Air Pollution And Its Control

The increasing human population exerts pressure on natural resources and contributes to pollution. Pollution is any undesirable change in the physical, chemical, or biological characteristics of air, land, water, or soil. Pollutants are the agents causing such changes. To address this, the Government of India passed the Environment (Protection) Act, 1986.

Air pollution affects living organisms by causing respiratory problems, reducing crop yield, and damaging plants. Harmful effects depend on pollutant concentration, exposure duration, and the organism's sensitivity.

Major sources of air pollution include smokestacks of thermal power plants, smelters, and other industries, as well as automobiles. These release particulate and gaseous pollutants.

Methods to control air pollution:

• Electrostatic precipitator: Widely used to remove over 99% of particulate matter from industrial exhausts. It uses an electric field to charge dust particles and attract them to collecting plates. Air velocity must be low to allow particles to settle.
• Scrubber: Removes gaseous pollutants like sulfur dioxide. Exhaust gases are passed through a spray of water or lime, which absorbs or reacts with the pollutant.

Fine particulate matter, especially those 2.5 micrometers or less in diameter (PM 2.5), is a significant health concern. These can penetrate deep into the lungs, causing respiratory problems, irritation, inflammation, lung damage, and premature death.

Automobiles are a major source of air pollution in urban areas. Pollutants from vehicles include hydrocarbons, carbon monoxide, and nitrogen oxides. Reducing vehicular pollution involves:

• Proper maintenance of vehicles.
• Using lead-free petrol or diesel (lead inactivates catalysts in catalytic converters).
• Fitting catalytic converters in vehicles. These contain expensive metals (platinum-palladium, rhodium) that convert toxic pollutants into less harmful substances (unburnt hydrocarbons to $\textsf{CO}_2$ and water; CO to $\textsf{CO}_2$; nitric oxide to nitrogen gas).

The Air (Prevention and Control of Pollution) Act in India (1981, amended 1987) also includes noise as an air pollutant. Noise is undesirable high-level sound, causing psychological and physiological disorders (sleeplessness, increased heart rate, altered breathing). Chronic exposure to noise can cause permanent hearing damage. Reducing noise pollution involves using sound-absorbent materials, muffling noise, and enforcing regulations on noise levels, horn-free zones, and loudspeaker usage timings.

---

Controlling Vehicular Air Pollution: A Case Study Of Delhi

Delhi faced severe air pollution problems due to its large number of vehicles. In the 1990s, it was among the world's most polluted cities. Following a Public Interest Litigation (PIL) and Supreme Court directives, the government implemented measures to reduce vehicular pollution:

• Transitioning public transport (buses) from diesel to Compressed Natural Gas (CNG) by the end of 2002. CNG burns more efficiently and completely than petrol or diesel, producing very little unburnt pollutants. CNG is also cheaper and harder to adulterate. Challenges include infrastructure for distribution.
• Phasing out old vehicles.
• Using unleaded petrol and low-sulfur petrol/diesel.
• Mandatory use of catalytic converters in vehicles.
• Implementing stricter emission norms for vehicles (e.g., Bharat Stage norms, equivalent to Euro norms). Newer norms (like Bharat Stage IV) stipulate reduced sulfur and aromatic content in fuels.

Table of Mass Emission Standards in India:

Type of Vehicles	Norms	Cities of Implementation
4 Wheelers	Bharat Stage IV	Throughout the country since April 2017
3 Wheelers	Bharat Stage IV	Throughout the country since 1st April 2017
2 Wheelers	Bharat Stage IV	Throughout the country since April 2017

These efforts have led to a significant improvement in Delhi's air quality, with a substantial reduction in levels of $\textsf{CO}_2$ and $\textsf{SO}_2$ observed between 1997 and 2005.

Water Pollution And Its Control

Water bodies are essential lifelines, but they are often polluted by human disposal of various wastes, including domestic sewage, industrial effluents, and agricultural runoff. This degrades water quality worldwide.

To protect water resources, the Government of India passed the Water (Prevention and Control of Pollution) Act, 1974.

---

Domestic Sewage And Industrial Effluents

Domestic sewage is waste water from homes and towns, primarily containing human excreta. Even a small amount (0.1%) of impurities makes domestic sewage unfit for human use. Sewage contains suspended solids, colloidal materials, and dissolved substances (salts, nutrients, organic compounds).

Sewage should be treated in Sewage Treatment Plants (STPs) before discharge into water bodies. While solids are removed in primary treatment, removing dissolved impurities (nitrates, phosphates, toxic metal ions) is more challenging.

Domestic sewage contains biodegradable organic matter that is readily decomposed by bacteria and other microorganisms. The amount of biodegradable organic matter in sewage is measured by Biochemical Oxygen Demand (BOD). Microorganisms decomposing organic matter consume dissolved oxygen. High BOD indicates high organic pollution and high oxygen consumption by microbes, leading to a drop in dissolved oxygen levels in the water body.

Discharge of untreated sewage into rivers causes a sharp decline in Dissolved Oxygen (DO) downstream, leading to fish mortality and death of other aquatic organisms.

High nutrient content (especially nitrates and phosphates) in polluted water causes excessive growth of planktonic algae, forming algal blooms. Algal blooms give water bodies a distinct color, deteriorate water quality, cause fish mortality, and some are toxic. Water hyacinth (*Eichhornia crassipes*), an invasive aquatic weed often called 'Terror of Bengal', grows rapidly in nutrient-rich (eutrophic) waters, blocking waterways and disturbing ecosystem dynamics.

Untreated sewage, especially from hospitals, can contain pathogenic microorganisms causing outbreaks of diseases like dysentery, typhoid, jaundice, and cholera.

Industrial effluents, from industries like petroleum, paper, metal processing, and chemical manufacturing, often contain toxic substances, notably heavy metals (mercury, cadmium, lead) and organic compounds.

Toxic substances that accumulate in organisms and are not metabolised or excreted can increase in concentration at successive trophic levels in a food chain. This phenomenon is called biomagnification or biological magnification. It is well-known for mercury and DDT.

Example: DDT concentration can increase from 0.003 ppb in water to 25 ppm in fish-eating birds through biomagnification. High DDT levels in birds disrupt calcium metabolism, causing thin eggshells that break prematurely, leading to population decline.

Eutrophication: The natural aging process of a lake due to nutrient enrichment. Over millennia, nutrients accumulate, increasing aquatic life, and organic matter/silt fills the lake, making it shallower and warmer, eventually converting it to land (bog). Cultural or accelerated eutrophication is caused by human activities that accelerate this process (sewage, industrial, and agricultural wastes adding nitrates and phosphates).

Accelerated eutrophication leads to algal blooms, unpleasant odors, and depletion of dissolved oxygen as organic matter decomposes, harming other aquatic life. This can cause the lake to 'choke to death'.

Thermal pollution: Heated wastewater from power plants can raise water temperature. This reduces DO, eliminates temperature-sensitive organisms, and can harm indigenous flora and fauna, though it might enhance growth of some species in cold regions.

---

A Case Study Of Integrated Waste Water Treatment

Wastewater can be treated using a combination of artificial and natural processes. The town of Arcata, California, developed an integrated wastewater treatment process:

1. Conventional treatment: Sedimentation, filtering, and chlorine treatment (removes solids and some pollutants).
2. Natural treatment: The treated water flows through a series of six constructed marshes (60 hectares). Appropriate plants, algae, fungi, and bacteria were introduced. These organisms naturally neutralise, absorb, and assimilate residual pollutants like heavy metals.

As water passes through the marshes, it gets purified naturally. The marshes also serve as a sanctuary with high biodiversity (fish, animals, birds). A citizens' group (Friends of the Arcata Marsh - FOAM) manages and protects the project.

Ecological sanitation ('EcoSan'): A sustainable system for handling human excreta using dry composting toilets. It avoids using water for waste disposal, saving large amounts of water. Excreta is recycled into natural fertilizer, reducing the need for chemical fertilizers. EcoSan toilets are operational in parts of Kerala and Sri Lanka.

Solid Wastes

Solid wastes include everything discarded as trash from homes, offices, schools, hospitals, etc., collected and disposed by municipalities (municipal solid wastes). They comprise paper, food waste, plastics, glass, metals, rubber, textiles, etc.

Methods of solid waste disposal:

• Burning: Reduces waste volume but often incomplete combustion occurs in open dumps. Open dumps attract rodents and flies.
• Sanitary landfills: Replaced open dumps. Waste is compacted and dumped in trenches/depressions, covered daily with dirt. Landfills are temporary solutions as they fill up, and there's a risk of leachate (liquid from waste) polluting groundwater.

Managing solid waste effectively requires reducing waste generation and proper segregation. Wastes can be categorised into: (a) biodegradable, (b) recyclable, and (c) non-biodegradable. Recyclable waste (paper, plastics, glass, metal) should be separated (often done by rag-pickers) and sent for recycling. Biodegradable waste (food waste, plant remains) can be decomposed naturally in composting pits to produce manure. Non-biodegradable waste (mostly plastics) is the most problematic and needs proper disposal.

Reducing the use of non-biodegradable materials, especially plastics in packaging, is crucial. Hospitals generate hazardous wastes (disinfectants, chemicals, pathogens) requiring careful disposal, often by incineration.

Electronic wastes (e-wastes): Irreparable electronic goods (computers, etc.). Disposed in landfills or incinerated. Developed countries export much e-waste to developing countries (China, India, Pakistan) for metal recovery through recycling, often under hazardous manual conditions for workers exposed to toxic substances. Environment-friendly recycling is the only viable solution.

---

Case Study Of Remedy For Plastic Waste

Ahmed Khan, a plastic sack manufacturer in Bangalore, developed 'Polyblend', a fine powder of recycled modified plastic. Polyblend is mixed with bitumen used for laying roads. Collaboration with R.V. College of Engineering and Bangalore City Corporation showed that using Polyblend-bitumen blends enhanced bitumen's water-repellent properties and significantly increased road life (by a factor of three). Polyblend uses any plastic film waste as raw material, providing a market for plastic waste and potentially reducing accumulation. By 2002, over 40 kms of road in Bangalore used this technique. This innovation offers a way to reuse plastic waste in a beneficial manner.

Agro-Chemicals And Their Effects

The Green Revolution led to increased use of inorganic fertilizers and pesticides (insecticides, herbicides, fungicides) to boost crop production. These chemicals can be toxic to non-target organisms in the soil ecosystem. Excess use of chemical fertilizers can also cause eutrophication in aquatic ecosystems (as discussed in water pollution).

The widespread use of agro-chemicals presents significant environmental and health challenges in modern agriculture.

---

Case Study Of Organic Farming

Integrated organic farming is a sustainable, zero-waste approach. Waste products from one process are used as nutrients or inputs for other processes, maximizing resource utilization and efficiency. Ramesh Chandra Dagar in Haryana practices this, integrating bee-keeping, dairy management, water harvesting, composting, and agriculture.

• Cattle excreta (dung) is used as manure for crops, eliminating the need for chemical fertilizers.
• Crop waste is composted for natural fertilizer or used to produce biogas for energy needs.

This cyclical system is economical and sustainable, reducing pollution and enhancing production efficiency. Dagar promotes these practices through the Haryana Kisan Welfare Club, helping other farmers adopt integrated organic farming.

Radioactive Wastes

Nuclear energy was initially seen as a clean energy source. However, it poses two major problems:

1. Risk of accidental leakage: Incidents like Three Mile Island and Chernobyl demonstrated the catastrophic consequences of nuclear accidents.
2. Safe disposal of radioactive wastes: Radioactive waste is highly damaging to organisms. Radiation causes mutations at a high rate. High doses are lethal, and lower doses cause disorders, particularly cancer. Radioactive waste is a potent and hazardous pollutant requiring utmost caution in handling and disposal.

Recommended disposal method: After pre-treatment, radioactive waste should be stored in shielded containers and buried deep (about 500m) within rocks below the Earth's surface. This method faces public opposition due to concerns about potential leakage over long periods and the long half-lives of some radioactive isotopes.

Greenhouse Effect And Global Warming

The Greenhouse effect is a natural phenomenon that warms the Earth's surface and atmosphere. Without it, Earth's average temperature would be much colder (around $-18^\circ\textsf{C}$ instead of $15^\circ\textsf{C}$).

Mechanism:

• About one-fourth of incoming solar radiation is reflected by clouds and gases.
• Some is absorbed by atmospheric gases.
• About half falls on Earth's surface, heating it.
• Earth's surface re-emits heat as infrared radiation.
• Greenhouse gases ($\textsf{CO}_2$, methane, $\textsf{N}_2\textsf{O}$, CFCs) in the atmosphere absorb a large fraction of this re-emitted infrared radiation.
• These greenhouse gas molecules then radiate heat energy in all directions, including back towards Earth's surface, further warming it. This creates a cycle that traps heat.

Increased concentrations of greenhouse gases in the atmosphere are primarily responsible for the enhanced greenhouse effect, leading to global warming (an increase in the Earth's average temperature).

Earth's temperature increased by $0.6^\circ\textsf{C}$ over the past century, mostly in the last three decades. This warming is causing changes in the environment, including altered climate patterns (e.g., El Niño), increased melting of polar ice caps and glaciers (Himalayan snow caps), potentially leading to a rise in sea level that could submerge coastal areas.

Controlling global warming requires:

• Reducing the use of fossil fuels.
• Improving energy efficiency.
• Reducing deforestation and promoting afforestation (planting trees).
• Slowing down human population growth.

International efforts are being made to reduce greenhouse gas emissions.

Ozone Depletion In The Stratosphere

Ozone ($\textsf{O}_3$) exists in two layers of the atmosphere: 'bad' ozone in the troposphere (lower atmosphere) is a pollutant harmful to plants and animals; 'good' ozone in the stratosphere (upper atmosphere) forms a protective shield that absorbs harmful ultraviolet (UV) radiation from the sun.

UV rays are dangerous as their high energy can break chemical bonds in DNA and proteins, causing mutations and damage to living organisms. The thickness of the ozone layer is measured in Dobson units (DU).

In the stratosphere, ozone is continuously formed by the action of UV rays on molecular oxygen ($\textsf{O}_2$), and also degraded back into $\textsf{O}_2$. Normally, there's a balance between ozone production and degradation.

This balance has been disrupted by human-made chemicals, particularly chlorofluorocarbons (CFCs), which are widely used as refrigerants and in aerosols. CFCs released in the troposphere slowly rise to the stratosphere. In the stratosphere, UV radiation breaks down CFCs, releasing chlorine (Cl) atoms.

Chlorine atoms act as catalysts in the breakdown of ozone: Cl atoms react with $\textsf{O}_3$ to form ClO and $\textsf{O}_2$. ClO then reacts with free oxygen atoms to release the Cl atom again, which can further destroy ozone. Since Cl atoms are not consumed in the reaction, a single Cl atom can destroy many ozone molecules, having a permanent effect on ozone levels.

Ozone depletion is occurring globally in the stratosphere, but it is most pronounced over the Antarctic region, particularly during the spring. This leads to the formation of a thinned area called the ozone hole.

Effects of enhanced UV radiation (particularly UV-B) due to ozone depletion:

• UV-B damages DNA and can cause mutations.
• Causes aging of skin and various types of skin cancers.
• In human eyes, UV-B is absorbed by the cornea. High doses can cause inflammation of the cornea (snow-blindness), cataract, and potentially permanent corneal damage.

To address ozone depletion, the Montreal Protocol was signed in 1987 (effective 1989) to control the emission of ozone-depleting substances (ODS), particularly CFCs. Subsequent efforts and protocols have set timelines for reducing ODS emissions by developed and developing countries.

Degradation By Improper Resource Utilisation And Maintenance

Natural resources can be degraded not only by pollution but also by unsustainable or improper utilization practices.

• Soil erosion and desertification: Fertile topsoil is formed slowly but can be easily lost due to human activities like over-cultivation, unrestricted grazing, deforestation, and poor irrigation. Loss of topsoil leads to less fertile land. When vegetation is lost and arid patches expand, it can lead to desertification, particularly exacerbated by increasing urbanization.
• Waterlogging and soil salinity: Irrigation without adequate drainage leads to waterlogging in the soil. Waterlogging can draw salts from deeper soil layers to the surface, accumulating as a crust or around plant roots. Increased soil salinity is harmful to crop growth and severely damages agriculture. These problems have become more prominent in areas practicing intensive irrigation, like those benefiting from the Green Revolution.

Deforestation

Deforestation is the conversion of forested areas for non-forest uses (agriculture, urban development, logging). Tropical forests have experienced significantly higher rates of deforestation (40% lost) compared to temperate regions (1% lost).

India's forest cover has shrunk significantly from ~30% at the start of the 20th century to 21.54% by its end, falling short of the recommended 33% for plains and 67% for hills by the National Forest Policy (1988).

Causes of deforestation:

• Conversion of forests to agricultural land to feed a growing population.
• Logging for timber, firewood, and cattle ranching.
• Slash and burn agriculture (Jhum cultivation): Practiced in northeastern India. Trees are cut and burned; ash is used as fertilizer for temporary farming/grazing. The land is left fallow to recover, but with increasing population and repeated cultivation without sufficient recovery time, it leads to deforestation.

Consequences of deforestation:

• Increased atmospheric carbon dioxide concentration (trees store large amounts of carbon).
• Loss of biodiversity due to habitat destruction.
• Disturbance of the hydrologic cycle (water cycle).
• Increased soil erosion.
• Potential for desertification.

Reforestation is the process of restoring forests in areas that were previously forested. It can occur naturally or be accelerated by planting trees, ideally restoring the original biodiversity of the area.

---

Case Study Of People’S Participation In Conservation Of Forests

Community involvement is crucial for forest conservation in India, with historical examples:

• Bishnoi community (Rajasthan): In 1731, the king of Jodhpur ordered trees to be cut for a palace. The Bishnois, known for nature coexistence, protested. Amrita Devi Bishnoi and her daughters, along with hundreds of other Bishnois, sacrificed their lives by hugging trees to prevent logging. This event is a powerful example of dedication to environmental protection. The Government of India instituted the Amrita Devi Bishnoi Wildlife Protection Award to honor such courage.
• Chipko Movement (Garhwal Himalayas): In 1974, local women protected trees from logging contractors by hugging them. This non-violent protest gained international recognition.

Recognizing the effectiveness of local participation, the Government of India introduced Joint Forest Management (JFM) in the 1980s. JFM involves local communities working with the forest department to protect and manage nearby forests. Communities benefit from forest products, which incentivizes them to conserve forests sustainably.

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer:

Answer: