Soil
Soil is a living material made up of minerals, organic matter, water, and air, all of
which interact to create a home for plants and a colony of microbes. The mineral fraction
of soil is formed by the weathering of rocks and is responsible for the fundamental
composition and structure of soil. Organic matter fills soils with carbon molecules, and
together with minerals, it offers the necessary nutrients required by plants. Water and
oxygen are, of course, essential to all living creatures, as well as the numerous chemical
and physical activities that take place in soil. Water is required for plants and microbes;
in reality, the energy that drives soil activities is derived from the sunlight that plants gather
during photosynthesis.
The ability to support rooted plants in a natural setting or horizons, or layers, that
can be distinguished from the original material due to additions, losses, transfers, and
transformations of energy and matter are two characteristics of soil, a natural body made
up of solids (minerals and organic matter), liquids, and gases that occurs on the land
surface and occupies space.
The five components that make up soil are minerals, organic materials, living
things, gas, and water. The percentages of particles in the three size classes of soil
minerals—clay, silt, and sand—are referred to as the soil texture. Soils have a wide
variety of mineralogy. When wet and dry, for instance, a clay mineral known as smectite
can shrink and swell so much that it can topple structures. Quartz is the most prevalent
mineral found in soils; it is not particularly reactive but forms lovely crystals. Plant, animal,
and microbial leftovers in varying stages of decomposition make up soil organic matter,
which is an essential component. In fact, the proportion of soil organic matter in a soil is
one of the greatest measures of agricultural soil quality. Common soil colors include
brown, yellow, red, gray, white, and black; uncommon soil colors include green and blue.
Types of Soil
A. Sandy Soil
Sandy soil is a type of soil that contains a higher proportion
of sand and less clay. Sandy soil is light, dry, and warm that
tends to be more acidic than other types of soil. Because
the size of the sand particle is larger than other particles,
they have low water retention capacity and fewer nutrients.
The lack of enough moisture and nutrients makes the soil
less suitable for crop production. However, the soil can be
made suitable by adding organic matter to increase water
and nutrient content.
B. Clay Soil
Clay soil is a type of soil that is comparatively heavy as it has higher water retention
capacity and a higher concentration of nutrients. The soil is made up of over 25% clay
particles that are smaller in size and thus hold a large amount of water. Clay soil drains
water slowly and thus takes longer to warm up in the summer without drying out. However,
because it is a heavy and dense type of soil, it doesn’t provide space for plant roots to
flourish.
C. Silt Soil
Silt soil is a light soil with a higher fertility rate with soil particles that are large than clay
but smaller than sand. The soil is smooth and of fine quality that holds water better than
the sandy soil. The soil can also be easily transported by moving currents, and it is found
near water bodies. Silt soil is considered the best type of soil for agricultural practices as
it has sufficient nutrients and enough moisture for plant growth.
D. Loam Soil
Loam soil is a mixture of sand, silt, and clay soil that combines the properties of all three
types of soil to make it more fertile. The soil has enough pores as well as water retention
capacity to promote crop production. The level of calcium and pH of loam soil is also of
the appropriate amount due to the presence of inorganic matter.
Key Components of Soil
Components
1. Mineral matter (45%)
 Sand
 Silt
 Clay
Description
This is the largest component of soil,
making up about 45-49% of the soil
volume. It's derived from the weathering of
rocks and minerals, and it provides the
structural framework of the soil
 Sand - The largest particles,
ranging from 0.05 to 2.00 mm in
diameter. Sand contributes to soil
drainage and aeration.
 Silt - Medium-sized particles,
ranging from 0.002 to 0.05 mm in
diameter. Silt has good waterholding capacity and contributes to
soil fertility
 Clay - The smallest particles, less
than 0.002 mm in diameter. Clay
particles have a large surface area,
which allows them to retain water
and nutrients. However, too much
clay can lead to poor drainage.
2. Organic matter (5%)
 Humus
 Living organisms
3. Water (25%)
4. Air (25%)
Layers of Soil
This component makes up about 5% of the
soil volume and is crucial for soil health
and fertility.
 Humus - A dark, spongy substance
formed from the decomposition of
plant and animal remains. Humus
improves soil structure, waterholding capacity, and nutrient
availability.
 Living organisms - Soil is teeming
with life, including bacteria, fungi,
earthworms, insects, and other
creatures. These organisms play
vital roles in decomposition, nutrient
cycling, and soil structure.
Water occupies the pore spaces between
soil particles and makes up about 25% of
the soil volume. It's essential for
transporting nutrients to plants and
facilitating chemical reactions. The amount
of water in the soil varies depending on
factors like rainfall, drainage, and soil
texture.
Air also occupies the pore spaces in the
soil, making up about 25% of the soil
volume. It’s crucial for the respiration of
plant roots and soil organisms. The
balance between water and air in the soil
is important for healthy plant growth.
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O (humus or organic): Mostly decaying leaves
and other organic materials. Some soils have a
thin O horizon, whereas others have a thick one,
and yet others have none at all.
A (topsoil): The majority of the minerals in
topsoil come from parent material, with some
organic materials mixed throughout. An
excellent material for living things, including
plants.
E (eluviated): Eluviated soils, which are
typically found in older soils and forest soils,
include a concentration of silt and sand particles
of quartz or other resistant elements that have
been leached from clay, minerals, and organic
matter.
B (subsoil): Minerals that leached (moved down) from the A or E horizons and
accumulated here are abundant in the B (subsoil).
C (parent material): The layer above the R Horizon and below the B Horizon is
also known as regolith. It is made of bedrock that has been slightly fractured. This
layer contains very little organic material and is not penetrated by plant roots.
R (bedrock): A mass of rock, such as granite, basalt, quartzite, limestone, or
sandstone, that, if it is near enough to the surface to weather, makes up the parent
material for various soils. This area, which is beneath the C horizon, is not soil.
What is soil pollution?
Over time, soil pollution has grown to be a significant obstacle that we must
overcome in order to create a healthy ecosystem. Soil is created by many processes that
weather the earth's crusts, and it builds up over ages. A significant portion of the
biodiversity of bacteria and other microscopic and macroscopic living things are found in
the soil.
HAZARDOUS POLLUTANTS

Heavy Metals: When present in very high concentrations, heavy metals like lead
and mercury can render soil extremely toxic to people.
TOXIC METALS THAT CAUSE
SOIL POLLUTION
ARSENIC
MERCURY
ANTIMONY
ZINC
LEAD
NICKEL
CADMIUM
THALLIUM
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SELENIUM
CHROMIUM
BERYLLIUM
COPPER
PAHs (polycyclic aromatic hydrocarbons): Only carbon and hydrogen atoms make
up the class of organic compounds known as PAHs (polycyclic aromatic
hydrocarbons) and they many aromatic rings in their molecular structure. PAHs are
found in soil from cigarette smoke, shale oil extraction, vehicle emissions, and coke
(coal) production. Phenalene, anthracene, and naphthalene are typical examples
of PAHs. Polycyclic aromatic hydrocarbon exposure has been connected to a
number of cancer types. Human circulatory disorders can also be brought on by
certain chemical substances.
Industrial Waste Soil: Whenever industrial waste is dumped into soils, pollution
may
result.

Industrial solvents that are chlorinated

Dioxins are created when garbage is burned, and insecticides are
manufactured.

The dispersants and plasticizers
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
PCBs, or polychlorinated biphenyls
Pesticides: Chemicals (or chemical mixtures) used to eradicate or stop the
reproduction of pests are known as pesticides.
Clean Soil vs. Dirty Soil
Characteristics
1. Contaminants
2. Organic Matter
Clean Soil
Free
from
harmful
contaminants like heavy
metals (lead, mercury,
arsenic),
pesticides,
herbicides,
industrial
chemicals, and excessive
levels of pollutants. It may
contain naturally occurring
substances, but at levels
that don't pose a risk to
human health or the
environment.
Typically has a good
amount of organic matter
(humus) which is essential
Dirty Soil
Contains contaminants at
levels that exceed safe
limits. This can be due to
industrial activity, improper
waste disposal, agricultural
practices,
or
natural
sources. Contaminated soil
can pose health risks
through direct contact,
inhalation, or ingestion, and
can harm plants and
wildlife.
May have low organic
matter content, especially if
contaminated. This
can
3. Biological Activity
4. Physical
Properties
for soil fertility, water
retention, and nutrient
cycling. This makes it
suitable for plant growth.
Teems
with
diverse
microorganisms (bacteria,
fungi), earthworms, and
other
organisms
that
contribute
to
nutrient
cycling, soil structure, and
overall health.
Often has a good structure,
with a balance of sand, silt,
and clay particles, allowing
for proper drainage and
aeration.
5. Suitability for use
Suitable
for
various
purposes,
including
agriculture,
gardening,
construction,
and
landscaping.
6. Color and odor
Typically has a rich, earthy
color and a pleasant, earthy
smell.
7. Testing
May not require extensive
testing unless there's a
reason
to
suspect
contamination.
reduce its fertility and ability
to support plant life.
May
have
reduced
biological activity due to the
presence of contaminants
that can harm or kill soil
organisms.
May have a poor structure
due to contamination or
lack of organic matter. This
can lead to compaction,
poor drainage, and reduced
aeration.
May be unsuitable for
certain uses due to
contamination.
It
may
require remediation or
special handling before it
can be used safely.
May have unusual colors or
odors due to the presence
of
contaminants.
For
example, it might have a
chemical smell or a strange
discoloration.
Often requires testing to
identify the type and level of
contaminants present. This
is important for assessing
the risks and determining
appropriate
remediation
strategies.
Clean soil
Type of soil
Properties
Example
1. Loamy soil
2. Sandy Loam
3. Silt Loam
4. Clay Loam
5. Organic Soil
It's a balanced mix of sand,
silt, and clay, which gives it
excellent drainage, water
retention, and nutrientholding capacity. It's also
easy to work with and has
good aeration.
Predominantly sand, but
with enough silt and clay to
hold some moisture and
nutrients. It drains quickly,
warms up fast in the spring,
and is easy to dig.
Mostly silt, with some sand
and clay. It holds moisture
well and is rich in nutrients,
but can be prone to
compaction.
More clay than sand or silt,
but still with enough of the
other particles to provide
some
drainage
and
aeration. It's nutrient-rich
but can be heavy and slow
to warm up
this
is
primarily
decomposed
organic
matter. When it's "clean," it
means it's free from harmful
pollutants
and
has
excellent fertility, water
retention, and biological
activity.
Many garden soils are
loamy or can be amended
to become loamy. It's ideal
for most plants.
Good for plants that prefer
well-drained soil, like root
vegetables
or
Mediterranean herbs.
Often found in areas with
fertile floodplains, good for
many garden plants.
Can be good for plants that
tolerate heavier soils, like
some trees and shrubs.
Compost,
well-rotted
manure, and peat moss
(though peat is less
sustainable).
Dirty soil
Type of soil
Properties
Examples
1. Heavy
Metal Heavy metals like lead,
 Industrial sites: Old
Contamination
mercury,
arsenic,
and
factories, mines, or
cadmium persist in soil for
smelters often leave
long periods. They can be
behind heavy metal
toxic to plants, animals, and
contamination.
humans, accumulating in
 Urban areas: Lead
the food chain.
from old paint or

2. Pesticide
and These chemicals, used to
Herbicide
control pests and weeds,
Contamination
can linger in soil and harm
non-target
organisms.
They may disrupt soil
ecosystems and pose
health risks.
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3. Industrial
Chemical
Contamination
A wide range of chemicals
from factories, spills, or
improper waste disposal
can
contaminate
soil.
These
may
include
solvents, oils, PCBs, and
dioxins, each with its own
specific toxic effects.
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4. Petroleum
Hydrocarbon
Contamination
Oil spills, leaks from
underground
storage
tanks,
and
improper
disposal
of
petroleum
products can contaminate
soil with hydrocarbons.


past use of leaded
gasoline
can
contaminate
soil,
especially
near
roads.
Agricultural
land:
Some pesticides or
fertilizers
may
contain
heavy
metals.
Farmlands: Overuse
or
improper
application
of
pesticides can lead
to
soil
contamination.
Gardens:
Even
home gardeners can
contribute if they use
pesticides
excessively.
Areas
near
agricultural runoff:
Chemicals can wash
into nearby soil.
Manufacturing sites:
Factories producing
chemicals, plastics,
or other goods can
have leaks or spills.
Dry cleaners: Some
solvents used in dry
cleaning
can
contaminate soil.
Landfills: Improperly
managed
landfills
can leach chemicals
into the surrounding
soil.
Oil refineries: Sites
where
oil
is
processed are at risk
of spills.
Gas stations: Leaky
underground tanks
These can harm plants and
animals and pose fire
hazards.
5. Radioactive
Contamination
Radioactive materials can
persist in soil for very long
periods, posing a risk of
radiation exposure.
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6. Pathogen
Contamination
Bacteria, viruses, and other
pathogens
can
contaminate soil through
sewage, animal waste, or
contaminated water. They
pose a risk of infection.
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
can
contaminate
nearby soil.
Areas near roads:
Runoff from roads
can contain oil and
other hydrocarbons.
Nuclear
facilities:
Sites where nuclear
materials
are
processed or stored
have the potential
for contamination.
Mining areas: Some
types of mining can
expose radioactive
elements.
Areas with poor
sanitation:
Improperly treated
sewage
can
contaminate soil.
Farms:
Animal
waste can be a
source
of
pathogens.
Organic Soil vs Inorganic Soil
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Organic soil is excellent for gardening and providing plants with the nutrients they
need. It's also great for improving soil structure and water retention.
Inorganic soil is often used as a base for construction or landscaping, and can be
amended with organic matter to improve its fertility.
Features
1. Composition
2. Nutrient Content
3. Structure
Organic
Primarily made up of
decomposed
organic
matter like plant and animal
residues. Think of things
like compost, decaying
leaves, and manure.
Rich in nutrients and
minerals, making it a great
"superfood" for plants.
Inorganic
Primarily made up of
inorganic materials like
sand,
silt,
and
clay
particles, along with some
rock fragments.
Lower than organic soil,
and may require additional
fertilizers to support plant
growth.
Generally has a loose and Varies depending on the
porous structure, which proportions of sand, silt,
4. Water
Capacity
helps with water retention
and aeration.
Holding High, meaning it can hold a
lot of water.
5. pH level
6. Biological Activity
and clay. Can be dense and
compact.
Varies depending on the
texture. Sandy soils drain
quickly, while clay soils
retain more water.
Can vary but tends to be Can vary, but often closer to
slightly acidic.
neutral.
teeming
with Lower than organic soil.
microorganisms,
worms,
and other beneficial life that
contribute to soil health.
IMPACT OF SOIL POLLUTION
Food security, which is necessary for human survival, is put at risk when soil
contamination reduces soil fertility. Additionally, it is harmful to human health, both directly
through contact to contaminated soil and indirectly through the ingestion of tainted food
and drinking water.
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HEALTH
PROBLEMS
IN
HUMANS
Through the food chain, soil pollutants reach our bodies and cause diseases.
Numerous contaminants found in soil can cause cancer. The risk of developing
cancer is significantly higher for people who are exposed to them than for those
who are not. Other health issues like central nervous system depression,
headaches, nausea, exhaustion, eye irritation, and skin rashes can also be brought
on by contaminated soil. People who are exposed to high levels of mercury in the
soil are more likely to develop liver or kidney damage. High levels of lead or
mercury, for instance, can harm developing children's brains and result in
neurological issues.
FOOD CHAIN DISRUPTION
The metabolisms of microorganisms and arthropods can be adversely affected by
soil pollution, which can kill some food chain rungs and harm predators. The toxic
substances in the soil are consumed by smaller organisms, which subsequently
make their way up the food chain to larger creatures, increasing mortality rates
and possibly causing extinction.
LOWER
AIR
QUALITY
Air pollution can result from the emission of volatile chemicals into the atmosphere
by contaminated soil. The soil will have a greater impact on air quality the more
harmful substances it contains.
DECREASED
SOIL
FERTILITY
Pollution can raise the soil's salinity, rendering it unusable for the majority of plant
growth. Any crops that could survive under those circumstances would be
poisonous enough to be harmful if consumed. Sulfur dioxide, an acidic substance
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
released by burning fossil fuels, has the potential to pollute soil. Worms and other
microbes that typically enhance soil health by breaking down organic matter and
encouraging water circulation are negatively impacted by the acidic environment it
produces. Acidity also has a detrimental effect on bacteria and fungi that aid in soil
binding, which can cause soil erosion.
PLANT
GROWTH
PROBLEMS
When soil chemistry changes significantly over a short period of time owing to
contamination, most plants are unable to adjust. Their growth may be hampered
by soil contamination, which can change their metabolism and lessen their
capacity to take in nutrients and carry out photosynthesis.
GROUNDWATER
CONTAMINATION
One of the primary sources of drinking water for many communities is groundwater,
which can become contaminated by soil degradation. Any contaminants in the soil
can seep into the water and contaminate it since groundwater gathers beneath soil
layers. Long-term usage of contaminated water might have detrimental effects.
Soil Erosion
Soil erosion is the process by which the top layer of nutrient-rich soil is removed due
to natural forces and human activities. Water erosion, caused by rainfall and surface
runoff, leads to different types of soil loss, including sheet erosion (uniform soil
removal), rill erosion (small channel formation), and gully erosion (deep channels or
gullies). Wind erosion is common in arid and semi-arid regions, where strong winds
carry away loose, dry soil. Human activities such as deforestation, overgrazing,
unsustainable farming practices, and urbanization also contribute significantly to soil
erosion. The effects of soil erosion include the loss of fertile topsoil, sedimentation in
water bodies, increased flooding risk, and desertification. To prevent and mitigate soil
erosion, various strategies can be employed, including maintaining vegetative cover,
contour plowing, terracing, planting windbreaks, and practicing conservation tillage.
Soil Leaching
Soil leaching occurs when water dissolves and transports nutrients, minerals, or
pollutants from the soil into deeper layers or groundwater. This process is influenced
by excessive rainfall, soil composition, and over-fertilization. As a result, essential
nutrients are depleted from the soil, reducing its fertility, while harmful substances may
contaminate groundwater. Additionally, prolonged leaching can lead to soil
acidification, making it less suitable for plant growth. To minimize soil leaching,
strategies such as controlled irrigation, soil amendment, and proper fertilizer
management should be implemented.
Soil Weathering
Soil weathering is the natural process by which rocks and minerals break down into
smaller particles, ultimately forming soil. It can occur through physical, chemical, or
biological processes. Physical weathering is caused by temperature fluctuations, frost
action, and the impact of wind and water. Chemical weathering involves reactions
such as hydrolysis, oxidation, and carbonation, which alter the composition of
minerals. Biological weathering occurs when plant roots, microorganisms, and
burrowing animals contribute to the breakdown of rocks. The effects of soil weathering
include soil formation, the release of essential nutrients, landscape changes, and the
promotion of erosion and sedimentation.
Soil Minerals and Their Importance
Soil contains essential minerals that support plant growth and maintain soil fertility.
These minerals are classified into macronutrients, which are needed in large amounts,
and micronutrients, which are required in smaller quantities but are still vital for plant
health. Macronutrients such as nitrogen, phosphorus, potassium, calcium,
magnesium, and sulfur play key roles in plant metabolism, structural development,
and overall health. Micronutrients, including iron, manganese, zinc, copper, boron,
molybdenum, and chlorine, are crucial for various physiological and biochemical
processes in plants. Other minerals like silicon, aluminum, and sodium also influence
soil properties, though excessive amounts of some minerals, like aluminum and
sodium, can be harmful.
Soil Contamination and Treatment
Soil contamination occurs when harmful substances accumulate in the soil, posing
risks to plant growth, water quality, and overall environmental health. To restore
contaminated soil, several treatment methods can be used. Bioremediation, or
biological treatment, utilizes microorganisms to break down pollutants, including
heavy metals and pesticides. Chemical oxidation involves the use of reactive
chemicals to destroy contaminants, making it an effective solution for deeply polluted
soils. Soil stabilization prevents pollutants from spreading by either immobilizing them
or altering them into a less harmful state. Soil washing is another technique that
separates contaminated fine particles from clean soil, requiring further treatment of
the extracted pollutants. These methods are crucial in mitigating environmental
hazards
and
restoring
soil
health
for
sustainable
use.
WAYS TO PREVENT SOIL POLLUTION

3R’s
Landfills are used to dispose of a large portion of residential trash. Plastics and
other items gradually decompose in landfills, releasing harmful compounds into
the ground. Some of these compounds are important sources of contamination
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and are highly harmful to the health of the soil. Limiting the quantity of garbage
that ends up in landfills and contributing to soil pollution can be achieved by
reducing the usage of disposable products and recycling and reusing objects as
much as feasible.
Limit the usage of chemical fertilizer
Chemical fertilizers can increase soil fertility in the right amounts, but applying
them excessively can damage the soil in a number of ways. An excessive amount
of chemical fertilizer can harm beneficial microbes and alter the pH values of the
soil. Water is often contaminated by fertilizer runoff from the soil. Manure and other
natural fertilizers ought to be preferred over chemicals because of this.
Improve
Hazard
ways
management
To Safeguard the environment, hazardous waste management laws are in effect
in most jurisdictions. It's critical that governments actively and rigorously enforce
these laws.
Tree planting
Deforestation-induced soil erosion is one of the primary sources of soil
contamination.
In locations that are dry and deforested, planting trees should be promoted. Plant
roots hold the soil together and can even aid in soil remediation.