The haze problem, which is dominated by fine particulate matter, has a certain impact on people's health and normal production and life. The commonly used definition of aerosol is a relatively stable suspension system formed by the uniform distribution of liquid or solid particles in a gas. In simple terms, atmospheric aerosols refer to tiny particulate matter suspended in the atmosphere, usually between nanometers and micrometers in size. Although these tiny particles are often overlooked in our daily lives, they have a profound impact on our environment and health. This article will introduce you to the sources, types, and relationship of atmospheric aerosols to the environment and health.
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Source vs. type
Aerosol particles in atmospheric haze are mainly divided into primary aerosols and secondary aerosols. Primary aerosols refer to particulate matter that is directly emitted into the atmosphere from emission sources, while secondary aerosols are particulate matter produced by primary aerosols in the atmosphere through chemical reactions with gas components.
Atmospheric aerosols can also be divided into natural and anthropogenic sources from sources. Natural sources include volcanic eruptions, plant emissions, marine aerosols, and sandstorms, while anthropogenic sources include industrial emissions, traffic exhaust, combustion emissions, and building construction.
Depending on the composition, source, and size of the particles, atmospheric aerosols can be classified into different categories. The main categories include sulfate aerosols, nitrate aerosols, organic aerosols, black carbon (also known as carbon black), trace element aerosols, biological aerosols, dust particles, etc., which can be divided into total suspended particulate matter, floating dust, dust reduction, PM10, PM2.5, and ultrafine particulate matter according to particle size. The presence of these aerosols in the atmosphere is complex and diverse, ranging from liquid to solid, and their properties directly affect their environmental effects.
Of these aerosols, secondary organic aerosols (SOAs) are particularly important, as they are an important component of fine particulate matter in the ambient air of urban and suburban areas. SOA is mainly formed by the oxidative degradation process of some moderate and semi-volatile organic compounds (I/SOCs) in the atmosphere. SOA is harmful to atmospheric visibility, air quality, climate change, tropospheric oxidation, and public health.
Atmospheric particulate matter is solid and liquid particles suspended in the atmosphere, and the particle size range is generally between 0.001~100 microns. In the standard of measuring particulate matter, according to the particle size, it can be divided into total suspended particulate matter (TSP), PM10, PM2.5, and ultrafine particulate matter (UFPs).
TSP is a general term for various particles dispersed in the atmosphere, and TSP concentration refers to the mass concentration of particulate matter with an aerodynamic diameter of less than or equal to 100 microns (mostly less than 10 microns), measured in micrograms per cubic meter. Its sources are complex, including pollen and spores produced by plants, including soot generated during fuel combustion, dust generated during production and processing, construction and traffic dust, wind-blown sand dust, and gaseous pollutants through complex physical and chemical reactions to produce corresponding salt particles in the air.
PM10 refers to particulate matter with an aerodynamic diameter of less than or equal to 10 microns, usually expressed in mass concentrations in micrograms per cubic meter. PM10 is also known as inhalable particulate matter because of its small particle size and can be directly inhaled into the respiratory tract and cause health hazards.
PM2.5, also known as fine particulate matter or particulate matter that can enter the lungs, refers to particulate matter with an aerodynamic diameter of 2.5 microns or less. It is usually expressed in mass concentrations in micrograms per cubic meter. PM2.5 has a greater impact on human health and atmospheric environmental quality due to its small particle size, abundant in a large number of toxic and harmful substances, and its long residence time in the atmosphere and long transportation distance.
UFPs are defined as particulate matter with an aerodynamic diameter of 0.1 microns or less. It is usually expressed in number concentrations and is measured in units per cubic centimeter. UFPs are small in size and have insignificant mass concentrations, but they contribute most of the total particulate matter concentrations. UFPs have a small particle size, are easy to be deposited deep in the respiratory system, and break through the protective barrier in the human body and enter the deep human body, causing greater harm. And the sources of UFPs and PM2.5 are very different, UFPs mainly come from the combustion process, the formation of new particles, of which traffic is a major emission source. UFPs are difficult to remove by sedimentation, mainly by growing into larger particles.
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Environmental impact
Atmospheric aerosols play an important role in the Earth's energy balance, climate change, and atmospheric optics. First, they are able to scatter and absorb solar radiation, affecting the energy budget of the Earth's surface. Second, aerosols play a key role in the formation and nature of clouds, influencing precipitation and the radiative effects of clouds. Finally, certain types of aerosols are also capable of influencing chemical reactions in the atmosphere, which in turn can affect atmospheric quality.
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Health Impacts
Atmospheric aerosols also have an important impact on human health. Fine aerosol particles can be inhaled into the lungs, causing respiratory diseases and cardiovascular problems. Particulate matter smaller than 2.5 microns in diameter (PM2.5) is particularly dangerous because they can penetrate deep into the lungs and enter the bloodstream, causing more serious health effects.
Aerosol particles floating in the air are easily adsorbed and deposited in the bronchial tubes and lungs, and the smaller the particles, the easier it is to enter the lungs through the respiratory tract, where particles smaller than 1 micron in size can reach the alveoli directly. Particles entering the lungs can cause harm to the human body due to their toxicity (such as sulfuric acid droplets, PbO, PbBr, etc.) or carrying toxic substances (such as SO2 adsorbed by soot).
The greatest impact on human health are particles with a particle size of less than 2.5 microns. This part of the particle size is small, easier to enter the human circulatory system, the specific surface area is larger, more able to absorb toxic and harmful substances, so it will be more harmful to human health. For example, the asbestos adsorbed on small particles and aromatic compounds represented by benzopyrene can cause carcinogenesis of tissue cells after entering the human body, and after the sulfuric acid droplets enter the human body, they can be loaded on the alveoli to stimulate the alveoli, increase airflow resistance, and make it difficult to breathe. Therefore, in hazy weather, we should try to stay indoors and reduce outdoor activities to reduce the harm of particulate matter to the human body.
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Measures to mitigate the impact
There are a number of measures we can take to mitigate the effects of atmospheric aerosols.
1. Reduce emissions from anthropogenic sources, including improving industrial production processes, promoting clean energy, and strengthening traffic management.
2. Strengthen the monitoring and research of atmospheric aerosols in order to better understand their impact mechanisms and trends.
3. Popularizing public awareness of environmental protection and advocating a low-carbon lifestyle are also the key to reducing the impact of atmospheric aerosols.
4. Some small Xi in life will also reduce the risk of exposure, such as staying away from the road during morning and evening traffic rushes, wearing masks, closing car windows, closing windows on smog days, reducing travel, and so on.
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epilogue
Atmospheric aerosols, though small, have a huge impact. From climate change to human health, they play an important role in our lives. With a deeper understanding of where aerosols come from, what types they are, and what impacts they are, we can better take steps to protect our environment and health. Let's work together to create a cleaner, healthier future.
Source: Zibo Environment, VOCs Frontier / "Changji Environmental Protection" public account