soil pollution assignment

• Environmental Chemistry

Soil Pollution

What is soil pollution.

Soil pollution refers to the contamination of soil with anomalous concentrations of toxic substances.

It is a serious environmental concern since it harbours many health hazards. For example, exposure to soil containing high concentrations of benzene increases the risk of contracting leukaemia. An image detailing the discolouration of soil due to soil pollution is provided below. It is important to understand that all soils contain compounds that are harmful/toxic to human beings and other living organisms. However, the concentration of such substances in unpolluted soil is low enough that they do not pose any threat to the surrounding ecosystem. When the concentration of one or more such toxic substances is high enough to cause damage to living organisms, the soil is said to be contaminated.

The root cause of soil pollution is often one of the following:

• Agriculture (excessive/improper use of pesticides)
• Excessive industrial activity
• Poor management or inefficient disposal of waste

The challenges faced in soil remediation (decontamination of soil) are closely related to the extent of soil pollution. The greater the contamination, the greater the requirement for resources for remediation.

What are the Pollutants that Contaminate Soil?

Some of the most hazardous soil pollutants are xenobiotics – substances that are not naturally found in nature and are synthesized by human beings. The term ‘xenobiotic’ has Greek roots – ‘Xenos’ (foreigner), and ‘Bios’ (life). Several xenobiotics are known to be carcinogens. An illustration detailing major soil pollutants is provided below.

The different types of pollutants that are found in contaminated soil are listed in this subsection.

Heavy Metals

The presence of heavy metals (such as lead and mercury, in abnormally high concentrations) in soils can cause it to become highly toxic to human beings. Some metals that can be classified as soil pollutants are tabulated below.

These metals can originate from several sources such as mining activities, agricultural activities, and electronic waste (e-waste), and medical waste.

Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (often abbreviated to PAHs) are organic compounds that

• Contain only carbon and hydrogen atoms.
• Contain more than one aromatic ring in their chemical structures.

Common examples of PAHs include naphthalene, anthracene, and phenalene. Exposure to polycyclic aromatic hydrocarbons has been linked to several forms of cancer. These organic compounds can also cause cardiovascular diseases in humans.

Soil pollution due to PAHs can be sourced to coke (coal) processing, vehicle emissions, cigarette smoke, and the extraction of shale oil.

Industrial Waste

The discharge of industrial waste into soils can result in soil pollution. Some common soil pollutants that can be sourced from industrial waste are listed below.

• Chlorinated industrial solvents
• Dioxins are produced from the manufacture of pesticides and the incineration of waste.
• Plasticizers/dispersants
• Polychlorinated biphenyls (PCBs)

The petroleum industry creates many petroleum hydrocarbon waste products. Some of these wastes, such as benzene and methylbenzene, are known to be carcinogenic in nature.

Pesticides are substances (or mixtures of substances) that are used to kill or inhibit the growth of pests. Common types of pesticides used in agriculture include

• Herbicides – used to kill/control weeds and other unwanted plants.
• Insecticides – used to kill insects.
• Fungicides – used to kill parasitic fungi or inhibit their growth.

However, the unintentional diffusion of pesticides into the environment (commonly known as ‘pesticide drift’) poses a variety of environmental concerns such as water pollution and soil pollution. Some important soil contaminants found in pesticides are listed below.

• Phenoxyalkyl acids
• Aliphatic acids

Insecticides

• Organophosphates
• Chlorinated hydrocarbons
• Arsenic-containing compounds
• Mercury-containing compounds
• Thiocarbamates
• Copper sulfate

These chemicals pose several health risks to humans. Examples of health hazards related to pesticides include diseases of the central nervous system, immune system diseases, cancer, and birth defects.

What are the Processes that Cause Soil Pollution?

Soil pollution can be broadly classified into two categories –

• Naturally caused soil pollution
• Anthropogenic soil pollution (caused by human activity)

Natural Pollution of Soil

In some extremely rare processes, some pollutants are naturally accumulated in soils. This can occur due to the differential deposition of soil by the atmosphere. Another manner in which this type of soil pollution can occur is via the transportation of soil pollutants with precipitation water.

An example of natural soil pollution is the accumulation of compounds containing the perchlorate anion (ClO 4 – ) in some dry, arid ecosystems. It is important to note that some contaminants can be naturally produced in the soil under the effect of certain environmental conditions. For example, perchlorates can be formed in soils containing chlorine and certain metals during a thunderstorm.

Anthropogenic Soil Pollution

Almost all cases of soil pollution are anthropogenic in nature. A variety of human activities can lead to the contamination of soil. Some such processes are listed below.

• The demolition of old buildings can involve the contamination of nearby soil with asbestos.
• Usage of lead-based paint during construction activities can also pollute the soil with hazardous concentrations of lead.
• Spillage of petrol and diesel during transportation can contaminate soils with the hydrocarbons found in petroleum.
• Activities associated with metal casting factories (foundries) often cause the dispersion of metallic contaminants into the nearby soils.
• Underground mining activities can cause the contamination of land with heavy metals.
• Improper disposal of highly toxic industrial/chemical waste can severely pollute the soil. For example, the storage of toxic wastes in landfills can result in the seepage of the waste into the soil. This waste can go on to pollute groundwater as well.
• Chemical pesticides contain several hazardous substances. Excessive and inefficient use of chemical pesticides can result in severe soil pollution.
• Sewage produced in urbanized areas can also contaminate soil (if not disposed of correctly). These wastes may also contain several carcinogenic substances.

Other forms of waste that can pollute soil include nuclear waste, e-waste, and coal ash.

What are the Negative Consequences of Soil Pollution?

Soil pollution harbours a broad spectrum of negative consequences that affect plants, animals, humans, and the ecosystem as a whole. Since children are more susceptible to diseases, polluted soil poses a greater threat to them.  Some important effects of soil pollution are detailed in this subsection.

Effects on Human Beings

Soil contaminants can exist in all three phases ( solid, liquid, and gaseous ). Therefore, these contaminants can find their way into the human body via several channels such as direct contact with the skin or through the inhalation of contaminated soil dust.

The short term effects of human exposure to polluted soil include

• Headaches, nausea, and vomiting.
• Coughing, pain in the chest, and wheezing.
• Irritation of the skin and the eyes.
• Fatigue and weakness.

A variety of long-term ailments have been linked to soil pollution. Some such diseases are listed below.

• Exposure to high levels of lead can result in permanent damage to the nervous system. Children are particularly vulnerable to lead.
• Depression of the CNS (Central Nervous System).
• Damage to vital organs such as the kidney and the liver.
• Higher risk of developing cancer.

It can be noted that many soil pollutants such as petroleum hydrocarbons and industrial solvents have been linked to congenital disorders in humans. Thus, soil pollution can have several negative effects on human health.

Effects on Plants and Animals

Since soil pollution is often accompanied by a decrease in the availability of nutrients, plant life ceases to thrive in such soils. Soils contaminated with inorganic aluminium can prove toxic to plants. Also, this type of pollution often increases the salinity of the soil, making it inhospitable for the growth of plant life.

Plants that are grown in polluted soil may accumulate high concentrations of soil pollutants through a process known as bioaccumulation. When these plants are consumed by herbivores, all the accumulated pollutants are passed up the food chain. This can result in the loss/extinction of many desirable animal species. Also, these pollutants can eventually make their way to the top of the food chain and manifest as diseases in human beings.

Effects on the Ecosystem

• Since the volatile contaminants in the soil can be carried away into the atmosphere by winds or can seep into underground water reserves, soil pollution can be a direct contributor to air and water pollution .
• It can also contribute to acid rain (by releasing huge quantities of ammonia into the atmosphere).
• Acidic soils are inhospitable to several microorganisms that improve soil texture and help in the decomposition of organic matter.  Thus, the negative effects of soil pollution also impact soil quality and texture.
• Crop yield is greatly affected by this form of pollution. In China, over 12 million tons of grain (worth approximately 2.6 billion USD) is found to be unfit for human consumption due to contamination with heavy metals (as per studies conducted by the China Dialogue).

How can Soil Pollution be Controlled?

Several technologies have been developed to tackle soil remediation. Some important strategies followed for the decontamination of polluted soil are listed below.

• Excavation and subsequent transportation of polluted soils to remote, uninhabited locations.
• Extraction of pollutants via thermal remediation – the temperature is raised in order to force the contaminants into the vapour phase, after which they can be collected through vapour extraction.
• Bioremediation or phytoremediation involves the use of microorganisms and plants for the decontamination of soil.
• Mycoremediation involves the use of fungi for the accumulation of heavy metal contaminants.

Frequently Asked Questions – FAQs

What are the key causes of soil pollution.

Some common causes of soil pollution are listed below,

• Improper disposal of industrial waste: industries are believed to be one of the leading causes of soil pollution due to improper management and disposal of the toxic wastes generated during industrial activities.
• Excessive and inefficient usage of pesticides and fertilizers: the agriculture industry makes extensive use of chemical fertilizers and pesticides for the growth and maintenance of crops. However, excessive and inefficient use of these toxic chemicals can seriously contaminate the soil.
• Petroleum or diesel spills: leaks in fuel transportation pipes can cause fuel spills. These fuels are known to contain toxic hydrocarbons which can cause soil contamination.

What are the effects of soil pollution on human health?

The contaminants found in polluted soil can enter human bodies through several channels such as the nose, the mouth, or the skin. Exposure to such soils can cause a variety of short-term health problems such as headaches, coughing, chest pain, nausea, and skin/eye irritation. Prolonged exposure to contaminated soil can lead to the depression of the central nervous system and damage to vital organs (such as the liver). Long-term exposure to polluted soils has also been linked to cancer in humans.

List some examples of the contaminants that pollute soils.

Some common soil pollutants are:

• Polycyclic aromatic hydrocarbons

How can soil pollution be avoided?

Many crucial changes must be brought about in order to control soil contamination and soil pollution without making huge compromises on the economy. For example, the use of toxic substances in industrial activities can be avoided wherever suitable alternatives exist. Also, the recycling of waste products will also contribute to a reduction in soil contamination due to landfills. Promoting healthy agricultural practices such as the use of organic manure and organic farming methods can help reduce the number of chemical fertilizers used on agricultural soils. Efficient and limited use of chemical pesticides must also be advocated.

What are the environmental remediation processes that can be employed to curb the negative effects of soil pollution?

• The contaminated soil can be excavated and transported to a remote disposal site.
• Thermal remediation of contaminated soil, involves heating up the soil in order to vaporize the volatile toxic pollutants.
• Soil decontamination via surfactant leaching.

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Soil Pollution

What causes Soil Pollution? Human activities are the primary cause of soil pollution and land degradation. By the end of this topic, you will know how different forms of human activities are responsible for the majority of different types of soil pollution.

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What is Soil Pollution

Soil Pollution has gradually become a major challenge that we need to overcome for establishing a healthy environment . Weathering of the earth’s crusts by different processes leads to the formation of soil that accumulates over the centuries. The soil is the home for a large part of bacterial biodiversity and other microscopic and macroscopic living organisms .

Example of Soil Pollution (Source: Wikipedia)

However, let us consider our very own country India. Indian economy is largely dependent on agriculture. Thus, we Indians give very high priority to the development of agriculture , fisheries, and livestock. Therefore, for surplus production, it is very important to protect crops from any type of damage that occurs due to insects, weeds, rodents and other crop diseases.

So, how do we protect crops? The very obvious answer is pesticides and herbicides. However, do you know these pesticides and herbicides is a leading cause of soil pollution? Therefore, it is very important to judiciously use pesticides because it contains lots of different harmful chemicals. Therefore, to improve soil and prevent soil pollution it is important to limit the use of pesticides and herbicides.

Causes of Soil Erosion  here.

Types of Soil Pollutants

• Heavy metals (such as lead and mercury, at excessively high amounts) in the soil can make it very poisonous to humans.
• PAHs (polycyclic aromatic hydrocarbons) are a class of organic chemicals where only carbon and hydrogen atoms are present.
• Coke (coal) production, automobile emissions, cigarette smoke, and shale oil extraction are all sources of PAHs in the soil.
• Industrial Waste Soil contamination can come from the dumping of industrial waste into soils.
• Pesticides are chemicals (or chemical mixes) that are used to kill or prevent pests from reproducing.

However, unintended pesticide dispersion into the environment (often referred to as “pesticide drift”) raises a number of environmental issues, including water and soil degradation.

Definition of Soil Pollution

Soil pollution refers to anything that causes contamination of soil and degrades the soil quality. It occurs when the pollutants causing the pollution reduce the quality of the soil and convert the soil inhabitable for microorganisms and macro organisms living in the soil.

Soil contamination or soil pollution can occur either because of human activities or because of natural processes. However, mostly it is due to human activities. The soil contamination can occur due to the presence of chemicals such as pesticides, herbicides, ammonia , petroleum hydrocarbons , lead, nitrate, mercury, naphthalene, etc in an excess amount.

The primary cause of soil pollution is a lack of awareness in general people. Thus, due to many different human activities such as overuse of pesticides the soil will lose its fertility. Moreover, the presence of excess chemicals will increase the alkalinity or acidity of soil thus degrading the soil quality. This will in turn cause soil erosion . This soil erosion refers to soil pollution.

Causes of Soil Pollution

Soil pollution can be natural or due to human activity. However, it mostly boils down to the activities of the human that causes the majority of soil pollution such as heavy industries, or pesticides in agriculture.

Before World War II , the chemical nicotine chemical present in the tobacco plants was used as the pest controlling substance in agricultural practices. However, DDT was found to be extremely useful for malaria control and as pest control of many insects during World War II. Therefore, it was used for controlling many diseases.

Hence, post-war, people started using it as pest control in agriculture for killing rodents , weeds, insects, etc and avoiding the damages due to these pests. However, everyone gradually the adverse effects of this chemical which led to the ban of this chemical in many parts of the world including India.

Moreover, pests became resistance to DDT due to the chemicals regular use. Hence this led to the introduction of other harmful chemicals such as Aldrin and Dieldrin. Pesticides are synthetic toxic chemicals that definitely kill different types of pests and insects causing damage to agriculture but it has many ecological repercussions.

They are generally insoluble in water and non-biodegradable. Therefore, these chemicals will not gradually decompose and keep on accumulating in the soil. Therefore, the concentration of these chemicals will increase when the transfer of these chemicals take place from lower to higher trophic level via the food chain . Hence, it will cause many metabolic and physiological disorders in humans.

Chlorinated Organic toxins

The harmful effect of DDT and other chemicals led to the introduction of less persistent organic and more-biodegradable substance such as carbamates and organophosphates. However, these chemicals act as harmful toxins for nerves , hence they are more dangerous to humans. It led to pesticides related to the death of field workers in some agricultural fields.

Learn about the Causes and Effects of Water Pollution  here.

Slowly, the industries began production of herbicides like sodium arsenite (Na 3 AsO 3 ), sodium chlorate (NaClO 3 ), etc. Herbicides can decompose in a span of few months. However, even they affect the environment and are not environmental friendly. Even though they are not as harmful as organo-chlorides but most of the herbicides are toxic. They are known to cause birth defects.

Furthermore, research suggests that spraying herbicides causes more insect attack and diseases of plants in comparison to manual weeding. One thing to note here is all the above factors occupy just a small portion of the causes. Majority of the causes is related to manufacturing activities in chemical and industrial processes that are released in nature or environment.

Inorganic Fertilizers

Excessive use of inorganic nitrogen fertilizers leads to acidification of soil and contaminate the agricultural soil. Also known as agrochemical pollution.

Industrial Pollution

The incorrect way of chemical waste disposal from different types of industries can cause contamination of soil. Human activities like this have led to acidification of soil and contamination due to the disposal of industrial waste , heavy metals, toxic chemicals, dumping oil and fuel, etc.

Inferior Irrigation Practices

Poor irrigation methods increase the soil salinity. Moreover, excess watering, improper maintenance of canals and irrigation channels, lack of crop rotation and intensive farming gradually decreases the quality of soil over time and cause degradation of land.

Solid Waste

Disposal of plastics, cans, and other solid waste falls into the category of soil pollution. Disposal of electrical goods such as batteries causes an adverse effect on the soil due to the presence of harmful chemicals . For instance, lithium present in batteries can cause leaching of soil.

Urban Activities

Lack of proper waste disposal, regular constructions can cause excessive damage to the soil due to lack of proper drainage and surface run-off. These waste disposed of by humans contain chemical waste from residential areas. Moreover leaking of sewerage system can also affect soil quality and cause soil pollution by changing the chemical composition of the soil.

Download Soil Pollution Cheat Sheet PDF

Effects of Soil Pollution

Soil pollution is not only the problem in India but it is a global problem. It causes harmful effect on the soil and the environment at large. Contamination of soil will decrease the agricultural output of a land. Major soil pollution after effects are:

Inferior Crop Quality

It can decrease the quality of the crop. Regular use of chemical fertilizers, inorganic fertilizers, pesticides will decrease the fertility of the soil at a rapid rate and alter the structure of the soil. This will lead to decrease in soil quality and poor quality of crops. Over the time the soil will become less productive due to the accumulation of toxic chemicals in large quantity.

Harmful Effect on Human Health

It will increase the exposure to toxic and harmful chemicals thus increasing health threats to people living nearby and on the degraded land. Living, working or playing in the contaminated soil can lead to respiratory diseases, skin diseases , and other diseases. Moreover, it can cause other health problems.

Water Sources Contamination

The surface run-off after raining will carry the polluted soil and enter into different water resource. Thus, it can cause underground water contamination thereby causing water pollution. This water after contamination is not fit for human as well as animal use due to the presence of toxic chemicals.

Negative Impact on Ecosystem and Biodiversity

Soil pollution can cause an imbalance of the ecosystem of the soil. The soil is an important habitat and is the house of different type of microorganisms , animals, reptiles, mammals, birds, and insects. Thus, soil pollution can negatively impact the lives of the living organisms and can result in the gradual death of many organisms. It can cause health threats to animals grazing in the contaminated soil or microorganisms residing in the soil.

Therefore, human activities are responsible for the majority of the soil pollution. We as humans buy things that are harmful and not necessary, use agricultural chemicals (fertilizers, pesticides, herbicides, etc.), drop waste here and there. Without being aware we harm our own environment.

Therefore, it is very important to educate people around you the importance of environment if they are not aware. Prevention of soil erosion will help to cease soil pollution. Thus, it is our small steps and activities that can help us to achieve a healthier planet for us. Therefore, it is essential for industries, individuals and businesses to understand the importance of soil and prevent soil pollution and stop the devastation caused to plant and animal life.

The solution to reduce the soil pollution

• Use of correct farming techniques
• Recycling of Waste before disposal, Recycle and Reuse Products
• Use of organic fertilizers instead of chemical fertilizers and pesticides
• Community education and awareness, Get the Locals Involved
• Proper maintenance of sewage system, Proper disposal method of household and industrial waste
• Reforestation and Afforestation Should be Promoted
• Planting new trees and plants is afforestation. We live because plants live. If the plants die, all living things will also die. Thus, whenever trees are cut down new trees should be planted. Planting trees in hilly areas are most effective for conservation.

How are people exposed to soil contaminants?

Contaminants in the soil can be present in all three periods (solid, liquid, and gaseous). As a result, these pollutants can enter the human body through a variety of routes, including direct skin contact or inhalation of contaminated soil dust.

Solved Examples for You

Question: List down some preventive measures of soil pollution?

• Recycling of Waste before disposal
• Proper disposal method of household and industrial waste
• Community education and awareness
• Proper maintenance of sewage system

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Global Assessment of Soil Pollution

Soil pollution is a chemical degradation process that consumes fertile soils, with implications for global food security and human health. Soil pollution hampers the achievement of Sustainable Development Goals (SDGs), including achieving zero hunger, ending poverty, ensuring healthy lives and human well-being, halting and reversing land degradation and biodiversity loss, and making cities safe and resilient. Most contaminants originate from human activities and enter into the environment because of unsustainable production chains, consumption patterns or inappropriate waste disposal practices.

In May 2018, FAO and its Global Soil Partnership (GSP), the World Health Organization (WHO), the Secretariat of the Basel, Rotterdam and Stockholm Convention and the United Nations Environment Programme (UNEP) organized the Global Symposium on Soil Pollution (GSOP18) to bring together science and policy to understand the status, causes, impacts and solutions to soil pollution. The Outcome document of the symposium, ‘ Be the solution to soil pollution ’ paved the way to the implementation of a coordinated set of actions to # StopSoilPollution .

This report considers both point source contamination and diffuse pollution, and detail also the risks and impacts of soil pollution on human health, the environment and food security, without neglecting soil degradation and the burden of disease resulting from exposure to polluted soil.

The Global Assessment of Soil Pollution report and its Summary for Policy makers will be launched on 4th June are a response to this request and as part of the World Environment Day celebrations and the launch of the UN Decade on Ecosystem Restoration. This report and its summary, coordinated by the FAO’s GSP, the ITPS, and UNEP, are the product of an inclusive process involving scientists from all regions.

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A Complete Guide To Soil Pollution: Causes, Effects, And Solutions

• October 27, 2023

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Soil pollution refers to the contamination of soil by harmful substances, such as chemicals, heavy metals, and waste materials. These pollutants can have a detrimental impact on the soil’s fertility, as well as the plants and animals that depend on it. Soil pollution can occur due to various human activities, including industrial waste disposal, agricultural practices, and improper waste management.

Soil pollution is a significant environmental issue that poses risks to human health, ecosystems, and the overall well-being of the planet. 

What Is Soil Pollution?

Soil pollution is the contamination of soil with toxic substances, making it unsuitable for its intended use. It is a complex issue that poses significant risks to human health and the environment. Soil plays a crucial role in supporting plant growth, providing nutrients, and regulating water and air quality. When the soil is polluted, it can have detrimental effects on the entire ecosystem.

Soil pollution can occur due to both natural processes and human activities, also known as anthropogenic factors. Natural sources of soil pollution include volcanic eruptions, weathering of rocks, and the deposition of pollutants from the atmosphere through rainfall. However, the majority of soil pollution is caused by anthropogenic factors, such as industrial activities, agricultural practices, improper waste disposal, and accidental spills.

What Are The Causes Of Soil Pollution?

There are six main causes of soil pollution: 

• Industrial activities & chemical contamination
• Agricultural practices & pesticide use
• Improper waste disposal & landfills
• Accidental oil spills
• Mining activities

1: Industrial Activities And Chemical Contamination

Industrial activities are a major contributor to soil pollution as the production and disposal of chemical substances, including heavy metals, pesticides, and industrial waste, can contaminate the soil. Industrial processes such as mining, manufacturing, and waste disposal often result in the release of toxic substances into the environment, which can seep into the soil and cause major pollution.

Chemicals used in industries, such as solvents, dyes, and heavy metals, can persist in the soil for a long time and have harmful effects on soil quality. Improper storage and disposal of industrial waste can lead to soil contamination, as toxic substances leach into the soil and groundwater. Industrial accidents, such as oil spills or chemical leaks, can also have severe consequences for soil health.

2: Agricultural Practices And Pesticide Use

Agricultural practices, particularly the use of pesticides and fertilizers, contribute significantly to soil pollution. Pesticides are chemicals designed to kill or control pests, including insects, weeds, and fungi. While pesticides are essential for crop protection and increased agricultural productivity, their excessive and improper use can contaminate the soil.

When pesticides are sprayed on crops, they can be absorbed into the surrounding soil, leading to contamination. One of the main issues is that pesticides can persist in the soil for extended periods, negatively affecting soil health and the organisms that depend on it. Additionally, the use of chemical fertilizers can lead to nutrient imbalances in the soil, altering its composition and affecting overall fertility resulting in poor crop yields and plant growth.

3: Improper Waste Disposal And Landfills

Improper waste disposal, including the dumping of solid waste and hazardous materials in landfills, is a significant cause of soil pollution. Landfills are designated areas for waste disposal, but if they are not properly managed, harmful substances can leach into the soil and contaminate it.

When organic waste decomposes in landfills via anaerobic decomposition, it produces leachate (a liquid that can contain toxic substances), methane (CH4), and carbon dioxide (CO2). If not adequately contained, leachate can seep into the soil and pollute groundwater sources and landfills can release methane gas – a potent greenhouse gas that contributes to climate change.

4: Accidental Oil Spills

Accidental oil spills, such as those that occur during transportation or due to industrial accidents, can have severe impacts on soil quality. When oil is spilled, it can coat the soil surface and block pores, reducing soil aeration and water infiltration.

The presence of oil in the soil can also alter its pH, making it less suitable for crop growth. Oil spills can also lead to the contamination of nearby water sources, further exacerbating the environmental impact. The cleanup and remediation of oil-contaminated soil can be a challenging and lengthy process.

5: Acid Rain

Acid rain occurs when pollutants, such as sulfur dioxide and nitrogen oxide, mix with rainwater and fall to the ground. Acid rain can dissolve essential nutrients in the soil, making them less available to plants, and change the soil’s pH, making it more acidic, affecting plant growth.

6: Mining Activities

Mining activities, such as the extraction of minerals and metals from the earth, can cause significant soil pollution. Mining operations often involve the removal of topsoil and vegetation, leading to soil erosion and degradation. The exposed soil is vulnerable to contamination from mining waste, including heavy metals and toxic chemicals.

The extraction and processing of minerals can release harmful substances into the soil and surrounding environment. Acid mine drainage, a phenomenon where acidic water is generated from mining activities, can contaminate soil and water sources, making them unsuitable for plant growth and other organisms to occupy the environment.

The Effects Of Soil Pollution

Soil pollution has numerous detrimental effects on both human health and the environment. The contamination of soil with toxic substances can have far-reaching consequences, affecting ecosystems, water quality, and agricultural productivity. Understanding these effects is crucial to developing effective strategies for soil remediation and pollution prevention.

Health Risks To Humans

One of the most significant impacts of soil pollution is the health risks it poses to humans. When soil is contaminated with toxic substances, these pollutants can enter the food chain and accumulate in plants, animals, and ultimately, humans. Consuming food grown in polluted soil can lead to the ingestion of harmful substances, including heavy metals and pesticides.

Exposure to these contaminants can cause a range of health problems, including organ damage, developmental disorders, neurological disorders, and an increased risk of cancer. Children, pregnant women, and individuals with compromised immune systems are particularly vulnerable to the health effects of soil pollution.

Biodiversity Loss

Soil is home to a diverse range of microorganisms, invertebrates, and plant roots that contribute to ecosystem functioning. When the soil is contaminated, these organisms can be harmed or even killed, disrupting the delicate balance of the ecosystem.

The loss of biodiversity in the soil can have cascading effects on the entire ecosystem. For example, soil-dwelling organisms play important roles in nutrient cycling, decomposition, and soil structure formation. Their decline can lead to imbalances in nutrient availability, reduced soil fertility, and increased susceptibility to erosion.

Impact On Agricultural Productivity

Agriculture heavily relies on healthy soil for crop growth and productivity. Soil pollution negatively affects agricultural lands, reducing crop yields and quality. When soil is polluted, plants may struggle to obtain essential nutrients and water, leading to stunted growth and poor productivity.

Contaminants in the soil can also affect the physiological processes of plants, making them more susceptible to diseases and pests, which conversely results in crop losses and reduced food production. Therefore, soil pollution poses a significant threat to global food security, especially in regions where agriculture is a primary source of livelihood, such as India .

Contamination Of Water Sources

Soil pollution can also lead to the contamination of important water sources, including groundwater and surface water pollution . When pollutants from the soil leach into water bodies, they can affect water quality and make it unfit for human consumption or irrigation purposes, negatively affecting both human and ecosystem health.

Groundwater contamination is particularly concerning, as it is the primary source of drinking water for many communities. Surface water pollution can also impact aquatic ecosystems, leading to the decline of fish populations and other aquatic organisms.

Climate Change

Soil pollution can contribute to climate change through various mechanisms. For example, the release of greenhouse gases from contaminated soil can contribute to global warming. Contaminated soil can release methane, a potent greenhouse gas, during the decomposition of organic matter.

Additionally, soil pollution can affect the carbon and nutrient cycling processes in the soil, leading to imbalances in greenhouse gas emissions. Changes in soil microbial communities and nutrient availability can influence the rates of carbon sequestration and greenhouse gas fluxes.

How To Measure Soil Pollution?

Several methods can be employed to measure and monitor soil pollution, ranging from laboratory analysis to remote sensing techniques.

One of the most common methods used to measure soil pollution is through laboratory analysis. Soil samples are collected from different locations and analyzed for the presence of pollutants such as heavy metals, pesticides, and organic contaminants. These samples are then tested using various techniques, such as atomic absorption spectroscopy, gas chromatography, and mass spectrometry, to determine the concentration of pollutants in the soil. This method provides accurate and detailed information about the extent and types of pollutants present in the soil.

Another method is through the use of field-based techniques. These techniques involve the use of portable instruments that can detect and quantify pollutants in real-time. For example, portable X-ray fluorescence (XRF) analyzers can be used to measure the concentration of heavy metals in the soil. Similarly, field-based gas analyzers can be used to measure the concentration of volatile organic compounds (VOCs) in the soil. These techniques are relatively quick and cost-effective, making them suitable for large-scale monitoring programs.

In addition to laboratory and field-based techniques, remote sensing can also be used to monitor soil pollution. Remote sensing involves the use of satellite imagery or aerial photography to assess changes in land use and vegetation health, which can be indicators of soil pollution. For example, changes in vegetation color or density may indicate the presence of pollutants in the soil. Remote sensing can provide valuable information about large areas, making it useful for regional or national-scale monitoring programs.

Apart from these direct methods, there are also indirect indicators that can be used to monitor soil pollution. For example, the presence of certain plants or organisms can indicate high levels of pollutants in the soil – these indicator species are known as bioindicators and their presence or absence can provide insights into the health of the soil.

Additionally, soil properties such as pH, organic matter content, and nutrient levels can also be monitored as they can be influenced by soil pollution.

How Can We Address Soil Pollution?

Addressing soil pollution requires a multifaceted approach that involves sustainable practices, proper waste management, and remediation techniques. By implementing these solutions, we can mitigate the harmful effects of soil pollution and protect the environment for future generations!

Sustainable Farming Practices

One of the key solutions to soil pollution is the adoption of sustainable farming practices. This includes practices such as organic farming, crop rotation, and integrated pest management. Organic farming reduces the reliance on synthetic pesticides and fertilizers, minimizing their impact on soil health.

Crop rotation helps to prevent nutrient depletion and the buildup of pests and diseases in the soil; farmers can maintain soil fertility and reduce the need for chemical inputs by rotating crops. Integrated pest management involves the use of natural predators, crop diversification, and cultural practices to manage pests, reducing the reliance on chemical pesticides.

Implementing Proper Waste Management And Recycling

Proper waste management is essential in preventing soil pollution. This includes properly disposing and recycling waste materials, such as plastics, electronic waste, and hazardous substances. Recycling and reusing materials help to reduce the generation of waste and minimize the disposal of harmful substances into the environment.

Landfills should be properly designed and managed to prevent the leaching of contaminants into the soil and groundwater. Efforts should be made to minimize the generation of waste and promote recycling and composting practices.

Employing Remediation And Restoration Techniques

Remediation and restoration techniques can be employed to clean up contaminated soil and restore its health and fertility. These techniques involve the removal or treatment of pollutants to reduce their concentration in the soil.

Bioremediation is a commonly used technique that utilizes microorganisms to degrade or transform pollutants into less harmful substances. Phytoremediation involves the use of plants to absorb and remove contaminants from the soil. 

Other techniques, such as soil vapor extraction, soil washing, and electrokinetic remediation, can also be employed depending on the type and extent of contamination.

Spreading Awareness And Educating Others

Increasing awareness and education about soil pollution is crucial in promoting sustainable practices and pollution prevention. Educating farmers, gardeners, and the general public about the harmful effects of soil pollution and the importance of soil conservation can help to drive positive change.

Government agencies, non-profit organizations, and educational institutions should collaborate to develop educational programs and campaigns that raise awareness about soil pollution and provide information on sustainable practices. This can include workshops, training sessions, and the dissemination of educational materials.

Historical Soil Pollution Events

Love canal, new york.

One notable case of soil pollution is the Love Canal incident in New York. In the 1940s and 1950s, a chemical company dumped thousands of tons of toxic waste into an abandoned canal. The area was later sold to a school district, and homes and schools were built on the site.

In the 1970s, residents began experiencing health problems, including birth defects and high rates of cancer. It was discovered that the soil and groundwater were contaminated with toxic chemicals, including dioxins and benzene . The incident led to the evacuation of the area and sparked national attention on the issue of soil pollution.

Bhopal Gas Tragedy, India

The Bhopal gas tragedy in India in 1984 was one of the worst industrial disasters in history. A pesticide plant leaked methyl isocyanate gas, resulting in the deaths of thousands of people and causing long-term health effects on the survivors.

The incident also led to soil pollution, as the gas and other chemicals released during the disaster contaminated the surrounding soil. The contaminated soil posed risks to human health and agricultural productivity in the area, which was devastating to India’s community where more than 50% of people rely on agriculture as their livelihood . 

Chernobyl Disaster, Ukraine

The Chornobyl nuclear disaster in Ukraine in 1986 resulted in the release of radioactive materials into the environment. The radioactive fallout contaminated the soil, making it unsuitable for agricultural activities.

The contaminated soil posed risks to human health and ecosystems in the affected areas , but since the disaster, major efforts have been made to remediate the soil and mitigate the long-term effects of the disaster.

Preventing Soil Pollution: Regulations And Policies

Addressing soil pollution requires the implementation of regulations and policies at the international, national, and local levels. 

Although the US currently has no legislation addressing soil pollution exclusively, the Food and Agricultural Organization of the United Nations (FAO) said that “ soil protections are woven into all major environmental legislative actions ”. 

However, many countries have developed regulations and policies to address soil pollution. These may include laws on waste management, pollution prevention, and the use of chemicals in agriculture. For example, in China, The Soil Pollution Prevention Law, which involves investigating, remediating, and managing soil contamination, is the first comprehensive framework law to address soil pollution in the country. 

Local governments can also play a crucial role in enforcing these regulations and promoting sustainable practices in their communities.

Future Perspectives And Emerging Technologies For Preventing Soil Pollution

Advances in technology and scientific research offer new opportunities to address soil pollution and develop more sustainable solutions. Several emerging technologies show promise in soil remediation and pollution prevention.

Soil Bioremediation

Soil bioremediation involves the use of microorganisms, such as bacteria and fungi, to degrade or transform pollutants in the soil. These microorganisms can break down organic pollutants and convert them into less harmful substances.

Bioremediation techniques can be applied in situ, where the microorganisms are introduced directly into the contaminated soil, or ex-situ, where the soil is excavated and treated in a controlled environment. Bioremediation offers a cost-effective and environmentally friendly approach to soil pollution cleanup.

Nanotechnology And Soil Pollution Remediation

Nanotechnology has the potential to revolutionize soil pollution remediation by providing new tools and materials for pollutant removal. Nanoparticles, such as zero-valent iron and titanium dioxide, can be used to adsorb or degrade contaminants in the soil.

Nanoremediation techniques offer advantages such as high efficiency, selectivity, and the ability to target specific pollutants. However, the potential risks and long-term effects of nanotechnology on soil and ecosystem health need to be carefully evaluated.

Circular Economy Approaches

Transitioning to a circular economy can help to prevent soil pollution by promoting resource efficiency, waste reduction, and the reuse of materials. The concept of a circular economy involves designing products and systems that minimize waste generation and maximize the value of resources.

By implementing strategies such as recycling, reusing, and repurposing waste materials, we can reduce the demand for new resources and minimize the generation of pollution. Circular economy approaches can contribute to a more sustainable and resilient soil ecosystem.

Soil Pollution In Conclusion

Soil pollution is a significant environmental problem that poses risks to human health, ecosystems, and agricultural productivity. 

By taking action to prevent and mitigate soil pollution, we can protect the environment and ensure the health and well-being of future generations.

If you have any questions regarding soil pollution or how to prevent it, do not hesitate to contact the world-class team at Atlas Scientific .

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Global assessment of soil pollution

Study Session 7  Pollution: Types, Sources and Characteristics

Introduction.

You were introduced to wastes and pollutants in Study Session 1, where we discussed the interactions between humans and our environment. Pollution was defined as the introduction into the environment of substances liable to cause harm to humans and other living organisms. Many human activities pollute our environment, adversely affecting the water we drink, the air we breathe, and the soil in which we grow food.

In this and the next study session we will look more closely at pollution. In this session you will learn about the different types and sources of pollution and the various human activities that can cause pollution. We will also describe the ways pollution can affect different sectors of the environment: water, air and soil. Study Session 8 describes some of the significant effects of pollution on the environment and on human health. It also discusses options for preventing and controlling pollution.

Learning Outcomes for Study Session 7

When you have studied this session, you should be able to:

7.1  Define and use correctly all of the key words printed in bold . (SAQs 7.1, 7.2, 7.3 and 7.4)

7.2  Describe the main types of pollution. (SAQ 7.3)

7.3  Describe the sources of pollution and the way pollutants reach the environment. (SAQ 7.4)

7.4  Describe the main characteristics of water, air and soil pollution. (SAQ 7.5)

7.1  What is pollution?

If you hold up a glass of water in front of you, how can you tell if it’s polluted? You would expect drinking water to be colourless, odourless and transparent (not turbid with suspended particulates). If it was not all of these things, then it could be polluted. If you were looking at water in a river, it is unlikely to be as clear as drinking water in a glass, but you could deduce it was probably not polluted if you observed that the water did not look dirty or smell bad. You might also observe that animals were drinking the water without ill effects and fish were swimming in it. However, if the water was discoloured or had an unpleasant odour, or you could see dead fish floating on the surface you could conclude that pollution was the problem.

Let us consider the human activity that could have caused the pollution. Imagine a river that flows through an area of land on the edges of a town. The water is used by the community for drinking and other domestic uses and also for vegetable farming. Several residents use this water to irrigate small areas of land where they cultivate vegetables and many of the farmers use fertiliser and pesticide to improve productivity (Figure 7.1). Fertilisers are made of chemicals such as nitrogen, potassium and phosphorus, which are essential plant nutrients. Pesticides are chemicals that destroy pests but can be harmful to other forms of life – including humans.

Imagine that one farmer has finished spreading the chemicals on his crop and decides to wash the empty pesticide sack he has been using in the river. Later that day, it rains heavily and rainwater is seen running off the field into the river. What do you think happens? The river is receiving run-off containing fertiliser and pesticide chemicals that had been applied to the crops, which is made worse by the farmer washing his sack that had contained the pesticide. This could harm fish and other organisms living in the water – possibly killing them. The river is also used by the community so the chemicals could get into drinking water that is consumed by humans. The river has been polluted by the careless action of the farmer washing his sack and by the action of rainwater washing the chemicals into the river.

Pollution always has a source and a recipient. The source is where the pollution comes from, that is, where the pollution is released into the environment. The recipient is where the pollution ends up, which may be a part of the environment or people or animals that become contaminated or damaged.

In the above example about the farmer washing the pesticide sack in the river, what is the source and what is the recipient of the pollution?

The pollution source is the activity of urban farming with pesticides and fertilisers and washing sacks so that pollutants get into the river. In this example, the primary recipient is the water body that receives the pollutants. Other recipients are the people who drink the contaminated water and animals such as fish that also are affected.

There are a number of ways of identifying pollution. These include finding symptoms of damage to aquatic plants and animals (such as dead fish), finding chemicals in the water, comparing the previous history of the quality of water with the present quality, and getting complaints from water users. Even when a problem has been found, investigations to identify the source may take time. For example, water samples from several different points upstream and downstream will need to be analysed to locate precisely where the problem originated.

There are several different ways of classifying pollutants. They can be categorised by their physical nature, by their source, by the recipient or by the sector of the environment affected. In the following sections we will look at each of these classification groups

7.2  Physical nature of the pollutant

Pollutants may be in the form of gas, liquid, solid or energy.

What polluting gases can you think of?

Greenhouse gases are pollutants that contribute to human-induced climate change (mentioned in Study Session 1). The main greenhouse gases are carbon dioxide, methane and nitrogen oxides.

Liquid pollutants usually come from liquid waste. Liquid waste includes human excreta (both faeces and urine), industrial wastewaters and other forms of waste from water-using activities (Figure 7.2). Factories generate liquid waste from activities related to washing in the manufacturing process, cleaning objects and chemical mixing. Sewage is a mixture of human excreta from water-flushed toilets and other wastewater from houses and businesses. Sewage and human waste from overflowing septic tanks and latrines are frequent sources of pollution.

Urban run-off is another type of liquid waste that can cause pollution. Rainwater washes many different types of waste from the land surface into lakes and rivers. Urban run-off can contain a lot of organic matter. This may come from open defecation or inappropriate handling of organic wastes produced from households and businesses. Organic matter includes anything that is derived from living organisms, such as human and animal wastes, decaying plants and food wastes.

Pollutants also come in solid form. Plastic bags are one of the most common solid wastes. Solid waste is any solid material that is assumed not to be useful and is therefore thrown away. Factories, businesses and households produce different kinds of solid waste such as paper, plastics, metals, chemicals in solid form, pieces of cloth or food and animal remains (Figure 7.3). Sometimes you may have observed faecal matter discarded with solid waste, which adds to the problems.

There is a fourth type of pollution that is common in urban communities. This is energy in the form of noise pollution. Noise pollution means unacceptable levels of noise in work, residential and recreational places. Noise makes it difficult to have a conversation and also irritates and disturbs us and in the long term can damage our hearing. Loud music from music shops and clubs in an urban community is a known source of noise disturbance. Such noise may please some, but it disturbs many other people because it interferes with communication in the daytime and sleeping at night.

7.3  Sources of pollution

Another way of classifying pollution is by the sector of human activity that produces it. Before we look at the various sectors, there is an important distinction to be made about pollution sources. Sources of pollution can be categorised as point or non-point sources. Point sources are identifiable points or places that you can easily locate. An example is a diesel truck that produces visible black exhaust fumes from its tailpipe. Liquid waste released from a pipe into a river is another example (Figure 7.4). A non-point source (also known as ‘diffuse pollution’) is one where it is difficult to identify the exact origin of the pollution. A good example is floodwater that washes all types of waste from the land (possibly including faecal matter) into a river. In this situation you cannot identify the individual or household or establishment that has caused the water pollution (Figure 7.5).

Can you think of examples of point and non-point source pollution from earlier in this study session?

The farmer washing his sack is an example of a point source because you could identify where he washed his sack. However, the pesticide washing from the field is an example of a non-point source. The pollutant would wash into the river at several places, and could possibly also have come from other fields. This is an example of how difficult it can sometimes be to accurately identify the source.

7.3.1  Domestic sources

Domestic sources of pollution include toilets, latrines and wastewater from kitchens and bathrooms. If these wastes are properly contained and prevented from getting into the environment, they will not cause pollution. However, frequently this is not the case. Open defecation obviously releases human waste into the environment, which can then be washed into rivers and other surface waters.

What types of organic waste are produced by a typical household?

The organic wastes from domestic sources include human excreta and also food waste and other kitchen waste such as cooking oil residues.

Solid wastes from households and also from shops, markets and businesses include food waste, packaging materials and other forms of rubbish. Domestic sources are also responsible for gaseous pollutants in the form of smoke and carbon dioxide from domestic fires.

7.3.2  Industry

Pollution from the industrial sector in Ethiopia has been on the rise, posing a serious problem to the environment. Many industrial processes produce polluting waste substances that are discharged to the environment, frequently through chimneys (to the air) or through pipes (to surface water) (Figure 7.6). Among the most polluting industries are food processing, tanneries and textiles with processing plants and factories that produce liquid effluents which are discharged into rivers, often without treatment (Ademe and Alemayehu, 2014; Wosnie and Wondie, 2014). In practice, rivers frequently receive polluting discharges from many different sources all at the same time. The Little Akaki River in Addis Ababa, for example, is polluted by several different industrial sources as well as by domestic wastes (Tegegn, 2012).

7.3.3  Agriculture

Like industry, agricultural activities are also increasing in Ethiopia, and changing too. Nowadays, agricultural activities in Ethiopia use more pesticides and fertilisers. Ethiopia imports over 3000 tons of various types of pesticides annually (Federal Environment Protection Authority, 2004). Fertiliser use in Ethiopia has increased from 140,000 metric tons in the early 1990s to around 650,000 metric tons in 2012 (Rashid et al., 2013). Fertiliser contains phosphate and nitrate and if these reach water bodies they can cause excessive plant growth (Figure 7.7).

Agriculture is also responsible for gaseous pollutants in the form of methane produced by livestock and solid pollutants from crop residues, packaging materials and other wastes similar to those produced domestically. Animals also contribute to waste products and potential pollutants with their excrement.

7.3.4  Transport

Do you live in a city or have you visited a city close to where you live? If so you will no doubt be familiar with the variety of vehicles on our roads (Figure 7.8). Some are small cars, others are heavy motor trucks. These vehicles differ not only in their size, but also by using different types of fuel such as petrol, diesel, and blended fuel (10% ethanol and petrol). If you observe the tailpipe of diesel engine vehicles, you will have seen the black exhaust gas produced. The intensity of the black colour is greater for poorly maintained vehicles, to the extent sometimes that it makes the air hazy or smoky and causes coughs and eye irritation. The lack of a policy to remove old vehicles from the roads adds to the problem. Tiwari (2012) found that nearly a third of vehicles in Addis Ababa were over 30 years old, resulting in high levels of tailpipe emissions. Traffic jams, common in all big cities, make the problems worse.

7.4  Pathways of pollution

We said earlier that pollution always has a source and a recipient. The pathway of pollution is the way the pollutant moves from the source, enters into the environment, and finally how it reaches the human body or other recipient. The pathway between source and recipient can take several different forms depending on the type of pollutant. Primary recipients for pollution are water, air, and soil. Pollutants usually reach humans through the consumption of contaminated and polluted water and food, and breathing polluted air.

Once released into the environment, the worst effects of many pollutants are reduced by one or more of the following processes:

• Dispersion – smoke disperses into the air and is no longer noticeable away from the source.
• Dilution – soluble pollutants are diluted in the water of a river or lake.
• Deposition – some suspended solids carried in a river settle (are deposited) on the river bed.
• Degradation – some substances break down (degrade) by natural processes into different, simpler substances that are not polluting.

In each case the effect is to reduce the concentration of the pollutant. Concentration is a measure of the amount of the substance in a known volume of water or air. The units used for water pollutants are usually milligrams per litre (mg/l, also written as mg l -1 ), although sometimes you may see ppm which stands for ‘parts per million’.

These processes do not apply to all pollutants. There are some persistent pollutants which remain intact when released into the environment because they do not break down by natural processes. These are described in Study Session 8.

7.5  Sector of the environment affected by pollution

Classifying pollution by the sector of the environment affected – water, air, soil and land – is probably the most commonly used method.

7.5.1  Water pollution

Water pollution can affect surface water such as rivers and lakes, soil moisture and groundwater in aquifers, and the oceans. As you know from Study Session 4, the actions of the water cycle connect all these different reservoirs of water. For example, a polluted river will discharge into the ocean and could damage the marine environment. However, the volume of water in the ocean can disperse and dilute the pollutant so that its worst effects are only felt near the mouth of the river.

Water pollution is characterised by the presence of excess physical, chemical or biological substances that change the qualities of the water and are capable of causing harm to living organisms. We mentioned earlier that natural or unpolluted water is colourless, odourless and transparent. Water that tastes or smells bad or is cloudy can be said to have the symptoms of water pollution. However, some water pollutants cannot be seen or tasted, for example some chemicals, such as pesticides, and most of the micro-organisms that cause waterborne diseases. So, water pollution involves more than just the appearance of the water. Polluted water should not be used for drinking, washing, bathing or agriculture. If polluted water is used by humans, then it can adversely affect the body in different ways, depending on the type and concentration of pollutant.

You also read in Study Session 4 that most rivers and streams in Ethiopia contain significant quantities of suspended solids that are carried along in the flow and make the water look brown in colour, especially in the rainy season (Figure 7.9). Most of the solids are fine particles of soil that have been washed into the river from surrounding land by rain, often following cultivation or construction work. Large quantities of solids in the water can reduce light penetration into the water which can affect the growth of plants.

Biological water pollutants are micro-organisms that are harmful to humans and other forms of life. They are responsible for many different waterborne diseases. The original source of these pollutants is people or animals already infected with the micro-organisms concerned. If faeces from infected people are not correctly contained and treated, the pollutants can get into surface and groundwater. The main groups of biological pollutants are bacteria, viruses, protozoa and helminths (worms).

Chemical water pollutants take many different forms depending on their source. They include plant nutrients (compounds of phosphorus and nitrogen) used as fertilisers which, as you read earlier, can be washed from fields into rivers. These nutrients are also produced by the breakdown of human and animal wastes and are common pollutants of surface waters.

Chemical pollutants also include heavy metals , pesticides and other persistent pollutants. Heavy metals are a group of toxic chemical pollutants that contain compounds of persistent metals such as mercury, cadmium, lead and chromium. The presence of heavy metals in water in excess of acceptable levels can cause illness and death among animals and humans if consumed through drinking and food (Zinabu and Pearce, 2003).

Persistent organic pollutants (POPs) are also toxic to humans and wildlife. They include many different synthetic organic chemicals manufactured for use as pesticides and in industrial processes, e.g. DDT, aldrin and PCBs (polychlorinated biphenyls). Many of these persistent chemicals have been banned in some countries. Their persistence in the environment creates specific problems that are described in Study Session 8.

7.5.2  Air pollution

Air pollution can exist at all scales, from local to global, and can include gases and solid particles. It can affect you in your own home, or in your town or city, and can contribute to global atmospheric changes. The most common sources of air pollution in the urban centres of Ethiopia include the burning of wood, charcoal and other biomass fuel by households, small businesses such as bakeries, manufacturing industries, and vehicles.

Air pollution is defined as the presence in the air of abnormal amounts of chemical constituents capable of causing harm to living organisms. Clean air consists of nitrogen (78% by volume), oxygen (21%) and trace gases (< 1%). Polluted air may contain particulate matter (such as black soot) and many different gaseous chemicals such as carbon monoxide, carbon dioxide, nitrogen oxides, sulphur oxides, ozone, nitrates, sulphates, organic hydrocarbons and many others. Many of these are also found in clean air as trace gases but they become pollutants if present in abnormal quantities.

The emission of black smoke is an indication of intense pollution. However, not all air pollution is visible or can be smelled. Gases such as carbon monoxide and carbon dioxide are invisible and odourless. Carbon monoxide is very dangerous to humans. It can be produced by inefficient burning of fuel (for example a charcoal stove in a home with inadequate air supply) and if breathed in large quantities it can be deadly. Carbon dioxide is an important pollutant that is involved in climate change. (You will learn about in climate change in Study Sessions 9, 10 and 11.)

7.5.3  Soil and land pollution

Soil pollution, also called land pollution, is linked to water pollution. Liquid wastes containing toxic chemicals or pathogenic micro-organisms on the surface of the land can seep slowly into the soil and may percolate down to contaminate groundwater, which can affect people using springs or wells in the area. Possible sources include open defecation, pit latrines or leaking storage containers for industrial chemicals and wastes.

Solid waste can cause soil pollution. A collection of solid wastes in one place or scattered around is unsightly and might smell bad to you as you pass by (Figure 7.10). Household waste typically consists mostly of food waste that will gradually decompose. This produces a bad odour and attracts insects and rats, both of which contribute to the transmission of disease. As the waste decomposes it produces a liquid called leachate which trickles down into the soil. Leachate is a highly concentrated liquid pollutant that may contain toxic chemicals and pathogenic micro-organisms as well as high levels of organic compounds. Rainwater falling on, and washing through, solid waste adds to the problem.

Summary of Session 7

In Study Session 7, you have learned that:

• Environmental pollution is the result of human activity and development that occurs when physical, biological and chemical agents are released to the environment in such quantities that the pollution adversely affects human health and damages the environment.
• Pollution can be classified by its physical nature, by its source, by its recipient, by the sector affected or by its effects.
• Pollution may be in the form of a gas, liquid, solid or energy.
• Sources of pollution may be point sources, which are easily identified, or non-point sources, where the pollution comes from diffuse sources that are not easy to pinpoint.
• There are different types of pollution: water pollution, air pollution, solid waste pollution and noise pollution. All of these can be found in urban areas.
• The main sources of pollution are household activities, factories, agriculture and transport.
• Once they have been released into the environment, the concentration of some pollutants is reduced by dispersion, dilution, deposition or degradation.
• Water can be contaminated by physical pollutants (solid material), biological pollutants (such as bacteria that cause waterborne diseases), and many different chemical pollutants.
• Air pollution can be caused by gases or solid particulates.
• Soil pollution is linked to groundwater pollution. Solid waste can produce highly polluting leachate which contaminates soil groundwater.

Self-Assessment Questions (SAQs) for Study Session 7

Now that you have completed this study session, you can assess how well you have achieved its Learning Outcomes by answering these questions.

SAQ 7.1 (tests Learning Outcome 7.1)

Why is a point source of pollution easier to identify than a non-point source of pollution?

Point sources of pollution are easier to identify because they come from points or places that you can easily locate, such as a pipe discharging waste into a river. A non-point source is more difficult to identify because it does not come from just one place, but can come from a wide area, for example fertiliser washing off a number of fields or floodwater that washes waste from latrines.

SAQ 7.2 (tests Learning Outcome 7.1)

Rewrite the sentences below using terms from the list provided to fill the gaps:

concentration, heavy metals, organic matter, persistent pollutant, sewage.

……………… consists of human excreta and wastewater. It has a high ……………… of ………………

Some pollutants, called ………………, do not break down naturally in the environment. Examples are mercury, cadmium and other ………………

Sewage consists of human excreta and wastewater. It has a high concentration of organic matter .

Some pollutants, called persistent pollutants , do not break down naturally in the environment. Examples are mercury, cadmium and other heavy metals .

SAQ 7.3 (tests Learning Outcomes 7.1 and 7.2)

Describe what is meant by the terms liquid waste and solid waste, using examples from your own experience to illustrate your answer.

Liquid waste is liquid material that is thrown away, or discharged into the environment. From the household you might include human excreta (both faeces and urine) and other wastewaters. In your area you might also see urban run-off when rain washes waste from the land surface. You might also see liquid waste discharged from factories through a pipe into a river.

Solid waste is any solid material that is assumed not to be useful and is therefore thrown away; examples that you might use include food waste, cloth, paper and plastic that are thrown out from your own household or that you see in the area where you live.

SAQ 7.4 (tests Learning Outcomes 7.1 and 7.3)

For the scenarios (a) to (d), fill in the table below to show the pollutant, the source of pollution, the possible pathways and the recipients:

• a. A farmer washes an empty pesticide sack in a river; the river flows into a lake which is used for drinking water by people from a local town.
• b. Rain falls on a waste dump used to collect household waste; the waste dump isn’t properly sealed and liquid percolates down into the soil and into groundwater that is extracted from a nearby well for domestic use.
• c. A tannery based in a town produces liquid waste that contains organic matter and chemicals used in the tanning process; this effluent is discharged into the local river which flows out of the town and through a nature park.
• d. A bus driving through a busy town emits black smoke from its tailpipe.

SAQ 7.5 (tests Learning Outcome 7.4)

Describe how water pollution can change the characteristics of water.

Natural or unpolluted water is colourless, odourless and transparent. Water pollution changes the characteristics of water by the presence of excess physical, chemical or biological substances that change the qualities of the water and are capable of causing harm to living organisms.

Polluted water can taste or smell bad or be cloudy. Polluted water can contain suspended solids that make the water look brown in colour; most of the solids are fine particles of soil that have been washed into the river by rain from surrounding land. Large quantities of solids in the water can reduce light penetration into the water which can affect the growth of plants.

Water pollution changes more than just the appearance of the water. Polluted water can also contain chemicals, such as pesticides, fertilisers and heavy metals that are toxic. Polluted water also can contain biological substances such as organic matter and micro-organisms that cause waterborne diseases.

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Soil Pollution and Remediation

Jorge paz-ferreiro.

1 School of Engineering, RMIT University, GP.O. Box 2476, Melbourne VIC 3001, Australia; [email protected]

2 Centre for Environmental Sustainability and Remediation, RMIT University, GP.O. Box 2476, Melbourne VIC 3001, Australia

Gabriel Gascó

3 Departamento de Producción Agraria, E.T.S.I. Agronómica, Alimentaria y de Biosistemas, Universidad Politécnica de Madrid, Ciudad Universitaria, 28004 Madrid, Spain; [email protected]

Ana Méndez

4 Departamento de Ingeniería Geológica y Minera, E.T.S.I. Minas y Energía, Universidad Politécnica de Madrid, C/Ríos Rosas No. 21, 28003 Madrid, Spain; [email protected]

Suzie M. Reichman

Industrialized economies and developing countries are affected by soil pollution originating from mining, industrial activities, improper disposal of waste, and mechanized agriculture. Soil pollution could lead to impacts on crop productivity and human health. Investigating the sources, fate and occurrence of soil pollution, and the risks posed to human health has thus been an important area of research.

An increasing amount of research has been devoted to finding innovative and sustainable solutions for the remediation of contaminated land. The multiple challenges associated with the remediation of polluted soils have been overcome by the use of soil amendments, thermal desorption, soil washing, electrokinetic remediation, and bioremediation.

This Special Issue collects research papers aimed at a wide range of soil remediation topics, presenting an integrated view of the trends in solving the problems associated with the obtaining successful soil remediation. This special issue contains eleven articles that have been selected as emerging studies dealing with the above-mentioned topics.

Two of the articles presented in this special issue were directly devoted to assisted phytoremediation. Phytoremediation has been increasingly used in recent years as it has significant co-benefits, including providing a plant cover to the soil which contributes to reduced erosion. The success of phytoremediation approaches depends ultimately on plant growth and the concentration of the element of interest absorbed by the plant. Thus, Radziemska et al. [ 1 ] used different materials for assisted phytostabilization, including diatomites, halloysite, and chalcedonite. They found the last two to be more effective when combined with Brassica napus . Huang et al. [ 2 ] pyrolyzed organic matter, a technique which can contribute to reduce waste streams while producing a material with better characteristics for soil addition called biochar. Biochar has been used as a soil amendment due to its ability to immobilise heavy metals, including Zn [ 3 ] and Cd [ 4 ], while contributing to carbon sequestration [ 5 ]. Huang et al. [ 2 ] produced three biochars with different characteristics which were then trialled for assisted phytostabilization using Cassia alata , of a mine tailing contaminated with several heavy metals. Their biochar improved plant growth and generally enhanced the root uptake of several elements. However, the risk of As release was observed at higher biochar doses.

The addition of innovative materials to the soil was also a focus of Jiang et al.’s study [ 6 ]. A nanometallic aluminium/calcium oxide dispersion mixture was shown to be highly efficient for the dechlorination of hexachlorobenzene. The material prepared by these authors has the potential to result in a more cost-effective remediation than the more commonly utilised Ca/CaO dispersion mixtures.

Structural differences in pollution patterns were a focus of several articles in this special issue. Skala et al. [ 7 ] studied the contribution of organochlorine pesticides, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls to human health risks in floodplains. Health risk assessment was also a focus of the study by Retamel-Salgado et al. [ 8 ]. In this case, the health risk posed by the consumption of maize growing in three soils with contrasting characteristics polluted with cadmium was evaluated.

Wang and Zhang [ 9 ] studied the influence of soil properties, vegetation, and road age on heavy metal concentrations in roadside soils in Hangzhou. Hu et al [ 10 ] and Jia et al. [ 11 ] studied the spatial variability of heavy metals in soils using geostatistics. Zhou et al. [ 12 ] studied the variability of chromate in a topsoil and its corresponding subsoil concentrations.

Yang et al. [ 13 ] used composted sewage sludge as an additive to an urban garden soil. Total concentrations, nonresidual fractions, and bioaccessibility of Cr, Cu, Pb, and Zn increased after addition of composted sewage sludge to the soil.

Zhu et al. [ 14 ] studied Ni toxicity to barley and correlated it with a single EDTA extraction and three sequential extractions with EDTA. They found that multiple extractions improved the prediction of the toxicity models.

This body of work presented in this special issue shows the potential for assessing and remediating polluted soils. The work showcased to stakeholders how innovative systems can be integrated into traditional soil remediation

Conflicts of Interest

The authors declare no conflict of interest.

• Agriculture
• Environmental Science
• Soil Pollution

Soil Pollution Education: A Broad View of Knowledge on Soil Pollution and Educational Activities for Undergraduate Students

• Universitat Politècnica de València

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