In fact, what we usually call "smog prevention" can be divided into two aspects: one is to reduce the number of smog particles inhaled by the human body; The second is to minimize the density of smoke particles in the ambient air. If we carefully study these slogans of "anti-smog plants", we will find that the merchants are playing the signboard that plants can "dust down", which is the second aspect mentioned above. However, the dust removal ability of plants cannot be equated with "preventing smog" and "reducing PM2.5".
In our daily life, we often see a layer of dust on the surface of plant leaves, which is the source of "plant dust", from which "plants can prevent smog" is derived. However, plants can't "breathe". The adsorption of dust by plants is not active, but the dust particles carried in the air will be blocked by the microstructure of the leaves when they flow over the surface of the leaves.
The surface of plant leaves is not as smooth as meat and eyes. In fact, the surface of plant leaves usually has waxy or horny hairs, scales and other structures. In addition, many small gullies are formed on the surface of leaves at the seams where gas exchange takes place between plant epidermal cells and stomata. If you look under a microscope, the surface of the leaves is very rough. It is because of these rough surfaces that plant leaves can block tiny particles in the air. It can be seen that the important factor of plant dust removal is that air must flow over the surface of leaves, and then leaves can stop dust. This is also a shelter forest, street trees and so on. Can reduce the dust density of outdoor air-when the dust flows over the surface of the blade with the airflow, the plant blade can not only stop the dust, but also reduce the air velocity and accelerate the deposition of suspended particles in the air. So outdoors, plants can really play the role of "dust removal".
However, in the room, the air flow is very slow. It is estimated that the indoor wind speed is generally below 0.3m/s. Such a small wind speed makes the suspended particles in the indoor air unable to effectively contact with the plant leaves, so the indoor plants can't play the role of "dust removal", at best, they just accept the settled particles in the air, "ash". For example, the leaves of plants are similar to the filters in air purifiers. Only when the fan in the air purifier works to make the air pass through the filter screen completely can the dust be adsorbed and filtered. The plants in the room are like air purifiers without power. With "filters" and no airflow, they can't purify the air, so it is wrong to say that indoor green plants can "prevent smog and reduce PM2.5".