What Is an Aerosol Machine?

Aerosol is a colloidal dispersion system formed by solid or liquid small particles dispersed and suspended in a gas medium, also known as a gas dispersion system. The dispersed phase is a solid or liquid small particle with a size of 0.001 to 100 m, and the dispersion medium is a gas. Liquid aerosols are often referred to as fog, and solid aerosols are often referred to as foggy smoke ^[1] .

A gaseous dispersion system composed of solid or liquid particles suspended in a gaseous medium. The density of these solid or liquid particles can differ slightly from the density of the gaseous medium, or they can vary widely. The size of the particles is generally from 0.001 to 100 m. The shape of the particles is varied, and can be nearly spherical, such as liquid mist beads, flakes, needles, and other irregular shapes. In engineering technology, especially in labor protection and environmental protection engineering, in order to distinguish from clean air, dust-containing gas or polluted gas is often used to call aerosol. From the perspective of fluid mechanics, aerosols are essentially multiphase fluids in which the gaseous phase is a continuous phase and the solid and liquid phases are dispersed phases ^[2]

According to their sources, aerosols can be divided into two types: primary aerosols (which enter the atmosphere directly from the source in the form of particles) and secondary aerosols (which are generated by the conversion of primary pollutants in the atmosphere). They can come from fine ash and fine dust raised by the wind, salt particles evaporated from splashing sea water, scattered volcanic eruptions, and forest burning

In 1926,

The concentration of aerosol can be expressed by the total mass of particles in a certain volume. The basic unit is micrograms / meter, and it can also be expressed by the number density, that is, the number of particles in a unit volume. The distribution characteristics of aerosols can usually be described by their particle number ( n ), particle surface area ( S ), particle volume ( V ), or mass ( m ) according to the particle size ( D ) distribution. Generally, it is d n / d lg D , d S / d lg D and d V / d lg D vs. lg D , they are basically

The chemical composition of aerosol is very complex. It contains various trace metals, inorganic oxides,

Can be divided into two major categories of dispersion method and condensation method. Dispersion method is to split solid or liquid into smaller parts by external force, and it is divided into solid mechanical grinding method and liquid spray method. The aerosol obtained is often not highly dispersed.

Aerosols have been widely used in industry, agriculture, defense and other fields.

Industry: Aerosol can accelerate the burning rate and make full use of fuel. Spray drying can improve product quality. It has been widely used in the pharmaceutical industry and the production of laundry powder. Aerosol fire extinguishing technology is a fire extinguishing technology developed in recent decades and has become a ha One of the substitutes for dragon fire extinguishing products is also a sharp weapon used in the field of fire protection for workers and civil construction. The development of aerosol firefighting technology pyrotechnic technology and ultrafine particle technology. In the process of continuous development, it gradually perfects itself, showing better and better performance when used for fire fighting and rescue ^[8]

Aerosol Research Progress

Aerosol generation process

According to a research report, field studies in the northern forests of Hyytiälä, Finland, and experiments in the laboratory revealed how gas molecules form atmospheric aerosols. These findings may have implications for the role of new aerosol formation on atmospheric aerosol budgets and their impact on climate.

Most aerosols-they are tiny airborne particles from volcanoes, dust, pollutants and other sources-are generated from their own environment, not from land, sea or space. Completely and directly transported. These aerosols come from a growth process, which starts as molecules and clusters in the atmosphere, and its size grows larger as it acquires other molecules, clusters and particles.

In the 1990s, scientists had discovered clues to the mechanism of atmospheric particle formation, but at that time it was impossible to know the exact mechanism because they did not have enough capacity to detect tiny particles to observe the Start.

Markku Kulmala and colleagues have developed sensitive new technologies that enable people to detect and count these small origins, so that they can outline the process of aerosol formation in detail. Researchers have discovered that the initial step of aerosol formation begins with clusters with a diameter of less than 0.002 m, and sulfuric acid and organic molecules are the key components of the particle growth process. Researchers have found that sulfuric acid and organic molecules like carbon are linked together to form a key cluster that grows into an aerosol particle. The accumulation of clusters sufficiently stable to achieve sustained growth is the key to aerosol formation.

Understanding how aerosols form is critical to understanding the impact of these particles on climate change. ^[10]

MODIS Aerosol MODIS image

Since the release of the global PM2.5 distribution map in the United States, Beijing, etc.

Inversion process ^[11]

The city's PM2.5 content has attracted attention, especially the continuous "haze" weather has made the citizens panic, and the prevention and treatment of PM2.5 pollution is imminent. In 2012, a lot of PM2.5 monitoring stations were added nationwide, but after all, ground monitoring stations cannot be evenly distributed in every place. Satellite remote sensing methods make it possible to quickly monitor aerosol conditions on a large scale due to its high timeliness, wide coverage, and high resolution. become possible.

MODIS is an advanced multispectral remote sensing sensor with 36 observation channels, covering the main observation data of current major remote sensing satellites. Using the inversion aerosol optical thickness spatial distribution data combined with PM2.5 measured data to establish a relevant model, PM2.5 remote sensing monitoring can be achieved. This micro-lecture teaches how to retrieve the spatial distribution of aerosol optical thickness based on ENVI 5.0.

effect

Aerosol particles can affect weather and climate in two ways. On the one hand, it can reflect sunlight into space, thereby cooling the atmosphere and deteriorating the visibility of the atmosphere. On the other hand, it can scatter, diffuse, and absorb part of the solar radiation through particles to reduce the outflow of long-wave radiation on the ground, so that The atmosphere is warming.