beware china's 'anti-smog tower' and other plans to pull pollution from the air - air purifier no filter

An air-
The size of the purification tower is a small high-
The rise of China's Xi'an city has been established.
The report of scientists behind the project seems quite positive at first glance, providing a technical route to help clean air pollutants on a scale across the city.
But since there is no hard data publicly available to support this claim, there may be some level of doubt at the moment.
This is not the first project to try to clean up nitrogen oxide pollution using technology or natural intervention (NOx)
And other pollutants from the ambient air.
In India, a high-pressure water gun has been used recently to remove particles, while in London, NOx-
Edible paint has been promoted as a solution for harmful nitrogen oxides.
Many cities have proposed planting more trees and shrubs to purify the air.
All of this, even the purification tower, is supported by at least some seemingly reasonable science.
There is no doubt that the tower that filters the air will take away tiny harmful particles from the air, titanium oxide paint will react with NOx, and trees will also become a sink to air pollution.
The more important but often overlooked question, however, is whether or not these effects really have useful effects.
Pollution is spreading far away, which is the biggest challenge in trying to eliminate air pollution (
Not the exhaust pipe)
It was very diluted.
While humans mainly live a few meters below the atmosphere, what we breathe is severely affected by a deeper layer of air that extends from the surface to about 1 km, it is called the planetary boundary layer in meteorological terms.
Due to turbulence and hot air flow, pollution is quickly mixed in the boundary layer, and if the pollution is really to be reduced on a large scale, the amount of air that needs to be scrubbed and cleaned is much larger. Anti-
Haze paint is a good example.
In 2016, the British government reported the possible effectiveness of using paint as a NOx sink in London.
The conclusion is that basic chemistry is reasonable, just as some beneficial reactions do occur, but the basic aerodynamics of moving pollution through the boundary layer to the painted surface is a key limiting step.
At any time, the atmosphere of only a small part of the city is exposed to paint.
Therefore, the report says that even if London's White paint covers a completely incredible amount, there is little to no beneficial effect.
Star Trek's darling, analysis boils this down to the truth that you can't break the laws of physics.
Emissions of pollutants to the surface of trees and shrubs have similar problems;
Widely beneficial vegetation (
There are many other excellent qualities)
But in fact, it has little effect on the overall air quality.
The approach adopted by air filtration projects in China is slightly different.
It is not passive, but active movement of air through the cleaning system, using greenhouses to generate warm air currents rising through filters.
On the surface, these numbers look big-clean 10 million cubic meters of air a day.
But in the context of a medium-sized Chinese city, such as an area of 10 km x 10 km and a boundary layer of 1 km deep, the purifier may have only released 0.
01 of the air in the "air box" is over the city.
The result may be that when the boundary layer is particularly shallow, the benefits of the surface may be greater and more.
But it is worth mentioning that the city is not a sealed box, and the pollution that they continue to flow into needs to be removed.
More directly, for any system that releases clean air from the chimney, only those areas with direct downwind will have any benefit.
It is hard to say that the actual work of scientists on this project will have quite a bit of work to do to finally prove that their intervention has indeed changed and can change naturally in the atmosphere.
The benefits of the air pollution detection policy usually need to be measured before, during and after, and this change must be of sufficient size to compete with other factors.
Individual local interventions may only have a small impact, which can be superimposed on a wide range of pollution conditions that are largely controlled by natural changes in the weather.
Special care is given to any study that claims to be short-lived local interventions that lead to reduced pollution.
People tend to have a strong social and political desire to "see the effect", but the reality can be disappointing and the evidence is often uncertain.
It is expected that in the coming months and years, there will be many conflicting reports about the effectiveness of the UK's clean air zone.
If we only come to a conclusion from this point, and previous attempts to remove air pollution, that is, it would be much easier to come up with technologies and solutions to stop harmful emissions from the source, instead of trying to catch the resulting pollution once it is free and enters the air.
Alastair Lewisis is professor of atmospheric chemistry at the National Atmospheric Science Center at York University.
The article was originally published in the dialogue (Dialogue. com)