Pollution
An ecosystem is defined as 'a self-contained interacting
community of organisms and the environment in which
these organisms live and react'. A pollutant may be
considered as any substance or form of energy, usually
an unwanted by-product or waste which is released into
the environment as a result of human activities that
alters the chemical, physical and biological
characteristics of the environment. Such substances
may be solids, liquids or gases.
Water pollution
Water covers over 70% of the Earths surface and is a very important resource to people and
the environment. Water pollution affects drinking water, rivers, lakes and oceans all over the
world. This consequently harms human health and the natural environment.
Heat pollution
When power stations generate energy, they use water in their cooling towers. As the water
cools the air in the tower, the water becomes heated and is pumped into a nearby river or the
sea. Once in the water, it heats up the area around and downstream of where it is discharged,
disturbing the wildlife, which prefer cooler water. This increase in heat can increase the rate
of reproduction of some species. It can lead to the successful colonisation by alien species that
prefer warm conditions. This can have drastic effects on the other wildlife, including species
that feed on the aquatic animals and plants.
Oil pollution
Oceans are polluted by oil on a daily basis from oil
spills, routine shipping, run-offs and dumping. Oil spills
make up about 12% of the oil that enters the ocean. The
rest come from shipping travel, drains and dumping. An
oil spill from a tanker is a severe problem because there
is such a huge quantity of oil being spilt into one place.
Oil spills cause a very localised problem but can be
catastrophic to local marine wildlife such as fish, birds
and sea otters. Oil cannot dissolve in water and forms a
thick sludge in the water. This suffocates fish, gets
caught in the feathers of marine birds stopping them
from flying and blocks light from photosynthetic aquatic
plants.
Sewage
Domestic households, industrial and agricultural practices
produce wastewater that can cause pollution of many lakes and
rivers. Sewage is the term used for wastewater that often
contains faeces, urine and laundry waste. There are billions of
people on Earth so treating sewage is a big priority. Sewage disposal is
a major problem in developing countries as many people in these areas don’t have access to
sanitary conditions and clean water. Untreated sewage water in such areas can infect the
environment and cause diseases such as diarrhoea. Sewage in developed countries is carried
away from the home quickly and hygienically through sewage pipes. Sewage is treated in water
treatment plants and the waste is often disposed into the sea. Sewage is mainly biodegradable
and most of it is broken down in the environment. In developed countries, sewage often causes
problems when people flush chemical and pharmaceutical substances down the toilet. When
people are ill, sewage often carries harmful viruses and bacteria into the environment causing
health problems.
Organic pollutants are a problem because they encourage the growth of bacteria and algal
blooms which thrive in rich conditions. They break down the pollutants using up oxygen from the
water as they respire and producing carbon dioxide (CO2). Areas of water such as ponds or
lakes, in which the water does not move, suffer from pollution more than rivers as they are not
able to get rid of the pollutants as effectively as a river, or any other fast moving water body.
As the water becomes more polluted, there are more organic nutrients available for the
bacteria to break down which leads to an increase in mineral salts. This is known as
eutrophication ("good eating" conditions). However, the breakdown of these nutrients leads to a
depletion in oxygen and an increase in CO2, which can lead to the death of many of the other
organisms such as fish and invertebrates Eutrophication encourages the growth of algal blooms,
which cover the surface and prevent light from reaching the submerged plants in the water
thus preventing photosynthesis.
www.water-pollution.org.uk/
Deforestation
Forests are vital for life, home to m illions of species, they protect soil from erosion, produce
oxygen, store carbon dioxide, and help control climate. Forests are also vital for us to live as they
provide us with food, shelter and medicines as well as many other useful things. They also pur ify
the air we breathe and water that we need to survive. Deforestation by humans is causing all of
these necessary functions to be lessened, and hence damaging the atmosphere even further.
Forests play a huge role in the carbon cycle on our planet. When forests are cut down, not only
does carbon absorption cease, but also the carbon stored in the trees is released into the
atmosphere as CO 2 if the wood is burned or even if it is left to rot after the deforestation
process. Smaller crops e.g. plants and ag ricultural crops also draw in carbon dioxide and release
oxygen, however forests store up to 100 times more carbon than agricultural fields of the same
area.
Global warming is the increase in the average temperature of the Earth's atmosphere and oceans
in recent decades, and projected evaluations on how this is set to continue in the future . It is
predicted that global temperatures could increase by 1.1 to 6.4°C between now and 2100. It is
difficult to predict a more exact temperature as we do not know the amount of greenhouse gases
that man will produce in this time. Global warming is caused when carbon dioxide and other gases
warm the surface of the planet naturally by trapping solar heat in the atmosphere. This is a good
thing because it keeps our planet at a temperature where humans, animals and plants can live.
However, by burning fossil fuels such as coal and oil and cutting down forests humans have
dramatically increased the amount of carbon dioxide in the Earth’s atmosphere and hence the
overall temperatures are rising.
Scientists agree that global warming is happening and that it is the result of our activities and not
a natural occurrence. We’re already seeing changes, glaciers are melting, plants and animals are
being forced from their habitat, and the number of severe storms and droughts is increasing.
Acid Rain
What is it?
Acid rain is a term which you may have heard, but not quite understood. It
certainly sounds very nasty doesn't it? But, unlike in cartoons, acid rain does not
burn through everything that it touches! It does cause a lot of damage to
buildings, plants, animals, and even humans, however. It is also a bit misleading,
because even pure rainwater is slightly acidic. 'Acid rain' just means that the rain
is more acidic than it should be. Before we look at what damage acid rain
actually does, it is best to look at why it happens.
How acid rain is formed
The main elements which are responsible for acid rain, are sulphur and nitrogen (in gas form).
Both of these can be caused by a number of things, including some human activities, but they
are also made naturally.
Human activities which produce sulphur dioxide and nitrous oxides include burning fossil fuels
(like coal, and crude oil). Two things that are highly responsible for causing acid rain are power
stations and factories. Although these are essential to human life in this day and age, they
make large amounts of sulphur dioxide and nitrous oxides. In fact, power stations produce 70%
of all of the chemicals which are responsible for acid rain.
Vehicles also play a large part in making sulphur dioxide and nitrous oxide, because petrol and
diesel are produced from crude oil. So every time someone uses a car or a bus, they are
increasing the amount of acid rain. The effect of one car or bus on acid rain is very small, but
you think how many cars and buses are used by people every day, and imagine how much sulphur
dioxide and nitrous oxides (the gas forms of sulphur and nitrogen) is made!
The acid rain problem is also added to by natural causes, such as volcano eruptions, lightning and
bacterial action in soil.
Its effects: human health
The main effect that acid rain has on humans is increasing breathing problems. The sulphur
dioxide and nitrous oxides that are responsible for acid rain increase breathing problems such
as asthma and coughs. They can also cause headaches and inflammation (swelling and redness)
of the eyes, nose and throat.
Another problem which is caused by acid rain is that some poisonous (toxic) metals which are
dissolved into the rain water can be absorbed by fruit, vegetables and sometimes even through
the skin of animals. Although this may not affect the animal very much, it is a problem for us
when we eat them. Chemicals such as mercury which collect in the organs of animals can be very
nasty if taken into the body, because mercury has been linked to brain damage in children, as
well as nervous disorders and even death. Also another metal, aluminium, which can be found in
the bodies of animals, has been linked to kidney problems and recently it has been suggested
that it may lead to an illness called Alzheimer's.
Its effects: trees and soil
One of the most serious impacts of acid rain is on forests and soils. A lot of harm is caused
when sulphuric acid falls to the earth as rain. Nutrients in the soil, which plants and animals
need to survive, are washed away. Not all of the sulphur dioxide is turned into sulphuric acid,
and in fact, lots of it can float in the atmosphere, move over to another area, and return to the
soils, still as sulphur dioxide. This gas can then clog up the leaves of the plants, and stop them
from making their own food using sunlight (photosynthesising).
Soot
Soot is defined as "mainly black carbon, the dusty by-product of incomplete combustion
of fossil fuels, plants and wood". Sooty particles are most dangerous when very small as they
are easily inhaled and reach deep into the lungs where they can trigger an inflammatory
response. Breathing in air heavy with tiny particles can be dangerous even over a short time.
Because these particles are so minuscule, they can enter the circulatory system and damage
blood vessels. Children are especially vulnerable because their lungs are still developing.
Particulate pollution is associated with heart attacks, irregular heartbeat, asthma attacks,
reduced lung function and bronchitis. These impacts result in tens of thousands of premature
deaths from heart and lung disease annually, as well as hospital admissions, emergency room
visits, absences from school or work, and restricted activities related to asthma attacks.
When these soot particles settle they blacken buildings and damage leaves of trees.
Smoke in the atmosphere cuts down on the amount of light reaching the ground and covers
leaves and the stomata (pores) on the leaves clog up. This reduces the amount of
photosynthesis that they are able to do and as a result plant growth is poor in smoky areas.
Catalytic converters
There are millions of cars on the road and each one is potentially a source of air pollution.
Especially in large cities, the amount of pollution that all the cars produce together can create
big problems.
To solve those problems many laws have been enacted that restrict the amount of pollution that
cars can produce. To keep up with these laws, car makers have made many changes to car
engines and fuel systems. To help reduce the emissions further, they have developed an
interesting device called a catalytic converter, which treats the exhaust before it leaves the
car and removes a lot of the pollution.
How Catalytic Converters Reduce Pollution
Most modern cars are equipped with catalytic converters. These help to reduce
emissions of -- carbon monoxide, VOCs and NOx molecules. The converter uses two different
types of catalysts, a reduction catalyst and an oxidation catalyst. Both types consist of a
ceramic structure coated with a metal catalyst, usually platinum, rhodium and/or palladium. The
idea is to create a structure that exposes the maximum surface area of catalyst to the exhaust
stream, while also minimizing the amount of catalyst required (they are very expensive).