, while hot air is light and will float up, forming a convection.
However, at certain times, such as autumn and winter nights, the temperature of the lower atmosphere near the ground is very low because the temperature of the ground drops sharply. The upper air does not cool down so quickly, but the temperature is higher than that of the lower layer, and the phenomenon of "temperature reversal" occurs. Once this inversion layer is formed, the air cannot be convected up and down, and it is difficult for pollutants to diffuse.
In winter, the ground is a cold source for the atmosphere, especially at night, the radiation is low, the cooling is obvious, and the atmospheric temperature near the ground is lower than the upper atmospheric temperature, resulting in stable atmospheric stratification, the air can not be convected up and down, and it is difficult to spread the accumulation of pollutants. In summer, on the contrary, the ground is a heat source for the atmosphere, and the vertical movement of the atmosphere is active, so it is not easy to have temperature inversion.
Winter is the season of high incidence of haze
David is here to remind everyone
Keep an eye on the air quality index
Adjust protective measures and the frequency of outdoor activities
Breathe "good" air
Make life better
Source: Yutong Sanitation