GATE Environmental Engineering Global and Regional Environmental Issues Syllabus

Which industrial sectors are the dominant sources of $\ce{SO2}$ and $\ce{NO_x}$ causing acid rain?

$\ce{SO2}$: combustion of sulfur-bearing coal/oil in thermal power plants and smelters. $\ce{NO_x}$: high-temperature combustion in power plants and automobile engines (vehicular exhaust).

What is the ozone layer and where is it located?

A region of the stratosphere (about $15\text{--}35\ \text{km}$ altitude) with relatively high $\ce{O3}$ concentration that absorbs harmful solar ultraviolet (UV-B and UV-C) radiation, protecting life on Earth.

Write the Chapman reactions for natural ozone formation and destruction.

Formation: $$\ce{O2 ->[h\nu] 2O}$$ $$\ce{O + O2 -> O3}$$ Destruction: $$\ce{O3 ->[h\nu] O2 + O}$$ $$\ce{O + O3 -> 2O2}$$

How do CFCs catalytically destroy stratospheric ozone?

UV releases chlorine radicals: $\ce{CFCl3 ->[h\nu] Cl^{.} + ...}$, then the catalytic cycle: $$\ce{Cl^{.} + O3 -> ClO^{.} + O2}$$ $$\ce{ClO^{.} + O -> Cl^{.} + O2}$$ One Cl atom can destroy thousands of $\ce{O3}$ molecules.

What is the 'ozone hole' and where is it most severe?

A severe seasonal thinning of the stratospheric ozone layer, most pronounced over Antarctica during the southern spring (Sept–Oct), driven by chlorine/bromine chemistry on polar stratospheric clouds.

Which international treaty controls ozone-depleting substances?

The Montreal Protocol (1987), which phased out CFCs, halons, and other ozone-depleting substances. The Kigali Amendment (2016) added phase-down of HFCs (potent GHGs).

Define Ozone Depletion Potential (ODP).

ODP is the ratio of ozone destruction caused by a unit mass of a substance to that caused by the same mass of CFC-11 (trichlorofluoromethane), for which $\text{ODP} = 1$ by definition.

Distinguish 'good ozone' from 'bad ozone'.

Stratospheric ozone ('good') shields Earth from UV radiation. Tropospheric (ground-level) ozone ('bad') is a secondary pollutant and component of photochemical smog, harmful to lungs, crops, and a greenhouse gas.

How is ground-level (tropospheric) ozone formed?

By photochemical reactions among $\ce{NO_x}$ and volatile organic compounds (VOCs) in sunlight: $$\ce{NO2 ->[h\nu] NO + O}$$ $$\ce{O + O2 -> O3}$$ VOCs consume NO, allowing $\ce{O3}$ to accumulate.

Define biodiversity and name its three levels.

Biodiversity is the variety of life forms in an ecosystem. Three levels: (1) Genetic diversity (within a species), (2) Species diversity (number/variety of species), (3) Ecosystem (community/habitat) diversity.

What is a biodiversity hotspot?

A region with exceptionally high endemic species richness ($\geq 1500$ endemic vascular plant species) that has lost $\geq 70\%$ of its original habitat. India contains four: Himalaya, Western Ghats, Indo-Burma, and Sundaland (Nicobar).

List the major causes of biodiversity loss (HIPPO).

HIPPO: Habitat destruction/fragmentation; Invasive species; Pollution; (Human) Population growth; Overexploitation. Climate change is an increasingly important added driver.

Define an endemic species and a keystone species.

Endemic species: found naturally only in a particular geographic region and nowhere else. Keystone species: a species whose presence has a disproportionately large effect on its ecosystem relative to its abundance; its loss causes major structural change.

What do the Simpson and Shannon indices measure in biodiversity?

They quantify species diversity. Simpson's index: $$D = 1 - \sum_{i=1}^{S} p_i^{2}$$ Shannon–Wiener index: $$H' = -\sum_{i=1}^{S} p_i \ln p_i$$ where $p_i$ is the proportion of individuals of species $i$ and $S$ the number of species.

Distinguish in-situ from ex-situ biodiversity conservation.

In-situ: conservation within natural habitats (national parks, wildlife sanctuaries, biosphere reserves). Ex-situ: conservation outside natural habitats (zoos, botanical gardens, gene/seed banks, captive breeding).

What are the IUCN Red List categories from most to least threatened?

Extinct (EX) → Extinct in the Wild (EW) → Critically Endangered (CR) → Endangered (EN) → Vulnerable (VU) → Near Threatened (NT) → Least Concern (LC), plus Data Deficient (DD) and Not Evaluated (NE).

List the main factors influencing the increase in human population.

Declining death/mortality rates (better medicine, sanitation, food); high birth/fertility rates; increased life expectancy; immigration; early marriage; low literacy and lack of family planning; agricultural/industrial development raising carrying capacity.

Write the exponential population growth equation.

$$\frac{dN}{dt} = rN \quad\Rightarrow\quad N_t = N_0 e^{rt}$$ where $N$ is population size, $r$ the intrinsic growth rate, and $N_0$ the initial population. Produces a J-shaped curve.

Write the logistic population growth equation and its curve shape.

$$\frac{dN}{dt} = rN\left(1 - \frac{N}{K}\right)$$ where $K$ is the carrying capacity. It yields an S-shaped (sigmoid) curve that levels off at $N = K$.

How is population doubling time estimated?

Using the 'rule of 70': $$t_{double} \approx \frac{70}{r\,(\%)}$$ where $r$ is the annual percentage growth rate. Exactly, $t_{double} = \frac{\ln 2}{r}$.

What is demographic transition?

The shift of a society from high birth and death rates to low birth and death rates as it develops. Stages: (1) high birth & death, (2) declining death rate (rapid growth), (3) declining birth rate, (4) low birth & death (stable), (5) possible decline.

Define carrying capacity ($K$).

The maximum population size of a species that an environment can sustainably support indefinitely given available resources (food, water, habitat). Denoted $K$ in the logistic growth model.

What is total fertility rate (TFR) and the replacement level?

TFR is the average number of children a woman bears in her lifetime. The replacement-level fertility is about $2.1$ children per woman; below this, population eventually declines (absent migration).

Define environmental degradation.

The deterioration of the environment through depletion of natural resources (air, water, soil, biodiversity) and ecosystem destruction, reducing the environment's capacity to meet ecological and human needs.

What does the IPAT equation express?

$$I = P \times A \times T$$ where environmental Impact ($I$) equals Population ($P$) times Affluence (consumption per person, $A$) times Technology (impact per unit of consumption, $T$).

What is desertification and its main causes?

The process by which fertile land becomes desert-like (degraded) in arid/semi-arid regions. Causes: overgrazing, deforestation, unsustainable agriculture, over-extraction of groundwater, soil salinisation, and climate change.

How does global energy consumption relate to environmental issues?

Most energy comes from fossil fuels, so rising energy consumption increases $\ce{CO2}$, $\ce{SO2}$ and $\ce{NO_x}$ emissions—directly driving global warming, acid rain, and air pollution. Energy demand grows with population and affluence (the $A\times T$ terms of IPAT).

Classify energy resources as renewable vs non-renewable with examples.

Renewable: solar, wind, hydro, geothermal, tidal, biomass—naturally replenished. Non-renewable: coal, petroleum, natural gas, nuclear (fissile fuel)—finite stocks formed over geological time.

Compare the carbon intensity of major fossil fuels.

Per unit of energy, $\ce{CO2}$ emissions follow: Coal > Oil > Natural gas. Natural gas ($\ce{CH4}$) emits the least $\ce{CO2}$ per joule because of its higher H/C ratio; coal emits the most.

What is the Kyoto Protocol and how does it differ from the Paris Agreement?

Kyoto Protocol (1997) set legally binding emission-reduction targets only for developed (Annex-I) countries. The Paris Agreement (2015) is universal, with all nations submitting voluntary Nationally Determined Contributions (NDCs) to limit warming to well below $2\,^{\circ}\text{C}$, aiming for $1.5\,^{\circ}\text{C}$, above pre-industrial levels.