[Mission 2022] QUIZ – 2020: INSIGHTS STATIC QUIZ , 25 September 2021 – Environment – INSIGHTSIAS

Solution: b)

• Depending upon the source and composition of the coal being burned, the components of fly ash vary considerably, but all fly ash includes substantial amounts of silicon dioxide (SiO2), aluminium oxide (Al2O3) and calcium oxide (CaO), the main mineral compounds in coal-bearing rock strata.
• Minor constituents include: arsenic, beryllium, boron, cadmium, chromium, hexavalent chromium, cobalt, lead, manganese, mercury, molybdenum, selenium, strontium, thallium, and vanadium, along with very small concentrations of dioxins and PAH compounds. It also has unburnt carbon.

Solution: d)

However, fly ash can be used in the following ways:

• Concrete production, as a substitute material for Portland cement, sand.
• Fly-ash pellets which can replace normal aggregate in concrete mixture.
• Embankments and other structural fills.
• Cement clinker production – (as a substitute material for clay).
• Stabilization of soft soils.
• Road subbase construction.
• As aggregate substitute material (e.g. for brick production).
• Agricultural uses: soil amendment, fertilizer, cattle feeders, soil stabilization in stock feed yards, and agricultural stakes.
• Loose application on rivers to melt ice.
• Loose application on roads and parking lots for ice control.

Solution: d)

Smokestacks of thermal power plants, smelters and other industries release particulate and gaseous air pollutants together with harmless gases, such as nitrogen, oxygen, etc. These pollutants must be separated/ filtered out before releasing the harmless gases into the atmosphere.

There are several ways of removing particulate matter; the most widely used of which is the electrostatic precipitator, which can remove over 99 per cent particulate matter present in the exhaust from a thermal power plant.

A scrubber can remove gases like Sulphur dioxide. In a scrubber, the exhaust is passed through a

spray of water or lime.

Catalytic converters, having expensive metals namely platinum-palladium and rhodium as the

catalysts, are fitted into automobiles for reducing emission of poisonous gases.

Solution: b)

Ground level or tropospheric ozone is created by chemical reactions between oxides of nitrogen (NOx gases) and volatile organic compounds (VOCs). The combination of these chemicals in the presence of sunlight form ozone. About 90% of total ozone in the atmosphere is in the stratosphere, and 10% is in the troposphere.

Ozone in the troposphere is considered a greenhouse gas, and may contribute to global warming.

There is ‘good’ ozone; this ozone is found in the upper part of the atmosphere called the stratosphere, and it acts as a shield absorbing ultraviolet radiation from the sun.

The thickness of the ozone in a column of air from the ground to the top of the atmosphere is measured in terms of Dobson units (DU).

Solution: c)

• Phosphorus is a major constituent of biological membranes, nucleic acids and cellular energy transfer systems. Many animals also need large quantities of this element to make shells, bones and teeth. The natural reservoir of phosphorus is rock, which contains phosphorus in the form of phosphates. When rocks are weathered, minute amounts of these phosphates dissolve in soil solution and are absorbed by the roots of the plants.
• Herbivores and other animals obtain this element from plants. The waste products and the dead organisms are decomposed by phosphate-solubilising bacteria releasing phosphorus. Unlike carbon cycle, there is no

respiratory release of phosphorus into atmosphere.