Where has the best air?

People often think that the morning air is the freshest, but this is actually a misunderstanding. Whether the air is fresh or not depends on the severity of air pollution. The main sources of air pollution include smoke, exhaust gas emitted by various motor vehicles, smoke from residential stoves, and carbon dioxide gas emitted by nighttime metabolism of green plants. According to scientists, air pollution is very light in the morning, noon and afternoon, so the air is relatively fresh and clean. The air is freshest around 10 am and 3-4 pm. Air pollution is more serious in the morning, evening and night. Among them, around 7 pm and 7 am are the peak hours of pollution. Of course, the air at this time is the least fresh.

The difference in air freshness throughout the day is due to meteorological factors. The vertical temperature difference between day and night changes significantly. When the ground temperature is higher than the high-altitude temperature, the air on the ground is easy to rise, and pollutants are easily carried to high altitudes for diffusion; when the ground temperature is lower than the high-altitude temperature, an "inversion layer" is formed in the sky. , this "inversion layer" presses down above the ground like a big lid, preventing ground air from rising and various pollutants in the air from diffusing. Generally, inversion layers tend to appear at night, morning and evening, so the air is the most polluted at these times.

In the daytime, when the sun comes out, the ground temperature rises rapidly, and the temperature inversion layer will gradually dissipate. As a result, the pollutants spread quickly. Generally, after 10 a.m., the ground air is very fresh. Therefore, the time to exercise in the morning should be after sunrise, preferably between 10 a.m. and 3-4 p.m., because the air is freshest at this time.