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Air pollution is the introduction of
https://en.wikipedia.org/wiki/Biomoleculebiological molecules, or other harmful materials into
https://en.wikipedia.org/wiki/Earth%27s_atmosphereEarth's atmosphere, causing diseases, death to humans, damage to other living organisms such as animals and food crops, or the
Air pollution can come from various sources both anthropogenic and natural.
Air pollution can have adverse effects on health, environment and industry. Hence we need to take several steps in order to control air pollution.
To study the various air pollutants
To study sources of air pollution
To study effects of air pollution
To study treaties to control air pollution
To study devices to control air pollution
An air pollutant is a substance in the air that can have adverse effects on humans and the ecosystem. The substance can be solid particles, liquid droplets, or gases. Pollutants are classified as primary or secondary. Primary pollutants are usually produced from a process, such as ash from a volcanic eruption. Other examples include
https://en.wikipedia.org/wiki/Carbon_monoxidecarbon monoxide gas from motor vehicle exhaust, or the
https://en.wikipedia.org/wiki/Sulfur_dioxidesulfur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact.
https://en.wikipedia.org/wiki/Ground_level_ozoneGround level ozone is a prominent example of a secondary pollutant. Some pollutants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants.
Major primary pollutants produced by human activity include:
https://en.wikipedia.org/wiki/Sulfur_oxideSulfur oxides (SOx) - particularly sulfur dioxide, a chemical compound with the formula SO2. SO2 is produced by volcanoes and in various industrial processes. Coal and petroleum often contain sulfur compounds, and their combustion generates sulfur dioxide.
https://en.wikipedia.org/wiki/Nitrogen_oxideNitrogen oxides (NOx) - Nitrogen oxides, particularly
https://en.wikipedia.org/wiki/Nitrogen_dioxidenitrogen dioxide, are expelled from high temperature combustion, and are also produced during
https://en.wikipedia.org/wiki/Electric_dischargeelectric discharge. They can be seen as a brown
https://en.wikipedia.org/wiki/Hazehaze dome above or a
https://en.wikipedia.org/wiki/Plume_(hydrodynamics)plume downwind of cities.
https://en.wikipedia.org/wiki/Carbon_monoxideCarbon monoxide (CO) - CO is a colorless, odorless, toxic yet non-irritating gas. It is a product by
https://en.wikipedia.org/wiki/Incomplete_combustionincomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide.
https://en.wikipedia.org/wiki/Volatile_organic_compoundsVolatile organic compounds (VOC) - VOCs are a well-known outdoor air pollutant. They are categorized as either methane (CH4) or non-methane (NMVOCs). Methane is an extremely efficient greenhouse gas which contributes to enhanced
https://en.wikipedia.org/wiki/ParticulatesParticulates, alternatively referred to as particulate matter (PM), atmospheric particulate matter, or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to combined particles and gas.
https://en.wikipedia.org/wiki/Metalmetals, such as
https://en.wikipedia.org/wiki/Mercury_(element)mercury, especially their compounds.
https://en.wikipedia.org/wiki/ChlorofluorocarbonsChlorofluorocarbons (CFCs) - harmful to the
https://en.wikipedia.org/wiki/Radioactive_pollutantsRadioactive pollutants - produced by
https://en.wikipedia.org/wiki/Nuclear_explosionsnuclear explosions, nuclear events, war
https://en.wikipedia.org/wiki/Explosivesexplosives, and natural processes such as the
https://en.wikipedia.org/wiki/Radioactive_decayradioactive decay of
Secondary pollutants include:
Particulates created from gaseous primary pollutants and compounds in photochemical smog.
https://en.wikipedia.org/wiki/SmogSmog is a kind of air pollution. Classic smog results from large amounts of coal burning in an area caused by a mixture of smoke and sulfur dioxide. Modern smog does not usually come from coal but from vehicular and industrial emissions that are acted on in the atmosphere by
https://en.wikipedia.org/wiki/Ultravioletultraviolet light from the sun to form secondary pollutants that also combine with the primary emissions to form photochemical smog.
https://en.wikipedia.org/wiki/Ground_level_ozoneGround level ozone (O3) formed from NOx and VOCs. Ozone (O3) is a key constituent of the troposphere.. At abnormally high concentrations brought about by human activities (largely the combustion of fossil fuel), it is a pollutant, and a constituent of smog.
https://en.wikipedia.org/wiki/Peroxyacetyl_nitratePeroxyacetyl nitrate (PAN) - similarly formed from NOx and VOCs.
Sources of air pollution
There are various locations, activities or factors which are responsible for releasing pollutants into the atmosphere. These sources can be classified into two major categories.
Anthropogenic (man-made) sources:
These are mostly related to the burning of multiple types of fuel.
Stationary sources include smoke stacks of
https://en.wikipedia.org/wiki/Power_plantpower plants, manufacturing facilities (factories) and waste incinerators, as well as furnaces and other types of fuel-burning heating devices. In developing and poor countries, traditional biomass burning is the major source of air pollutants; traditional biomass includes wood, crop waste and dung.
Mobile sources include
https://en.wikipedia.org/wiki/Roadway_air_dispersion_modelingmotor vehicles, marine vessels, and aircraft.
https://en.wikipedia.org/wiki/Controlled_burnControlled burn practices in agriculture and forest 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.
https://en.wikipedia.org/wiki/Aerosol_sprayaerosol sprays and other solvents
Waste deposition in
https://en.wikipedia.org/wiki/Landfilllandfills, which generate
https://en.wikipedia.org/wiki/Methanemethane. Methane is highly flammable and may form explosive mixtures with air. Methane is also an
https://en.wikipedia.org/wiki/Asphyxiantasphyxiant 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 resources, such as
https://en.wikipedia.org/wiki/Germ_warfaregerm warfare and
https://en.wikipedia.org/wiki/DustDust from natural sources, usually large areas of land with little or no vegetation
https://en.wikipedia.org/wiki/Flatulenceemitted by the
https://en.wikipedia.org/wiki/Digestiondigestion of food by
https://en.wikipedia.org/wiki/Animalanimals, for example
https://en.wikipedia.org/wiki/RadonRadon gas from
https://en.wikipedia.org/wiki/Radioactive_decayradioactive decay within the
https://en.wikipedia.org/wiki/Earth%27s_crustEarth's crust. Radon is a colourless, odourless, naturally occurring, radioactive
https://en.wikipedia.org/wiki/Noble_gasnoble 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
https://en.wikipedia.org/wiki/Carbon_monoxidecarbon monoxide from
Vegetation, in some regions, emits environmentally significant amounts of
https://en.wikipedia.org/wiki/Volatile_organic_compoundsVolatile organic compounds (VOCs) on warmer days. These VOCs react with primary anthropogenic pollutants—specifically, NOx, SO2, and anthropogenic organic carbon compounds — to produce a seasonal haze of secondary pollutants.
https://en.wikipedia.org/wiki/Air_pollution Black gum, poplar, oak and willow are some examples of vegetation that can produce abundant VOCs. The VOC production from these species results in ozone levels up to eight times higher than the low-impact tree species.
Air pollution is a significant risk factor for a number of health conditions including respiratory infections, heart disease,
https://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_diseaseCOPD, stroke and lung cancer. The health effects caused by air pollution may include difficulty in breathing, wheezing, coughing,
https://en.wikipedia.org/wiki/Asthmaasthma and worsening of existing respiratory and cardiac conditions. The human health effects of poor air quality are far reaching, but principally affect the body's respiratory system and the cardiovascular system. Individual reactions to air pollutants depend on the type of pollutant a person is exposed to, the degree of exposure, and the individual's health status and genetics. The most common sources of air pollution include particulates, ozone, nitrogen dioxide, and sulphur dioxide. Children aged less than five years that live in developing countries are the most vulnerable population in terms of total deaths attributable to indoor and outdoor air pollution.
A 2007 review of evidence found ambient air pollution exposure is a risk factor correlating with increased total mortality from cardiovascular events (range: 12% to 14% per 10 microgram/m3increase).
Air pollution is also emerging as a risk factor for stroke, particularly in developing countries where pollutant levels are highest. A 2007 study found that in women, air pollution is not associated with hemorrhagic but with ischemic stroke. Air pollution was also found to be associated with increased incidence and mortality from coronary stroke in a cohort study in 2011. Associations are believed to be causal and effects may be mediated by vasoconstriction, low-grade inflammation and
https://en.wikipedia.org/wiki/Atherosclerosisatherosclerosis. Other mechanisms such as autonomic nervous system imbalance have also been suggested.
https://en.wikipedia.org/wiki/Chronic_obstructive_pulmonary_diseaseChronic obstructive pulmonary disease (COPD) includes diseases such as chronic bronchitis and emphysema.
Research has demonstrated increased risk of developing asthma and COPD from increased exposure to traffic-related air pollution. Additionally, air pollution has been associated with increased hospitalization and mortality from asthma and COPD.
It is believed that much like
https://en.wikipedia.org/wiki/Cystic_fibrosiscystic fibrosis, by living in a more urban environment serious health hazards become more apparent. Studies have shown that in urban areas patients suffer
https://en.wikipedia.org/wiki/Mucusmucus hypersecretion, lower levels of lung function, and more self-diagnosis of chronic bronchitis and emphysema.
A review of evidence regarding whether ambient air pollution exposure is a risk factor for cancer in 2007 found solid data to conclude that long-term exposure to PM2.5 (fine particulates) increases the overall risk of non-accidental mortality by 6% per a 10 microg/m3 increase. Exposure to PM2.5 was also associated with an increased risk of mortality from lung cancer (range: 15% to 21% per 10 microg/m3 increase) and total cardiovascular mortality (range: 12% to 14% per a 10 microg/m3 increase). The review further noted that living close to busy traffic appears to be associated with elevated risks of these three outcomes --- increase in lung cancer deaths, cardiovascular deaths, and overall non-accidental deaths. The reviewers also found suggestive evidence that exposure to PM2.5 is positively associated with mortality from coronary heart diseases and exposure to SO2 increases mortality from lung cancer, but the data was insufficient to provide solid conclusions. Another investigation showed that higher activity level increases deposition fraction of aerosol particles in human lung and recommended avoiding heavy activities like running in outdoor space at polluted areas.
Central nervous system
Data is accumulating that air pollution exposure also affects the
https://en.wikipedia.org/wiki/Central_nervous_systemcentral nervous system.
In a June 2014 study conducted by researchers at the
https://en.wikipedia.org/wiki/University_of_RochesterUniversity of Rochester Medical Center, published in the journal
https://en.wikipedia.org/wiki/Environmental_Health_PerspectivesEnvironmental Health Perspectives, it was discovered that early exposure to air pollution causes the same damaging changes in the brain as
https://en.wikipedia.org/wiki/Schizophreniaschizophrenia. The study also shows that air pollution also affected short-term memory, learning ability, and impulsivity. Lead researcher Professor Deborah Cory-Slechta said that "When we looked closely at the ventricles, we could see that the white matter that normally surrounds them hadn't fully developed. It appears that inflammation had damaged those brain cells and prevented that region of the brain from developing, and the ventricles simply expanded to fill the space. Our findings add to the growing body of evidence that air pollution may play a role in autism, as well as in other neurodevelopment disorders." Air pollution has a more significant negative effect of males than on females.
VARIOUS TREATIES TO CONTROL AIR POLLUTION
The Kyoto Protocol is an international
https://en.wikipedia.org/wiki/Treatytreaty which extends the 1992
https://en.wikipedia.org/wiki/United_Nations_Framework_Convention_on_Climate_ChangeUnited Nations Framework Convention on Climate Change(UNFCCC) that commits State Parties to reduce
https://en.wikipedia.org/wiki/Greenhouse_gasesgreenhouse gases emissions, based on the premise that (a)
https://en.wikipedia.org/wiki/Global_warmingglobal warming exists and (b) man-made
https://en.wikipedia.org/wiki/Carbon_dioxide_in_Earth%27s_atmosphereCO2 emissions have caused it. The Kyoto Protocol was adopted in
https://en.wikipedia.org/wiki/JapanJapan, on 11 December 1997 and entered into force on 16 February 2005. There are currently 192 parties (
https://en.wikipedia.org/wiki/CanadaCanada withdrew effective December 2012) to the Protocol.
The Kyoto Protocol implemented the objective of the UNFCCC to fight global warming by reducing greenhouse gas concentrations in the atmosphere to "a level that would prevent dangerous anthropogenic interference with the climate system" (Art. 2). The Protocol is based on the principle of common but differentiated responsibilities: it puts the obligation to reduce current emissions on developed countries on the basis that they are historically responsible for the current levels of greenhouse gases in the atmosphere.
The main goal of the Kyoto Protocol is to control emissions of the main anthropogenic (i.e., human-emitted) greenhouse gases (GHGs) in ways that reflect underlying national differences in GHG emissions, wealth, and capacity to make the reductions. The treaty follows the main principles agreed in the original 1992 UN Framework Convention. According to the treaty, in 2012, Annex I Parties who have ratified the treaty must have fulfilled their obligations of greenhouse gas emissions limitations established for the Kyoto Protocol's first commitment period (2008–2012). These emissions limitation commitments are listed in Annex B of the Protocol.
The United Nations Framework Convention on Climate Change (UNFCCC) is an
https://en.wikipedia.org/wiki/Environmental_protocolenvironmental treaty negotiated at the
https://en.wikipedia.org/wiki/Earth_SummitEarth Summit in
https://en.wikipedia.org/wiki/Rio_de_JaneiroRio de Janeiro from 3 to 14 June 1992, then entered into force on 21 March 1994. The UNFCCC objective is to "stabilize
https://en.wikipedia.org/wiki/Greenhouse_gasgreenhouse gas concentrations in the atmosphere at a level that would prevent dangerous
https://en.wikipedia.org/wiki/Human_impact_on_the_environmentanthropogenic interference with the
https://en.wikipedia.org/wiki/Climate_systemclimate system". The framework set no binding limits on greenhouse gas emissions for individual countries and contains no enforcement mechanisms. Instead, the framework outlines how specific international treaties (called "protocols" or "Agreements") may be negotiated to set binding limits on greenhouse gases.
The United Nations Framework Convention on Climate Change (UNFCCC) was opened for signature at the 1992
https://en.wikipedia.org/wiki/United_Nations_Conference_on_Environment_and_DevelopmentUnited Nations Conference on Environment and Development (UNCED) in
https://en.wikipedia.org/wiki/Rio_de_JaneiroRio de Janeiro (known by its popular title, the
https://en.wikipedia.org/wiki/Earth_SummitEarth Summit). On 12 June 1992, 154 nations signed the UNFCCC, that upon ratification committed signatories' governments to reduce atmospheric concentrations of greenhouse gases with the goal of "preventing dangerous anthropogenic interference with Earth's climate system". This commitment would require substantial reductions in greenhouse gas emissions (see the later section,
https://en.wikipedia.org/wiki/United_Nations_Framework_Convention_on_Climate_Change"Stabilization of greenhouse gas concentrations")
Article 3(1) of the Convention states that Parties should act to protect the climate system on the basis of "common but differentiated responsibilities", and that developed country Parties should "take the lead" in addressing climate change. Under Article 4, all Parties make general commitments to address climate change through, for example, climate change mitigation and adapting to the eventual impacts of climate change.
In 2011, parties adopted the "Durban Platform for Enhanced Action". As part of the Durban Platform, parties have agreed to "develop a protocol, another legal instrument or an agreed outcome with legal force under the Convention applicable to all Parties". At Durban and Doha, parties noted "with grave concern" that current efforts to hold global warming to below 2 or 1.5 °C relative to the pre-industrial level appear inadequate.
In 2015, all (then) 196 then parties to the convention came together for the
https://en.wikipedia.org/wiki/2015_United_Nations_Climate_Change_ConferenceUN Climate Change Conference in Paris 30 November - 12 December and adopted by consensus the Paris Agreement, aimed at limiting global warming to less than two degrees Celsius, and pursue efforts to limit the rise to 1.5 degrees Celsius. The
https://en.wikipedia.org/wiki/Paris_Agreement_(climate_change)Paris Agreement is to be signed in 2016 and will enter into force upon ratification by 55 countries representing over 55% of greenhouse gas emissions.
The aim of the convention is described in Article 2, "enhancing the implementation" of the UNFCCC through:
"(a) Holding the increase in the global average temperature to well below 2 °C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels, recognizing that this would significantly reduce the risks and impacts of climate change;
(b) Increasing the ability to adapt to the adverse impacts of climate change and foster climate resilience and low greenhouse gas emissions development, in a manner that does not threaten food production;
(c) Making finance flows consistent with a pathway towards low greenhouse gas emissions and climate-resilient development."
Countries furthermore aim to reach "global peaking of greenhouse gas emissions as soon as possible".
The Montreal Protocol on Substances that Deplete the Ozone Layer (a protocol to the
https://en.wikipedia.org/wiki/Vienna_Convention_for_the_Protection_of_the_Ozone_LayerVienna Convention for the Protection of the Ozone Layer) is an international
https://en.wikipedia.org/wiki/Treatytreaty designed to protect the
https://en.wikipedia.org/wiki/Ozone_layerozone layer by phasing out the production of numerous substances that are responsible for
https://en.wikipedia.org/wiki/Ozone_depletionozone depletion. It was agreed on 16 September 1987, and entered into force on 1 January 1989, followed by a first meeting in
https://en.wikipedia.org/wiki/HelsinkiHelsinki, May 1989. Since then, it has undergone eight revisions, in 1990 (
https://en.wikipedia.org/wiki/LondonLondon), 1991 (
https://en.wikipedia.org/wiki/NairobiNairobi), 1992 (
https://en.wikipedia.org/wiki/CopenhagenCopenhagen), 1993 (
https://en.wikipedia.org/wiki/BangkokBangkok), 1995 (
https://en.wikipedia.org/wiki/ViennaVienna), 1997 (
https://en.wikipedia.org/wiki/MontrealMontreal), 1998 (
https://en.wikipedia.org/wiki/AustraliaAustralia), 1999 (
https://en.wikipedia.org/wiki/BeijingBeijing) and 2007 (
https://en.wikipedia.org/wiki/MontrealMontreal). As a result of the international agreement, the ozone hole in Antarctica is slowly recovering.
https://en.wikipedia.org/wiki/Montreal_Protocol Climate projections indicate that the ozone layer will return to 1980 levels between 2050 and 2070. Due to its widespread adoption and implementation it has been hailed as an example of exceptional international co-operation, with
https://en.wikipedia.org/wiki/Kofi_AnnanKofi Annan quoted as saying that "perhaps the single most successful international agreement to date has been the Montreal Protocol". In comparison, effective burden sharing and solution proposals mitigating regional conflicts of interest have been among the success factors for the
https://en.wikipedia.org/wiki/Ozone_depletionOzone depletion challenge, where global regulation based on the
https://en.wikipedia.org/wiki/Kyoto_ProtocolKyoto Protocol has failed to do so. In case of the ozone depletion challenge, there was global regulation already being installed before a scientific consensus was established. As well in comparison, lay people and public opinion were more convinced about possible imminent risks.
DEVICES TO CONTROL AIR POLLUTION
An electrostatic precipitator (ESP) is a filtration device that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced
https://en.wikipedia.org/wiki/Electrostatic_chargeelectrostatic charge minimally impeding the flow of gases through the unit.
In contrast to
https://en.wikipedia.org/wiki/Wet_scrubberwet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).
The most basic precipitator contains a row of thin vertical wires, and followed by a stack of large flat metal plates oriented vertically, with the plates typically spaced about 1 cm to 18 cm apart, depending on the application. The air or gas stream flows horizontally through the spaces between the wires, and then passes through the stack of plates.
A negative voltage of several thousand
https://en.wikipedia.org/wiki/Voltvolts is applied between wire and plate. If the applied voltage is high enough, an electric
https://en.wikipedia.org/wiki/Corona_dischargecorona discharge ionizes the gas around the electrodes.
https://en.wikipedia.org/wiki/Negative_ionsNegative ions flow to the plates and charge the gas-flow particles.
The ionized particles, following the negative electric field created by the power supply, move to the grounded plates. Particles build up on the collection plates and form a layer. The layer does not collapse, thanks to electrostatic pressure (due to layer resistivity, electric field, and current flowing in the collected layer).
A two-stage design (separate charging section ahead of collecting section) has the benefit of minimizing ozone production, which would adversely affect health of personnel working in enclosed spaces. For shipboard
https://en.wikipedia.org/wiki/Engine_roomengine rooms where
https://en.wikipedia.org/wiki/Gearboxgearboxes generate an
https://en.wikipedia.org/wiki/Oil_mistoil mist, two-stage ESP's are used to clean the air, improving the operating environment and preventing build-up of flammable oil fog accumulations. Collected oil is returned to the gear lubricating system.
The term wet scrubber describes a variety of devices that remove
https://en.wikipedia.org/wiki/Pollutantpollutants from a
https://en.wikipedia.org/wiki/Flue_gasflue gas or from other gas streams. In a wet scrubber, the polluted gas stream is brought into contact with the scrubbing liquid, by spraying it with the liquid, by forcing it through a pool of liquid, or by some other contact method, so as to remove the pollutants.
Wet scrubbers remove dust particles by capturing them in liquid droplets. The droplets are then collected, the liquid dissolving or absorbing the pollutant gases. Any droplets that are in the scrubber inlet gas must be separated from the outlet gas stream by means of another device referred to as a
https://en.wikipedia.org/wiki/Entrainment_(engineering)mist eliminator or
https://en.wikipedia.org/wiki/Entrainment_(engineering)entrainment separator (these terms are interchangeable). Also, the resultant scrubbing liquid must be treated prior to any ultimate discharge or being reused in the plant.
Wet scrubbers that remove gaseous pollutants are referred to as absorbers. Good
https://en.wikipedia.org/wiki/Liquid-to-gas_ratiogas-to-liquid contact is essential to obtain high removal efficiencies in absorbers. A number of wet scrubber designs are used to remove gaseous pollutants, with the
https://en.wikipedia.org/wiki/Packed_bedpacked tower and the
https://en.wikipedia.org/wiki/Theoretical_plateplate tower being the most common.
If the gas stream contains both particle matter and gases, wet scrubbers are generally the only single air pollution control device that can remove both pollutants. Wet scrubbers can achieve high removal efficiencies for either particles or gases and, in some instances, can achieve a high removal efficiency for both pollutants in the same system. However, in many cases, the best operating conditions for particles collection are the poorest for gas removal.
In general, obtaining high simultaneous gas and particulate removal efficiencies requires that one of them be easily collected (i.e., that the gases are very soluble in the liquid or that the particles are large and readily captured) or by the use of a scrubbing reagent such as
Advantages and disadvantages
For particulate control, wet scrubbers (also referred to as wet collectors) are evaluated against
https://en.wikipedia.org/wiki/Fabric_filterfabric filters and
https://en.wikipedia.org/wiki/Electrostatic_precipitatorelectrostatic precipitators (ESPs). Some advantages of wet scrubbers over these devices are as follows:
Wet scrubbers have the ability to handle high
In wet scrubbers, flue gases are cooled, resulting in smaller overall size of equipment.
Wet scrubbers can remove both gases and particulate matter.
Wet scrubbers can neutralize
Some disadvantages of wet scrubbers include corrosion, the need for entrainment separation or mist removal to obtain high efficiencies and the need for treatment or reuse of spent liquid.
Wet scrubbers have been used in a variety of industries such as
https://en.wikipedia.org/wiki/Asphaltasphalt plants, and large
A catalytic converter is an emissions control device that converts toxic gases and
https://en.wikipedia.org/wiki/Exhaust_gasexhaust gas to less toxic pollutants by
https://en.wikipedia.org/wiki/Chemical_reactionreaction (oxidation or reduction). Catalytic converters are used with
https://en.wikipedia.org/wiki/Internal_combustion_engineinternal combustion engines fuelled by either
https://en.wikipedia.org/wiki/Petrolpetrol (gasoline) or
https://en.wikipedia.org/wiki/Lean-burnlean-burn engines as well as kerosene heaters and stoves.
Although catalytic converters are most commonly applied to
https://en.wikipedia.org/wiki/Exhaust_systemexhaust systems in automobiles, they are also used on
https://en.wikipedia.org/wiki/Forkliftforklifts, mining equipment,
https://en.wikipedia.org/wiki/Motorcyclemotorcycles. They are also used on some wood stoves to control emissions. This is usually in response to
https://en.wikipedia.org/wiki/Regulationregulation, either through direct environmental regulation or through health and safety regulations.
A two-way (or "oxidation") catalytic converter has two simultaneous tasks:
https://en.wikipedia.org/wiki/Carbon_monoxidecarbon monoxide to
https://en.wikipedia.org/wiki/Carbon_dioxidecarbon dioxide: 2CO + O2 → 2CO2
https://en.wikipedia.org/wiki/Unburned_hydrocarbonhydrocarbons (unburned and partially burned fuel) to carbon dioxide and
https://en.wikipedia.org/wiki/Waterwater: CxH2x+2 + [(3x+1)/2] O2 → xCO2 + (x+1) H2O (a combustion reaction)
This type of catalytic converter is widely used on
https://en.wikipedia.org/wiki/Diesel_enginediesel engines to reduce hydrocarbon and carbon monoxide emissions. They were also used on gasoline engines in American- and Canadian-market automobiles until 1981. Because of their inability to control
https://en.wikipedia.org/wiki/NOxoxides of nitrogen, they were superseded by three-way converters.
Three-way catalytic converters (TWC) have the additional advantage of controlling the emission of
https://en.wikipedia.org/wiki/Nitric_oxidenitric oxide and
https://en.wikipedia.org/wiki/Nitrogen_dioxidenitrogen dioxide (both together abbreviated with
https://en.wikipedia.org/wiki/NOxNOx and not to be confused with
https://en.wikipedia.org/wiki/Nitrous_oxidenitrous oxide), which are precursors to
https://en.wikipedia.org/wiki/Acid_rainacid rain and
Since 1981, "three-way" (oxidation-reduction) catalytic converters have been used in vehicle emission control systems in the United States and Canada; many other countries have also adopted stringent
https://en.wikipedia.org/wiki/Vehicle_emissions_controlvehicle emission regulations that in effect require three-way converters on gasoline-powered vehicles. The reduction and oxidation catalysts are typically contained in a common housing; however, in some instances, they may be housed separately. A three-way catalytic converter has three simultaneous tasks:
https://en.wikipedia.org/wiki/RedoxReduction of nitrogen oxides to
https://en.wikipedia.org/wiki/Oxygenoxygen: 2NOx → xO2 + N2
https://en.wikipedia.org/wiki/RedoxOxidation of carbon monoxide to carbon dioxide: 2CO + O2 → 2CO2
Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and
https://en.wikipedia.org/wiki/Waterwater: CxH2x+2 + [(3x+1)/2]O2 → xCO2 + (x+1)H2O.
These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the
https://en.wikipedia.org/wiki/Stoichiometricstoichiometric point. For gasoline combustion, this ratio is between 14.6 and 14.8 parts air to one part fuel, by weight. The ratio for
https://en.wikipedia.org/wiki/Liquefied_petroleum_gasliquefied petroleum gas LPG),
https://en.wikipedia.org/wiki/Natural_gasnatural gas and
https://en.wikipedia.org/wiki/Ethanolethanol fuels are slightly different for each, requiring modified fuel system settings when using those fuels. In general, engines fitted with 3-way catalytic converters are equipped with a
https://en.wikipedia.org/wiki/Fuel_injectionfuel injection system using one or more
https://en.wikipedia.org/wiki/Oxygen_sensoroxygen sensors, though early in the deployment of three-way converters,
https://en.wikipedia.org/wiki/Carburetorcarburettors equipped with feedback mixture control were used.
Solar panel refers to a panel designed to absorb the sun's rays as a source of energy for generating electricity or heating. It reduces air pollution as solar panels are a green source of energy.
https://en.wikipedia.org/wiki/Photovoltaicphotovoltaic (in short PV) module is a packaged, connected assembly of typically 6×10
https://en.wikipedia.org/wiki/Solar_cellsolar cells. Solar Photovoltaic panels constitute the solar array of a
https://en.wikipedia.org/wiki/Photovoltaic_systemphotovoltaic system that generates and supplies
https://en.wikipedia.org/wiki/Solar_electricitysolar electricity in commercial and residential applications. Each module is rated by its
https://en.wikipedia.org/wiki/Direct_currentDC output power under standard test conditions, and typically ranges from 100 to 365 watts. The
https://en.wikipedia.org/wiki/Solar_cell_efficiencyefficiency of a module determines the area of a module given the same rated output – an 8% efficient 230 watt module will have twice the area of a 16% efficient 230 watt module. There are a few solar panels available that are exceeding 19% efficiency. A single solar module can produce only a limited amount of power; most installations contain multiple modules. A photovoltaic system typically includes a panel or an array of solar modules, a
https://en.wikipedia.org/wiki/Solar_invertersolar inverter, and sometimes a
https://en.wikipedia.org/wiki/Solar_trackersolar tracker and interconnection wiring.
The price of solar power, together with batteries for storage, has continued to fall so that in many countries it is cheaper than ordinary
https://en.wikipedia.org/wiki/Fossil_fuelfossil fuel electricity from the grid (there is "
Thus we can conclude that air pollution is a harmful process that is deleterious to human health and environment. With proper information awareness can be spread about air pollution.
Various treaties have been signed to control air pollution. Better technologies have now been designed. With proper education among people, air pollution can be controlled.
SMOG IN CHINA
INDUSTRIAL AIR POLLUTION
POSTER SPREADING AWARENESS
13toichiometricstoichiometric point. For gasoline combustion, this ratio is between 14.6 and 14.8 parts air to one part fuel, by weight. The ratio for
Various treaties have been signed to