SOURCES OF AIR POLLUTION

Air pollution sources are categorized here in five categories. These are as follows:

• Natural Sources
• Domestic Sources
• Agriculture Sources
• Industrial Sources
• Transportation related sources

1) NATURAL SOURCES

Natural sources of pollutants varied from location to location depending on the seasons, vegetation type, meteorological and geological conditions. Human activities may also influence the conditions and enhance the pollutants emerging from natural sources. For example in dust bowl that occurred in 1930 in southwestern United States, the cultivation for agricultural purposes causes the spread of spores of ragweed plant on the unplanted earth banks at construction sites and alongside the roads. These spores contribute to the hey fever. 

Volcanic eruptions are a source of all the pollutant gases. For example Mount St. Helens eruption occurred in May 18, 1990, emitted almost 4 km3 of solids into the atmosphere. This amount is several orders of magnitude higher than the amount of particles discharged from human activities annually in North America.

The chemical composition and particle size o dust (ash) depends upon its distance from the source. This depicts certain chemicals are concentrated in specific particle size ranges. 

2) DOMESTIC SOURCES

In residential areas the domestic activities are the source of air pollution. Some activities and types of pollutants released from the domestic activities are as follows:

Space Heating released the pollutants such as CO, CO2, SO, NOx, soot and smoke.

Cooking emits the fats (solids, liquids, vapors), particles, odors.

Cleaning emits Solvent vapors, dust, lint and spray.

Gardening produce the pollutants pesticides and fertilizers.

Painting produce principally solvent vapors.

Washing releases the detergent particles, soap particles and lint.

Before industrial revolution domestic fires were the source of pollutant in London, England. Modern domestic furnaces are better but pollutants are still released from low chimneys. 

3) AGRICULTURAL SOURCES

Agricultural sources consist of slaughterhouses and animal feedlot operations. For Example chicken production for meat purpose is done on large scale operations. Hundreds or thousands of birds have to be concentrated at one location. At Pennsylvania State University, the observations showed that the pollutants emitted from ventilation system at small house produces more than 40 % of particles smaller than 5 microns in diameter. These are in the range of respiratory size.

4) INDUSTRIAL SOURCES

Industrial sources are noticed because these are emitted from single stack or duct. 

NOx are produced from high combustion units. Main plants of sources are manufacturing fertilizers and explosives.

SOx are released from combustion of fuel oil and coal at stationary sources. Small amount of SOx are emitted from combustion of gasoline and diesel fuels. 

Hydrogen Sulphide are emitted from paper plants, oil refineries, natural gas cleaning and processing plants. 

Carbon Monoxide are released in the production of cast iron and other metallurgical processes. 

Hydrocarbons are released from petroleum and natural gas industries. Hydrocarbons are also released from plastics manufacturing plants and rubber manufacturing and processing plants. 

5) TRANSPORTATION RELATED SOURCES

The spark ignition engine in automobiles released the carbon monoxide, hydrocarbons and Nitrogen Oxides to the North American atmosphere than all other urban and industrial sources. Most hydrocarbons are emitted from tailpipe. Researchers have found the need of nitrogen oxides emissions reduction to reduce the photochemical smog and acid rain precursor emissions. Lead free gasoline has made necessary because lead ( 3 g per gallon in high octane leaded gasoline) poisons the catalysts in the reactors reducing their effectiveness.