AIR POLLUTION TYPES SOURCES EFFECS AND CONROL MEASURES 

Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to living organisms, or cause damage to the environment or atmosphere

Pollutants

Primary pollutants (directly emitted from a process)

·         Sulfur oxides (SO_x)

·         Nitrogen oxides (NO_x)

·         Carbon monoxide

·         Carbon dioxide (CO₂)

·         Volatile organic compounds – (VOCs)

• Methane (CH₄) & non-methane (NMVOCs).
• Methane-enhanced global warming
• NMVOCs, the aromatic compounds benzene, toluene & xylene - carcinogens and may lead to leukemia through prolonged exposure. 1,3-butadiene is another dangerous compound which is often associated with industrial uses.

·         Particulate matter 

·         Persistent free radicals

·         Toxic metals, such as lead, cadmium and copper.

·         Chlorofluorocarbons (CFCs)

·         Ammonia (NH₃) –

·         Radioactive pollutants

Secondary pollutants (Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact) include:

·         Photochemical smog:

• Classic smog -large amounts of coal burning in an area (mixture of smoke & sulfur dioxide).
• Modern smog -Vehicular emissions (acted on in the atmosphere by ultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions).

·         Ground level ozone (O₃):

•  a pollutant, and a constituent of smog. formed from NO_x and VOCs. largely the combustion of fossil fuel

·         Peroxyacetyl nitrate (PAN) - similarly formed from NO_x and VOCs.

·         Persistent organic pollutants (POPs)

• long-range transport, bioaccumulate in human and animal tissue, biomagnify in food chains, and to have potential significant impacts on human health and the environment.

Sources

Anthropogenic sources (human activity) mostly related to burning different kinds of fuel

·         "Stationary Sources" include smoke stacks of power plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices

·         "Mobile Sources" include motor vehicles, marine vessels and aircraft etc.

·         Chemicals, dust and controlled burn practices in agriculture and forestry management.

·         Fumes from paint, hair spray, varnish, aerosol sprays and other solvents

·         Waste deposition in landfills, which generate methane

·         Military, such as nuclear weapons, toxic gases, germ warfare and rocketry

Natural sources

·         Dust from natural sources, usually large areas of land with little or no vegetation

·         Methane, emitted by the digestion of food by ruminants

·         Radon gas (second most frequent cause of lung cancer, after cigarette smoking) (decay of radium) from radioactive decay within the Earth's crust. Accumulate in confined areas such as the basement of buildings.

·         Smoke and carbon monoxide from wildfires

·         Volcanic activity, which produce sulfur, chlorine, and ash particulates

Health effects

The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing and aggravation of existing respiratory and cardiac conditions. Affect the body's respiratory system and the cardiovascular system. Chronic obstructive pulmonary disease (COPD) includes diseases such as chronic bronchitis, emphysema, and some forms of asthma.

Control measures

Efforts to reduce pollution from mobile sources includes primary regulation, expanding regulation to new sources (such as cruise and transport ships, farm equipment, and small gas-powered equipment such as lawn trimmers, chainsaws, and snowmobiles), increased fuel efficiency (such as through the use of hybrid vehicles), conversion to cleaner fuels (such as bioethanol, biodiesel, or conversion to electric vehicles).

Control devices

Particulate control

o    Mechanical collectors (dust cyclones, multicyclones)

o    Electrostatic precipitators : Highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.

o    Baghouses: A dust collector Designed to handle heavy dust loads distinguished from air cleaners which utilize disposable filters to remove the dust.

• Scrubbers
• Baffle spray scrubber
• Cyclonic spray scrubber
• Ejector venturi scrubber
• Mechanically aided scrubber
• Spray tower
• Wet scrubber

·         NOx control

o    Low NOx burners

o    Selective catalytic reduction (SCR)

o    Selective non-catalytic reduction (SNCR)

o    NOx scrubbers

o    Exhaust gas recirculation

o    Catalytic converter

·         VOC abatement

o    Adsorption systems, such as activated carbon

o    Flares

o    Thermal oxidizers

o    Catalytic converters

o    Biofilters

o    Absorption (scrubbing)

o    Cryogenic condensers

o    Vapor recovery systems

·         Acid Gas/SO₂ control

o    Wet scrubbers

o    Dry scrubbers

o    Flue gas desulfurization

·         Dioxin and furan control

Plasma pyrolisis

Planned burning (at more than 850⁰C), Avoiding open burning