Air Pollution: Sources, Types, and Dispersion
1.10 Air Pollution
The presence in the atmosphere of materials, substances, or forms of energy that involve a risk of serious discomfort, injury to health, or damage to the safety of the environment, people, and other property of any nature. Air contamination at certain times.
A. Pollution Sources
Natural
They include emissions of pollutants generated by natural activity:
- Volcanic eruptions, contributing to atmospheric pollutants.
- Forest fires occur naturally and emit high concentrations of smoke, dust, and ash.
- Activities of living organisms increase CO2; anemophilous processes (pollination through the air) cause respiratory allergies like hay fever.
- Electric shocks generated during storms lead to the formation of nitrogen oxides.
- Sea salt particles emitted into the air.
- Strong winds or gales transfer particles to other areas.
Artificial or Man-Made
They result from human activities. The problem of air pollution is mainly associated with this cause:
- Homes: Use of heaters, appliances, fossil fuels (coal), as well as the design and condition of equipment.
- Transport: Automobiles and airplanes cause a high degree of contamination. The impact of rail transport is comparatively lower.
- Industry.
- Agriculture and livestock.
- Disposal of solid waste.
Note: Natural emissions are highest globally.
B. Types of Pollutants
Air pollutants, at certain concentrations, can cause discomfort, damage, or risks to people and other living beings. They may also alter the functioning of ecosystems, material goods, and climate.
Residence time: The period a pollutant stays in the atmosphere, either as it is or participating in chemical reactions.
Chemicals
Aerosols are particles with a diameter less than 10µm.
1. Primary Pollutants
Substances directly emitted into the atmosphere from various sources:
- Particles such as ions, aerosols, and fumes.
- Sulfur compounds: sulfur dioxide (SO2), sulfur trioxide (SO3), and dihydrogen sulfide (H2S).
- Nitrogen oxides: dinitrogen monoxide (N2O), nitrogen monoxide (NO), and nitrogen dioxide (NO2).
- Oxides of carbon: carbon monoxide (CO) and carbon dioxide (CO2).
- Organic compounds: hydrocarbons (volatile organic compounds, VOCs), polychlorinated biphenyls (PCBs), dioxins, and furans.
- Halogenated compounds: hydrogen chloride (HCl), hydrogen fluoride (HF), halocarbons, and chlorofluorocarbons (CFCs).
- Heavy metals: lead, mercury, and cadmium.
- Odors.
2. Secondary Pollutants
They originate from primary pollutants through chemical reactions in the atmosphere:
- SO3, NH2, SO4, HNO3, O3 (tropospheric ozone), and PAN (peroxyacetyl nitrate).
Forms of Energy
1. Ionizing Radiation
Particles or electromagnetic waves that ionize atoms or molecules, altering their chemical balance and functions. They have a significant impact on the atmosphere and humans. Four types: alpha, beta, gamma, and X-rays.
Alpha and beta particles are electrically charged and differ in their penetration power (alpha has lower penetration). X-rays and gamma rays, being electromagnetic waves, have high penetrating power.
2. Non-Ionizing Radiation
Electromagnetic waves that do not change the structure of matter by causing ionization. Natural sources include the sun and the earth’s surface; anthropogenic sources include electric power cables and electrical appliances. Ultraviolet radiation, infrared radiation, radio frequency, and microwave. Observed effects depend on the intensity of the electromagnetic field generated.
3. Noise
It is now considered a special type of air pollution with a major impact on populations.
C. Pollutant Dispersion
Emission: The quantity of pollutants discharged from a source into the atmosphere over a period. Emission values are measured at the source’s output. The evolution of pollutants in the atmosphere involves transport, distribution, mixing, or storage.
Immission: The amount of pollutants present in a certain atmosphere after being transported, distributed, and mixed. This determines exposure levels for living beings and materials.
If immission levels are inadequate, they negatively affect air quality and various receptors.