Environmental Science

UNIT 2: Water and Air Pollution

What is Water Pollution?

Water pollution occurs when harmful substances contaminate bodies of water, making them unsafe for human use or the environment. These substances can include chemicals, microorganisms, trash, or energy in the form of heat or radioactivity.

Water Resources of India

India accounts for about 2.45 per cent of world's surface area, 4 per cent of the world's water resources and about 16 per cent of world's population.

Surface Water Resources

There are four major sources of surface water. These are rivers, lakes, ponds, and tanks. In the country, there are about 10,360 rivers and their tributaries longer than 1.6 km each. The mean annual flow in all the river basins in India is estimated to be 1,869 cubic km. However, due to topographical, hydrological and other constraints, only about 690 cubic km (32 per cent) of the available surface water can be utilised.

Groundwater Resources

The total replenishable groundwater resources in the country are about 432 cubic km. The level of groundwater utilisation is relatively high in the river basins lying in north- western region and parts of south India. The groundwater utilisation is very high in the states of Punjab, Haryana, Rajasthan, and Tamil Nadu.

Lagoons and Backwaters

India has a vast coastline and the coast is very indented in some states. Due to this, a number of lagoons and lakes have formed. The States like Kerala, Odisha and West Bengal have vast surface water resources in these lagoons and lakes. Although, water is generally brackish in these water-bodies, it is used for fishing and irrigating certain varieties of paddy crops, coconut, etc.

The Hydrologic Cycle / Water cycle

The hydrologic cycle involves the continuous circulation of water in the Earth-Atmosphere system. At its core, the water cycle is the motion of the water from the ground to the atmosphere and back again.

The hydrological cycle, also known as the water cycle, is a continuous process that circulates water throughout the Earth's atmosphere, surface, and underground. Here's a breakdown of the key stages:

1. Evaporation

Evaporation is the process by which water changes from a liquid to a gas, or vapor, due to the heat from the sun. This process occurs primarily in oceans, rivers, and lakes, but it can happen on any wet surface. As water vapor rises into the atmosphere, it cools and eventually condenses to form clouds.

2. Transpiration

Transpiration is the release of water vapor from plants and soil into the atmosphere. Plants absorb water through their roots, which travels up to the leaves where it is used in photosynthesis. Excess water then escapes as vapor through tiny pores on the leaf surface called stomata. Together with evaporation, this stage is often called "evapotranspiration."

3. Condensation

Condensation is the process by which water vapor cools and changes back into liquid droplets. This occurs when warm, moist air rises and cools in the upper atmosphere. Condensation leads to the formation of clouds and mist, as water droplets cluster around tiny particles like dust in the air.

4. Precipitation

Precipitation occurs when water droplets in clouds become heavy enough to fall to Earth due to gravity. Precipitation can take various forms, including rain, snow, sleet, or hail, depending on the temperature of the atmosphere. This process returns water to the Earth's surface.

5. Runoff

Runoff is the movement of water across the Earth's surface. When precipitation reaches the ground, it can flow over land as surface runoff, entering rivers, lakes, and eventually oceans. Some water infiltrates into the soil, replenishing groundwater. Runoff is essential in connecting water sources, ensuring that water travels through various landscapes and reaches larger bodies of water.

Methods of Water Conservation & Management

Water conservation refers to the prudent management and preservation of water resources to ensure their sustainable use for present and future generations. It involves reducing wastage, improving efficiency in water usage, and implementing strategies to replenish and protect water sources.

Water Recycling and Reuse

Water recycling and reuse involve treating wastewater to make it suitable for various non-potable purposes, such as irrigation, industrial processes, and urban landscaping. In India, wastewater treatment plants are being increasingly deployed in cities to treat sewage and industrial effluents.

Afforestation and Soil Conservation

Forests play a crucial role in regulating the water cycle by influencing rainfall patterns, reducing soil erosion, and maintaining groundwater recharge. Afforestation and soil conservation measures such as reforestation, agroforestry, and contour bunding help preserve watersheds, enhance soil moisture retention, and prevent runoff.

Rainwater Harvesting

It is the process of collection and storage of rainwater, rather than allowing it to run off. Rainwater is collected from the roof and is redirected to a tank, reservoir, cistern, or natural tanks, etc.

Groundwater Harvesting

It is a method for saving water placed under the ground to control the groundwater flow in an aquifer and to raise the water table.

Dams

Dams are simple hydraulic structures that act as a barrier between the source and destination of flowing water. Earlier times, these dams were very small and hand-made while in modern times, new engineering techniques and methods are used to construct large dams.

Drip Irrigation

It is a type of irrigation that saves water and fertiliser by dripping water slowly to the roots of various crops, either on the soil surface or directly to the root zone, through a network of pipes, tubing, and valves. This process saves more water compared to the traditional watering method.

Rain water harvesting and their Legal aspects

Rainwater harvesting is the simple process or technology used to conserve rainwater by collecting, storing, conveying and purifying of rainwater that runs off from rooftops, parks, roads, open grounds, etc. for later use.

The rainwater harvesting system is one of the best methods practised and followed to support the conservation of water. Today, scarcity of good quality water has become a significant cause of concern. However, rainwater, which is pure and of good quality, can be used for irrigation, washing, cleaning, bathing, cooking and also for other livestock requirements.

Method:

Rainwater harvesting systems consists of the following components:

Catchment - Used to collect and store the captured rainwater.
Conveyance system - It is used to transport the harvested water from the catchment to the recharge zone.
Flush - It is used to flush out the first spell of rain.
Filter - Used for filtering the collected rainwater and removing pollutants.
Tanks and the recharge structures: Used to store the filtered water which is ready to use.

The process of rainwater harvesting involves the collection and the storage of rainwater with the help of artificially designed systems that run off naturally or man-made catchment areas like- the rooftop, compounds, rock surface, hill slopes, artificially repaired impervious or semi-pervious land surface.

In India, due to increasing water scarcity, both central and state governments have implemented legal frameworks to promote and, in some cases, mandate RWH systems.

Compulsory Rainwater Harvesting in Government Establishments and Schools Bill, 2019

This bill proposes mandatory RWH systems in government buildings and schools across Union Territories to promote water conservation.

Model Building Bye-Laws 2016

Issued by the Ministry of Housing and Urban Affairs, these bye-laws include provisions for RWH. They recommend that all residential plots above 100 square meters incorporate RWH systems. As of March 2020, 33 States and Union Territories have adopted these provisions.

National Water Policy 2012

This policy emphasizes the need for rainwater harvesting to enhance water availability in urban and industrial areas. It encourages the revival of traditional water harvesting structures and the adoption of RWH practices across the country.

River Action Plans in India

India has implemented several River Action Plans to address the pollution and degradation of its rivers. These initiatives aim to improve water quality, restore ecosystems, and ensure sustainable management of river resources.

➢ National River Conservation Plan (NRCP): Launched in 1995, the NRCP is a centrally funded scheme by the Ministry of Environment and Forests (MoEF) focused on preventing river pollution and enhancing water quality. It encompasses various action plans for multiple rivers, including the establishment of sewage treatment plants, riverfront development, and water quality monitoring.
➢ Ganga Action Plan (GAP): Initiated in 1985, the GAP was one of the earliest efforts to combat pollution in the Ganga River. It involved constructing sewage treatment facilities, improving sanitation, and promoting public awareness. The program was later expanded to include the Yamuna and Gomti rivers under GAP Phase II in 1993.
➢ Namami Gange Programme: Building upon the GAP, the Namami Gange Programme was launched in 2014 as an integrated conservation mission to rejuvenate the Ganga River. It focuses on pollution abatement, river surface cleaning, afforestation, and biodiversity conservation.
➢ Yamuna Action Plan (YAP): Specifically targeting the Yamuna River, the YAP was initiated in 1993 under the NRCP. It aims to reduce pollution through sewage treatment, public participation, and environmental education.
➢ State-Specific Initiatives: Various states have undertaken their own river conservation projects. For instance, the Ramnadi Restoration Mission in Pune involves local colleges, environmental groups, and residents working together to restore the Ramnadi River.

Challenges and Progress

Despite these efforts, many rivers in India continue to face significant pollution challenges. A 2018 report by the Central Pollution Control Board identified 351 polluted river stretches across 323 rivers in the country. Continuous monitoring, public participation, and stricter enforcement of environmental regulations are essential to the success of these action plans.

Ground and surface water pollution

Groundwater and surface water pollution are significant environmental issues that affect water quality and availability for human use, agriculture, and natural ecosystems. Both types of pollution result from various sources and have severe consequences for health and the environment.

➢ Surface Water Pollution

Surface water includes rivers, lakes, ponds, streams, and oceans. Pollution in these bodies is often visible and easier to identify and measure than groundwater pollution. Major causes include:

Industrial Waste: Factories discharge heavy metals, toxic chemicals, and pollutants into rivers and lakes, contaminating water bodies.
Agricultural Runoff: Pesticides, herbicides, and fertilizers wash into water bodies, leading to nutrient pollution that can cause harmful algal blooms and disrupt aquatic life
Municipal Waste: Untreated sewage, garbage, and plastics from urban areas often end up in rivers and oceans, affecting water quality and marine ecosystems.
Oil Spills: Accidental oil spills from ships, pipelines, and offshore platforms lead to catastrophic contamination in water bodies.
Erosion and Sedimentation: Soil erosion from construction, deforestation, and mining activities increases sediment levels, which can block sunlight, harm aquatic plants, and disrupt aquatic habitats.

➢ Groundwater Pollution

Groundwater resides in underground aquifers and is usually harder to clean once polluted. Pollution sources often include:

Agricultural Chemicals: Pesticides and fertilizers seep through the soil and contaminate groundwater.
Leaking Storage Tanks: Underground storage tanks, especially those containing petroleum or industrial chemicals, can leak and pollute aquifers.
Landfills and Waste Sites: Poorly managed waste disposal sites allow contaminants to leach into the soil and reach groundwater.
Septic Systems: Malfunctioning septic systems release bacteria, viruses, and chemicals into the soil, which can then enter groundwater.
Mining Activities: Acid mine drainage from mines and mineral extraction sites contaminates groundwater with heavy metals and other harmful substances.

Wastewater Management

Wastewater management involves the collection, treatment, and safe disposal or reuse of water that has been contaminated by human, industrial, or agricultural activities. Effective wastewater management is crucial for protecting public health, preserving ecosystems, and ensuring the sustainable use of water resources.

➢ Key Components of Wastewater Management

Collection: Wastewater from households, industries, and agriculture is collected through a network of pipes and sewers. Proper infrastructure is essential to avoid leakage, contamination, and overflow, especially during heavy rains.
Treatment: Wastewater treatment involves physical, chemical, and biological processes to remove contaminants. Treatment processes can be divided into several stages:
- Primary Treatment: Physically removes large solids and sediments through screening and sedimentation.
- Secondary Treatment: Uses biological processes like activated sludge or biofilms to break down organic matter and reduce pathogens.
- Tertiary Treatment: Involves advanced filtration, chemical disinfection, and nutrient removal to further purify water, making it safe for discharge or reuse.
- Advanced Treatment: Some facilities apply processes like membrane filtration, UV treatment, or reverse osmosis for high-quality reuse, especially for industrial or potable applications.
Disposal: Treated wastewater is either released into nearby rivers, lakes, or oceans, or applied to land. Proper treatment is essential before disposal to protect water bodies from pollution and prevent harm to aquatic life.
Reuse and Recycling: Treated wastewater can be reused for non-potable applications, such as irrigation, industrial processes, and landscape watering, or even potable uses in water-scarce regions with advanced treatment. Recycling reduces the strain on freshwater sources.

Challenges

Inadequate Infrastructure
High Costs
Complex Industrial Waste
Population Growth and Urbanization
Water Scarcity and Climate Change

Benefits

Environmental Protection
Public Health
Water Conservation
Economic Savings

AIR POLLUTION

Air Pollution and Air Pollutants

Air pollution is contamination of the indoor or outdoor environment by any chemical, physical or biological agent that modifies the natural characteristics of the atmosphere. Household combustion devices, motor vehicles, industrial facilities and forest fires are common sources of air pollution.

➢ Causes of Air Pollution / sources of air pollution

Air Pollutants of major public health concern include particulate matter, carbon monoxide, ozone, nitrogen dioxide and sulfur dioxide. Outdoor and indoor air pollution cause respiratory and other diseases and are important sources of morbidity and mortality.

1) Natural Causes

Volcanic eruptions (release of sulfur dioxide and ash).
Forest fires (emission of carbon monoxide and particulate matter).
Dust storms.

2) Human Activities

Burning fossil fuels (coal, oil, and natural gas for energy and transport).
Industrial emissions (chemical byproducts, particulates, and volatile organic compounds).
Agriculture (ammonia from fertilizers and methane from livestock).
Deforestation (reduced capacity of plants to absorb carbon dioxide).

1) Primary Pollutants

Directly emitted from a source. Examples:

Carbon monoxide (CO): From vehicle exhaust and incomplete combustion.

Secondary Pollutants

Formed in the atmosphere through chemical reactions of primary pollutants.

📌 Examples:

Ozone (O₃)

From NOx and volatile organic compounds (VOCs) under sunlight.

Acid Rain

From SO₂ and NOx reacting with water vapor.

Smog

A mixture of air pollutants, including ozone and particulates.

Did You Know?

Secondary pollutants are often more harmful than primary pollutants because they form new chemical compounds that can be toxic or cause environmental damage.

Effects of Air Pollution

On Human Health

Respiratory Issues:
• Exposure to particulate matter (PM2.5 and PM10) can cause asthma, bronchitis, and lung cancer.
• Ozone can irritate the respiratory tract and exacerbate conditions like chronic obstructive pulmonary disease (COPD).
Cardiovascular Problems:
• Air pollutants like carbon monoxide and particulate matter can increase the risk of heart attacks and strokes.
Nervous System Effects:
• Prolonged exposure to heavy metals like lead can damage the nervous system.
• Neurodevelopmental issues in children due to air toxins.
Chronic Diseases:
• Long-term exposure can lead to cancers, weakened immune systems, and premature aging.
Acute Health Effects:
• Eye irritation, headaches, and throat discomfort due to exposure to pollutants like nitrogen dioxide and sulfur dioxide.

On Vegetation

Growth Inhibition:
• Ozone damages plant tissues, reducing photosynthesis and growth.
Crop Yield Reduction:
• Acid rain affects soil fertility, impacting crops like wheat, rice, and maize.
• Particulate deposition blocks sunlight, reducing plant productivity.
Leaf Damage:
• Airborne pollutants like fluorides and sulfur compounds cause leaf chlorosis (yellowing) and necrosis (cell death).
Reduced Nutrient Absorption:
• Acid rain leaches essential nutrients from the soil, affecting plant health.
Forest Decline:
• Prolonged exposure to pollutants weakens trees, making them more susceptible to diseases and pests.

1) Primary Pollutants

Directly emitted from a source. Examples:

Carbon monoxide (CO): From vehicle exhaust and incomplete combustion.
Sulfur dioxide (SO₂): From burning coal and oil.
Nitrogen oxides (NOx): From vehicles and power plants.
Particulate matter (PM): Dust, soot, or tiny solid particles.
Methane (CH₄): From agricultural activities and landfills.

2) Secondary Pollutants

Formed in the atmosphere through chemical reactions of primary pollutants. Examples:

Ozone (O₃): From NOx and volatile organic compounds (VOCs) under sunlight.
Acid rain: From SO₂ and NOx reacting with water vapor.
Smog: A mixture of air pollutants, including ozone and particulates.

Prevention and Control of Air Pollution

Use renewable energy sources like solar and wind.
Promote public transportation and electric vehicles.
Implement stricter industrial emission standards.
Encourage afforestation and sustainable land use practices.
Adopt cleaner cooking and heating solutions in households.

Greenhouse Effect

The greenhouse effect is a natural process that warms the Earth's surface by trapping heat from the sun in the atmosphere. This process is essential for life on Earth, keeping the planet's average temperature around 33°C warmer than it would be without it.

Here's how the greenhouse effect works:

Sunlight: The sun's energy reaches the Earth's atmosphere, and some of it is reflected back into space.
Absorption: The remaining energy is absorbed by the Earth's surface and atmosphere.
Radiation: The Earth radiates heat back into space as infrared radiation.
Trapping: Some of the infrared radiation is trapped by greenhouse gases in the atmosphere, preventing it from escaping into space.

Key Greenhouse Gases

Water Vapor (H₂O)
Carbon Dioxide (CO₂)
Methane (CH₄)
Nitrous Oxide (N₂O)
Chlorofluorocarbons (CFCs) and Hydrofluorocarbons (HFCs)

Natural Causes

Water Vapor (H₂O):
• Evaporation: Water evaporates from oceans, rivers, and lakes, increasing atmospheric water vapor.
• Amplification: Warmer temperatures lead to more evaporation, enhancing the greenhouse effect.
Volcanic Eruptions:
• Release of carbon dioxide (CO₂), water vapor, and other gases during eruptions contributes to the greenhouse effect.
• Volcanic aerosols may also temporarily cool the Earth by reflecting sunlight.
Natural Methane Emissions:
• Wetlands and other water-logged ecosystems release methane due to the anaerobic decomposition of organic matter.
Forest Fires:
• Emit CO₂, methane (CH₄), and particulate matter into the atmosphere.

Human Activities (Anthropogenic Causes)

Burning Fossil Fuels:
• Combustion of coal, oil, and natural gas for energy and transportation produces significant amounts of CO₂.
• Primary sources: power plants, vehicles, industrial activities, and residential heating.
Deforestation:
• Trees act as carbon sinks by absorbing CO₂.
• Clearing forests for agriculture or urbanization releases stored CO₂ and reduces the Earth's capacity to absorb atmospheric carbon.
Industrial Processes:
• Manufacturing and chemical industries emit potent greenhouse gases like nitrous oxide, methane, and fluorinated gases (CFCs, HFCs).
• Cement production releases CO₂ during the chemical reaction to produce lime.
Landfills and Waste Management:
• Organic waste in landfills decomposes anaerobically, releasing methane.
• Improper waste combustion emits CO₂ and other harmful gases.
Transportation:
• Cars, airplanes, ships, and trucks emit CO₂ and other greenhouse gases.

Effects of Greenhouse Effect

The main effects of increased greenhouse gases are:

Global Warming

It is the phenomenon of a gradual increase in the average temperature of the Earth's atmosphere. The main cause for this environmental issue is the increased volumes of greenhouse gases such as carbon dioxide and methane released by the burning of fossil fuels, emissions from the vehicles, industries and other human activities.

Depletion of Ozone Layer

Ozone Layer protects the earth from harmful ultraviolet rays from the sun. It is found in the upper regions of the stratosphere. The depletion of the ozone layer results in the entry of the harmful UV rays to the earth's surface that might lead to skin cancer and can also change the climate drastically. The major cause of this phenomenon is the accumulation of natural greenhouse gases including chlorofluorocarbons, carbon dioxide, methane, etc.

Smog and Air Pollution

Smog is formed by the combination of smoke and fog. It can be caused both by natural means and man-made activities. In general, smog is generally formed by the accumulation of more greenhouse gases including nitrogen and sulfur oxides. The major contributors to the formation of smog are automobile and industrial emissions, agricultural fires, natural forest fires and the reaction of these chemicals among themselves.

Acidification of Water Bodies

Increase in the total amount of greenhouse gases in the air has turned most of the world's water bodies acidic. The greenhouse gases mix with the rainwater and fall as acid rain. This leads to the acidification of water bodies. Also, the rainwater carries the contaminants along with it and falls into the river, streams and lakes thereby causing their acidification.