Air pollution and its control - class-XII

Scrubber separator is a type of dust separator device and not particulate matter separator.

A catalytic converter is an emissions control device that converts toxic pollutants in exhaust gas to less toxic pollutants by catalyzing a redox reaction 

Incinerators are used to burn garbage which produces toxic ash, nitrogen oxides, carbon dioxides etc and thus, contributes to the air pollution. This method is mainly used to reduce solid wastes. Using renewable energy like solar and wind energy are the natural energy source that does not contribute to the air pollution. Catalytic converters reduce air pollution as it converts the harmful gas into the useful like it converts the carbon monoxide into the carbon dioxide which then absorbed by the plants. Thus, the correct answer is option B.

A cyclonic separation is a method of removing particulates from an air stream, without the use of filters, through vortex separation. 

Air Prevention and Control of Pollution Act, 1981 is an Act of the Parliament of India to control and prevent air pollution in India. It is different from the Environment (Protection) act, 1986 and not a part of it.

The adiabatic lapse rate for wet (saturated) air is approximately 0.6 degrees Celsius per 100 meters, which is lower than the dry adiabatic lapse rate due to the release of latent heat during condensation.

Pollution is the addition of contaminants in the environment which degrades its quality. The air pollution is the major threat which needs to be regulated. A catalytic converter is a device used to reduce the emissions from an internal combustion engine (automobiles and vehicles). Enough oxygen is not available to oxidize the carbon fuel in these engines completely into carbon dioxide and water; thus toxic by-products are produced. Catalytic converters are used in exhaust systems to provide a site for the oxidation and reduction of toxic by-products (like nitrogen oxides, carbon monoxide, and hydrocarbons) of fuel into less hazardous substances, such as carbon dioxide, water vapour, and nitrogen gas.

The combustion of the fuel in the automobiles result in the production of emissions which contains toxic gases. The use of barium salts help in the reduction in the emissions from the burning of the fuels like petrol and diesel. However, the emissions which are released along with the barium salts have toxic effects on ingestion. The use of alkali metal salts like sodium, calcium, magnesium, potassium, etc which do not cause any effect are been used nowadays. 

During Photosynthesis plants i.e. leaves take in carbon dioxide (CO2CO2) to make glucose. This reduces the carbon dioxide in the atmosphere. This is why trees, grasses, and algae all are solutions to global warming caused by excessive carbon dioxide (CO2CO2). All three of the other processes involve taking in oxygen (O2O2) and releasing carbon dioxide (CO2CO2), thus increasing the carbon dioxide in the atmosphere.

The method abatement of the pollution is generally adopted to reduce the sources of pollution and the impact and its consequences on the environment and health. There are techniques like the scrubbers, filters, etc., which reduce the emission of the harmful and toxic gases. The catalytic converters in automobiles are used to minimize the release of oxides of nitrogen and sulphur and unburnt hydrocarbons. This helps to reduce the air pollution. 

The Supreme Court, under its directives, asked the government of India to switch over the entire fleet of public transport, i.e., buses, from diesel to compressed natural gas (CNG). Compressed natural gas (CNG) (methane stored at high pressure) can be used in place of gasoline (petrol), diesel fuel and propane/LPG. CNG combustion produces fewer undesirable gases than the fuels mentioned above. It is safer than other fuels in the event of a spill because natural gas is lighter than air and disperses quickly when released. CNG may be found above oil deposits or may be collected from landfills or wastewater treatment plants where it is known as biogas.

Adsorption is the phenomena where the atoms, ions or molecules from the gases, liquid and solids to a surface. It is a surface-based phenomenon and it easily absorbs the gas molecules and can reduce gaseous pollutants.

In modern times major types of pollution in urban areas are atmosphere, water and noise. Atmospheric pollution can be controlled to a large extent by location of factories and industries away from cities. Widening of roads will lead to less congestion, reduce idling time of engines of vehicles and ultimately be helpful in controlling atmospheric pollution due to vehicles. Sewage treatment plants and control on use of pesticides will reduce pollution of water bodies and prevent eutrophication of natural ponds and lakes. Clean city surroundings and proper waste disposal will reduce or eliminate breeding grounds of stray animals and disease spreading insect and non insect vectors. 

The electrostatic precipitators work on the principles of the electrostatic force. It consists of discharge wires and collecting plates. An application of high voltage to the discharge wires create an electric field between the wires and the plates. When the air containing the dust and suspended particulate matter like aerosols and solid particles is passed through this electrostatic field, the particles get charged and are collected onto the plate as per Coulomb's Law. This makes the air free of dust and SPM. Electrostatic precipitators are used in vehicles and coal-fired power plant to restrict the entry of dust and SPM into the atmosphere

Air pollution is caused by the release of harmful oxides of nitrogen, sulphur and carbon from the vehicular exhausts and industrial emissions primarily. Using precipitators allow the removal of dust from these emissions. Keeping the air clean by minimizing the combustion of fossil fuels, less use of vehicles, use of catalytic converters can help in reducing the air pollution. Reusing waste allows the minimal production of non-degradable waste. Hence, the correct answer is 'Reusing wastes'.

From April 1995, mandatory fitment of catalytic converters in new petrol passenger cars sold in the four metros, Delhi, Calcutta, Mumbai and Chennai along with the supply of Unleaded Petrol (ULP) was affected. Availability of ULP was further extended to 42 major cities and it is now available throughout the country. 

• Electrostatic precipitator is used to remove particulate matter present in the air. The particulate matter are charged and passed through a chamber where they the particles lose their charge and settle down.
• Scrubbers are used to remove gases like sulphur dioxide (SO₂). The exhaust is passed though a spray of lime or water.
• Catalytic convertors consist of expensive metals like platinum- palladium and rhodium as catalysts which are fitted in the automobiles to reduce the emission of poisonous gases. When the exhaust passes through catalytic convertor, unburnt hydrocarbons get converted into carbon dioxide and water, carbon monoxide is converted to carbon dioxide and nitric oxide is converted to nitrogen gas.

• An electrostatic precipitator is a device that removes suspended dust particles from a gas or exhaust by applying a high-voltage electrostatic charge and collecting the particles on charged plates. It can remove 99% of particulate matter from thermal power plant exhaust.
• BOD(Biochemical oxygen demand) is a measure of, the amount of oxygen that require for the bacteria to degrade the organic components present in water/wastewater. Hence based on the BOD it is possible to estimate the amount of organic matter in sewage water.
  
• Hence b and c are correct statements.
• So, the correct answer is 'b and c correct'.

• Compressed natural gas (CNG) (methane stored at high pressure) is a fuel which can be used in place of gasoline, diesel fuel, and propane/LPG. 
• CNG combustion produces fewer undesirable gases than the aforementioned fuels.
• The main difficulty of was laying down pipelines for delivering CNG through distribution points up to the CNG pumps and to ensure uninterrupted supply.
• Hence it is difficult to lay down pipelines for delivery of CNG.
• So, the correct answer is 'Option E'.

Catalytic converter is a device in automobiles that controls the exhaust emission. It has some expensive metals which acts as a catalyst on pollutants such as platinum, palladium and rhodium. These catalysts converts harmful nitrogen oxides into nitrogen gas and carbon monoxide into carbon dioxide. Thus, the correct answer is 'Platinum, Palladium and Rhodium'.

An electrostatic precipitator is widely used to eliminate particulate and gaseous pollutants from the air with the help of a high-voltage electrostatic charge. Thermal power plants release various harmful gases and particulate matter in the environment such as sulfur dioxide, carbon dioxide, nitrogen oxides, and other harmful emissions. Electrostatic precipitators are known to be very effective in removing the harmful chemicals present in the emissions. They are the best device for controlling air pollution.

A point source of air pollution refers to a single, identifiable stationary location, such as a factory smokestack or a power plant, which releases pollutants into the atmosphere.

MTBE is a gasoline additive, used as an oxygenate to raise the octane number. It is one of a group of chemicals commonly known as oxygenates because they raise the oxygen content of gasoline. It has been used in gasoline at low levels to replace tetraethyl lead and to increase its octane rating to help prevent engine knocking. Oxygenates help gasoline burn more completely, which causes emission of CO$ _2$ instead of CO.

• Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials.
•  Incineration and other high temperature waste treatment systems are described as "thermal treatment".
•  Incineration of waste materials converts the waste into ash, flue gas and heat.
• Hence, Incinerator is not a device used to control a particulate matter.

• Coal burning results in the generation of large quantities of coal residues, which contains very fine particles that tend to become airborne and which contribute to the formation of suspended particulate matter (SPM). 
  
  
• An electrostatic precipitator (ESP) is a filtration method that removes fine particles, like dust and smoke, from a flowing gas using the force of an induced electrostatic charge minimally impeding the flow of gases through the unit.
  
  Hence, option D is correct.

The Cyclone Collector is the device that is used for minimizing air pollution by trapping the suspended particles like coarse dust generated due to activities like mining, cement and wood factories. These are the dry scrubbers that work on the principle of inertia. Cyclone collector work similar to a centrifuge, but with a continuous feed of dirty air.

The prevention of addition of undesirable and toxic substances will result in prevention of pollution. Banning atomic blasts would prevent soil and water pollution from the harmful release of radiations. Use of electrically operated automobiles would prevent the release of oxides of sulphur, nitrogen and carbon and so, air pollution would be prevented. Sewage treatment would remove the toxic components and would prevent water pollution.

Large cities have a big human population and concentration of industries and factories. So, the management of the industrial effluents and the domestic sewage a bif challenge because these cause massive water pollution. Further, the location of industries have to be decided so that the air pollutants emitted from them do not enter the populated areas directly. So, cleanliness and less use of insecticides, proper disposal of organic wastes, sewage and industrial effluents and broader roads and shifting of factories out of residential areas are considered to be essential steps in minimizing the pollution in large cities. Hence, the correct answer is 'All of the above'

Antiknocking agents are the chemical derivatives that are added to petrol. These agents increase the octane number of petrol due to which the pressure and temperature of petrol increases and so these protect petrol from detonation at low pressure. This is done to maintain the quality of the engines. Tetramethyl or tetraethyl lead, dibromoethane, benzole toluene are used as the antiknocking agents.

Unleaded petrol is not doped with lead so it has a high knocking ability. It means it can be ignited before the actual ignition spark occurs. This is harmful to the engines. Lead is not used because it has shown severe adverse effects on the environment. Instead, methyl tertiary butyl ether is added which is easily miscible with petrol. However, it also has shown the carcinogenic properties.

Incineration is also called as a thermal process, it involves combustion of organic substances contained in waste material. It converts the waste material into ash, gases, particles and heat which are then put into the application for generation of electricity. The incinerator is the device where waste is burnt e.g. furnace. Now incinerators are equipped with systems to reduce the emission of highly toxic gases during the process. The output of incinerator is gases, particles and heat thus for controlling particulate pollutant filtration and precipitators are installed to clean out the gases as a result of incineration. These do not have any control over particulate pollutants.

A pyrogallol is also called as 1,2,3-trihydroxybenzene. It is a benzenetriol. It is a reducing agent. It is used as a developer in photography. It is also used as a coupling agent in printing. It undergoes rapid autooxidation in alkaline solution. Hence, its alkaline solution is used in the gas analysis because it absorbs oxygen.