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

Concept (atomic H/C ratio): As carbonaceous materials mature from peat → lignite→ bituminous → anthracite, they lose hydrogen and become more carbon-rich; hence H/C decreases with rank. Hydrocarbons (petroleum, methane) have much higher H/C.

Ordering logic:

E. Anthracite: Highest rank coal, very carbonrich, lowest H/C (~0.3-0.5).
D. Lignite: Low-rank brown coal, more volatiles than anthracite, H/C below peat.
B. Peat: Partially decomposed biomass, still hydrogen-rich, H/C above lignite.
A. Petroleum: Mixture of alkanes/alkenes, typical H/C≈ 2 (atomic).
C. Methane: CH₄ H/C = 4 (highest).
Thus (increasing H/C): Anthracite < Lignite < Peat < Petroleum < Methane ⇒ E, D, B, A, C.

Rubbish: Refers to the broader class of solid wastes that include non-biodegradable and generally non-putrescible items like paper, cardboard, glass, metals, plastics, textiles, and construction debris.

Rubbish can be further subdivided into combustible (e.g., paper, rags, wood) and non-combustible (e.g., glass, ceramics, metals) categories.

Garbage: A specific subset of solid waste, consisting of biodegradable putrescible organic matter, such as food scraps, vegetable residues, and other materials subject to decomposition.

Garbage is thus narrower in definition and falls within the overall umbrella of solid waste.

Why statement 1 is incorrect: By standard definitions, rubbish does not inherently exclude garbage. In municipal waste management, garbage is considered part of the broader refuse stream, and refuse itself is made up of rubbish + garbage.

Therefore, saying "rubbish does not contain garbage" is misleading because rubbish is not defined as something separate from all organic wastes; it is often categorized alongside garbage under the broader term refuse.
Why other statements are correct:

Refuse contains both rubbish and garbage: Correct, since refuse is the inclusive term used in solid waste management to denote all discarded materials, combining both organic garbage and inorganic rubbish.

Garbage contain both garbage and rubbish: While phrased redundantly, the intent is that garbage, as a waste stream within refuse, overlaps with rubbish under the broad category of solid waste. In practice, garbage is a subset, and refuse includes both.

Refuse has less water content (%) than garbage: Correct, because garbage, made up of kitchen and food wastes, has very high moisture content (50-70%), whereas rubbish (dry wastes like paper, plastics, and metals) has a much lower water content.

When garbage is combined with rubbish to form refuse, the overall average water content decreases compared to garbage alone.

Concept of Ventilation Coefficient (VC): The ventilation coefficient is a measure of the atmosphere's ability to disperse pollutants. It is defined as:
VC = u×H
where:
u = average wind speed (m/s),
H = mixing height (m), i.e., the depth of the atmosphere available for vertical mixing of pollutants.

From the figure:
The mixing height is the vertical distance between the ground and the top of the mixing layer.

In the diagram, the region marked B represents the mixing height (up to where the atmosphere is unstable/neutral and mixing can occur).

Region A lies below with stable stratification, and region C above is capped by inversion, limiting upward dispersion.

Thus, the effective mixing height = B.
Given data:
Wind speed, u = 10 m/s.
Mixing height, H = В.
Calculation: VC = 10 × B = 10 B m²/s.

Stratification (epilimnion, metalimnion/ thermocline, hypolimnion) and seasonal turnover are natural limnological cycles, not the cause of eutrophication.

Eutrophication is driven primarily by nutrient enrichment (N, P). While stratification can modulate oxygen/nutrient distribution (e.g., hypolimnetic anoxia → internal P loading), the processes themselves are not inherently harmful. Other statements are correct:

1. Hypolimnion is poorly mixed vs epilimnion during stratification.

2. As summer advances, stability increases (warm epilimnion overlays cooler, nearconstant hypolimnion).

3. Temperate lakes typically exhibit at least one stratification-turnover cycle annually (monomictic/dimictic), barring special cases (e.g., meromictic lakes).

In a salinity-gradient solar pond, heat is stored in the Lower Convective Zone (LCZ)-the hot, dense brine at the bottom.

The Upper Convective Zone (UCZ) is shallow, low-salinity (< ~5%), well mixed, and near-ambient temperature; it does not store the captured heat.

Supporting concepts:
Non-Convective Zone (NCZ): Middle gradient layer that suppresses convection, trapping solar heat below.

1. Water as HTF: Common and correct.
2. Salinity gradient: Essential to prevent convective losses.
4. Salt solubility vs temperature: Should not vary strongly to maintain a stable gradient (hence salts like NaCl are preferred).

Decreasing abundance (dry air): Argon (~0.934%) > Carbon dioxide (~0.04%) > Neon (~0.0018% = 18 ppm) > Helium (~0.00052% ≈ 5 ppm) > Methane (~0.00019% ≈1.9 ppm).

Reasoning: Among minor gases, Ar is the dominant noble gas; CO, is next at tens of thousands of ppm; Ne and He are trace noble gases (Ne > He); CH is present at only~2 ppm. Hence, B > A > D > C > E.

Common field worm → Helodrilus caliginosus (A-III): Widely distributed soil dweller; often termed the common field earthworm in older nomenclature (now Aporrectodea caliginosa).

Manure worm → Eisenia foetida (B-IV): The "red wiggler", classic vermicomposting species thriving in rich organic manures.

Green worm → Helodrilus chloroticus (C-I): Characteristically greenish appearance; prefers moist soils.

Slim earthworm → Diplocardia verrucosa (D-II): Slender (“slim") body form; reported from lighter textured soils.
Thus: A-III, B-IV, C-I, D-II.

How the 16 goals (excluding Goal 17: Partnership) split across pillars:

Ecological (4): 6 Clean Water & Sanitation, 13 Climate Action, 14 Life Below Water, 15 Life on Land.

Reason: These are environment-centric-water resources, climate, oceans, and terrestrial ecosystems.

Social (8): 1 No Poverty, 2 Zero Hunger, 3 Good Health & Well-being, 4 Quality Education, 5 Gender Equality, 10 Reduced Inequalities, 11 Sustainable Cities & Communities, 16 Peace, Justice & Strong Institutions.

Reason: These focus on human well-being, equity, safe/inclusive settlements, and institutions that underpin social outcomes.

Economic (4): 7 Affordable & Clean Energy, 8 Decent Work & Economic Growth, 9 Industry, Innovation & Infrastructure, 12 Responsible Consumption & Production.

Reason: These drive production systems, energy and infrastructure, productivity, and consumption/production patterns in the economy.

Check: 4 (Ecological) + 8 (Social) + 4 (Economic) = 16 goals (Goal 17 excluded), matching the required ratio 4: 8: 4.

B. Aerobic degradation → first: Freshly placed waste has entrained air; aerobic microbes rapidly oxidize readily degradable organics.

D. Hydrolysis & fermentation: As oxygen is depleted, facultative/anaerobic consortía break down complex polymers to VFAs, alcohols, H₂, CO₂.

C. Acetogenesis: Fermentation products are converted to acetate, H₂, CO₂ by acetogens.

E. Methanogenesis: Methanogens convert acetate/H₂/CO₂ to CH₄ + CO₂, establishing the long methane fermentation phase.

A. Oxidation → last: Methane oxidation occurs later in the aerobic cover soil by methanotrophs, consuming a portion of emitted CH₄

Therefore: B →D→C→E→ А.

Phosphate → Stromatolites (A-II): Phosphorite associations occur with stromatolitic and upwelling settings in some sedimentary basins; stromatolites are microbial carbonate structures that can host/ associate with phosphate accumulations.

Sulphate→ Anhydrite (B-III): CaSO₄ (anhydrite) is a classic evaporite sulphate mineral/rock.

Mg-Fe rich silicate → Basalt (C-IV): Basalt is mafic, dominated by Mg-Fe silicates (pyroxene, olivine, Ca-plagioclase).

Al oxyhydroxides → Bauxite (D-1): Bauxite comprises gibbsite/boehmite/diaspore (Aloxyhydroxides), the principal aluminium ore.