Air pollution (Environmental Science) Grade 7
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Air pollution is caused by both natural phenomena and human activities that introduce harmful chemicals, particulate matter, or biological materials into the atmosphere. It can damage human health and the environment. Primary pollutants are emitted directly, such as carbon monoxide from vehicle exhaust, while secondary pollutants form when primary pollutants interact chemically in the air to produce things like smog. Major human-caused primary air pollutants include sulfur and nitrogen oxides, carbon monoxide, volatile organic compounds, particulate matter, and others such as ammonia and radioactive pollutants.
Air pollution (Environmental Science) Grade 7
- 2. Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or cause damage to the natural environment, into the atmosphere. The atmosphere is a complex dynamic natural gaseous system that is essential to support life on planet Earth. Stratospheric ozone depletion due to air pollution has long been recognized as a threat to human health as well as to the Earth’s ecosystems.
- 3. Indoor air pollution and urban quality are listed as two of the world’s worst problems in the 2008 Blacksmith Institute World’s Worst Polluted Places report. A substance in the air that can cause harm to humans and the environment is known asan air pollutant. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man – made. Pollutants can be classified as primary or secondary. Usually, primary pollutants are directly emitted from a process, suchas ash from volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust of sulfur dioxide released from factories.
- 4. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone – one of the many secondary pollutants that make up photochemical smog. Some pollutants may be both primaryand seconday: that is, they are both emitted directly and formed from other primary pollutants.
- 5. MAJOR PRIMARY POLLUTANTS BY HUMAN ACTIVITY INCLUDE: •Sulphur oxides ( SOx ) – especially sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2 , forms H2SO4, and thusacid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
- 6. •Nitrogen oxides ( NOx ) – especially nitrogen dioxide are emitted from high temperature combustion, and are also produced naturally during thunderstorms by electrical discharge. Can be seen as the brown haze dome above or plume downwind of cities. Nitrogen dioxide is the chemical compound with the formula NO2. it is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting odor. NO2 is one of the most prominent air pollutants.
- 7. Carbon monoxide ( CO ) – is a colorless, odorless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Volatile organic compound – ( VOCs ) are an important outdoor air pollutant. In this field they are often divided into the separate categories of methane ( CH4 ) and non-methane ( NMVOCs ). Carbon dioxide( CO2 ) – a colorless, odorless, non-toxic greenhouse gas also associated with ocean acidification,emitted from sources such as combustion, cement production, and respiration. It is otherwise recycled in the atmosphere in the carbon cycle.
- 8. Methane is an extremely efficient greenhouse gas which contributes to enhanced global warming. Other hyrocarbon VOCs are also significant greenhouse gases via their role in creating ozone and in prolonging the life of methane in the atmosphere, although the effect varies depending on local air quality. Within the NMVOCs, the aromatic compounds benzene, toleune and xylene are suspected carcinogens and may lead to leukemia through prolonged exposure. 1-3 butadiene is another dangerous compound which is often associated with industrial uses.
- 9. •Particulate matter – Particulates, alternatively referred to as particulate matter ( PM ) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be man made or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosol. Averaged over the globe, anthropogenic aerosols – those made by human activities – currently account for about 10 percent of the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function and lung cancer.
- 10. •Persistent free radicals connected to airborne fine particles could cause cardiopulmonary diseas. •Toxic metals, such as lead, cadmium and copper. Cloroflourocarbons ( CFCs ) – harmful to the ozone layer emitted from products currently banned from use. •Ammonia ( NH3 ) – emitted from agricultural processes. Ammonia is a compound with the formula NH3. it is normally encountered as a gas with a characteristic pungent odor. Ammonia contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to foodstuffs andfertilizers. Ammonia, etheir directly or indirectly, is also a building block for the synthesis of many pharmaceuticals. Although in wide use, ammonia is both caustic and hazardous.
- 11. Odors – such as from garbage, sewage, and industrial processes. Radioactive pollutants – produced by nuclear explosions, nuclear events, war explosives, and natural processes such as the radioactive decay of radon.
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