🚬 Environmental Pollution

Environment

• The word environment means to “encircle” or “surround.”
• Environment can be defined as the physical, chemical and biological world that surrounds us, as well as the complex of social and cultural conditions affecting an individual or community.
• Environmental science is essentially the application of scientific methods and principles to the study of environmental issues, so it has probably been around in some form as long as science itself. Environmental science is not ecology, though that discipline may be included. They mostly focus on the environmental problem, which may be purely physical in nature.

Impact of man on the environment

• Increased deforestation and associated forest cover decrease
• Decreasing habitat both in quantity and quality
• Extinction of flora and fauna
• Adverse effect on environment such as global warming, ozone depletion, acid rain, etc.
• Adverse effect on plants such as increased pest and disease occurrence, decreasing productivity, etc.
• Increasing environmental hazards such as cyclone, drought, flood, hurricanes, etc.

Deforestation

• Deforestation is the major causal agent of desertification of habitat.
• Deforestation brings about soil erosion.
• Deforestation is caused due to construction roads, etc.
• Desertification will decrease rainfall.

Environmental Pollution

• Pollution is defined as an undesirable change in physical, chemical and biological characteristics of air, water and land that may be harmful to living organisms, living conditions and cultural assets. It is the unfavourable alteration of our surrounding because of pollutant addition.
• The pollution may be due to human activities or natural processes.
• Natural processes include storms, forest fire, volcanoes and methane from marshy lands. Nature has its own ability to recycles its pollutants and renders them less harmful, whereas man-made pollutants threaten the integrity of the nature. The substances, which cause pollution, are called pollutants.
• Pollutant is defined as any substance that is released intentionally or inadvertently by man into the environment in such a concentration that may have adverse effect on environmental health.
• It may be noted that pollution coming from all sources kills almost 9 million people each year? It is the leading cause of death in the world’s poorest nations and a growing epidemic in many cities. Pollution is a solvable problem, but it isn’t getting enough attention or financing from world leaders.
• Pollution in the form of greenhouse gases is the root causes of global climate change. Reducing this form of pollution is key to stopping global climate change.

Types of pollution

👉🏻 A) Based on environment

• Soil pollution
• Water pollution
• Air pollution

👉🏻 B) Based on source of pollution

• Automobile pollution
• Agricultural pollution
• Industrial pollution (tanneries, distilleries, nuclear plants, chemical industries)

👉🏻 C) Based on nature of pollutants

• Pesticide pollution
• Plastic pollution
• Heavy metal pollution
• Radiation pollution
• Oil pollution
• Sewage pollution
• Noise pollution

👉🏻 D) Based on the origin of pollution

• Point source pollution (The source of pollutant is known)
• Non-point source pollution (The source of pollutant is unknown)

Soil pollution

• Soil pollution refers to the undesirable changes in the soil physical, chemical and biological properties due to the contaminants addition by anthropogenic activities as well as natural processes.

Soil pollutants

• Industrial effluents and wastes
• Plastics and polythenes
• Organic sediments
• Agrochemicals
• Sewage
• Radioactive wastes

Consequences and Combative measures

• Industrial effluents containing huge amount of heavy metals and organic sediments causes soil Pollution.
• Plastics and polythenes, being non-biodegradable, accumulates in soil as waste that takes longer time for its degradation. This can be alleviated by the use of photodegradable plastic or biodegradable plastic. Photodegradable plastic are sensitive to UV rays, which result in the breakdown of long polymeric chain into small fragments.
• The use of various agrochemicals in farming accumulates in soil as residues and creates pollution by contaminating soil and water. Use of easily degradable pesticides and bio-pesticides can reduce the pesticide accumulation in soil. Continuous application of chemical fertilizers without organics leads to deterioration of soil physical and biological properties. Some fertilizers reduce the soil pH. This can be alleviated by the practice of integrated nutrient management practices, which involves balanced use of inorganic and organic fertilizers in addition to biofertilizer.

Water Pollution

• In general terms, water is considered to be polluted if it contains enough foreign material to render it unfit for specific use, such as drinking, recreation, etc. Water, being a universal solvent, dissolves many of the substances that facilitate easy contamination.
• Water pollutant can be classified according to the nature of its origin as a point source or a dispersed source pollutant.
• A point source pollutant is one that reaches the water from a pipe, channel or any other confined and localized source. e.g., sewage pipe and industrial effluent discharge.
• A dispersed non-point source is a broad, unconfined area from which pollutants received. Surface runoff from agricultural areas carries silt, fertilizers, pesticides, and animal wastes into streams. Point source pollutants are easily managed compared to dispersed source pollutants.

Water pollutants

• Domestic waste
• Pathogenic organisms
• Organic sediments
• Plant nutrients
• Toxic organic and inorganic chemicals
• Radioactive substances
• Heat
• Oil residues

Consequences

• Decrease of dissolved nutrients, increase of pathogenic microorganisms, presence of sediments, development of bad odour and change of colour from transparent to black are some of the results of water pollution. The extent of water pollution can be assessed by the use of standards. Dissolved oxygen, BOD, COD, colour are some yard sticks for measuring the water quality.

Dissolved Oxygen

• The higher the concentration of dissolved oxygen, the better is the water quality.
• At 20°C, water has 9 mg/L of oxygen.
• Changes in water temperature have a significant effect on dissolved oxygen concentrations.

Biological Oxygen Demand (BOD)

• Presence of organic sediments and microbial biomass increases the BOD.
• BOD measures only the biodegradable organic material in water.
• BOD is the amount of oxygen required for biological oxidation by microbes in unit volume of water. BOD values give an idea about the amount of oxidisable organic matter in water as a measure of pollution. The addition of sewage and waste, increases the organic sediment load of the water there by increases the BOD value.
• Higher the BOD values means higher the pollution.
• BOD values is useful in evaluation of self-purification capacity of a water body.

Chemical Oxygen Demand (COD)

• COD measures all organics, including the non-biodegradable substances.
• The COD test can be performed in 2h compared to BOD test that requires 5 days to complete the test.
• COD values are always higher than BOD values for the same sample.

Combative Measures

• Preventive measures such as strict implementation of laws related to solid and hazardous waste disposal is to be needed.
• Proper treatment of industrial effluents is essential before disposal.
• Provision of physical barriers between the waste and the groundwater is required.
• Monitoring wells also required as an early warning mechanism.
• Effective land use reduces aquifer contamination.
• Regulations on construction of septic systems can reduce sewage contamination of private wells.
• Prudent application of pesticides and fertilizers in agricultural areas can reduce water pollution.

Air pollution

• Air pollution refers to the presence of certain substances in the air in enough concentrations and durations to cause undesirable effects.
• The five primary pollutants include sulfur dioxide (SO₂), nitrogen oxides (NO_x), carbon monoxide (CO), solid or liquid particulates and particulate lead.
• Sulfur dioxide is a colorless gas with a sharp, choking odour which are released from burning of fossil fuels. The sulfuric acid (H₂SO₄) mist is a secondary pollutant because it is formed subsequently which causes acid rain.
• Among the nitrogen oxides, nitrogen dioxide (NO₂) is most important. Initially, nitric oxide (NO) is formed, which is readily oxidized to NO₂ which contributes to acid rain, considerably.
• Incomplete combustion of fossil fuels produces carbon monoxide. Seventy percent of the total carbon monoxide emissions come from vehicles.
• Extremely small fragments of solids or liquid droplets suspended in air are called particulates, which are in the range of 0.1 to 100 µm. The particulate materials of less than 10 µm in size cause human health problems. Suspended solids roughly 1 to 100 µm in size are called dust particles
• Smoke is a common product of incomplete combustion; smoke particles consist mostly of carbonaceous material.
• The major source of lead (Pb) is motor vehicles.

Consequences

• The adverse effects of air pollution include impaired human health, building facades and changes in vegetation, agricultural crops and climatic elements.
• There is a link with lung cancer to air pollution.
• The sulfur dioxide, oxides of nitrogen, and ozone cause eye and throat irritation, coughing and chest pain.
• Nitrogen dioxide causes pulmonary edema and ozone produces pulmonary congestion and altered breathing patterns.

Combative measures

• Air pollution control strategies can be divided into two categories, the control of particulate emissions and the control of gaseous emissions.
• Physical separation of the particulates from the air using settling chambers, cyclone collectors, impringers, wet scrubbers, electrostatic precipitators, and filtration devices, are some of the particulate emission control measures.
• Gaseous emissions are controlled by similar devices and typically can be used in conjunction with particulate control options. Such devices include scrubbers, adsorption systems, condensers, flares, and incinerators. Activated carbon is commonly used as an adsorbent.
• The prevention measures such as effective utilization of fossil fuels, substitution of fossil fuels, utilization of renewable resources like solar, wind, tidal energy, etc. is also needed to control the air pollution.
• The proper operation and maintenance practices to minimize the air pollution.

Noise pollution

• Noise is an undesirable and unwanted sound. Noise is one of the most undesirable products of modern mechanized lifestyle that harms human health and well-being. The sources of noise are radio, machine, human voice, airplane and musical instrument.
• The human ear can detect sounds in the frequency range of about 20 to 20,000 Hz.

Adverse impacts

• It decreases the ear sensitivity
• Prolonged term or continuous exposure to high noise leads to deafness
• It cause mental illness and increase restlessness in human
• It increases the general anger of human
• It decreases the working efficiency

Combative measures

• Adding insulation and sound-proofing to doors, walls, and ceilings
• Use of ear muffs
• Planting vegetation to absorb and screen out noise pollution
• Zoning urban areas to maintain a separation between residential areas and zones of excessive noise

Industrial pollution

• Industrial pollution is caused by the various industrial activities and process.
• The most polluting industries include tan industry, dye industry, leather factories, paper industries, textile industries, etc.
• The effluents from industries are disposed into water courses and on land which detoriates the quality of soil and water and make them unfit for beneficial uses.
• These effluents contain a wider variety of materials of both organic and inorganic toxic substances which includes toxic metals, pesticides, cyanide, dyes, oils, detergents, resins, rubbers, radioactive materials, etc. The nature and extent of pollution depends on the materials present in the effluent and on the quantity discharged.
• The solid wastes are either recycled or disposed off in remote places.
• Liquid industrial wastes are of more concern because of their harmful effects.

Consequences

• The effects of the effluents on water characteristics and quality are many.
• The effluents containing dyes changes the colour of the water and inhibits photosynthesis by aquatic vegetation.
• Water reaction become acidic or alkaline depends up on the added effluents and it is undesirable for aquatic life.
• The colloidal and suspended impurities produce turbidity in the receiving waters. The heavy organic load in effluents decreases the dissolved oxygen in water.
• Chromium, sulfide, chlorine and aniline dyes are toxic to human as well aquatic life.
• The temperature of water is increased due to the mixing of hot effluent with water bodies.
• Land quality characters are considerably detoriated because of the industrial wastes addition to the soil.
• Sodium and boron concentration increases more than the desirable limit.
• Infiltration is reduced because of increased sodium in soil, which increases the runoff and soil erosion indirectly.
• Structural degradation resulted from sodium renders the soil to become less porous and inhibits soil aeration.
• The beneficial microbial load in soil is decreased due to toxic chemical actions. As a result of all these, the plant growth is impaired notably.

Combative Measures

• Provide proper effluent/waste treatment plant wherever it is essential.
• Replace the wear and tear of instrument and machines ideally. This reduces the waste generation by avoiding malfunctioning.
• Use the chemicals and other inputs of standard quality.
• If wastes are non-treatable, keep the waste materials away from the human approach.

Heavy Metal Pollution

• Heavy metals include all metals with atomic numbers greater than 23 (with few exceptions) or have a density of more than 5 g per ml. Heavy metals are hazardous, toxic and not acceptable to biological system. These metals act as a slow poisons and cause disorders.
• Mercury, lead, arsenic, chromium and cadmium are the common toxic heavy metals.
• The wide use of heavy metals in industrial processes results heavy metals accumulation in environment. These cause public health hazards and ecological problems. Biodegradation of metals is not possible, as metals cannot be mineralized to non-toxic compounds. Toxic heavy metals can biaccumulate as they are hard to metabolize. Modified strains of the plants can accumulate heavy metals in their biomass.

• The common lead accumulating plants are ragweed (Ambrosia artemisiifolia) and hemp dogbane (Apocynum cannabinum).
• Eukaryotic organisms detoxify heavy metals by binding to polythiols and bacteria have developed different and efficient mechanisms for tolerating heavy metals. Bioconversions involving changes in valency and resulting in production of volatile or less toxic compounds. e.g. Oxidation of As (III) to As (V).
• Transformation of metals into organometallic compounds by methylation is also possible. e.g. lead, mercury.

Radioactive Pollution

• Radioactive pollution is defined as the release of radioactive substances or high-energy particles into the air, water, or earth as a result of human activity, either by accident or by design. Nuclear weapon testing, nuclear fuel recycling, mining wastes and accidental release of radioactive material from nuclear power plants, are the common sources of radioactive pollution and are highly harmful to human health.
• Radioactive pollution that is spread through the earth’s atmosphere is termed fallout.
• There are three types of fallouts:
  • Local fallout is quite intense but short-lived.
  • Tropospheric fallout is deposited at a later time and covers a larger area, depending on meteorological conditions.
  • Stratospheric fallout, which release extremely fine particles into the upper atmosphere, may continue for years after an explosion and attain a worldwide distribution.

Thermal Pollution

• The vast array of human activities results in the release of heat to the environment. It includes such as fossil fuel burning, mechanical heat generation, industrial processes, etc. The decay of organic matter in landfills releases heat to the atmosphere.
• The amount of heat released will increase with increase of these activities. Human activity in urban area increases the air temperature. As a result, personal discomfort and health related problem arises.
• Thermal pollution designates heating of lakes, river, streams, and other bodies of water, by various use processes such as power generation, factories, etc.
• Thermal pollution of water body reduces dissolved oxygen in water. The decreased oxygen level may not support many of the living organisms.
• Organisms become susceptible to disease too. The water heated by thermal pollution has useful applications such as establishment of aquatic farms, to heat buildings, to remove snow, to fill swimming pools, to use for irrigation, to de-ice canals, and to operate industrial processes, etc.

Space Pollution

• In the most general sense, the term space pollution includes both natural and man-made orbital debris components of the space environment; however, space pollution here refers to only man-made orbital debris.
• Orbital debris poses a threat to both manned and unmanned spacecraft as well as the earth’s inhabitants. Since the 1950s, many satellites have been launched to serve as communications relay devices and image sensors.
• Today, space is littered with non-functional satellites and booster rockets. These pieces of space wreckage continue to orbit the earth on paths that cannot be controlled from the ground.
• Collisions are increasingly common and pose a danger to active satellites. There are now more than 10,000 known objects larger than four inches in diameter in space and 700 of them are operating satellites. The rest is discarded flotsam.

Reasons for space pollution

• More and more countries are launching satellites into space
• Costs of clean up the space pollutant is higher
• Costs of redesigning ships is higher
• Lack of control and standards in space technology in many countries

Consequences of space pollution

• Abrasion of space craft which causes frequent replace of spacecraft parts such as windows and surface elements.
• Broken down of spacecraft due to collision. This poses a big threat to return of space scientist. Debris poses a hazard to the surface of the Earth. High-melting-point materials such as titanium, steel, ceramics, or large or densely constructed objects can survive atmospheric re-entry to strike the earth’s surface.

Measures

• Casing and shielding of space crafts to protect against collisions with orbiting garbage
• Utilize intelligent design practices to minimize the effects of debris impact
• Adopt international standards for defined and wise use of space
• Use reusable technology for many space applications
• Track the non-working satellites back to earth
• Passive techniques include venting residual fuels or pressurized vessels aboard rockets and spacecraft, retaining operational debris, and placing spacecraft into disposal orbits at the end of a mission

Impact of pollution on vegetation

• Pollution not only impacts humans and animals. It affects plants too because plants is the main source of sink for many pollutants besides altering its environmental conditions.
• All these affects plant growth and developments. The effect of pollution on vegetation is discussed hereunder under three sub heads.

Morphological impacts

• SO₂ affects flowering in conifers
• Acid rain causes bleaching effect on leaves
• Leaf injuries such as colouration, pigmentation, chlorosis, yellowing and necrosis are common.
• Reduced leaf size and stunted growth

Biochemical impacts

• Essential biochemical substances such as proteins, amino acids, sugars, alkaloids, etc are decreased
• Reduction of chloroplast content

Physiological impacts

• Opening of stomata is altered
• Rate of photosynthesis is decreased due to dust settlement and altered environment
• Transpiration and respiration are increased under certain circumstances
• Enzyme activation and production is altered

Effects of different pollutants on Human Beings

Bioremediation

• Bioremediation is defined as the process whereby organic wastes are biologically degraded under controlled conditions to an innocuous state, or to levels below concentration limits established by regulatory authorities. Simply, it is the use of living organisms, primarily microorganisms, to degrade the environmental contaminants into less toxic forms.
• Bioremediation has its own limitations. Some contaminants, such as chlorinated organic or high aromatic hydrocarbons, are resistant to microbial attack. They are degraded either slowly or not at all.
• The various microorganisms involved in the biodegradation process is classified as follows:
  • Aerobic microorganism: Pseudomonas, Sphingomonas, Rhodococcus and Mycobacterium.
  • Anaerobic microorganism is one which in the absence of oxygen.
  • Lignolytic fungi: Phanaerochaete chrysosporium
  • Methylotrophs uses methane as carbon and energy.

Phytoremediation

• Phytoremediation is an emerging bioremediation technology that uses plants to remove contaminants from soil and water. It designates all vegetation based remediation measures.
• Plant has a potential for accumulating, immobilizing, and transforming a low level of persistent contaminants. In natural ecosystems, plants act as filters and metabolize hazardous substances.

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