Air Quality (1)

Air Pollution and Pollutants

Air pollution generally refers to the phenomenon that, due to human activities or natural processes, certain substances enter the atmosphere in sufficient concentrations and for a sufficient period of time, thereby jeopardizing human comfort, health and welfare or the environment. At a specific time and place, air quality is affected by many factors. Man-made emissions from fixed and mobile pollution sources are one of the most important factors affecting air quality. Urban building density, topography and meteorological conditions are also important factors affecting air quality. .

Air pollutants are mainly divided into two categories, namely gaseous pollutants and particulate matter. Gaseous pollutants mainly include sulfur dioxide (SO2), nitrogen oxides (NOx), carbon monoxide (CO), hydrocarbons, ozone (O3), etc.; particulate matter mainly includes dust, acid mist, aerosols, etc.

Particulate Pollution

Substances in solid and liquid particulate state in the air are collectively referred to as air particulate matter. Particulate matter can be divided into total suspended particulate matter (TSP), inhalable particulate matter (PM10) and fine particulate matter (PM2.5) according to size.

1. Total Suspended Particulate Matter (TSP)

Total Suspended Particulate Matter (TSP) refers to particulate matter with an aerodynamic diameter of 100 microns or less. Smoke and dust from coal combustion, dust from industrial waste gas and ground dust are important sources of TSP in the atmosphere.

2. Inhalable particulate matter (PM10)

Respirable particulate matter (PM10) refers to particulate matter with an aerodynamic diameter less than or equal to 10 microns, also known as fly ash. PM10 in cities mainly comes from direct emissions from pollution sources such as road dust, building construction, production emissions, and fine particles formed by the interaction of sulfur oxides, nitrogen oxides, volatile organic compounds and other compounds in the ambient air.

PM10 hazards include health hazards and environmental hazards. PM10 will accumulate in the respiratory system, causing damage to the respiratory system and cardiovascular system, leading to asthma, lung cancer, cardiovascular disease, birth defects and premature death; the scattering effect and absorption effect of inhalable particulate matter on light is the atmospheric visibility the main factor for the reduction.

3. Fine particulate matter (PM2.5)

Fine particulate matter (PM2.5) refers to particulate matter in ambient air with an aerodynamic equivalent diameter of less than 2.5 microns. It has a wide range of sources and complex causes. Its main chemical components include inorganic components, organic components, trace metal elements, elemental carbon (EC), and biological substances (bacteria, germs, molds, etc.). The sources of PM2.5 are mainly divided into natural sources (dust, sea salt, plant pollen, bacteria, etc.) and anthropogenic sources (fossil fuel combustion, motor vehicle exhaust, biomass combustion, etc.). Compared with PM10, PM2.5 has a small particle size, is rich in a large amount of toxic and harmful substances, and has a long residence time in the atmosphere and a long transportation distance, so it has a greater impact on human health and the quality of the atmospheric environment. After PM2.5 is inhaled into the human body, it will directly enter the bronchi, interfere with the gas exchange in the lungs, cause diseases including heart disease, lung disease, respiratory disease, and reduce lung function; if it enters the blood through the bronchi and alveoli, harmful substances such as heavy metals are dissolved in the Blood is more dangerous. In addition, PM2.5 is one of the main culprits of haze weather, which directly reduces urban visibility and seriously endangers production, life and human health.