Carbon dioxide is one of the major gases which contributes towards air pollution. It is mainly produced during the combustion of fuel in factories, power stations, household etc. The increasing CO2 in the atmosphere is likely to have the following effects:

(i) A rise in atmospheric temperature or global warming due to greenhouse effect. It also causes climate change.

(ii) Reduced productivity of the marine ecosystem. This is due to the fact that water in the oceans would be more acidic due to increased concentration of CO2 in the air, which dissolves in the water. Hence, statement 1 is incorrect.

(iii) Due to Global warming, the increased surface temperature would cause melting of continental and mountain glaciers and thus would cause flooding of coastal areas of some countries. Hence, statements 2 and 3 is correct.

Statement 1 is incorrect. Fluorides are emitted to the atmosphere in both gaseous and particulate forms, but studies typically only report total fluoride content. Routes of exposure:

1. Air
2. Drinking-water
3. Food

Statement 2 is correct. Upon heating rocks, soils and minerals that contain fluorides, give out hydrogen fluoride gas. This is an extremely toxic gas, which causes serious injury to livestock and cattle.

Statement 3 is incorrect. Fluoride has been classified by the United States National Academy of Sciences as an essential nutrient. It is beneficial as well as its toxic effects in humans have important public health implications.

Peroxyacetyl nitrate (PAN) is formed by the interaction of nitrogen oxides and hydrocarbons. The acute toxicity of PAN is less than that of ozone, similar to NO2 and higher than SO2.

PAN is an oxidant that is more stable than ozone. Hence, it is more capable of long-range transport than ozone. It serves as a carrier for oxides of nitrogen (NOx) into rural regions and causes ozone formation in the global troposphere.

All the statements are correct. Particulate matter is the sum of all solid and liquid particles suspended in air many of which are hazardous. This complex mixture includes both organic and inorganic particles, such as dust, pollen, soot, smoke, and liquid droplets. These particles vary greatly in size, composition, and origin.

Particles in the air are either:

1. directly emitted, for instance when fuel is burnt and when dust is carried by wind, or
2. indirectly formed, when gaseous pollutants previously emitted to air turn into particulate matter.

Suspended particulate matter (SPM) consists of solids in the air in the form of smoke, dust, and vapour that can remain suspended for extended periods and is also the main source of haze which reduces visibility. In nature, forest fires, wind erosion and volcanic eruptions add suspended particulate matter into air.

• Fires in forests may be caused when lightening strikes the trees. Burning of tree produces a lot of CO2 which is released to the atmosphere.
• Soil erosion increases suspended particulate matter and dust in air. These may even enter water bodies as they are washed down by rain or natural water falls.
• Volcanic eruptions also add pollutants like SO2 and solid particles to the environment.

Suspended particulate matter is also emitted by exhaust of polluting diesel vehicles and ill-managed coal fired power plants. Examples of particulate pollutants are soot, flyash from thermal power plants, cement dust, petrocoke from petroleum refineries. 

Tropospheric, or ground-level ozone, is not emitted directly into the air, but is created by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOC). This happens when pollutants emitted by cars, power plants, industrial boilers, refineries, chemical plants, and other sources chemically react in the presence of sunlight.

The occurrence of ground-level ozone often linked to heavy traffic, high temperatures, and calm winds. When the wind speed is low, it causes the smoke and fog to stagnate near the ground; hence pollution levels can increase near ground level. Hence, statement 1 is incorrect.

Pair 1 is correctly matched. Coal-fired power plants are the largest single source of mercury air pollution.

Pair 2 is incorrectly matched. Silicon quarries are a source of Silica dust. Silica dust is not a result of industries and vehicular pollution. 

Cotton textile factories release Cotton dust which is also an air pollutant.

Pair 3 is correctly matched. Refrigerators, sprays, emissions from jets are the primary sources of Chlorofluorocarbons.

Statement 1 is incorrect. A catalytic converter is an exhaust emission control device that reduces toxic gases and pollutants in exhaust gas from an internal combustion engine into less-toxic pollutants by catalyzing a redox reaction. Catalytic converters have expensive metals namely platinum-palladium and rhodium as the catalysts, are fitted into automobiles for reducing the emission of poisonous gases. As the exhaust passes through the catalytic converter, unburnt hydrocarbons are converted into carbon dioxide and water, and carbon monoxide and nitric oxide are changed to carbon dioxide and nitrogen gas, respectively. Motor vehicles equipped with catalytic converter should use unleaded petrol because lead in the petrol inactivates the catalyst.

Statement 2 is incorrect. An electrostatic precipitator is a filtration device 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. 

An electrostatic precipitator has electrode wires that are maintained at several thousand volts, which produce a corona that releases electrons. These electrons attach to dust particles giving them a net negative charge. The collecting plates are grounded and attract the charged dust particles.

Dust suppressant is a powder which is mixed with water or a polymer and sprayed to form a layer of moisture over surfaces, thus controlling dust being raised into the air. Recently, the Delhi Pollution Control Committee has ordered that all construction and road-owning agencies have to spray dust suppressants at construction sites and dusty patches of roads to control emissions.

Statement 3 is correct. According to Central Pollution Control Board (CPCB), particulate size 2.5 micrometers or less in diameter (PM 2.5) are responsible for causing the greatest harm to human health. These fine particulates can be inhaled deep into the lungs and can cause breathing and respiratory symptoms, irritation, inflammations and damage to the lungs and premature deaths.