Environmental Pollution: Causes and Pollutants

Environmental Pollution

• Pollution occurs when harmful substances are added to the surroundings like air, water, and land
• Makes them dirty and unsafe for living things

Causes of Pollution

• Pollution can be caused by several factors
• Natural causes of pollution include:
• Volcanic eruptions
• Earthquakes
• Storms and dust
• UV radiations
• Decay of organic matter
• Release of H2S and micro organisms
• Man-made causes of pollution include:
• Commercial activities
• Industrial activities
• Overpopulation
• Urbanization
• Use of insecticides and pesticides
• Organic chemicals
• Use of vehicles
• Mining
• Nuclear explosions
• Explosives used in wars
• Construction of buildings, roads, and dams

Pollutants

• Pollutants are substances or energy introduced into the environment
• Have undesired effects
• Adversely affect of the usefulness of a resource

Types of Pollutants:

• Pollutants can be classified by nature of material:
• Biodegradable pollutants
• Degraded/decomposed naturally by the action of bacteria
• Example: municipal waste water, wood, paper, garbage, and cardboard
• Non-biodegradable pollutants
• Cannot be degraded/decomposed naturally, or degrade very slowly
• Example: DDT, plastic, glass, polythene bags, and e-waste
• Pollutants can be classified by their concentration in nature:
• Quantitative pollutants
• Substances that normally occur in the environment, but become pollutants when their concentration increases above the allowable limit
• Example: CO2, when released in excess amounts, can cause a greenhouse effect
• Qualitative pollutants
• Substances that do not occur naturally in the environment, but are added by humans for different purposes
• Example: Insecticides, pesticides, and germicides
• Pollutants can be classified by their form:
• Primary pollutants
• Substances which remain in the environment in the same form in which they are added
• Also called direct pollutants
• Example: Smoke, ash, dust and aldehydes
• Secondary pollutants
• Substances which do not occur naturally in the environment, but are added by humans for different purposes
• Formed from primary pollutants
• Considered more toxic than primary pollutants
• Example: SO3, ketones, PAN, ozone, aldehydes
• Pollutants can be classified by their sources:
• Natural pollutants
• Pollutants released naturally
• Due to volcanic eruptions, forest fires, storms, decay of organic material, wind, and dust
• Man-made pollutants
• Pollutants generated by different human activities
• Industrialization
• Deforestation
• Mining
• Urbanization
• Explosions in wars
• Use of fertilizers

Types of Pollution

• There are different types of pollution
• Water pollution
• Air pollution
• Land pollution
• Noise pollution
• Radioactive pollution
• Thermal pollution

Air Pollution

• The condition when harmful substances get mixed into the air we breathe
• Changes its normal makeup
• These harmful things can be gases or tiny particles
• Originate from things like cars, factories, or even natural events like fire

Air Pollutants

• Anything that makes the air dirty and unhealthy
• Can be classified based on origin, states of matter, and presence in the environment:
• Classification based on origin of pollutant:
• Primary air pollutants
• Directly released from the source into the atmosphere and remains in the same form
• Sulfur oxides, nitrogen oxides, carbon monoxide, hydrocarbons, radioactive materials, particulate matter (ash, smoke, dust, mist)
• Result from man-made sources like transport, fuel combustion, industrial operations and solid waste disposal
• Secondary air pollutants
• Formed by chemical reactions among primary pollutants and atmospheric chemical things
• Ozone, sulphur trioxide, ketones, PAN
• Classification based on state of matter:
• Gaseous air pollutants
• Particulate air pollutants
• Gaseous air pollutants
• Found in the gaseous state at normal temperature and pressure in the atmosphere
• Common examples: carbon monoxide, carbon dioxide, nitrogen oxide, sulfur oxide
• Particulate air pollutants
• Tiny specks of dust or smoke that are so small that you can breathe them in
• Come from cars, factories
• Not good for lungs
• Further classified as aerosols, dust, fumes, mist, smoke, fly ash, soot
• Classification based on presence in environment
• Indoor air pollutants
• Outdoor air pollutants

Indoor Air Pollutants

• Generated from households
• Include cleaning agents, mosquito repellents, pesticides, paints, glues, varnishes, cigarette smoke, and gases from stoves

Outdoor Air Pollutants

• Generated outside the building
• Include automobile pollutants, industrial and mining emissions, natural emissions from decaying organic matter and animals

Units of Measurement for Air Pollutants

• µg/m³ = micrograms per cubic meter
• ppm = parts per million

Sources of Air Pollutants

• Classified into two groups
  • Natural sources
  • Man-made sources

Natural Sources of Air Pollution

• In the atmosphere, different types of chemical reactions are always ongoing
• In the lower atmosphere the gases and vapours are converted in solids and liquids
• Types of natural sources:
• Volcanoes: Explode and send out dusty, smelly gases
• Wildfires: Burn forests and make smoky air
• Dust Storms: Blow lots of dusty dirt around
• Plants: Release natural smells that can mix with other stuff in the air
• Ocean: Splashes up fine salt bits into the air
• Things Rotting: Release gases as they break down
• Lightning: Makes some air chemicals change

Man-Made Sources of Air Pollution

• Cars and Trucks: Burn fuel, which releases gases and tiny particles into the air
• Factories: Often burn fuel or use chemicals that create pollution
• Power Plants: Many power plants burn coal or natural gas, which releases pollutants
• Burning Trash: Burning trash, wood, or anything else releases smoke and harmful particles
• Farming: Some farming practices release gases like ammonia into the air
• Construction: Construction sites release dust and particles into the air

Effects of Air Pollution

• Harm to Human Health
• Respiratory diseases like asthma and bronchitis
• Increases the risk of stroke, heart disease, and lung cancer
• Vulnerable groups, such as children and the elderly, are at higher risk
• Harm to Plants & Vegetation
• Damages plants by affecting photosynthesis, causing leaf discoloration, and reducing growth -Pollutants like SO2, NOx, and ozone weaken plants
• Acid rain and heavy metals harm soil health, leading to lower crop yields and ecosystem disruption
• Harm to Materials & Buildings
• Causes corrosion, discoloration, and structural damage to buildings and materials
• Acid rain erodes stone and metal
• Pollutants like soot stain surfaces, accelerating degradation and increasing maintenance costs
• Harm to Climate
• Contributes to climate change by trapping heat
• Accelerating ice melt
• Disrupting weather patterns
• Greenhouse gases warm the earth
• Aerosols affect cloud formation & rainfall, leading to long-term climate instability
• Harms to Animals
• Causes respiratory issues and contamination of feed and water sources
• Results in habitat damage, disrupted ecosystems and migration

Aesthetic Pollution

• Diminishes aesthetic beauty by staining buildings, reducing visibility with smog, and damaging natural landscapes and monuments

Control of Air Pollution

• Less Smoky Stuff
• Use electric cars or cleaner ways to make things to make less smoke
• Saving Energy
• Turn off lights
• Helps use less energy from power plants which make pollution

Other methods of Air Pollution Control

• Planting Trees
• Walking & Biking
• Recycling

Air Pollution Control Equipments

• Gravitational settling chamber
• Cyclone separator
• Electrostatic precipitators
• Fabric filters
• Wet scrubbers

Gravitational Settling Chamber

• Consists of a large circular expansion chamber
• Separates dust from the gas by reducing the velocity of the gas
• Dust particles settle down under gravity
• Set horizontally,
• Can be constructed in black or concrete
• Advantages:
• Low initial cost
• Simple to design
• Low pressure drop
• Low maintenance cost
• Disadvantages:
• Requires large space
• Less collection efficiency
• Size restrictions

Electrostatic Precipitator (ESP)

• A device used to remove fine particles like dust, smoke and soot from an exhaust gas stream
• Employs electrostatic forces
• Commonly used in industrial applications to control air pollution
• Works by charging the dust particles
• Attracts them to oppositely charged plates or electrodes, where they accumulate and are later removed
• Highly efficient for removing fine particulates from large volumes of gas
• Advantages
• Particles as small as 0.1 μm can be removed
• High collection efficiency
• Low power requirement
• Large gas columns can be handled

Fabric Filters

• Function like giant vacuum cleaner bags for industrial settings
• Used to clean air by trapping dust and other tiny particles
• Often called bag houses because they often use fabric bags to do the filtering
• Advantages:
• High collection efficiency
• Collection & disposal of particles in dry form
• Low pressure -disadvantages -Large size equipment -High collection cost The fabric is liable to chemical attack

Cyclone Separators

• Uses centrifugal force to separate solid particles or liquid droplets from a fluid stream (gas or liquid)
• Without using filters, by creating a swirling vortex Advantages:
• low Initial cost -Simple to design and maintain
• requires less floor area
• how to medium pressure lase

Wet Scrubber

• Dirty air is similar to 'air with tiny bits of dust
• Similar inside like a 'shower of water
• Water sprays to catch tiny dust or other heavy particles making them wet
• Types include:
• Spray
• Cyclone
• Packed bed Advantages:
• Simultaneous removal of gases and particulates
• Effective over wide-ranging loads
• Hazards - explosive dusts reduced

Water Pollution

• High water usage, corrosion issues, energy consumption can exist
  Water pollution is the contamination of water bodies by harmful substances
• Renders them unsafe for human use
• Harms aquatic ecosystems Major sources of surface water pollution -Includes agricultural runoff industrial waste
  • sewage, oil spills, mineral
  • All can contaminate waters/lakes

Spray Tower

Functions by water running down and dirty gas floats up

• Air and water contact
  • The water catches the dirt, cleaning the air

Packed Bed Towers

Function by mixing a gas and a liquid

• Allows transfer functions from one source