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How much do you know about the basics of air pollution?



Our country has declared war on air pollution with unprecedented strength and defended the blue sky with unshakable determination. So how much do you know about the basics of air pollution? Let's find out together~

In recent years, there have been more and more blue skies and better air quality. Not only in Beijing, blue sky has become the norm all over the country. The data shows that from 2017 to 2021, the PM2.5 concentration in cities at the prefecture level and above nationwide will drop by 25% to 30 micrograms/m3; the proportion of good days will increase by 5.0 percentage points to 87.5%; the number of days with heavy pollution will drop by nearly 40% , the proportion fell to 0.9%. my country has declared war on air pollution with unprecedented strength and defended the blue sky with unshakable determination. So how much do you know about the basics of air pollution? Let's find out together~


01 What is air pollution?

Air pollution is caused by various human activities

Air pollution is caused by gases and particles emitted into the atmosphere by various human activities, such as the inefficient burning of fuels, agriculture and farming. There are also natural factors that contribute to air pollution, including soil dust particles and salt from ocean waves.

Air pollutants can be emitted directly from the source (i.e. primary pollutants) or formed from chemical reactions in the atmosphere (i.e. secondary pollutants). When these substances reach critical levels in the air, they can harm humans, animals, plants and ecosystems, reduce visibility, and corrode materials, buildings and cultural sites.


02 Is air pollution a new problem?

Air pollution has existed for thousands of years

Air pollution is closely related to humans and has existed for thousands of years, starting with the use of fire for cooking and heating. Dangerously high levels of outdoor air pollution became a problem during the Industrial Revolution, and the massive use of coal caused many severe urban air pollution incidents.
The London smog of 1952 is an extreme case. That year, pollution blanketed London and killed more than 12,000 people in a matter of days as residential coal burning, coal for power generation, dirty fuel for transport and industrial pollution interacted with weather phenomena. After a public outcry, the UK passed the Clean Air Act (1956).


03 Where does air pollution come from?

mostly caused by human activities

Air pollution comes from a wide range of sources, both natural and man-made. Natural sources include volcanic eruptions, ocean waves, soil dust, natural vegetation fires, and lightning. Some of the most common anthropogenic sources include power generation, transportation, industry, residential heating and cooking, agriculture, solvent use, oil and gas production, waste combustion, and building construction. Some sources, such as forest and savanna fires and wind-blown mineral dust, occur naturally but are exacerbated by human activity.
Different pollutants have different sources. In cities, air pollution comes from inside and outside the city, some from far away. Major sources of pollution in cities include vehicles, burning of natural gas, coal and charcoal, wood for cooking and heating, and industrial sources still located within cities. Many large industrial sources, such as cement plants, steel mills and power plants, are far from cities but still contribute to urban air pollution because pollutants can travel great distances with the air. Pollutants emitted by the oil and gas industry and the maritime sector can also spread over great distances.
Agricultural sources, including burning forests for arable land and forest fires, contribute to urban and rural air pollution. In very dry regions, near deserts and eroded land, wind-blown dust makes up a large portion of PM2.5. Most ammonia is emitted from agricultural and human waste disposal.


04 Will air pollution spread?

Air pollution can spread

Air pollution has a significant impact on places near its source, but because it can travel great distances in the atmosphere, air pollution produced in one place can also affect great distances. For example, pollutants that form fine particulate matter (PM2.5) and ozone (O3) can travel hundreds or thousands of kilometers, affecting entire regions and continents.

Although long-range air pollutants are one of the causes of local air pollution, nearby pollution sources are still a very important determinant of local air quality. Concentration levels of pollutants like nitrogen dioxide (NO2) and sulfur dioxide (SO2) are highest near their sources (transportation, energy production and industry). Within a city, the areas closest to large pollution sources can have extremely high concentrations of pollutants, while other areas in the same city can be much cleaner.

Atmospheric conditions, such as wind, affect the spread of pollutants and can vary widely. Strong winds enable long-distance travel, while a windless environment can lead to a buildup of pollutants. Large cities in subtropical and tropical regions have severe pollution events due to very little wind and a lot of sunshine hours. Local weather conditions, such as mountains around cities, land-sea winds, etc., can affect the diffusion of pollutants and the formation of secondary pollutants.


05 Does air pollution cause other environmental degradation?

Acid rain is a typical case

Some air pollutants cause "acid rain," which received particular attention in Europe and North America in the 1980s and 1990s. Sulfur dioxide (SO2) and nitrogen oxides (NOx) react with water in the atmosphere to produce sulfuric and nitric acids, which return to Earth as "acid rain."
Acid rain affects the environment by destroying the leaves of plants, reducing their productivity and depriving the soil of the nutrients that plants depend on to survive. Acidification of soil and river water kills fish and insects and affects other species that feed on them. Acid rain can also cause damage to buildings and monuments.


06 What is the connection between air pollution and climate change?

Major air pollutants all have an impact on climate

Air pollution and climate change are intrinsically linked. All major air pollutants contribute to the climate, and most share sources with greenhouse gases (GHGs), especially those associated with the burning of fossil fuels. They also exacerbate each other's influence in a number of ways. Greenhouse gases such as methane, for example, contribute to the formation of ground-level ozone, and levels of ground-level ozone increase with temperature. Rising temperatures have increased the frequency of wildfires, which in turn have further increased levels of particulate air pollution.

Pollutants of "Short Term Climate Pollutants" (SLCPs) such as black carbon, ozone, methane and hydrofluorocarbons (HFCs) are powerful climate forcers and (in the case of ozone and black carbon) dangerous air pollutants . Many measures to reduce short-lived climate pollutants also reduce other air pollutants, such as nitrogen oxides. For example, measures to reduce black carbon affect regional climate change and slow the rate of near-term global warming. They also greatly reduce emissions of pollutants that cause PM2.5, thereby benefiting human health. Methane is a potent greenhouse gas that forms ozone in the atmosphere. Actions to reduce methane go a long way toward preventing climate change, protecting human health and crop yields.

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