Environment Studies 03605101 PDF

ENVIRONMENT STUDIES 03605101 Ms Namira Saiyed, Assistant Professr Civil Engineering  CHAPTER-2 Air & Noise Pollution  What is pollution ?. Pollution is the introduction of harmful materials into the environment. These harmful materials ar...

ENVIRONMENT STUDIES 03605101 Ms Namira Saiyed, Assistant Professr Civil Engineering  CHAPTER-2 Air & Noise Pollution  What is pollution ?. Pollution is the introduction of harmful materials into the environment. These harmful materials are called pollutants. Pollutants can be natural, such as volcanic ash. They can also be created by human activity, such as trash or runoff produced by factories. Pollutants damage the quality of air, water, and land.  What are pollutants ?. A pollutant is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. A pollutant may cause long- or short-term damage by changing the growth rate of plant or animal species, or by interfering with human amenities, comfort, health, or property values. Some pollutants are biodegradable and therefore will not persist in the environment in the long term.  Air Pollution. Air pollution is a change in the physical, chemical and biological characteristic of air that causes adverse effects on humans and other organisms. The ultimate result is a change in the natural environment and/or ecosystem. The substances that are responsible for causing air pollution are called air pollution. These air pollutants can be either natural (e.g. wildfires) or synthetic (man-made); they may be in the form of gas, liquid or solid.  Types of air pollutants. An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In addition, they may be natural or man-made. Pollutants can be classified as either: 1. Primary pollutants 2. Secondary pollutants.  Types of air pollutants. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon monoxide gas from a motor vehicle exhaust or sulphur dioxide released from factories. Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level ozone — one of the many secondary pollutants that make up photochemical smog. Major primary pollutants produced by human activity include. Sulphur oxides (SOx): SO2 is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulphur compounds, their combustion generates sulphur dioxide. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources. Major primary pollutants produced by human activity include. Nitrogen Oxide (NOx): Especially nitrogen dioxide are emitted from high temperature combustion. Nitrogen dioxide is the chemical compound with the formula N02. It is responsible for photochemical smog, acid rain etc. Major primary pollutants produced by human activity include. Carbon Mono Oxide: It is a colourless, odourless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular exhaust is a major source of carbon monoxide. Major primary pollutants produced by human activity include. Carbon Di Oxide: A greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere. Major primary pollutants produced by human activity include. Particulate matter: Particulates, alternatively referred to as particulate matter (PM) or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol refers to particles and the gas together. Sources of particulate matter can be manmade or natural. Some particulates occur naturally, originating from volcanoes, dust storms, forest and grassland fires, living vegetation, and sea spray. Human activities, such as the burning of fossil fuels in vehicles, power plants and various industrial processes also generate significant amounts of aerosols.  Primary & Secondary Pollutants. Primary pollutants directly contaminate the air by mixing with it. As for example carbon dioxide gas is a primary pollutant. Similarly Sulphur dioxide is a primary pollutant. Secondary pollutant mix with air and react chemically with other constituents of air producing another harmful pollutions. Moisture in the air mixes with sulphur dioxide mixes with producing sulphuric acid is secondary pollutant.  Aerosols. Microscopic particles of solids, liquids, and gases are called aerosols. These aerosols are of size 0.01 micron to 100 micron. Different types of aerosols 1. Dust particles: these particles are produced as a result of grinding, crushing and pulverizing of clay, sand, limestone and etc. the crushing and grinding mills produce lots of dust. 2. Smoke: incomplete combustion produces smoke. All dried organic matters burnt partially produce black smokes.  Aerosols. 3. Fog: when very small particles of water condense due to low temperature, the fog is produced. Usually in the winter morning large clouds of fog are deposited over city area. Due to fog vision problem created. 4. Mist: mist is also the type of fog but contains larger size of water particles. The mist also creates less visibility causing collision of vehicles. 5. Fumes: fumes are one form of pollution in which temperature of gases falls below freezing temperature producing fumes. Fumes are also produced due to process of oxidation.  Effects of Air pollution. Carbon monoxide (source- Automobile exhaust, photochemical reactions in the atmosphere, biological oxidation by marine organisms, etc.)- Affects the respiratory activity as haemoglobin has more affinity for CO than for oxygen. Thus, CO combines with HB and thus reduces the oxygen-carrying capacity of blood. This results in blurred vision, headache, unconsciousness and death due to asphyxiation (lack of oxygen).  Effects of Air pollution. Carbon di oxide (source- Carbon burning of fossil fuels, depletion of forests (that remove excess carbon dioxide and help in maintaining the oxygen-carbon dioxide ratio) – causes global warming. Sulphur dioxide (source- Industries, burning of fossil fuels, forest fires, electric generation plants, smelting plants, petroleum refineries and volcanic eruptions)- Respiratory problems, severe headache, reduced productivity of plants, yellowing and reduced storage time for paper, yellowing and damage to limestone and marble, damage to leather, increased rate of corrosion of iron, steel, zinc and aluminium.  Effects of Air pollution. Chloro-fluoro carbons (CFCs) (source- Refrigerators, air conditioners, foam shaving cream, spray cans and cleaning solvents)- Destroy ozone layer which then permits harmful UV rays to enter the atmosphere. The ozone layer protects the earth from the ultraviolet rays sent down by the sun. Asbestos particles (source- Mining activities) – Asbestosis – a cancerous disease of the lungs. And many more bad effects.  Control of Air pollution. The following items are commonly used as pollution control devices by industry or transportation devices. They can either destroy contaminants or remove them from an exhaust stream before it is emitted into the atmosphere.  Particulate Control.  Mechanical collectors (dust cyclones, multi-cyclones)- Cyclonic separation is a method of removing particulates from an air, gas or water stream, without the use of filters, through vortex separation. Rotational effects and gravity are used to separate mixtures of solids and fluids.  A high speed rotating (air) flow is established within a cylindrical or conical container called a cyclone. Air flows in a spiral pattern, beginning at the top (wide end) of the cyclone and ending at the bottom (narrow) end before exiting the cyclone in a straight stream through the centre of the cyclone and out the top.  Particulate Control.  Electrostatic Precipitator. An electrostatic precipitator (ESP), or electrostatic air cleaner is a particulate collection device that removes particles from a flowing gas (such as air) using the force of an induced electrostatic charge. Electrostatic precipitators are highly efficient filtration devices that minimally impede the flow of gases through the device, and can easily remove fine particulate matter such as dust and smoke from the air stream.  Electrostatic Precipitator. In contrast to wet scrubbers which apply energy directly to the flowing fluid medium, an ESP applies energy only to the particulate matter being collected and therefore is very efficient in its consumption of energy (in the form of electricity).  Electrostatic Precipitator.  Catalytic Converter. In a catalytic converter, the catalyst's job is to speed up the removal of pollution. As the gases from the engine fumes blow over the catalyst, chemical reactions take place on its surface, breaking apart the pollutant gases and converting them into other gases that are safe enough to blow harmlessly out into the air.  Catalytic Converter.  Effects of Air pollutants due to Refrigerants. Many refrigerants, such as chlorofluorocarbons (CFCs) damage the ozone layer, while others are extremely potent greenhouse gases. In fact, one kilogram of the refrigerant R410a has the same greenhouse impact as two tonnes of carbon dioxide, which is the equivalent of running your car for six months. That's why Australia has specific laws that prohibit the importation of gases like CFCs and regulates the importation of synthetic greenhouse gases. Refrigerants leak into the atmosphere from faulty or poorly maintained equipment, or when equipment is improperly disposed of.  Noise Pollution. Noise pollution is generally defined as regular exposure to elevated sound levels that may lead to adverse effects in humans or other living organisms. According to the World Health Organization, sound levels less than 70 dB are not damaging to living organisms, regardless of how long or consistent the exposure is. Exposure for more than 8 hours to constant noise beyond 85 dB may be hazardous. If you work for 8 hours daily in close proximity to a busy road or highway, you are very likely exposed to traffic noise pollution around 85dB.  Noise Pollution. Sound, a normal feature of our life, is the means of communication and entertainment in most animals, including human beings. It is also a very effective alarm system. A low sound is pleasant whereas a loud sound is unpleasant and is commonly referred to as ‘noise’. Noise can be defined as an unpleasant and unwanted sound.  Noise Pollution. Whether a given sound is as pleasant as music or as unpleasant as noise depends on its loudness, duration, rhythm and the mood of the person. But loudness is definitely the most significant criterion which converts sound into noise. Exposure to loud noise is indeed annoying and harmful too. Noise is a physical form of pollution and is not directly harmful to the life supporting systems namely air, soil and water. Its effects are more directly on the receiver i.e. man. Noise pollution is the result of modern industrialized urban life and congestion due to over population.  Industrial Sources. Progress in technology (industrialization) has resulted in creating noise pollution. Textile mills, printing presses, engineering establishments and metal works etc. contribute heavily towards noise pollution. In industrial cities like Kolkata, Ludhiana, Kanpur etc., often the industrial zones are not separated from the residential zones of the city especially in the case of small scale industries. These operate from workshops located on the ground floors of the residential areas and cause annoyance, discomfort and irritation to the residents exposed to the noise that is inevitably produced..  Industrial Sources. The situation is much better in modern planned cities like Chandigarh where the industrial area is kept away from the residential areas and both are separated from each other by a sufficiently wide green belt.  Effects of Noise Pollution. Noise is more than a mere nuisance. At certain levels and durations of exposure, it can cause physical damage to the eardrum and the sensitive hair cells of the inner ear and result in temporary or permanent hearing loss. But most people repeatedly exposed to more than 105 dBA will have permanent hearing loss to some extent. In addition to causing hearing loss, excessive noise exposure can also raise blood pressure and pulse rates, cause irritability, anxiety, and mental fatigue, and interfere with sleep, recreation, and personal communication.  Effects of Noise Pollution. Noise pollution control is therefore of importance in the workplace and in the community. Noise-control ordinances and laws enacted at the local, regional, and national levels can be effective in mitigating the adverse effects of noise pollution.  Effects of Noise Pollution. Noise pollution control is therefore of importance in the workplace and in the community. Noise-control ordinances and laws enacted at the local, regional, and national levels can be effective in mitigating the adverse effects of noise pollution.  Measurement of Noise Pollution. Sound waves are vibrations of air molecules carried from a noise source to the ear. Sound is typically described in terms of the loudness (amplitude) and the pitch (frequency) of the wave. Loudness (also called sound pressure level, or SPL) is measured in logarithmic units called decibels (dB). The normal human ear can detect sounds that range between 0 dB (hearing threshold) and about 140 dB, with sounds between 120dB and 140 dB causing pain (pain threshold). The ambient SPL in a library is about 35 dB, while that inside a moving bus or subway train is roughly 85 dB; Building construction activities can generate SPLs as high as 105 dB at the source. SPLs decrease with distance from the source. www.paruluniversity.ac.in