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

A. Assessment → Identify baseline conditions; predict project-induced impacts on environmental receptors.

D. Evaluation → Judge the significance of predicted impacts (magnitude, duration, reversibility, sensitivity of receptors); weigh alternatives.

E. Mitigation → Design and commit to avoidance, minimization, restoration, and offset measures; integrate into the EMP/ EMC.

C. Decision Making→ Competent authority issues approval/conditions/rejection based on the EIA/EMP, public hearing, and appraisal.

B. Audit → Post-project environmental audit/ monitoring & feedback: verify predictions, check compliance and effectiveness of mitigation, and feed learning into future EIAs.

Incorrect statement: "Control rods in fission reactors are made from graphite, neutron absorbing element."

Why: Control rods are made of strong neutron absorbers like boron, cadmium, hafnium, AgIn-Cd alloys. Graphite is a moderator (slows neutrons) not a control-rod absorber. Checks on other items:

1 (True): Naturally occurring fissile uranium isotope is U-235 (U-238 and Th-232 are fertile, not fissile).

3 (True): Breeder reactors produce more fissile fuel (e.g., Pu-239 or U-233) than they consume.

4 (True): Thermal thorium breeder converts Th-232→ U-233 via neutron capture and beta decays.

Context: In many aquatic systems, phytoplankton have short lifespans and are heavily grazed; consumer biomass can exceed standing producer biomass, yielding an inverted biomass pyramid, even though energy pyramids always taper with trophic level.

A. (True): At any instant, heterotroph biomass can be greater than autotroph biomass (the hallmark of an inverted biomass pyramid).

B. (True): Energy produced by autotrophs (GPP/ NPP) still exceeds that passed to heterotrophs; energy pyramids are never inverted.

C. (True): Inversions are common in open, nutrient-poor waters with low producer standing stock and high turnover under strong grazing.

D. (Not selected): The detrital/microbial loop can be important even in oligotrophic systems; it is not generally correct to assert a lower proportional detrital contribution there relative to eutrophic waters.

E. (True): Heterotrophs/autotrophs biomass ratio > 1 indicates an inverted biomass pyramid.

A. - Correct. Impaction α Pᴘ. dᴘ² Inertial impaction efficiency rises with particle inertia. The Stokes number for impaction scales as Stkd α Pᴘdᴘ² (for fixed flow/ geometry), so higher particle density and diameter squared increase capture in devices (baffles, cyclones, mesh pads).

B. Resuspension vs size - Correct (exam convention). For typical dusts in air-pollution control (≈1- 100 µm), smaller deposited particles are more easily re-entrained under the same shear because aerodynamic lift/drag scale less steeply with size than weight; thus a common engineering rule is resuspension probability increases as particle size decreases (i.e., inversely with dᴘ).

(Very fine cohesive powders can be an exception, but the standard MCQ generalization treats the trend as inverse.)

C. Cyclones: force α velocity² - Correct (intended sense). Separation is driven by centrifugal force F🇨 = mv²lr, i.e., proportional to the square of the tangential velocity.

Design relations often connect cut-size to the particle's terminal settling characteristics, but the governing inertial term is the v² dependence captured in the statement.

D. "Activated alumina & H₂SO₄ used in demisters" - Incorrect. Demisters (mist eliminators) remove liquid droplets mechanically (impaction/ interception/centrifuging) using mesh or vane packs.

Activated alumina (adsorbent) and concentrated sulfuric acid (desiccant) are gas-drying media used in dryers/sampling trains-not the collection media in demisters.

E. Baghouses do not operate by sedimentation or electrostatics - Correct. Fabric filters capture particles by depth/ surface filtration (interception, impaction, diffusion, and cake sieving).

They do not rely on gravitational settling (settling chambers) or electrostatic attraction (ESPs). Any fiber charge is incidental; the principle is mechanical filtration.

C. Tropical forest - highest NPP: Warm year-round temperatures, high rainfall, intense insolation, and continuous growing seasons drive very high net primary productivity (typically ~1800-2500 g m⁻² yr⁻¹). Dense, multi-layered canopies and rapid nutrient cycling keep photosynthesis high nearly all year.

D. Temperate forest: Marked seasons but long enough growing periods, moderate temperatures, and adequate moisture support high NPP (about ~800-1400 g m⁻² yr⁻¹). Deciduous and mixed forests maintain substantial leaf area during the growing season, elevating carbon gain.

E. Crops: Although highly variable by crop typе and management, managed agro-ecosystems (fertilizers, irrigation, high-yield varieties, weed/pest control) often achieve moderate10-high NPP on a per-area basis (roughly - 500-1100 g m⁻² yr⁻¹ y on global averages), commonly exceeding many natural grasslands.

B.  Temperate grassland: Productivity is limited by seasonal water stress, periodic droughts, and strong herbivory/fire regimes; typical NPP ~400-800 m⁻² yr⁻.

While peak growth can be vigorous, shorter favorable windows and moisture constraints keep annual totals below most forests and well-managed crops.

A. Boreal forest - lowest among the five (on average): Cold climates, short growing seasons, low sun angles, nutrient-poor acidic soils, and, in places, permafrost depress photosynthesis and decomposition, yielding lower NPP (often ~300-700 g m⁻² yr⁻) than temperate systems and most croplands.

Decreasing order (global averages): Tropical forest > Temperate forest > Crops : Temperate grassland > Boreal forest, i.e., C, D, E, B, А.

The solid organic fraction (kerogen) in bituminous (oil) shales is predominantly derived from lower plants/algae lacking lignocellulosic tissues. In contrast, lignite, bituminous coal, anthracite originate mainly from higher land plants rich in lignocellulose, altered through diagenesis and coalification.

Incorrect statement: Composting is a biological, aerobic process requiring adequate moisture, typically~50-60% (wet basis) for microbial activity and heat transfer. Saying moisture "should not be present" is wrong.
Correct practices:
Particle size <~5 cm: Promotes aeration and surface area for microbes. Compost improves soil water-holding capacity: Humified organics enhance aggregation and porosity.
C:N~20-25:1 (often 25-30:1 optimal): Ensures balanced microbial growth and efficient decomposition.