Types and Consequences of Different Kinds of Pollution: Air, Water, Soil, and Noise, Schemes and Mind Maps of Environmental Science

Download Types and Consequences of Different Kinds of Pollution: Air, Water, Soil, and Noise and more Schemes and Mind Maps Environmental Science in PDF only on Docsity! ENVIRONMENTAL STUDIES BPO A Air and air pollution: its causes and impact on human settlements. Control measures of: (a) Air pollution (b) Water pollution (c) Soil pollution (d) Marine pollution (e) Noise pollution (f) Thermal pollution (g) Nuclear hazards – soil waste management: disaster management: floods, earthquake, cyclone and landslides. Environment protection act – Air (Prevention and Control of Pollution) act – Water (Prevention and control of Pollution) act – Wildlife protection act – Forest conservation act. • As stated before, there are different types of pollution, which are either caused by natural events (like forest fires) or by man- made activities (like cars, factories, nuclear wastes, etc.) These are further classified into the following types of pollution: • Air Pollution • Water Pollution • Soil Pollution • Noise Pollution • Besides these 4 types of pollution, other types exist such as light pollution, thermal pollution and radioactive pollution. The latter is much rarer than other types, but it is the deadliest. • There are various types of pollution chiefly arising as a result of anthropogenic causes. Also contributing to pollution is globalisation, where humanity’s constant need for natural resources has slowly started to change the face of the earth. • Though the quality of living has drastically improved, other new issues have risen that gradually impact human health and the environment. In this article, we shall explore the meaning, causes and types of pollution. Also, we shall analyse the repercussions of pollution on human health and the environment. Types of Pollution @ Air pollution | @ water pollution | © Soil pollution | @ Noise pollution • Water pollution is said to occur when toxic pollutants and particulate matter are introduced into water bodies such as lakes, rivers and seas. These contaminants are generally introduced by human activities like improper sewage treatment and oil spills. However, even natural processes such as eutrophication can cause water pollution. • Other significant causes of water pollution include: • Dumping solid wastes in water bodies • Disposing untreated industrial sewage into water bodies • Human and animal wastes • Agricultural runoff containing pesticides and fertilisers • The effects of water pollution are very pronounced in our environment. Furthermore, toxic chemicals can bioaccumulate in living beings, and these chemicals can travel their way up the food chain, ultimately reaching humans. Particulate matter is the sum of all solid and liquid particles suspended in air many of which are hazardous. Eutrophication is the process by which a body of water becomes overly enriched with minerals and nutrients which induce excessive growth of algae. Bioaccumulate- (of a substance) become concentrated inside the bodies of living things. Surface runoff is the flow of water occurring on the ground surface when excess rainwater, stormwater, meltwater, or other sources, can no longer sufficiently rapidly infiltrate in the soil. • Among the other types of pollution, water pollution has a more disastrous consequences on humans. For instance, in 1932, a grave case of water pollution incapacitated the inhabitants of an entire city in Japan with neurological diseases and mental illness for many decades. However, the immediate cause was not apparent but was eventually attributed to acute mercury poisoning. Methylmercury was dumped into the surrounding bay and had ultimately bioaccumulated inside the fish. The local population then consumed these fish, and this resulted in the manifestation of ill-effects and neurological diseases. Incapcitated- deprived of strength or power; debilitated. • Other consequences of water pollution include: • Disruption of the ecosystem • Threats to marine life • Increased risk of water-borne diseases • Increases toxic chemicals (such as mercury) in water bodies • Eutrophication • The effects of soil pollution are numerous. Specific wastes, such as radioactive waste become particularly hazardous when they are not well-contained. A well-documented example is a nuclear accident in Chernobyl, which has left an area of 2,600 km2 uninhabitable for several thousand years. • Other effects of soil pollution include: • Loss of soil nutrients, which renders the soil unfit for agriculture • Impacts the natural flora and fauna residing in the soil • Degrades vegetation due to the increase of salinity of the soil • Toxic dust (such as silica dust) can cause respiratory problems or even lung cancer • Noise pollution refers to the excessive amount of noise in the surrounding that disrupts the natural balance. Usually, it is man- made, though certain natural calamities like volcanoes can contribute to noise pollution. • In general, any sound which is over 85 decibels is considered to be detrimental. Also, the duration an individual is exposed plays an impact on their health. For perspective, a normal conversation is around 60 decibels, and a jet taking off is around 15o decibels. Consequently, noise pollution is more obvious than the other types of pollution. • Noise pollution has several contributors, which include: • Industry-oriented noises such as heavy machines, mills, factories, etc. • Transportation noises from vehicles, aeroplanes, etc. • Construction noises • Noise from social events (loudspeakers, firecrackers, etc.) • Household noises (such as mixers, TV, washing machines, etc.) • Air pollution refers to any physical, chemical or biological change in the air. It is the contamination of air by harmful gases, dust and smoke which affects plants, animals and humans drastically. • There is a certain percentage of gases present in the atmosphere. An increase or decrease in the composition of these gases is harmful to survival. This imbalance in the gaseous composition has resulted in an increase in earth’s temperature, which is known as global warming. • Air pollution is any gas or particle matter built up in the atmosphere that can cause harm to your health and the environment. Pollutants come from several sources, many are man-made from domestic fuel burning, industrial processes and transport. But they can also occur naturally. • Long-term exposure to air pollution has serious impacts on health, leading to a range of health conditions. • There are two types of air pollutants: • Primary Pollutants • The pollutants that directly cause air pollution are known as primary pollutants. Sulphur-dioxide emitted from factories is a primary pollutant. • Secondary Pollutants • The pollutants formed by the intermingling and reaction of primary pollutants are known as secondary pollutants. Smog, formed by the intermingling of smoke and fog, is a secondary pollutant. • Following are the important causes of air pollution: • Burning of Fossil Fuels • The combustion of fossil fuels emits a large amount of sulphur dioxide. Carbon monoxide released by incomplete combustion of fossil fuels also results in air pollution. • Automobiles • The gases emitted from vehicles such as jeeps, trucks, cars, buses, etc. pollute the environment. These are the major sources of greenhouse gases and also result in diseases among individuals. • The hazardous effects of air pollution on the environment include: • Diseases • Air pollution has resulted in several respiratory disorders and heart diseases among humans. The cases of lung cancer have increased in the last few decades. Children living near polluted areas are more prone to pneumonia and asthma. Many people die every year due to the direct or indirect effects of air pollution. • Global Warming • Due to the emission of greenhouse gases, there is an imbalance in the gaseous composition of the air. This has led to an increase in the temperature of the earth. This increase in earth’s temperature is known as global warming. This has resulted in the melting of glaciers and an increase in sea levels. Many areas are submerged underwater. • Acid Rain • The burning of fossil fuels releases harmful gases such as nitrogen oxides and sulphur oxides in the air. The water droplets combine with these pollutants, become acidic and fall as acid rain which damages human, animal and plant life. • Ozone Layer Depletion • The release of chlorofluorocarbons, halons, and hydro chlorofluorocarbons in the atmosphere is the major cause of depletion of the ozone layer. The depleting ozone layer does not prevent the harmful ultraviolet rays coming from the sun and causes skin diseases and eye problems among individuals. • Effect on Animals • The air pollutants suspend on the water bodies and affect the aquatic life. Pollution also compels the animals to leave their habitat and shift to a new place. This renders them stray and has also led to the extinction of a large number of animal species. 4. Although there are many practices in India, which focus on repairing the quality of air, most of them are either forgotten or not being enforced properly. There are still a lot of vehicles on roads which haven’t been tested for vehicle emissions. 5. An other way of controlling air pollution caused by industries is to modify and maintain existing pieces of equipment so that the emission of pollutants is minimized. 6. Sometimes controlling pollutants at the source is not possible. In that case, we can have process control equipment to control the pollution. 7. A very effective way of controlling air pollution is by diluting the air pollutants. 8. The last and the best way of reducing the ill effects of air pollution is tree plantation. Plants and trees reduce a large number of pollutants in the air. Ideally, planting trees in areas of high pollution levels will be extremely effective • Outdoor air pollution can be split into two sources: natural and man-made. Natural sources of air pollution include sea salt spray, dust, and volcano ash. Man-made sources of pollution include waste management, farming, agriculture, and industrial processes. • We spend around 90% of our time indoors. This means that many of us will at some point be affected by indoor air pollution, either in your home or workplace. • Many things can affect your home’s air quality, such as: • How you cook • Heating • Poor ventilation • Damp, mould and asbestos • Chemicals from cleaning products • Building materials • Daily Air Quality Index (DAQI) to measure outdoor pollution levels. It covers five main pollutants that are most likely to affect your daily health: • Particulate matter (PM10) • Fine particulate matter (PM2.5) • Ozone (O₃) • Nitrogen dioxide (NO₂) • Sulphur dioxide (SO₂) The DAQI is numbered from one to ten, with one being ‘low’ and ten ‘very high’. It’s then broken up into four bands: low, moderate, high, very high. Each band has its accompanying health advice and information about which individuals should be vary. Main types of Air Pollution and their impact on our Health and the Environment • Sulphur dioxide is an acidic, erosive gas that joins with water vapour to create acid rain. About 99% of SO₂ is man-made and is often found in high concentrations in industrial locations and dense urban areas. Health Impacts SO₂ is a common pollutant that we’re exposed to every day at low levels. It can enter the body through breathing, eating food or drink which has SO₂ as a preservative or through skin contact. Children and adults with asthma and people with impaired heart and lung functions are more likely to be affected as it’s a respiratory irritant. Symptoms can appear quickly; short-term exposure to extremely high concentrations can be life-threatening. Short-term effects include: •Irritation and burning to nose, throat and lungs •Headaches •Difficulty breathing •Damage to the respiratory system • VOCs are a large group of organic compounds that easily evaporate at room temperature, creating vapours or gas. All VOCs are made from carbon and a mixture of other elements. So, while they differ in their chemical structure, they all have similar effects in the atmosphere. VOCs can also make airborne PM and are indirectly a greenhouse gas. • VOCs mostly come from man-made products, many of which can be found in our homes. Some research shows that indoor levels of VOCs are two to five times higher than outdoors. Volatile organic compounds (VOCs) are emitted as gases from certain solids or liquids. VOCs include a variety of chemicals, some of which may have short- and long-term adverse health effects. Concentrations of many VOCs are consistently higher indoors (up to ten times higher) than outdoors • Health Impacts • Not all VOCs are toxic, but due to the different chemicals, some can be carcinogens (poisonous). VOCs can enter the body through breathing or touching products that hold or release VOCs. • Short-term effects may include: • Irritation to eyes and visual disorders • Irritation to upper airways • Headaches, fatigue • Skin irritation • Liver and/kidney damage • Long-term exposure to VOCs can cause damage to the liver, kidneys, and central nervous system, as well as certain types of cancer. • Air pollution is defined as the introduction of pollutants, organic molecules, or other unsafe materials into Earth’s atmosphere. This can be in the form of excessive gases like carbon dioxide and other vapours that cannot be effectively removed through natural cycles, such as the carbon cycle or the nitrogen cycle. 1. Man-made (Artificial) sources • These are mostly linked to the combustion of several kinds of fuel. • Immobile sources entail clouds of smoke from power plants, industrial facilities (manufacturing works) and waste furnaces, as well as incinerators and other sorts of fuel-burning heating devices. In poor and developing countries, archaic biomass burning is the chief cause of air pollution; traditional biomass embraces wood, crop leftovers and excrement. • Movable sources comprise automobiles, aquatic vessels, and planes. Archaic- very old or old-fashioned. Biomass is organic, meaning it is made of material that comes from living organisms, such as plants and animals. The most common biomass materials used for energy are plants, wood, and waste. Incineration is a waste treatment process that involves the combustion of organic substances contained in waste materials. An incinerator is a furnace for burning waste. 1. Man-made (Artificial) sources • Controlled burning is a procedure sometimes used in forest management, agriculture, prairie re-establishment. Fire is an accepted facet of both forest and grassland ecosystem and an organized fire can be an instrument for foresters. Precise burning kindles the sprouting of some desirable trees, thus renewing the forest. • Fumes from hair spray, paint, aerosol sprays, varnish and other solvents. 2. Natural sources Primary contaminants are typically created by the emission of carbon dioxide from vehicles and factories. Secondary pollutants are the contaminants which are not emitted directly into the atmosphere. They are formed in the atmosphere when prime pollutants react or intermingle. Ground-level ozone is an important example of a secondary pollutant. 2. Natural sources • Some contaminants may be both primary and secondary: they are both emitted directly and formed from other primary pollutants. • Respirational and cardio complications: The adverse impacts of Air pollution are distressing. They are the root of numerous respirational and cardiac conditions accompanied by Cancer, midst other threats to our body. More than a few million are known to have expired due to direct or unforeseen effects of Air contamination. Kids in areas open to air contaminants are said to suffer frequently from pneumonia and asthma. 2. Natural sources • Global warming: One more direct consequence is the speedy changes that the world is observing due to Global warming. With the increase in temperatures worldwide, an increase in sea levels and melting of ice from cold areas and icebergs, displacement and loss of habitat have already beckoned an imminent disaster if actions for protection and regulation aren’t undertaken soon. • Acid Rain: Dangerous gasses like NO2 and SO2 are released into the atmosphere during the incineration of fuels. When it rains, the droplets combine with these pollutants, become acidic and then fall on the ground in the form of acid rain. Acid rain is a source of great harm to human beings, wildlife and crops. • Secondary contaminants do not enter the atmosphere from direct emissions. • Instead, as primary contaminants react or communicate, they form secondary contaminants in the atmosphere. • An important example of a secondary pollutant is ground level ozone. • Some contaminants can be both primary and secondary: both directly emitted from natural or anthropogenic activity or produced from other primary pollutants. • Some important measures that can be adopted by individuals to contribute towards the prevention of air pollution have been listed below. • Usage of public transport and carpooling – by reducing the amount of fuel combusted for an individual’s transportation needs, he/she can lower the amount of pollutants being released into the atmosphere and cause less air pollution. Furthermore, these options are also economically efficient and can help save money as well. • Switching off the lights when they’re not in use – the majority of our electricity is produced from the combustion of fossil fuels, which are a huge contributor towards air pollution. Therefore, conserving electricity is an effective way of preventing air pollution. • Reusing and recycling products – By reusing products (that can be reused), the amount of energy that goes into manufacturing another one of those products is conserved. Furthermore, recycling of products is also more energy-efficient than the manufacture of new ones. Removing sulphur from coal (by washing or with the help of bacteria) ‘ Nitrogen Oxide (Nox) Removing NO, during the combustion process and controlling the flow of air and fuel in industrial boilers. Vehicular pollution can be checked b engines; replacem: Introduction • Water is vital to life. We use it for drinking, washing, cooking and a number of other human activities. Two-thirds of the earth’s surface is water, and the irony is that we are facing water scarcity problems today. With the ever-increasing population and pollution, the demand for water has increased and the quantity of usable water has decreased. • Water Pollution: The contamination of water bodies such as rivers, lakes, etc. due to several contaminants being discharged in them, directly or indirectly, is known as water pollution. Water pollution has severe and hazardous impacts on our environment. • Water pollution can be defined as the contamination of water bodies. Water pollution is caused when water bodies such as rivers, lakes, oceans, groundwater and aquifers get contaminated with industrial and agricultural effluents. • When water gets polluted, it adversely affects all lifeforms that directly or indirectly depend on this source. The effects of water contamination can be felt for years to come. An aquifer is an underground layer of water-bearing permeable rock, rock fractures or unconsolidated materials (gravel, sand, or silt). Groundwater can be extracted using a water well. The study of water flow in aquifers and the characterization of aquifers is called hydrogeology. Effluent- Liquid waste or sewage discharged into a river or the sea. • The effect of water pollution depends upon the type of pollutants and its concentration. Also, the location of water bodies is an important factor to determine the levels of pollution. • Water bodies in the vicinity of urban areas are extremely polluted. This is the result of dumping garbage and toxic chemicals by industrial and commercial establishments. • Water pollution drastically affects aquatic life. It affects their metabolism, behaviour, causes illness and eventual death. Dioxin is a chemical that causes a lot of problems from reproduction to uncontrolled cell growth or cancer. This chemical is bioaccumulated in fish, chicken and meat. Chemicals such as this travel up the food chain before entering the human body. Bioaccumulate- (of a substance) become concentrated inside the bodies of living things. • The effect of water pollution can have a huge impact on the food chain. It disrupts the food-chain. Cadmium and lead are some toxic substances, these pollutants upon entering the food chain through animals (fish when consumed by animals, humans) can continue to disrupt at higher levels. • Humans are affected by pollution and can contract diseases such as hepatitis through faecal matter in water sources. Poor drinking water treatment and unfit water can always cause an outbreak of infectious diseases such as cholera, etc. • The ecosystem can be critically affected, modified and destructured because of water pollution. The Minamata disease, sometimes referred to as Chisso-Minamata disease, is a neurological syndrome caused by severe mercury poisoning. Incident marked one of the worst cases of water pollution. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. • Pollution of the Ganges is also driving some of the distinct fauna to extinction. The Ganges River shark is a critically endangered species that belong to the order Carcharhiniformes. The Ganges River dolphin is another endangered species of dolphin that is found in the tributaries of the Ganges and Brahmaputra rivers. • As per a survey, by the end of 2026, around 4 billion people will face a shortage of water. Presently, around 1.2 billion people worldwide do not have access to clean, potable water and proper sanitation. It is also projected that nearly 1000 children die every year in India due to water- related issues. Groundwater is an important source of water, but unfortunately, even that is susceptible to pollution. Hence, water pollution is quite an important social issue that needs to be addressed promptly. Carcharhiniformes, the ground sharks, with over 270 species, are the largest order of sharks • Water pollution, to a larger extent, can be controlled by a variety of methods. Rather than releasing sewage waste into water bodies, it is better to treat them before discharge. Practising this can reduce the initial toxicity and the remaining substances can be degraded and rendered harmless by the water body itself. If the secondary treatment of water has been carried out, then this can be reused in sanitary systems and agricultural fields. • A very special plant, the Water Hyacinth can absorb dissolved toxic chemicals such as cadmium and other such elements. Establishing these in regions prone to such kinds of pollutants will reduce the adverse effects to a large extent. • Some chemical methods that help in the control of water pollution are precipitation, the ion exchange process, reverse osmosis, and coagulation. As an individual, reusing, reducing, and recycling wherever possible will advance a long way in overcoming the effects of water pollution. Water hyacinth is a free-floating perennial aquatic plant (or hydrophyte) native to tropical and sub-tropical South America. Reverse osmosis (RO) is a water purification process that uses a partially permeable membrane to separate ions, unwanted molecules and larger particles from drinking water. Coagulation- the action or process of a liquid, especially blood, changing to a solid or semi-solid state. • Industrial effluents and Industrial Usage: Some industries may directly pump their untreated wastes into water bodies such as rivers. Moreover, various industries also use water as a coolant, thereby causing thermal pollution. Increased water temperatures can cause a reduction in the levels of oxygen; which can cause the death of fish and other organisms. • Eutrophication Eutrophication is caused when large quantities of nutrients are introduced into a body of water, causing the rapid growth of algae. This can decrease the oxygen level in the water, rendering the fish unable to breathe. Moreover, this phenomenon can also introduce dangerous toxins into the water body, which can harm or kill most organisms, including humans RENDERING is the process that makes meat or fish waste into suitable substances for animal feed. • Deforestation Deforestation can cause soil erosion. When these loose soil particles enter a water body, they can make the water murky. This can make the water very murky, and it also has the potential to cause mechanical damage to aquatic organisms, (such as sand particles getting stuck in gills). • Agricultural run-offs Agricultural run-offs include fertilizers and other chemicals that can make the water toxic. Moreover, some of these fertilizers can induce eutrophication. Murky- dark and gloomy, especially due to thick mist. • Accidents Accidents can involve events such as leaks and oil spills. Oil spills, in particular, are very damaging to the environment and aquatic life. It occurs when large oil tankers, barges or drilling rigs are involved in accidents. The most well-known oil spill was that of the Deep Water Horizon, which occurred on 20th April 2010. A barge is a shoal-draft flat-bottomed boat, built mainly for river and canal transport of bulk goods. A drilling rig is an integrated system that drills wells, such as oil or water wells, in the earth's subsurface. The Deepwater Horizon oil spill was an industrial disaster that began on April 20, 2010, in the Gulf of Mexico on the BP-operated Macondo Prospect, considered to be the largest marine oil spill in the history of the petroleum industry • Let’s take a closer look at all that goes into our sacred Ganga River. Human Waste: • The River sustains the human population in an area the size of Mexico and a population of almost 500 million people and these people have shat into the river for years and years. • The sewage from the houses of all these people ends up in the Ganga River. • Along with the human faeces, we have chemicals such as the detergents and soaps we use. • This sewage has a higher organic load and therefore at least to some extent, the river can handle the water pollution, but when combined with other pollutants, our sacred Ganga River does not stand a chance. Industrial Waste: • Many industrial cities such as Kanpur, Allahabad, and Varanasi, etc. lie on the banks of the Ganga River. • All these cities are home to various industries and factories consisting of countless tanneries, chemical plants, textile mills, distilleries, slaughterhouses, and hospitals that grow and prosper thanks to the presence of Ganga. • In return for the gift of water, people along the river contribute to killing this river by dumping their effluents to add to the already high levels of water pollution. • Although industrial wastes are not as large in quantity as human wastes, they are even more harmful due to the presence of harmful chemicals and non-biodegradable toxic substances. A tannery is the place where the skins are processed. Tanning hide into leather involves a process which permanently alters the protein structure of skin, making it more durable and less susceptible to decomposition, and also possibly colouring it. Religious Wastes: • Taking a dip in the holy waters of Ganga is supposed to wash away all your sins and to this end, a huge number of people gather along its banks during festivities to ensure their righteousness. • In addition to this, since time immemorial, people have considered dying by the Ganga River as a sure shot way to reach heaven. • Therefore, the sights of dead bodies floating by on the river are a common sight. • This holy river has been made hellish by the people hoping to secure a berth in heaven. • This seriously has to stop since not only is it disgusting it is also dangerous as decaying corpses are host to many dangerous bacteria and viruses. (iv) Prevent run~ - Divert such run-o ment. The nutrient rich Water c sertiems"™ ds. fel (v) Separate drainage of Sewage and rain water revent overflow of sewage with rainwater. an Planting trees would reduce giso prevent soil erosion. should be provided pollution by sediments and will tewaters is essential before being discharged. Parameters which are was Total solids, biological oxygen demand (BOD), chemical oxygen demand (COD), nitrates and phosphates, oil and grease, toxic metals etc. . Waste waters should be properly treated by primary and so naaty treatments to reduce the BOD, COD levels up to the permissible levels for discharge. • 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. Leukaemia is a cancer which starts in blood-forming tissue, usually the bone marrow. • 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 of resources for remediation. • Polycyclic Aromatic Hydrocarbons • Polycyclic aromatic hydrocarbons (often abbreviated to PAHs) are organic compounds that: 1.Contain only carbon and hydrogen atoms. 2.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. Polycyclic aromatic hydrocarbons (PAHs) are a class of chemicals that occur naturally in coal, crude oil, and gasoline. They also are produced when coal, oil, gas, wood, garbage, and tobacco are burned. PAHs generated from these sources can bind to or form small particles in the air. • Industrial Waste • The discharge of industrial waste into soils can result in soil pollution. Some common soil pollutants that can be sourced to industrial waste are listed below. • Chlorinated industrial solvents • Dioxins 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 • 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. • 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 (ClO4 –) 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. • 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.