UGC NTA NET/JRF Exam, Environmental Sciences, June-2023

(b) Sandstone: Sandstone layers often serve as reservoir rocks that host coal beds. In coal-forming environments, sandstone layers can act as conduits for water and gases, influencing the chemical composition and conditions within the peat (the precursor to coal) and aiding in the transformation of organic material into coal.

(c) Shale: Shale, being a fine-grained sedimentary rock rich in clay minerals, functions as a sealing or trapping layer. Gases and fluids generated during the decomposition of plant material are trapped within the coal seams by the surrounding shale, contributing to the formation and preservation of coal beds.

The energy that a windmill can gather is proportional to the square of its blade length and the cube of the wind speed.

The energy harvested by a wind turbine is proportional to the area swept by the turbine and wind velocity.

The kinetic energy is proportional to the product of the mass of the air flowing through the given area in unit time and square of the velocity of the air.

The maximum wind energy available is proportional to the cube of the wind speed. This means that a small increase in wind speed may increase the wind power.

(a) SO₂ (Sulphur dioxide): Sulphur dioxide (SO₂) is a criteria pollutant under the National Ambient Air Quality Standards (NAAQS). It is a gas produced by the burning of fossil fuels containing sulphur, such as coal and oil. SO₂ can lead to the formation of particulate matter and can contribute to respiratory issues, among other health concerns.

(b) NOx (Nitrogen oxides): Nitrogen oxides (NOx), which include nitric oxide (NO) and nitrogen dioxide (NO₂), are criteria pollutants. They are produced by combustion processes, primarily in vehicles and industrial activities. NOx contributes to the formation of groundlevel ozone and particulate matter, both of which have adverse effects on human health and the environment.

(d) O₃ (Ozone): Ozone (O₃) is also a criteria pollutant regulated under NAAQS. While ozone in the upper atmosphere (stratospheric ozone) is beneficial for blocking ultraviolet radiation, groundlevel ozone is a harmful air pollutant.

Ground-level ozone is formed when pollutants like NOx and volatile organic compounds react in the presence of sunlight.

Secondary air pollutants undergo chemical and physical transformations in the atmosphere, a process that distinguishes them from primary pollutants emitted directly into the air.

Contrary to the notion, they are not inherently non-hazardous; in fact, many secondary pollutants pose risks to human health and the environment.

These pollutants encompass a diverse range of inorganic and organic species, including ozone, secondary aerosols, and other compounds formed through atmospheric reactions.

(b) This technique is used to mitigate sulphur dioxide (SO₂) emissions from power plants, particularly those burning fossil fuels like coal, Limestone, a calcium-based substance, is injected into the combustion process.

It reacts with sulphur compounds to form solid particles, which are then captured, reducing the release of SO₂ into the atmosphere.

(c) SCR is employed to reduce nitrogen oxides (NOx) emissions from combustion processes, commonly found in thermal power plants. In this method, a catalyst facilitates the reaction between nitrogen oxides and ammonia.

This chemical reaction converts the harmful NOx compounds into nitrogen and water, which are less detrimental to air quality.

(e) Fabric bag filters are an effective technology for controlling particulate matter emissions from industrial processes.

These filters consist of a series of fabric bags that capture solid particles from the gas stream. As the gas passes through the fabric, particulate matter adheres to the surface of the bags.

"Total Atmospheric pressure minus Barometric pressure only," we can interpret this statement as describing sound pressure in terms of the dynamic fluctuations in atmospheric pressure minus the static barometric pressure.

In this context, sound pressure is seen as the variable component, reflecting the changes in air pressure caused by sound waves. The subtraction of barometric pressure, a constant baseline representing the ambient atmospheric pressure at a specific location, aims to isolate the specific pressure variations introduced by sound.

Gas bubble disease (GBD), a condition characterized by the formation and accumulation of gas bubbles in the tissues of aquatic animals, notably fish, poses a threat to their well-being.

The excess dissolved oxygen in drinking water is the cause of GBD. It is based on the understanding that while oxygen is crucial for aquatic life, excessive levels can lead to supersaturation of water, resulting in the formation of gas bubbles within fish tissues and triggering the disease.

This explanation aligns with the fact that GBD is associated with the supersaturation of dissolved gases, including oxygen.

(a) Phosphorus is commonly found in geological formations, particularly in rocks. Over time, weathering processes release phosphorus into water bodies, contributing to its presence in aquatic environments.

(b) In water, phosphorus can exist in different forms, with orthophosphate (PO₄³⁻) being the inorganic form and organically bound phosphate representing the phosphorus incorporated into organic compounds.

(c) Soluble reactive phosphorus (SRP) is a term used to describe the fraction of phosphorus that is immediately available for uptake by organisms in its dissolved inorganic form.

(d) In many aquatic ecosystems, the availability of phosphorus can limit the growth of organisms like algae and aquatic plants. Therefore, phosphorus is considered a limiting nutrient that can influence the overall productivity of the system.

(e) Analyzing phosphorus in aquatic ecosystems can be challenging due to the complex nature of its various forms. Differentiating between phosphorus associated with zooplankton, bacteria, algae, and inorganic sources can be intricate and often requires sophisticated analytical techniques.

This weathering process leads to the leaching of basic cations from the soil, contributing to soil acidity. The tropics experience consistent high temperatures and abundant rainfall, creating favorable conditions for enhanced weathering.

Reason (R) complements Assertion (A) by specifically highlighting the impact of year-round high temperatures and high rainfall in the tropics.

The warmth and moisture accelerate chemical weathering processes, promoting the breakdown of primary rock-forming minerals and the subsequent leaching of basic cations.

This leaching, caused by the combination of temperature and rainfall, aligns with the assertion that weathering is a key factor in the development of acidic soils in the tropics.