寻找有关污染的作文（英）

Pollution is the introduction of contaminants into an environment that causes instability, disorder, harm or discomfort to the ecosystem i。e。 physical systems or living organisms 。[1] Pollution can take the form of chemical substances, or energy, such as noise, heat, or light energy。 Pollutants, the elements of pollution, can be foreign substances or energies, or naturally occurring; when naturally occurring, they are considered contaminants when they exceed natural levels。 Pollution is often classed as point source or nonpoint source pollution。 The Blacksmith Institute issues annually a list of the world's worst polluted places。 In the 2007 issues the ten top nominees are located in Azerbaijan, China, India, Peru, Russia, Ukraine and Zambia。 When people think about air pollution, they usually think about smog, acid rain, CFC's, and other forms of outdoor air pollution。 But did you know that air pollution also can exist inside homes and other buildings? It can, and every year, the health of many people is affected by chemical substances present in the air within buildings。 Sources of air pollution refer to the various locations, activities or factors which are responsible for the releasing of pollutants in the atmosphere。 These sources can be classified into two major categories which are: 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, aircraft and the effect of sound etc。 Chemicals, dust and controlled burn practices in agriculture and forestry management。 Controlled or prescribed burning is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement。 Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for foresters。 Controlled burning stimulates the germination of some desirable forest trees, thus renewing the forest。 Fumes from paint, hair spray, varnish, aerosol sprays and other solvents Waste deposition in landfills, which generate methane。Methane is not toxic; however, it is highly flammable and may form explosive mixtures with air。 Methane is also an asphyxiant and may displace oxygen in an enclosed space。 Asphyxia or suffocation may result if the oxygen concentration is reduced to below 19。5% by displacement 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 animals, for example cattle。 Radon gas from radioactive decay within the Earth's crust。Radon is a colorless, odorless, naturally occurring, radioactive noble gas that is formed from the decay of radium。 It is considered to be a health hazard。Radon gas from natural sources can accumulate in buildings, especially in confined areas such as the basement and it is the second most frequent cause of lung cancer, after cigarette smoking。 Smoke and carbon monoxide from wildfires。 Volcanic activity, which produce sulfur, chlorine, and ash particulates。 Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages 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。 CAUTION:Please don't just copy this for h。w。 or stuff。。I copied it from (internet)You can use the information though。。Bye bye!