UGC NTA NET/JRF Exam, Environmental Sciences, June-2025

Total Questions: 99

61. Choose the INCORRECT statement:

1. Clay particles act as colloids in water.
2. The pH of soils tends to buffer against large increase in pH as they have reserve acidity.
3. Precipitation reactions does not help in retaining heavy metals in soils.
4. Replacement of natural long rooted vegetation by wheat and other shallow rooted crops can increase soil salinity.

Correct Answer: 3. Precipitation reactions does not help in retaining heavy metals in soils.

Solution:

Incorrect statement: "Precipitation reactions does not help in retaining heavy metals in soils." Why: Precipitation is a key immobilization pathway: metals form insoluble hydroxides, carbonates, phosphates, and sulfides (e.g., PbCO₃, Zn(OH)₃, CuS), which reduce mobility and bioavailability.

Checks on others (correct):
1. Clay as colloids: Clay particles are colloidal in water (sub-2 µm, charged surfaces), influencing sorption and transport.

2. Reserve acidity buffers pH rises: Soils contain exchangeable/adsorbed acidity that buffers additions of base, resisting large increases in pH.

4. Shallow-rooted crops & salinity: Replacing deep-rooted vegetation with shallow-rooted cereals can raise water tables and increase salinization (less evapotranspiration, more capillary rise of salts).

62. From the analysis of water given below, calculate the amount of lime and soda (in mg/l as CaCO₃) necessary to soften water to 90.0 mg/l as CaCO₃:

1. ~235 and ~60
2. ~296 and no soda ash
3. ~262 and ~34
4. ~235 and no soda ash

Correct Answer: 2. ~296 and no soda ash

Solution:

63. How many methodologies under 'offset mechanism' of the Carbon Credit Trading Scheme (CCTS, 2023), allowing nonobligated entities to participate in voluntary climate mitigation projects, are proposed by the Government of India?

1. 5
2. 6
3. 8
4. 12

Correct Answer: 3. 8

Solution:

Under India's Carbon Credit Trading Scheme (CCTS, 2023), the Government approved eight methodologies under the Offset Mechanism for non-obligated entities (e.g., renewables including hydro/pumped-storage, green hydrogen, industrial efficiency, landfill methane, mangrove A/R).

64. Which of the following rules came in existence in the same calendar year in India?

A. The Hazardous and other Waste (Management and Transboundary Movement) Rules B. The Batteries (Management and Handling) Rules
C. The Biomedical Waste Management Rules
D. The Solid Waste Management Rules
E. The Public Liability Insurance Rules
Choose the correct answer from the options given below:

1. А, В and C only
2. B, C and D only
3. A, C and D only
4. C, D and E only

Correct Answer: 3. A, C and D only

Solution:

Same calendar year (2016):
A. Hazardous and Other Wastes (Management & Transboundary Movement) Rules, 2016 C. Biomedical Waste Management Rules, 2016
D. Solid Waste Management Rules, 2016

Different years:

B. Batteries (Management & Handling) Rules, 2001 (superseded by Battery Waste Management Rules, 2022),
E. Public Liability Insurance Rules, 1991.
Hence, the set that came into force in the same year is A, C and D.

65. Match the LIST-I with LIST-II.

Choose the correct answer from the options given below:

1. A-II, B-I, C-III, D-IV
2. A-III, B-IV, C-I, D-II
3. A-I, B-III, C-IV, D-II
4. A-III, B-I, C-II, D-IV

Correct Answer: 2. A-III, B-IV, C-I, D-II

Solution:

A→Simple Random Sampling (III): Selected units are scattered without pattern; every unit in the frame has an equal and independent chance of selection.

B→ Stratified Random Sampling (IV): The frame is split into strata (vertical division); samples arae chosen from each stratum to ensure representation of all subgroups.

C→ Systematic Sampling (I): Selections are evenly spaced (every kth unit) after a random start, giving a regular pattern across the frame.

D→ Cluster Sampling (II): Selected units occur together in a localized group, indicating selection of a cluster (e.g., choose a cluster, then take all or a subsample within it).

66. Consider the following statements about bioremediation.

A. One of the most common limiting factor for in-situ biodegradation in saturated zone is availability of oxygen.
B. N and P are common additives which enhance rate of biodegradation.
C. Bioventing and bioaccessibility adversely impact biodegradation in vadose zone.
D. Methanotropic organism are involved in/ example of cometabolism biodegradation.
E. In-situ biodegradation applications are based only on aerobic biodegradation.
Choose the correct answer from the options given below:

1. B, D and E only
2. A, B and D only
3. A, B, D and E only
4. B, С and D only

Correct Answer: 2. A, B and D only

Solution:

A. True (O₂ often limiting in saturated zone): Groundwater is typically oxygen-poor; aerobic biodegradation stalls without an electron acceptor. Hence in situ treatments often add air/oxygen, nitrate, or peroxide.

B. True (N & Pas biostimulants): Microbes need nitrogen and phosphorus to build biomass. Adding N/P (e.g., NH₄⁺/NO₃⁻, PO₄³⁻) frequently accelerates biodegradation.

C. False (bioventing & bioaccessibility help, not hinder): Bioventing supplies air/oxygen to the vadose zone to enhance aerobic degradation. Improving bioaccessibility (e.g., surfactants, desorption) increases degradation.

D. True (methanotrophs & cometabolism): Methanotrophs express methane monooxygenase that co-metabolizes pollutants (e.g., TCE, chlorinated solvents).

E. False (not only aerobic): In situ applications also exploit anaerobic processes (e.g., reductive dechlorination with electron donors).

67. The endangered species________ .

1. have a 50% or greater probability of extinction within 10 years
2. have a 50% or greater probability of extinction within 20 years
3. have a 20% or greater probability of extinction within 10 years
4. have a 20% or greater probability of extinction within 20 years

Correct Answer: 4. have a 20% or greater probability of extinction within 20 years

Solution:

Under IUCN quantitative criteria, Endangered (EN) corresponds to an extinction probability of ≥20% within 20 years or 5 generations (whichever is longer), distinct from Critically Endangered (≥50% in 10 years/3 generations).

68. Choose the INCORRECT statement about heat islands.

1. Low surface albedo is a likely cause of urban heat.
2. Surface albedo is also referred to as shortwave reflectivity.
3. Shading and evapotranspiration
4. Cool roofs/green roofs have high reflectivity and cause urban cooling.

Correct Answer: 3. Shading and evapotranspiration

Solution:

Incorrect statement: "Shading and evapotranspiration by urban forestry cause urban heating."

Why: Shading reduces shortwave gain; evapotranspiration removes heat via latent cooling → both mitigate urban heat islands.
Correct checks:
Low albedo → heating (absorbs more SW).
Albedo ≈ shortwave reflectivity.
Cool/green roofs raise reflectivity/latent cooling, lowering surface temps.

69. Remote sensing sensors can work on wavelengths 8 to 14 µm and 3 to 5 µm. Based on which of the following laws, wavelength of 8 to 14 µm is chosen to collect data?

1. Kirchoff's Law
2. Plank's Law
3. Stefan Boltzman Law
4. Wien's Displacement Law

Correct Answer: 4. Wien's Displacement Law

Solution:

Earth's surface (~300 K) emits thermal IR with a peak near 10 m. Wien's law (λₘₐₓ 2898/T) explains choosing the 8-14 µm band (and 3-5 µm) for thermal sensors, coinciding with atmospheric windows and peak terrestrial emission.