Environment and Ecology: UPSC Previous Year Questions (Prelims)

Explanation

Sustainable Agriculture is farming in such a way to protect the environment, aid and expand natural resources and to make the best use of nonrenewable resources. Options 1, 2 and 3 are correct:

Mixed cropping or diverse cropping: When two or more crops are cultivated concurrently on a field, it is known as mixed cropping or diversified cropping. In the unlikely event that one crop fails, the other crops will mitigate the risk of a complete crop failure. Legume intensification: A category of plants known as leguminous plants (legume) contain edible roots or knobs that help nitrogen-rich soil grow vegetables or other meals. A leguminous crop is typically cultivated alongside the primary crop. Legumes contribute to increased soil fertility by fixing nitrogen from the atmosphere. Crop Rotation: It entails the methodical planting of various crops in a specific order over the course of several years in the same growing space. It contributes to the preservation of soil nutrients, the reduction of soil erosion, and the prevention of pests and disease in plants. Tensiometer: A tensiometer is a device used to measure soil moisture levels, helping in precision irrigation. Farmers and other irrigation managers can use tensiometers to help them decide when to water the land. It helps in reducing excessive water use and promotes water conservation in agriculture. Option 4 is incorrect: Vertical farming is the process of raising crops in vertical layers and frequently combines soilless farming methods and controlled-environment agriculture, which attempts to maximise plant development.

Explanation

Biochar is a high-carbon, fine-grained residue that is currently produced through modern pyrolysis processes (direct thermal decomposition of biomass in the absence of oxygen and preventing combustion). The extremely porous nature of biochar is found to be effective at retaining both water and water-solu-ble nutrients. When applied to soil, biochar can improve water retention, increase soil fertility, and enhance microbial activity, leading to better crop yields.

Statement 1 is correct: The use of biochar in vertical farming, part of the growing medium, can increase output significantly. As biochar migrates vertically through the soil profile, therefore can be used as a part of the growing medium in vertical farming.

Statement 2 is correct: Its presence on the earth can improve water quality, increase soil fertility, raise agricultural productivity, and reduce pressure on old-growth forests. Using biochar in the soil promotes the growth of nitrogen-fixing microorganisms.

Statement 3 is correct: Biochar is hygroscopic. Thus it is a desirable soil material in many locations due to its ability to attract and retain water.

Explanation

At room temperature, benzene is a colorless or pale yellow liquid with a sweet odor and is highly flammable. It evaporates quickly into the air, and its vapor is denser than air, which can cause it to settle in low-lying areas. Benzene is a toxic air pollutant released from various sources and it can also contaminate water.

Option (a) is correct: Natural sources of benzene include volcanoes and forest fires. It is also present in gasoline, cigarette smoke, and crude oil, fuel evaporation, coal and oil combustion, and other activities. In various industries, benzene is used as a raw material to produce chemicals for making plastics, resins, nylon, and synthetic fibers. It is also found in the production of certain lubricants, rubbers, dyes, detergents, drugs, and pesticides. Although varnishes and paints may contain benzene, and the thermal breakdown of polyurethane can release benzene among other substances, these are not well-established as sources of benzene pollution.

Explanation

National Policy on Biofuels 2018 categorizes biofuels as "Basic Biofuels" viz. First Generation (1G) bioethanol & biodiesel and "Advanced Biofuels" - Second Generation (2G) ethanol, Municipal Solid Waste (MSW) to drop-in fuels, Third Generation (3G) biofuels, bio-CNG etc. to enable the extension of appropriate financial and fiscal incentives under each category. First-Generation Biofuels (also referred to as Basic biofuels) i.e. bioethanol and biodiesel, are produced from types of bio-mass that are often used for food, such as corn, soy, and sugarcane. These biofuels are made through fermentation or chemical processes that convert the oils, sugars, and starches in the bio-mass into liquid fuels. Second-Generation Biofuels (also referred to as Advanced bio-fuels) i.e, ethanol, municipal solid waste to drop-in fuels, are produced from non-food biomass, such as perennial grass and fast-growing trees. The processes to make them often involve converting fibrous non-edible material called "cellulose" into fuel. Third-generation biofuels are derived from algae and bacteria, which can produce large quantities of lipid oils or other biofuels like biomethanol or biohydrogen. Algae, in particular, grows quickly and has the potential to generate more biomass per unit of land compared to conventional crops.

Option (a) is correct: The Policy expands the scope of raw material for ethanol production by allowing the use of Sugarcane Juice, Sugar containing materials like Sugar Beet, Sweet Sorghum, Starch containing materials like Corn, Cassava, Damaged food grains like wheat, Broken rice, Rotten Potatoes.

Explanation

Social Cost of Carbon is best described as the measure of monetary value of long-term damage done by a tonne of CO₂ emissions in a given year. The social cost of carbon (SCC) is used to estimate in dollars all economic damage that would result from emitting one ton of carbon dioxide into the atmosphere. India’s country-level social cost of carbon emission was estimated to be the highest at $86 per tonne of CO₂. It means the Indian economy will lose $86 by emitting each additional tonne of CO₂. India is followed by the US ($48) and Saudi Arabia ($47).

Explanation

Statement 1 is correct: Coal ash contains contaminants like mercury, cadmium and arsenic. Without proper management, these contaminants can pollute waterways, groundwater, drinking water, and the air.

Statement 2 is correct: Burning of fossil fuels (which contain sulphur and nitrogenous matter) such as coal and oil in power stations and furnaces or petrol and diesel in motor engines produce sulphur dioxide and nitrogen oxides, which also leads to ‘acid rain’.

Statement 3 is correct: Indian Coal has comparatively higher ash content than imported coal due to the drift theory of the formation of coal deposits in India. Coal seams formed due to drift theory contain higher ash as compared to the in-situ theory of formation.

Explanation

The Wildlife Protection Act, 1972 has six schedules. Schedule VI mandates, ‘no person is allowed to cultivate a specified plant mentioned in schedule 6, except with a licence granted by the Chief WildLife Warden’. The plants mentioned in the sixth schedule includes:

Beddomes Cycad Blue Vanda Kuth Ladies slipper orchids Pitcher plant Red Vanda

Explanation

Steel Slag, a by-product of steel making, is produced during the separation of the molten steel from impurities in steel-making furnaces. The slag occurs as a molten liquid melt and is a complex solution of silicates and oxides that solidi-fies upon cooling.

Statement 1 is correct: Steel slag is widely used as a base course material in road construction, providing a strong and durable foundation beneath asphalt roads, tracks, and paved surfaces. Its high strength, resistance to deformation, and excellent drainage properties enhance pavement longevity.

Statement 2 is correct: Steel slag can be used in the agricultural sector due to its ability to correct soil acidity. In fact, developed countries like Japan, the USA have taken the lead in making fertilisers using steel-making slag.

Statement 3 is correct: Additionally, it is utilized in the production of Portland slag cement (PSC), where it is blended with ordinary Portland cement to improve durability and resistance to chemical attacks. This not only enhances cement quality but also promotes sustainable construction by recycling industrial byproducts.

Explanation

Option 1 is correct: Copper slag is a by-product obtained during smelting and refining of copper. The use of copper slag in cement and concrete provides potential environmental as well as economic benefits.

Option 2 is correct: Cold mix asphalt is produced by mixing unheated mineral aggregate with either emulsified bitumen or foamed bitumen. It is suitable for light to medium trafficked roads when used in base and surface courses.

Option 3 is correct: The Government has allowed the use of coir based geotextiles for construction of rural roads under the Pradhan Mantri Gram Sadak Yojana in 2020. Options 4 and 5 are incorrect: Hot Mix Asphalt (HMA) is a combination of approximately 95% stone, sand, or gravel bound together by asphalt cement, a product of crude oil. The wide use of hot mix technology leads to environmental pollution as these plants emit a huge amount of greenhouse gases. Portland cement is a major CO₂ emitter.

Explanation

Central Ground Water Board monitors groundwater levels throughout the country on a regional scale, four times in a year during the months of March/April/May, August, November and January. For monitoring of ground water level, CGWB has a dedicated network of about over 30000 monitoring stations called "National Hydrograph Network Stations (NHNS)", which comprises open dug wells and purpose built bore/tube wells for water level monitoring called piezometers.

Statement 1 is incorrect: 256 of our approximately 700 districts have groundwater levels which are "critical" or "overexploited" as per the latest data from the Central Ground Water Board (2017). As per the report ‘National Compilation on Dynamic Groundwater Resources of India, 2017 out of the total 6881 assessment units (Blocks/Mandals/ Talukas) in the country, 1186 units in various States (17%) have been categorized as ‘Over-Exploited’, 313 units (5%) are ‘Critical’. This adds to 22%.

Statement 2 is correct: The Central Ground Water Authority (CGWA), established under Section 3(3) of the Environment (Protection) Act, 1986. It operates under the Ministry of Jal Shakti, Government of India. Its primary mandate is to regulate and control the development and management of groundwater resources across the country.

Statement 3 is correct: FAO research paper shows the countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the USA (17 million ha).