GE203 Revision PDF

1- Introduction to the Environment and Ecosystems Environment All the conditions, circumstances, and influences that surround, and affect the development of an organism (or group of organisms) Environment includes Natural features Natural features includes mountains; Trees; Seas and Oceans; Air Water Energy Environmental Components of the Earth 1. Atmosphere (air): It is the gaseous 2. Hydrosphere (water): It includes Envelope of air surrounding the earth to all the Water on the surface of the A height of approximately 1000 km earth. Oceans, seas, lakes, glaciers, – It mainly consists of 21% oxygen, 78% etc. are Part of the Hydrosphere. Nitrogen, and 1% other gases, and – Water vapor, clouds, etc. may be Rotates with the earth, because of Considered part of the atmosphere Gravity or the hydrosphere. 3. Geosphere (rock, soil and sediment) Crust, mantle and Core together forms Geosphere 4. Biosphere (living things): It is the portion of Earth and its atmosphere that can support life. In other words it is that part of the earth where life exists. The Atmosphere Atmosphere is a thin spherical envelope of gases surrounding the earth’s surface. 1 Its inner layer, the troposphere, contains air that we breathe, which consists of: – nitrogen (78% of the total volume) – oxygen (21%). – The remaining 1% of the air includes water vapor, carbon dioxide, methane, etc. all of which are called greenhouse gases 2 The next layer is called the stratosphere, Its lower portion holds enough ozone (O3) gas to filter out about 95% of the sun’s harmful ultraviolet (UV) radiation The Hydrosphere Hydrosphere consists of all of the water on or near the‫ر‬earth’s surface. It is found as water vapor in the atmosphere, liquid water on the surface and underground, ice. The oceans, which cover about 71% of the globe, contain about 97% of the earth’s water. The geosphere Geosphere consists of the earth’s intensely hot core, a thick mantle composed mostly of rock, and a thin outer crust. Its upper portion contains nonrenewable fossil fuels and minerals that we use, as well as renewable soil chemicals (nutrients) that organisms need in order to live, grow, and reproduce. The biosphere Biosphere consists of the parts of the atmosphere, hydrosphere, and geosphere where life is found. ‫حيث توجد الحياة‬ Biodiversity ‫التنوع البيولوجي‬ 13 Biological diversity – or biodiversity – is the term given to the variety of life on Earth. Biodiversity refers to the existence of many different kinds of plants and animals in an environment It is the variety within and between all species of plants, animals and micro-organisms and the ecosystems within which they live and interact. Factors Sustain the Earth’s Life 1. The one-way flow of highquality energy from the sun, through living things in their feeding interactions. 2. The cycling of nutrients (the atoms, ions, and molecules needed for survival by living organisms) through parts of the biosphere. 3. Gravity, which allows the planet to hold onto its atmosphere and helps to enable the movement and cycling of chemicals through air, water, soil, and organisms Photosynthesis ‫عملية البناء الضوئي‬ Photosynthesis is the chemical reaction by which green plants use water, carbon dioxide and light from Sun to make glucose. Energy flow from sun to earth and within The earth’s systems Sun releases tremendous amounts of energy into the space, only a very small amount of this energy reaches the earth. This energy reaches the earth in the form of electromagnetic waves, composed mostly of visible light, ultraviolet (UV) radiation, and heat (infrared radiation). Much of this energy is absorbed or reflected back into space by the earth’s atmosphere and surface. The solar energy that reaches the atmosphere lights the earth during daytime, warms the air, evaporates and cycles water through the biosphere, and generate winds. Also, green plant and algae use solar energy to produce the nutrient they need through the photosynthesis process, and in turn, to feed the animal. The solar radiation reached the planet’s surface, interacts with the earth’s land, water, and life and is degraded to lower-quality infrared radiation. Some of the infrared radiation is reflected back to the lower atmosphere, where it will interact with greenhouse gases (water vapor, carbon dioxide, methane, etc.) and Some of it flows back into space as heat. When radiated heat from earth’s surface interact with greenhouses gases it warm the lower atmosphere and the earth’s surfaces, which is know as greenhouse effect. Without this natural greenhouse effect, the earth would be too cold to support the forms of life we find here today. Ecology is the science that focuses on how organisms interact with one another and with their nonliving environment of matter and energy. species is a group of animals or plants that interbreed in nature and produce young animals or plants. Blosphere Parts of the earth’s, water, and soil where lite is found Ecosystem A community of different species interacting with one another and with their no living environment of matter and energy Community Populations of different species living in a particular place, and potentially interacting with each other Population A group of of the same species living in a particular place Organism An individual living being Living and Nonliving Components of Ecosystem The ecosystems are made up of living (biotic) and nonliving (abiotic) components. (Biotic) Living components include (Abiotic) Nonliving components are plants, animals, microbes, and all other water, air, nutrients, rocks, heat, and solar organisms energy ------------------------------------------------------------------------------------------------------------------------------------------------ Producers and Consumers We can broadly classify the organisms as producers and consumers. Producers Organisms that make Consumers– All other organisms glucose during photosynthesis in an ecosystem are consumers. (Plants and some kind of bacteria) Consumers eat plants or other Producers, are also called autotrophs organisms to obtain their energy (self-feeders) because they make the – Consumers are those who do not nutrients they need from compounds make their own food, but get it from and energy obtained from their eating plants or other animals. environment. – Producers use most of the energy they make for themselves ------------------------------------------------------------------------------------------------------------------------------------------------ The trophic level ) ‫ (المستوى الغذائي‬of an organism is the position it occupies in a food chain. Living organisms transfer energy and nutrients from one trophic level to another within an ecosystem. Trophic level has five groups: 1– The producers ‫تعريفه فوق‬, 2– The primary consumers , 3– The secondary consumers 4 – The tertiary consumers 5 – The decomposers. ‫تعريفه قدام‬ Some animals such as bears eat both plants and other animals. They are called as ‘Omnivores’. Examples: human being, bear 2 The organisms 3 Secondary 4 Carnivores that that consume consumers are consume other producers are those animals that carnivores are called called ‘Primary eat other animals. tertiary consumers. Consumers’. They These animals are The hawk that eats are also called called Carnivores. a snake is a tertiary Herbivores.. consumer Lion feeding on the Giraffe feeding on dead Body of a giraffe ‫نتا‬the leaves Of a tree is is carnivores an herbivore Decomposers organisms that break down remains of dead organisms produced at all the trophic levels. Include) worms, bacteria, fungi and some insects. ( – Decomposers eat producers, primary, secondary and tertiary consumers and release nutrients from the wastes or the remains and then return those nutrients to the soil, water, and air for reuse by producers (bacteria and fungi). Fungus feeding on a dead tree is a decomposer Detritivores are organisms that obtain energy from organic wastes and dead bodies produced at all the trophic levels. They are the decomposers of the food chain. Decomposition of bodies and wastes releases nutrients back into environment to be recycled by other organisms. This helps release trapped energy (in the form of carbon) in dead organisms back to the earth. Scavengers: Consumers that eat other consumers that have already died In natural ecosystems the wastes and dead bodies of organisms serve as resources for other organisms, as the nutrients that make life possible are continuously recycled Without decomposer, the planet would be overwhelmed with plant litter, animal wastes, dead animal bodies, and garbage. Aerobic & Anaerobic respiration Consumers, and decomposers use the chemical energy stored in glucose and other organic compounds to fuel their life processes. This energy is released by: – Aerobic respiration which uses oxygen to convert glucose (or other organic nutrient molecules) back into carbon dioxide and water. – Anaerobic respiration, or fermentation, which breaks down organic compounds in the absence of oxygen. The end products of this process are compounds such as methane gas (CH4), hydrogen sulfide (H2S), etc. Food Chains and Energy Flow through Ecosystems Food chain is a sequence of organisms, each of which serves as a source of food or energy for the next. The chemical energy stored as nutrients in the bodies and wastes of organisms flows through ecosystems from one trophic (feeding) level to another. Food web In natural ecosystems, most consumers feed on more than one type of organism, and most organisms are eaten or decomposed by more than one type of consumer. Organisms in most ecosystems form a complex network of interconnected food chains called a food web. Each trophic level in a food chain or web contains a certain amount of biomass (the dry weight of all organic matter contained in its organisms). Primary productivity is the rate at which an ecosystem’s producers convert solar energy into chemical energy in the form of biomass found in their tissues. It is usually measured in (kcal/m2/yr) To stay alive, grow, and reproduce; producers must use some of the chemical energy stored in the biomass they make for their own respiration. Net primary productivity (NPP) is the rate at which producers use photosynthesis to produce and store chemical energy minus the rate at which they use some of this stored chemical energy through aerobic respiration. NPP ultimately limits the number of consumers that can survive on the earth. Review Question-1 1- The Sun is the source of energy for food chains. 2- The amount of energy always Decreases as you move up Trophic levels. 3- On land, the amount of biomass Decreases as you move up Trophic levels. 4- Food chain is sequence of feeding relationships describing. Review Question-2 1- Consumers cannot make their own food, they must eat or consume other organisms. 2- Producers use the energy of sunlight to make their own food through a process called photosynthesis 3- Detritus is the Waste matter and rotting remains of dead organisms. 4- Decomposers are organisms that eat Detritus and break down into nutrients Review Question-3 1- Primary consumer is the 1st consumer in a food chain. It eats producers 2- Secondary consumer is the second consumer in a food chain. It eats Primary consumers 3-Tertiary consumer is the third consumer in a food chain. It eats secondary consumers 4- Quaternary consumer is the 4th consumer in a food chain. It eats tertiary consumers 5- Nutrients are substances needed for an organism’s growth and repair Hydrologic & Nutrients Cycle Nutrients ‫المغذيات‬ The most important nutrients the Plants and other autotrophs (producers) need are carbon, hydrogen and oxygen. Other nutrients needed by plants are nitrogen, phosphorous, potassium, calcium, magnesium, and sulfur. Plants absorb nutrients from soil and water Nutrients Cycle within and among Ecosystems The elements and compounds that make up nutrients move continually through air, water, soil, and living organisms within ecosystems, as well as in the biosphere in cycles called nutrient cycles, or biogeochemical cycles. These cycles include the hydrologic (water), carbon, nitrogen, and phosphorus cycles. These cycles driven directly or indirectly by incoming solar energy \ earth’s gravity Water An average man consumes about 200 to 300 litres every day All plants and animals must have water to survive If there was no water there would be no life on earth Apart from drinking it to survive, people have many other uses for water water cycle describes the existence and movement of water on, in, and above the Earth. from liquid to vapor to ice and back again. This water cycle is also called hydrologic cycle. The Sun heats water in the oceans; some of it evaporates as vapor into the air. Ice and snow can sublimate directly into water vapor. ‫تبخر‬ Plants and soil also release water vapour into the air. This process is called transpiration. Condense ‫ التكثف‬into clouds. Cloud particles collide, grow, and fall out of the sky as precipitation. Some precipitation falls as snow and can accumulate as ice caps and glaciers. The precipitation and melted ice flow over the ground as surface runoff. Some water infiltrates deep into the ground and become ground water. A portion of runoff enters rivers which ultimately join the oceans, where the water cycle "ends" or "begins" again The water cycle is powered by energy from the sun and involves three major processes: evaporation, precipitation, and transpiration. Because water dissolves many nutrient compounds, it is a major medium for transporting nutrients within and between ecosystems Only 0.024% of the earth’s vast water available to humans \ other species as liquid freshwater Purification Processes for water Evaporation and subsequent precipitation ‫التبخر وهطول االمطار‬ act as a natural distillation process that removes impurities dissolved in water Water flowing above ground through streams and lakes is partially purified by chemical and biological processes (due to natural aeration and decomposer bacteria) Water flowing below ground in aquifers is naturally filtered by soil. The hydrologic cycle can be viewed as a cycle of natural renewal of water quality. Review Question-1 a) The energy that powers the water cycle come from The Sun b) The process in which water gets warm and changes from liquid water to water vapor is called Evaporation c). Sublimation is the transition of a substance directly from the solid to the gas phase without passing through the intermediate liquid phase. e) Moisture that falls to the ground from clouds is called Precipitation f) Three major stages of water cycle are Evaporation Condensation, and Precipitation g) Release and evaporation of water from the plant leaves is known as Transpiration h) Aquifer is a body of permeable rocks, which contain or transmit ground water. Importance of Carbon Carbon is found in things that are (or once were) living. Proteins, DNA, carbohydrates, and other molecules that distinguish living matter from inorganic material are all composed of carbon atoms bonded to each other and to atoms of other elements (H, O, N, S and P) Carbon comprises about 19% of the weight of an animal and about 12% of the weight of a plant. Note: - All organic compounds contain carbon، - but not every compound containing carbon is organi The carbon cycle is based on carbon dioxide (CO2) gas, which makes up 0.039% of the volume of the earth’s atmosphere and is also dissolved in water. Carbon dioxide (along with water vapor in the water cycle) is a key component of the atmosphere’s thermostat. – If the carbon cycle removes too much CO2 from the Atmosphere (Cooler) – if the carbon cycle generates too much CO2 to the Atmosphere (Warmer) Decomposers release the carbon stored in the bodies of dead organisms on land back into the air as CO2. In water, decomposers release carbon that can be stored as insoluble carbonates in bottom sediment. Marine sediments are the earth’s largest store of carbon. a) All of the carbon in existence is continually recycled in the Carbon cycle) T b) Carbon cycle begins with photosynthesis in plants (F c) Plants are primary consumers of Carbon dioxide) T d) Humans are producers of Carbon dioxide) T e) Carbon dioxide is easily dissolved in water) T f) The plants use the carbon that comes from air )T g) Carbon get into the soil when plant, animal, or human dies )T Importance of Nitrogen Nitrogen is important to plants for the production of proteins — the building blocks of life Nitrogen is an essential component of DNA, RNA and Proteins DNA(Deoxy-ribonucleic acid) RNA(Ribonucleic acid) Herbivores get their nitrogen from eating plants Carnivores get their nitrogen from eating animals Nitrogen Cycle (N-Cycle) Nitrogen in the atmosphere is about 78% but mostly in the form of N2 gas which plants and animals as is cannot use. The process of converting nitrogen into compounds that can be used by plants and animals is called the Nitrogen Cycle. By traveling through one of the four processes in the Nitrogen cycle the atmospheric nitrogen (N2) get changed into a form that can be used by most living organisms: – Nitrogen Fixation – Nitrogen assimilation – Ammonification – Nitrificatio – DEnitrification Nitrogen Assimilation: In Nitrogen Fixation this process, inorganic Ammonification is the process of releasing ammonia The conversion of free nitrogen in the form of by certain bacteria utilizing organic nitrogen nitrogen of atmosphere nitrates, nitrites, and (proteins) available in the dead organic remains of into the biologically ammonia is absorbed by plants and animals and excreta of animals. acceptable form of the green plants via their Note: Ammonia comes from both nitrogen fixation nitrogenous compounds. roots and then it is and ammonification There are following ways converted into to convert N2 into nitrogenous organic chemically reactive forms: Nitrification is the process that converts ammonia compounds like Amino Special bacteria (NH3) into nitrites (NO2) and Nitrates (NO3) acids. convert the nitrogen gas which most plants can use. – Amino acids are used in (N2) the Synthesis of proteins, to ammonia (NH3) enzymes, Chlorophylls, DE nitrification: Denitrification is the reduction of nucleic acids etc. nitrates back into the largely inert nitrogen gas which only some plants (N2). The process is performed by bacteria in the can use (peas, beans) soil. Review Question-3 a) Nitrogen that is used by plants is in the form of nitrates (T b) What do plants do with the nitrogen they absorb? Build proteins c) Animals absorb nitrogen through eating plants (T d) Animals do not use nitrogen to build proteins (F e) The breaking down of dead animals by fungi and bacteria releases Ammonia f) What is the function of nitrifying bacteria?) The conversion of ammonia into nitrates ( g) Where are nitrogen fixing bacteria found? In the roots of plants Importance of Phosphorous It is essential nutrient for plants and animals Phosphorous main role in the body is to work with calcium to form strong bone and teeth White phosphorous is used in some explosives including rockets. Red phosphorous is used in match heads Phosphorous is also used in fertilizers Phosphorous is essential to DNA and RNA. Phosphorus Cycle Phosphorous exists in the rocks and soil as phosphate salts. Rain and weathering cause rocks to release phosphate ions (inorganic phosphate) into soils and water. Plants absorb inorganic phosphate (phosphate ions) from the soil and water. Animals absorb phosphates by eating plants or plant-eating animals. Once in the plant or animal, the phosphate ions (inorganic phosphate) converts into organic phosphate and stored in DNA (Deoxyribonucleic acid), RNA (Ribonucleic acid), and ATP (Adenosine triphosphate). When the plant or animal dies, bacteria break down organic phosphate into inorganic forms of phosphorus and phosphorous then returns to the soils or oceans. The soil deposits as sediments to form rocks in millions of years. Eventually, phosphorus is released again through weathering and the cycle starts over. Review Question-4 a) Where does the Phosphorus Cycle start? Rocks b) Phosphorous is a highly reactive element (T c) Phosphorous is found everywhere except Atmosphere (or gas state) d) Phosphorous cycle includes erosion and weathering of rocks (T e) The reservoir for phosphorous exists in mineral form in rocks rather than in the atmosphere. f) How does the Phosphorus enter plants in the soil? Water in the soil g) How do humans impact the Phosphorus Cycle? _ Use fertilizers that are not natural The human population and its impact Major factors for population increase 1. Modern agriculture technique allow growing more food. 2. Death rates drop because of improved sanitation and health care and development of antibiotics and vaccines to help control infectious diseases. 3. Humans adaptability to live in any climate zones and habitats. Most of the increase in the world’s population during the last 100 years took place because of a sharp drop in death rates – not a sharp rise in birth rates. Carrying capacity Maximum population of a particular species that a given habitat can support over a given period Environmental resistance that control the carrying capacity is: shrinkage in resources such as food, water, and space (total fertility rate) is the key factor that determines population size Population change = (Births + Immigration) – (Deaths + Emigration) Fertility rate: the number of children born to a woman during her lifetime. Two types of fertility rates affect a country’s population size and growth rate: 1. Replacement-level fertility rate 2. Total fertility rate (TFR) – is the average number of children that is the average number of children couples in a population must bear to replace born to women in a population during themselves. their reproductive years. – This factor – It is slightly higher than two children per plays a key role in determining couple: 2.1 in more-developed countries and population size as high as 2.5 in some less-developed countries. Infant mortality rate (the number of babies out of every 1,000 born who die before their first birthday). Infant mortality is viewed as one of the best measures of a society’s quality of life because it reflects a country’s general level of nutrition and health care Factors affecting Death Rate Increased food supplies and distribution, better nutrition. Medical advances such as immunizations and antibiotics. Improved sanitation, and safer water supplies Age structure is the numbers or percentages of males and females in young, middle, and older age groups in that population. – Pre-reproductive (ages 0–14), consisting of individuals normally too young to have children – Reproductive (ages 15–44), consisting of those normally able to have children – Post-reproductive (ages 45 and older), with individuals normally too old to have children. Population Pyramid It is simply a representation of the human structure of a country/continent by age group and gender. Factors affecting the shape of the pyramid include: Rates of births and deaths Wars Immigration and migration Health care Epidemic diseases, etc... Advantages and Disadvantages of Population Growth Advantages – Stronger, happier, Diversified and Considering Society – Industrial, Agricultural and Medical Innovation – Economic Growth Disadvantages – Food Shortage – Space shortage – Aging Dependency Review Question-1 a) Carrying capacity is a Maximum population of a particular species that a given habitat can support over a given period. b Environmental resistance controls the population to go beyond carrying capacity. c) Population size increases through births (fertility)and immigration, and decreases through deaths (mortality) and emigration d) Total fertility rate (TFR) is the average number of children born to women in a population during their reproductive years. e). Infant mortality indicates a country’s general level of nutrition and health care. Review Question-2 a) Age structure is the numbers or percentages of males and females in young, middle, and older age groups in that population. b) Agricultural supply worldwide currently Exceeds the demand of the world population. c) Assembly-line manufacturing itself is an adaptation to an increasing population. d) Human resource development aims at solving the problems of population growth by giving them proper education and creating the necessary skills in the people to make them a productive resource and providing them gainful employment Water Pollution part-1 Potable water: or drinking water is water free of chemicals, microorganisms, and other contaminants, and is, therefore, safe to drink (and food preparation). Most water ( 97.4% ), is salty water found in the oceans. Water has such a strong tendency to dissolve other substances (universal solvent). Rivers carry dissolved salts to the ocean. Water evaporates from the oceans to fall again as rain and to feed the rivers, but the salts remain in the ocean. We cannot drink salt water or use it for crops because of the salt content. We can remove salt from ocean water, but the process is very expensive seawater in the world's oceans has a salinity of approximately 3.5%, or 35 parts per thousand (~35 gram/Liter) The most saline open sea is the Red Sea, where high temperatures result in high rates of surface evaporation and there is little fresh inflow from rivers. Water surfaces constitute 70% of the earth’s surface Seas and oceans (saltwater) forms approximately 97.4% of the earth’s water; i.e. only 2.6% is fresh water (sweet water) 78% of the fresh water is in glaciers, groundwater and the atmosphere, and 22% is in rivers, lakes and springs. Only small fraction (0.014%) in rivers, lakes and springs is readily available for human use. Water Resources 6 Surface water (rivers, lakes, springs) Groundwater (difficult to obtain) Ocean & Seawater (not economic to Desalinize) Reclaimed or Treated Wastewater (Generally not treated for drinking and cooking) Surface water High flows, easy to contaminate, relatively high suspended solids (total suspended solids, TSS), turbidity, and pathogens. Groundwater Lower flows but natural filtering capacity that removes suspended solids (TSS), turbidity, andpathogens. May be high in dissolved solids (total dissolvedsolids, TDS) Renewal times can be very long. Water Quantity Estimation Quantity = Per Capita Demand (Lpcd) x Population (Cap.) (Liters per capita perday, (Lpcd) Factors affecting the water consumption rate per person Standard of living (car wash, swimming pools, gardening) Environmental awareness Weather conditions and season of the year Availability of water conservation programs Metering and pricing Social and cultural habits (bathing and showering frequency, ablution, food festivals) Review Question-1 a) Our body is made up of about 75% water. b) About 1% water on earth is available to drink. c) 6-8 glasses of water one should drink daily for good health d) One can live about 7 days without water. e) A hundred years ago, earth had The same amount of water as it is now f) One half of the world's fresh water lies within the borders of Canada g) Water that is safe to drink is called Potable water. h) Water that is safe and pleasant to drink is known as palatable Water pollution Water pollution is any chemical, biological, or physical change in water characteristics that makes it unfit for a specific beneficial use. The distinction between polluted and unpolluted water depends on: – Type and concentration of impurities – Intended use of water Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds. Water pollution affects plants and organisms living in these bodies of water, which can result in damaging natural biological system. Sources of Water Pollution Water pollutants can be classified according to the nature of their origin as: Point Source Nonpoint or Dispersed source. Point Source Nonpoint or Dispersed source All dry weather pollutants that enter (multiple discharge points) watercourses through pipes or channels. Storm drainage is considered as nonpoint source pollution. Point source pollution comes mainly from Other nonpoint source pollution comes from urban and industrial facilities and municipal wastewater agricultural runoff, construction sites, and other land treatment plants disturbances. Water Pollutants Generic types of water pollutants: 1. Pathogenic organisms 2. Oxygen-demanding substances 3. Plant nutrients 4. Toxic organics 5. Inorganic chemicals 6. Sediment 7. Radioactive substances 8. Heat 9. Oil Sources of Water Pollution due to Human Activities 1. Domestic Sewage (Wastewater) The primary sources of the first three types of pollutants. Pathogens, or disease-causing microorganisms, are excreted in the feces of infected persons and may be carried into waters receiving sewage discharges. Oxygen-demanding substances: the organic wastes that exert a biochemical oxygen demand (BOD) as they are decomposed by microbes. 2. Agricultural activities The major source of water pollution is agriculture according (EPA). Farming is a source of silt, as well as nutrients, pesticides, and organic material. 3. Industrial activities: it may produce pollutants that may be extremely harmful to people and the environment. This wastewater may contain toxic chemicals, acids, alkalis, salts, poisons, oils and harmful bacteria. 4. Oil spill in oceans: Oceans are polluted by oil on a daily basis from oil spills, routine shipping, run-offs and dumping. Parameters of Water Quality 1. Physical Water Quality – are usually associated with the appearance of water, its taste and odor. – Turbidity, Color Total Solids, Suspended Solids, Total Dissolved Solids, Temperature, etc. 2. Chemical Water Quality – includes the identification of its components and their concentrations. – pH, Alkalinity, Hardness, Chlorides, Fe and Manganese, Sulfates, Nitrogen compounds, Dissolved oxygen, Biological oxygen demand, Chemical oxygen demand, etc. 3. Microbiological Water Quality – Microorganism: Bacteria, Algae, Protozoa, Viruses – Indicator organism: Coliforms Parameters of Physical Water Quality Total Suspended Solids (TSS) include colloids, supra-colloids, and settleable solids. Total Dissolved Solids (TDS) Dissolved Solids are the solids that can be recovered from water by evaporating the water after filtering the suspended solids Total Solids (TS) Total solids in water and wastewater include suspended solids and dissolved solids (TS= TSS + TDS). Color Types: True color caused by dissolved solids; Apparent color caused by suspended solids and includes true color. Measured by Colorimeter or Spectrophotometer (Units: True Color Unit) Turbidity Turbidity measures the clarity of water containing colloidal material (cloudy water). Measured by Turbidimeter (Units: Nephelometric Turbidity Unit, NTU) Parameters of Chemical Water Quality Dissolved Oxygen (DO) Dissolved Oxygen (DO) is generally considered to be one of the most important parameters of water quality in streams, rivers, and lakes. The higher dissolved the better is the water quality. pH (hydrogen ion concentration) pH is an intensity factor. o pH of most raw water sources: 6.5 - 8.5 - pH = 7: Neutral - pH < 7: Acidic - pH> 7: Alkaline Alkalinity – Ability of water to neutralize acids (buffering capacity of water). – Alkalinity is mostly due to bicarbonates (HCO3 -), of Ca, Mg, and Na. – Highly alkaline water often has a high pH and generally contains high levels of dissolved solids (harmful for water to be used in boilers and food processing). Hardness – Hardness is a characteristics of water that prevents lathering of soap and produces scale in hot water pipes and heaters – Hardness is due to the presence of calcium (Ca) and magnesium (Mg) which are common in groundwater Iron (Fe) and Manganese (Mn) – Ground waters that are devoid of dissolved oxygen can contain appreciable amounts of (Fe2+) & (Mn2+). – Iron in concentrations greater than 0.3 mg/L and manganese in concentrations greater than 0.05 mg/L are considered substantial. Trace or Toxic Metals – Trace metals include those metals that are harmful and toxic in relatively small amounts. – The main source of these metals is the discharges of industrial wastewater. – Examples of trace metals: arsenic, cadmium, chromium, mercury, lead, silver and barium. Nitrogen compounds – Inorganic: Ammonia NH3, Nitrite NO2 , Nitrate NO3 – Organic: Protein, amino acids – Main Sources: Discharge of domestic, agricultural (fertilizers), industrial wastewater. Animal wastes and decomposition of dead plants, animal. Organic Matter – Organic compounds are composed mainly of carbon and hydrogen along with other elements such as oxygen, nitrogen, phosphorus, and sulfur. – Organics can be classified on the basis of their origin into: Natural organics (e.g. plants and animal tissues, human feces) Synthetic organics (e.g. plastics, rubber) – Based on their microbial degradation, organics can be: Biodegradable Non-biodegradable – Methods of measurement the organic concentration in water: Biochemical Oxygen Demand, BOD Chemical Oxygen Demand, COD Biochemical Oxygen Demand – BOD is the amount of oxygen required (consumed) by microorganisms to biologically degrade organic matter in a water sample. – BOD indicates the amount of organic matter in the water (or organic strength of wastewater). – BOD is generally measured over a period of five days, and is expressed in mg/L. Chemical oxygen demand: – COD is the amount of oxygen required to chemically oxidize organics in water. – For domestic wastewater, COD > BOD5 because COD includes both biodegradable and non- biodegradable organics. Parameters of Microbiological Water Quality Disease causing microorganisms are called pathogens Indicator organisms for water quality: – Total Coliform used in laboratory testing referring to all coliform bacteria from faeces, soils or other origin. – Faecal Coliform refers to coliform bacteria originating from human or animal faeces. Review Question-2 a) The worst polluters are big factories that dump dirty water into lakes, rivers, and oceans (T b) What do you call stuff that is sprayed on plants to kill bugs Pesticides c) What is the word that means, "made dirty or unsafe Contaminated d) Algae blooms result from Nutrient type of surface pollution. e) Surface water with no dissolved oxygen is contaminated by Organic matter f) Sediment pollution comes primarily from non-point sources (T g) Lead, arsenic, and mercury are hazardous heavy metal pollutant (T_. h) Most industrial water pollution is non point-source pollution(F i) What is the source of most nitrogen pollution of surface water Fertilizers j) Nitrogen pollution of the groundwater is worst where surficial materials are permeable (T k) Thermal pollution results primarily from power generation (T l) Surface water with essentially no dissolved oxygen is anaerobic. Water Pollution Part-2 Thermal Pollution Heat is considered to be a water pollutant because of the adverse effect it can have on the oxygen levels and the aquatic life in a river or lake. The discharge of warm water into a river is usually called thermal pollution. Discharge of warm water is caused mainly for cooling purposes for power plants. The warmer temperature decrease the solubility of oxygen and increases the rate of metabolism of fish. Some species of fish actually prefer warmer waters. Control of Thermal Pollution controlled by passing the heated water through a cooling pond or a cooling tower after it leaves the condenser. The heat is dissipated into the air, and the water can then be either discharged to the river or pumped back to the plant for reuse as cooling water In locations where there is not enough room for a cooling pond, one or more cooling towers may be built to prevent thermal pollution A common type is the natural draft hyperbolic cooling tower, in which evaporation accounts for most of the heat transfer Soil Erosion and sediment Control The natural movement of soil particles by wind or water from one location to another is called soil erosion. Soil erosion has been identified as one of the sources of water pollutants. Soil particles suspended in water interfere with the penetration of sunlight. This in turn reduces photosynthetic activity of aquatic plants and algae, disrupting the ecological balance of the stream. When the water velocity decreases, the suspended particles settle out and are deposited as sediment at the bottom of the stream or lake. Sediment suppresses benthic, or bottom-dwelling, organisms and disrupts the reproductive cycles of fish and other life forms. There are two types of water caused soil erosion: – Sheet erosion is the uniform – Stream erosion is the removal of removal of soil in thin layers by the soils from streambeds and stream forces of raindrops and overland banks by the swiftly moving flow channelized water Best management practices (BMPs) include the following: – Temporary grass cover on exposed soils to reduce wind and water erosion. – Hay bales can be placed around stormwater inlets to intercept sediment. – A typical hay bale and gravel filter, which prevents sediment from entering a drainage system and then local streams, is usually used in the vicinity of active construction sites. – Channel stabilization for streams and drainageditches. – Diversion channels reduce the distance of overland sheet flow, thereby reducing soil erosion and sedimentation of nearby streams and lakes. Stream Pollution To a limited extent, streams and rivers have the ability to assimilate or degrade biodegradable wastes. Thus, they can recover from the effects of pollution naturally, without significant or permanent environmental damage. The capacity for self-purification depends on: – the strength and volume of pollutants, – the stream discharge or flow rate, – the level of turbulence in the water as it may cascade over rocks and boulders in the stream channel It used to be said that: the solution to pollution is dilution The effect of oxygen transfer between the air and the water (reaeration) is important factor for natural purification. Fast-flowing, shallow, turbulent streams are reaerated more effectively than slow, deep, twisting streams. Modem-day population densities are too high for most streams and rivers to assimilate raw sewage discharges. Some degree of treatment is required to remove enough of the BOD from the sewage so that stream can finish the job of the purification. A level of treatment called secondary treatment is generally sufficient for this purpose; it is the minimum level of treatment required. Stream Pollution—Dilution 1. Physical processes of dilution and reaeration occur. 2. Biological processes occur, in which microorganisms in the water use dissolved oxygen to metabolize organic pollutants and convert them into harmless substances One input to the system is a stream with a flow rate Qs (volume/time) and pollutant concentration Cs (mass/volume). The other input is assumed to be a waste stream with flow rate Qw and pollutant concentration Cw. The output is a mixture with flow rate Qm and pollutant concentration Cm 𝐐𝐬 + 𝐐𝐰 = 𝐐𝐦 𝐂𝐬𝐐𝐬 + 𝐂𝐰𝐐𝐰 = 𝐂𝐦𝐐𝐦 80 ‫ارجع ساليد رقم‬ Stream Pollution—Zones of Pollution Most streams that are polluted by a point source of biodegradable organic substances can be described and evaluated in terms of four distinct zones.‫صورة‬ Lake Pollution Water in lakes is not moving much and is detained for a relatively long period of time, that mean self-purification will requires more time not like river and stream. In lakes, water quality may be more dependent on plant nutrients than on organics from sewage. Phosphorus and nitrogen are the most critical plant nutrients. When pollutants containing phosphorus and nitrogen compounds accumulate in a lake, rooted aquatic plants and free-floating algae may grow plentifully. The algae and aquatic weeds eventually die and settle to the bottom of the lake, where they are decomposed by bacteria and protozoa. This exerts an oxygen demand on the water and may deplete the DO in parts of the lake The process of nutrient enrichment and gradual accumulation in a lake, as just described, is a natural process. It is called eutrophication and can be thought of as an inevitable an continual aging of the lake. Four stages in the life of a lake. All lakes go through a natural aging process called eutrophication. Human activity often accelerates this process. Cultural (or anthropogenic) eutrophication is the acceleration of the natural aging process due to human activity. Groundwater Pollution Groundwater is usually of excellent quality. This is primarily because of the natural filtration that occurs in the layers of soil through which the water slowly moves underground. An increasing number of contaminated groundwater in certain locations have been reported. The contaminants come from many different sources and include a variety of materials, most notably synthetic organic chemicals. Of all types of water pollution, this synthetic organic chemicals is perhaps the most insidious because at low concentrations the contaminants rarely impart any noticeable taste or odor to drinking water. Sources of Groundwater Contamination 1. Improper disposal of wastes, such as unlined landfills or industrial sewage lagoons. 2. Accidental spills of hazardous substances, especially from industrial activities. 3. Petroleum products leaking from old underground storage tanks (USTs). 4. Mining and petroleum production, especially from hydraulic fracturing technology. 5. Subsurface sewage disposal systems. 6. Agricultural activities. 7. Saltwater Intrusion. Groundwater can be polluted from on-site sewage disposal systems. Wells located downhill from septic absorption fields are susceptible to contamination. Natural purification of chemically contaminated groundwater can take decades and perhaps centuries, and cleanup efforts are sometimes much too expensive to be practical. If an aquifer that supplies drinking water is polluted, it may be necessary to abandon the contaminated well(s) and drill new ones some distance away. The best way to control groundwater pollution is to prevent it from occurring in the first place. Laws related to solid and hazardous waste disposal significantly reduce new contamination. Ocean Pollution Ocean water is naturally saline (salty), containing about 3.5% dissolved solids (35 grams per liter, or 35,000 mg/L). Despite the ocean provide a tremendous reservoir for dilution of pollution, the ocean volume is not infinite, and its capacity to assimilate pollution in estuaries and other sensitive coastal zones between ocean and land is finite and limited In some coastal areas, excessive chemical nutrients from sewage and dispersed agricultural runoff can cause seasonal formations of hypoxic areas, in which DO levels drop so low. Problems related to degradation of the ocean waters are global in scope. Sources of ocean pollution 1. Diffusion of sewage in Seawater. – Treated sewage effluent from cities and towns is discharged directly into the ocean in many coastal areas. 2. Ocean dumping of sludge – Used in the past but now is banned 3. Oil spills – Accidental discharges of oil into ocean and bay waters can cause serious ecological damage to marine system. 4. Floating plastic rubbish – Use of biodegradable plastics, as well as an emphasis on waste recycling and waste minimization can help to mitigate this problem. Review Question-1 a) The degradation of water quality by any process that changes ambient water temperature is called. Thermal Pollution. b) Stream erosion is the removal of soils from streambeds and stream banks by the swiftly moving channelized water. c) A simple solution to stream pollution is Dilution d) Millions of tiny and large pieces of plastics accumulate at Gyres. e) Algae blooms result from Nutrients type of Lake pollution. f) Surface water with no dissolved oxygen is contaminated by Organic matter Water Quality Standard Standards were established to limit the amount of pollutants discharged into streams, lakes, and coastal waters Water quality standards are limits on the amount of physical, chemical, or microbiological impurities allowed in water that is intended for a particular use. Types of Water Quality Standards There are three different types of water quality standards: 1. Stream standards – classification of surface waters on the basis of their beneficial use. 2. Effluent standards 3. Drinking water standards Water Treatment Plant and Water Pollution Control Raw water generally require treatment before consumption and wastewater need to be treated before the disposal Coagulation and flocculation processes are used to separate the suspended solids portion from the water. Naturally occurring silt particles suspended in water possess negative charges, and are thus prevented from coming together to form large particles that could more readily be settled out. The removal of these particles by settling requires first that their charges be neutralized and second that the particles be encouraged to collide with each other. The charge neutralization is called coagulation, and the building of larger flocs from smaller particles is called flocculation. Alum is often used as a coagulant in water treatment. Alum is the common name for Aluminium sulphate Al2(SO4)3, which forms a precipitated solid, Al(OH)3, when it comes into contact with water. It is a white, gelatinous sticky material that easily traps particles in the water. Filtration is the removal of particles by sieving through a granular media. Disinfection is the addition of chemicals (usually chlorine, chloramines, or ozone) or the application of UV radiation to reduce the number of pathogenic organisms to levels that will not cause disease. 95 ‫قانون ساليد‬ Equalization tank If a factory is discharging its wastewater during certain hours every day, the factory can reduce the flow rate by using an equalization tank. The new flow rate could be calculated as follows )96 ‫(قانون ساليد‬ Aeration removes gases and convert soluble iron and manganese to insoluble precipitate Membrane filtration, like reverse osmosis, removes dissolved solids Osmosis and Reverse Osmosis Osmosis: a process by which molecules of a solvent tend to pass through a semipermeable membrane from a less concentrated solution into a more concentrated one. Reverse Osmosis: a process by which a solvent passes through a porous membrane in the direction opposite to that for natural osmosis when subjected to a hydrostatic pressure greater than the osmotic pressure. Review Question a) Why are iron and manganese undesirable in water – They can cause undesirable color in water T – They can stain clothes and plumbing fixtures T – They can promote the growth of iron bacteria, which can cause tastes and odor (T b) Coagulation-flocculation gather together fine, light particles to form larger particles (floc) to aid the sedimentation and filtration processes. c) A corrosive water deteriorates metal pipes T d) The purpose of water treatment plant is to produce safe and pleasant drinking water. e) The main purpose of a water treatment plant's intake structure is to draw in water while preventing leaves and other debris from clogging or damaging pumps T f) The purpose of filtration is to filter out suspended particles g) The use of pre-chlorination often reduces chlorine requirements for post-chlorination. Municipal Wastewater Treatment (Sewage treatment or domestic wastewater treatment) Sewage treatment or domestic wastewater treatment is the process of removing contaminants from wastewater and household sewage, both runoff (effluents) and domestic. It includes physical, chemical, and biological processes to remove physical, chemical and biological contaminants. Its objective is to produce a waste stream (or treated effluent) and a solid waste or sludge suitable for discharge or reuse back into the environment. It is generally desired that a wastewater treatment plant produces an effluent with suspended solids level below 20 mg/L and BOD below 20 mg/L. Degrees of Treatment Wastewater treatment plants may use preliminary, primary, secondary, and/or tertiary treatments. Primary wastewater treatment is sedimentation (mechanical treatment) to remove settleable suspended solids from wastewater. Secondary wastewater treatment is typically biological oxidation (biological treatment) to remove dissolved and fine suspended organic matter (i.e. BOD) from wastewater. Advanced wastewater treatment or tertiary treatment is any other treatment needed. Conventional Wastewater Treatment Plant The purpose of Biological Treatment is to oxidize or remove organic matter (BOD), and in some cases nutrients (such as nitrogen and phosphorus) by using microorganisms (MOs). Organics + MOs + O2 -> CO2 + H2O + new cells + energy Oil Spill An oil spill is the release of a liquid petroleum hydrocarbon into the environment due to human activity, and is a form of pollution. The term often refers to marine oil spills, where oil is released into the ocean or coastal waters. The oil may be a variety of materials, including crude oil, refined petroleum products (such as gasoline or diesel fuel) or by-products. Spills take months or even years to clean up. Deepwater Horizon oil spill (An Accidental Oil Spill) The Deepwater Horizon was a semisubmersible, mobile, floating, dynamically positioned drilling rig that could operate in waters up to 3,000 m deep. Built by South Korean company Hyundai Heavy Industries and owned by Transocean, the rig operated under the Marshallese flag of convenience, and was chartered to BP (British Petroleum) from March 2008 to September 2013. It was drilling a deep exploratory well, 5,600 m below sea level, in approximately 1,600 m of water. The well is situated in the Gulf of Mexico, in the United States' exclusive economic zone. On the night of 20 April 2010, highpressure methane gas from the well expanded into the drilling riser and rose into the drilling rig, where it ignited and exploded, engulfing the platform. The Deepwater Horizon sank on the morning of 22 April 2010. The oil leak was discovered on the afternoon of 22 April when a large oil slick began to spread at the former rig site. The oil flowed for 87 days. The flow rate was about 62,000 barrels per day (9,900 m3/d) making it the world’s largest accidental spill. According to the satellite images, the spill directly impacted 68,000 square miles (180,000 km2) of ocean. Environmental Effects Damage to Fisheries – Oil spills present the potential for enormous harm to deep ocean and coastal fishing and fisheries. – Harms include: fish mass mortality and contamination, poisoning ocean organic substrate and shutting down fishing enterprises. Damage to Wildlife – Wildlife other than fish and sea creatures; including mammals, reptiles, amphibians and birds that live in or near the ocean, are also poisoned by oil waste. Damage to Recreation – Coastal areas are usually thickly populated and attract many recreational activities; for example fishing, boating, diving, swimming, natural parks and beaches, …etc. Popular Techniques for Cleaning up an Oil Spill The techniques used to clean up an oil spill depend on oil characteristics and the type of environment involved; for example, open ocean, coastal, or wetland. Like a home repair job, each oil spill has unique aspects that call for careful consideration when deciding which tool to use. Booms Floating booms are mechanical barriers that extend above and below the surface of the water to stop the flow of oil. Boom is used to contain oil, to collect oil, as a barricade to exclude oil from a certain area; to absorb oil; and to deflect oil. Skimming Skimming is a process that removes oil from the sea surface before it reaches sensitive areas along a coastline. This is achieved by the use of various mechanical devices such as pumps, vacuum systems etc. These devices attract oil to their surfaces before transferring it to a collection tank, often on a boat. Much like a vacuum picks up dirt from a carpet, a skimmer has to come in direct contact with the oil in order to remove it from the surface and, even then, it will still pick up some water. The efficiency of a skimmer depends upon the sea and weather conditions. Sorbents Sorbent booms and barriers are used to absorb a moving oil slick. They only work well when a slick is thin, because once their surfaces are saturated, they cannot absorb anymore. In-situ Burning In situ burning is the process of burning spilled oil where it is on the ocean (known as "in situ," which is Latin for "on site"). Through controlled burning of the oil, oil slick can be removed. In-situ burning can approximately remove around 100- gallons/day/square foot of surface area under excellent weather conditions. Similar to skimming, two boats will often tow a fire-retardant collection boom to concentrate enough oil to burn. Ideal conditions for in situ burning are daylight with mild or offshore winds and flat seas Bioremediation Oil, like many natural substances, will biodegrade over a period of time into simple compounds such as carbon dioxide, water and biomass. Bioremediation is the term used to describe a range of processes, which can be used to accelerate natural biodegradation. Bioremediation is the use of either naturally occurring or deliberately introduced microorganisms to consume and break down environmental pollutants, in order to clean a polluted site. Manual Clean up The other best way to clean up oil once it has hit the shore is by manual clean up. Since oil has chances of spreading and getting mixed with the soil or sand on the shore, the best method to contain oil spread is by manual methods. Produced Water Produced water is a term used in the oil industry to describe water that is produced as a by product along with the oil and gas. Oil wells have more produced water than gas wells Waterflooding (or water injection) is a technique that often used to increase the production of oil wells. The water composition ranges widely from well to well and even over the life of the same well. Much produced water is brine, and most formations result in total dissolved solids too high for beneficial reuse. All produced water contains oil and suspended solids. Produced water is considered an industrial waste. Historically, produced water was disposed of in large evaporation ponds. However, this has become an increasingly unacceptable disposal method from both environmental and social perspectives Air Pollution and Control Part 1 Air is necessary for the survival of all higher forms of life on earth. On the average, a person needs at least 13 kg of air every day to live, but only about 1.4 kg of water and 0.7 kg of food. Scientific studies have demonstrated that over the long term, the standard of health for people living and working in urban areas is lower than that for populations in rural areas, where air pollution is much less severe. There is much scientific evidence of a distinct relationship between generally dirty air and a higher incidence of respiratory diseases, including lung cancer. There is also compelling evidence that air pollution has a significant and lasting worldwide (global) impact on the Earth's climate. Atmospheric layers is divided into 5 layers, based on increase or decrease of temperature with altitude. Exosphere Troposphere Stratosphere Mesosphere Thermosphere Layer 1: Troposphere Troposphere is the layer where we live in. It is the closest layer to earth’s surface. It is also the thinnest layer. All the earth’s weather happens in this layer. The troposphere is mostly heated by transfer of energy from the surface, so on average the lowest part of the troposphere is warmest and temperature decreases with altitude. The troposphere, contains about 80 % of the total air mass (or atmosphere) Dry air in the troposphere is a mixture of: 78 % Nitrogen by volume 21 % Oxygen by volume 1 % Other gases: argon(about 0.9 %), carbon dioxide, methane, and water vapor. Gaseous Composition of the Troposphere It is in this relatively thin layer of air that oxygen-dependent life is sustained, clouds are formed, weather patterns develop, and most air pollution problems occur. The density of air (about 1.23 kg/m3 at sea level) decreases significantly with an increase in altitude. The depth of Troposphere layer is about on average 12 km. Troposphere is deeper in the tropics, up to 20 km, and shallower near the polar regions, approximately 7 km. The relative amount or concentrations of gases in air can be expressed in terms of parts per million (ppm) and in terms of percentage. For example, since 1 % = 10,000 ppm, an oxygen level of 21 % in air can also be expressed as 210,000 ppm. The concentration of carbon dioxide (CO2) in the atmosphere, now close to 0.04%, may be more conveniently expressed as 400 ppm. Layer 2: Stratosphere The stratosphere extends to about 51 km. About 90% of the ozone in our atmosphere is contained in the stratosphere. In stratosphere ozone concentrations are about 2 to 8 parts per million (ppm). It is mainly located in the lower portion of the stratosphere from about 15 to 35 km, though the thickness varies seasonally and geographically. Ozone absorbs ultraviolet light from the Sun. More light is absorbed at higher altitudes compared to the lower stratosphere, so the temperature increases with height which restricts turbulence and mixing Air Pollution Air pollution may be simply defined as the presence of certain substances in the air in high enough concentrations and for long enough durations to cause undesirable effects. –"Certain substances" may be any gas, liquid, or solid. –Those substances causing pollution are called pollutants. Worldwide, air pollution is responsible for large numbers of deaths and respiratory disease Effects of Weather Air pollutants are mixed, dispersed, and diluted within the troposphere by movement of air masses, both horizontally and vertically. Air movements and therefore air quality are very dependent on local and regional weather conditions. Knowledge of horizontal and vertical circulation patterns of air is of importance with regard to: –site selection for new industrial plants. –design of tall stacks or chimneys. Horizontal Dispersion of Pollutants Horizontal dispersion or spreading of air pollutants depends on wind speed and direction. Because soil and rock warm up and cool faster than water, winds near shorelines are directed toward the water at night and inland during the day. In an urban area, where steel, concrete, and masonry absorb and hold heat, a heat island cover the city at night, with a self-contained circulation pattern from which pollutants cannot readily escape. Wind Rose Diagram The wind rose indicates the frequency with which the wind blows from a given direction (N- North, S - South, E - East, W - West). For example, a wedge directed straight up (N) and extending 4 rings means that the wind blows from the North 4% of the time. Wind Rose Diagram Type II Shows direction, duration and intensity (wind speed) Radial lines – Wind direction Each wedge – Wind velocity Inside circle – Percentage of time wind blows in that direction. Vertical Dispersion of Pollutants Vertical mixing of air and dispersion of pollutants depends on the kind of atmospheric stability prevailing at any given time. The atmosphere is considered to be stable when there is little or no vertical movement of air masses and therefore little or no mixing and dispersion of pollutants in the vertical direction. An unstable atmosphere, on the other hand, is one in which the air moves naturally in a vertical direction, increasing mixing and dispersion of the pollutants. With regard to local or regional air quality, a condition of atmospheric instability is preferable to a stable condition. Air stability depends on the rate of change of air temperature with altitude, called the temperature gradient. The rate at which air temperature drops with increasing altitude in the troposphere is called the environmental lapse rate. The dry adiabatic lapse rate is the lapse rate of a dry mass of air which expands and cools as it rises. This rate is typically -10 °C per 1 km (or -1 °C per 100 m). Dry adiabatic lapse rate is independent of the prevailing atmospheric temperature gradient at any given time. When the environmental lapse rate exceeds the adiabatic lapse rate, the atmosphere is unstable and vertical mixing of air masses will occur A lapse rate characterized by an increase in air temperature with increasing altitude, called a temperature inversion, results in an extremely stable condition. –This prevents the upward mixing of pollutants and a major cause of severe air pollution episodes. Illustration of unstable atmospheric conditions, when the environmental lapse rate (e.g., –2° per 100 m) exceeds the adiabatic lapse rate. In this example, buoyant forces keep the air parcels moving in a vertical direction. When a temperature inversion begins above the ground because of local weather conditions, it acts as ceiling that prevents further vertical mixing and traps pollutants below it Trapping of pollutants below the inversion, allowing them to build up. If the sky is very hazy, or is sunsets are very red, there is likely an inversion somewhere in the lower atmosphere. This happens more frequently in high pressure zones, where the gradual sinking of air in the high pressure dome typically causes an inversion to form at the base of a sinking layer of air Sources of Air Pollutants Natural: Those pollutants which are introduced by volcanoes, fires, oceans, soils, plants and microbes etc. Anthropogenic: Those which are caused by human activities. For example, by combustion-type engines, by construction and destruction of structures, by chemical processing, mining and agriculture etc. Primary and Secondary Pollutants Those pollutants that are directly introduced into air by human activities are Primary Pollutants. The sources of primary air pollutants are either mobile (e.g., automobiles) or stationary (e.g., coal-fired electric power generating stations). –Example: Sulfur dioxide released directly from burning fossil fuel. Secondary pollutants are produced when primary pollutants react with other pollutants or water vapor to make a new substance. –Example: Sulfur dioxide mixes with water in atmosphere and causes acidic rain. –ozone is produced by hydrocarbons and oxides of nitrogen (both of which may be produced by car emissions) and sunlight Six Common Pollutants causing Air Pollution 1. Ground-level Ozone 2. Particulate matter (Particle pollution) 3. Carbon monoxide 4. Sulfur oxides (e.g. SO2) 5. Nitrogen oxides (e.g. NO2) 6. Lead These pollutants can harm human-health and the environment 1. Ground-level Ozone Ground-level ozone (O3) is a colourless and highly irritating gas that forms just above the earth's surface. It is a "secondary" pollutant because it is produced when two primary pollutants, Nitrogen oxides (NOx) and Volatile organic compounds (VOCs), react in sunlight and stagnant air. Most of NOx and VOCs come from combustion of fuels (e.g. gasoline or petrol). Ground-level ozone is the primary constituent of smog. Smog is a kind of visible air pollution, originally named for the mixture of smoke and fog in the air. Smog is composed of ozone, nitrogen oxides, sulphur oxides, smoke or particulates among others Ozone: Good and Bad Ozone has the same chemical structure whether it occurs miles above the earth or at groundlevel and can be "good" or "bad," depending on its location in the atmosphere. “Good” ozone occurs naturally in the stratosphere approximately 10 to 30 miles above the earth's surface and forms a layer that protects life on earth from the sun's harmful rays. In the earth's lower atmosphere, ground-level ozone is considered “Bad.” This ozone can damage lung tissue and plants. Particulate Matter Particulate matter (PM) are also known as particle pollution. Particulates are extremely small fragments of solid or liquid droplets suspended in air. Major sources of particulates include industrial materials handling processes, coal- and oil- burning power plants, residential heating systems, and highway vehicles. Particulates that penetrate deep into the lungs are harmful, and certain particulates can be toxic or carcinogenic (cause cancer) consider that the average human hair is about 65 μm in diameter PM smaller than 1 μm tend to remain suspended in the atmosphere indefinitely, whereas those larger than 1 μm can eventually settle out. The particulate materials of most concern with regard to adverse effects on human health are equal to or less than 10 μm in size and are referred to as PM10 Fine particles, those with diameters equal to or smaller than 2.5 μm (PM2.5) are of special concern because they are more likely to penetrate deep into the lungs when inhaled. Carbon Monoxide Carbon Monoxide (CO) is a colorless and odorless gas that is formed when carbon in fuel is not burned completely. Vehicular exhaust is a major source (about 56 percent of all) of CO emissions. Higher levels of CO generally occur in areas with heavy traffic congestion. Indoor CO sources are commonly woodstoves, gas stoves, cigarette smoke, unvented gas and kerosene space heaters. Nitrogen dioxide (NO2) NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. NO2 is one of a group of highly reactive gasses known as "oxides of nitrogen," or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid (HNO2) and nitric acid (HNO3). In addition to contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a number of adverse effects on the respiratory system. NOx reacts with ammonia, moisture, and other compounds to form small particles. Sulphur dioxide (SO2) Belongs to the family of sulfur oxide gases (SOx). These gases dissolve easily in water. SOx gases are formed when fuel containing sulfur, such as coal and oil, is burned, and when gasoline is extracted from oil, or metals are extracted from ore. SO2 may cause Respiratory illness, particularly in children and the elderly. In the longer-term exposures to high levels of SO2 gas and particles aggravate existing heart and lung diseases. Sulfate particles are the major cause of reduced visibility in many parts of the world. LEAD (Pb) The major sources of lead emissions have historically been motor vehicles (such as cars and trucks) and industrial sources. Today, the highest levels of lead in air are usually found near lead smelters. Other stationary sources are waste incinerators, utilities, and lead-acid battery manufacturers. Lead is a systemic poison, causes anemia (reduction in haemoglobin), affects kidney function, and damages brain. As a result of EPA's regulatory efforts to remove lead from gasoline, emissions of lead from the transportation sector dramatically declined by 95 percent between 1980 and 1999, and levels of lead in the air decreased by 94 percent between 1980 and 1999. Hazardous Air Pollutants Air pollutants associated with certain specific sources, and that pose an immediate threat to human health, are called air toxics or hazardous air pollutants (HAPs) examples are: –Asbestos –Benzene –Beryllium –Mercury –Vinyl chloride –Radionuclides (radioactive air pollutants) Gases Concentration Measurement Concentration of air gaseous pollutants in air are mostly expressed in volumetric terms 124‫قانون س‬ Sometimes concentrations are expressed as mass per unit volume, such as μg/m3 or mg/m3. The relationship between ppm and mg/m3 depends on the pressure, temperature, and molecular weight (MW) of the pollutant. The ideal gas law helps us establish that relationship Conversion between ppm and mg/m3 In general, the conversion from ppm to mg/m 3 is given by: 125‫قاون س‬ Where: MW = molecular weight of the compound (g/mol) T = absolute temperature (K) = °C + 273.15 P = absolute pressure (atm) = mmHg/760 Air Pollution and Control Part 2 Air Quality Measurement Number of methods are used to measure air quality, including mobile instrumentation and permanent monitoring stations These monitoring stations measure the presence of contaminants in the air, such as –Particulate matter (PM 2.5 and PM 10) –Carbon monoxide (CO –Nitrogen dioxide (NO2) –Sulphur dioxide (SO2) –Ozone (O3) –Hydrogen sulphide (H2S) Air Pollutants Control Devices are commonly used by industry to remove pollutants from an exhaust stream before it is emitted into the atmosphere. Air Quality Standards Emissions standards are requirements that set specific limits to the amount of pollutants that can be released into the environment. Many emissions standards focus on regulating pollutants released by automobiles (motor cars) and other powered vehicles. But they can also regulate emissions from industry, power plants, small equipment such as lawn mowers and diesel generators. Effects of Ambient Air Pollution Air pollution is known to have many adverse effects, including those on: –Human health –Building facades and other exposed materials –Vegetation and agricultural crops –Animals and aquatic habitat –The climate of Earth as a whole Generally, air pollution is most harmful to the elderly and to the baby. Major health effects are categorized as being either: –Acute short-lasting, but severe, and may even result in death –Chronic long-term effects usually include respiratory illnesses such as asthma and perhaps lung cancer –Temporary effects include intermittent periods of eye or throat irritation, coughing, chest pain, … Typical effects of sulfur dioxide, oxides of nitrogen, and ozone include eye and throat irritation, coughing, and chest pain. A threshold level for a given pollutant is a minimum level below which there will be no health effects Worldwide Air Quality Issues Air pollution problems are not necessarily confined to a local or regional scale. Atmospheric circulation can transport certain pollutants far away from their point of origin, expanding air pollution to continental or global scales. Worldwide air quality issues: –Acid rain –Global warming –Ozone layer depletion Acid Rain A rain which is unusually acidic i.e. rain whose pH is low is called acidic rain. Acid rain is mostly caused by emissions of sulfur, nitrogen, and carbon oxides which react with the water molecules in the atmosphere to produce acids, which fall to earth as rain, fog, snow, or dry particles. Some may be carried by the wind for hundreds of miles. Acid rain, for example, occurs largely on a regional and a continental scale. It has killed fish and plant life in thousands of lakes in Europe, China, Canada, and the northeast United States. It also causes deterioration of metals, concrete, painted surfaces, and other exposed objects. Impacts of Acid Rains Plant and Water Damage –Acid rain damages forests and crops, changes the makeup of soil, and makes lakes and streams acidic and unsuitable for fish. –Continued exposure over a long time, changes the natural variety of plants and animals in an ecosystem. Aesthetic Damage –Acid rain accelerates the decay of building materials and paints, including irreplaceable monuments, statues, and sculptures. Global Warming Global warming is a gradual increase in the overall temperature of the earth's atmosphere. Global warming is believed by most scientists to be caused by the accumulation of carbon dioxide and other greenhouse gases emitted as a result of human activities. Global warming may lead to rise in sea levels due to melting of glaciers and polar ice caps, as well as adversely affecting ecosystems in some parts of the world The average temperature of the Earth has risen between 0.4 and 0.8 °C over the past 100 years. Scientists have recently predicted that average global temperatures could increase between 1.4 and 5.8 °C by the year 2100. The amount of incoming energy from the sun is in equilibrium with the energy radiated and reflected back into space. The atmosphere acts as a "blanket" that regulates average temperatures at the Earth's surface. The "thicker" the blanket (i.e., the more "greenhouse gases" in the atmosphere), the warmer is the temperature in the lower atmosphere and Earth's surface. Infrared Radiation (Heat Radiation) Infrared (IR) radiation is just as important to the Earth's weather and climate as sunlight is. This is because, for all of the sunlight that the Earth absorbs, an equal amount of IR radiation must travel from the Earth back to outer space. If this was not the case, there would be global warming or global cooling. Ozone Layer Depletion Stratospheric ozone is important because it blocks harmful UV rays from the sun. But those ozone levels have been dropping, largely due to the presence of non biodegradable organic chemicals such as chlorofluorocarbons (CFC) from aerosol cans, refrigerants, and industrial solvents. CFC production and use is now banned in many Counties Air Quality Index The AQI is an index for reporting daily outdoor air quality. It tells how clean or polluted our air is, and what associated health effects might be a concern for us. The Environmental Protection Agency (EPA) uses 5 Major air pollutants to define AQI. Ground level ozone Particulate matter CO SO2 NO2 The AQI is divided into six categories. Each category corresponds to a different level of health concern. The higher the AQI value is, the greater the level of air pollution and the greater the health danger. Air Quality Index (AQI) :Category and Range AQI value ranges from 0 to 500. An AQI value of 100 generally corresponds to the national air quality standard for the pollutant, which is the level EPA has set to protect public health. AQI values below 100 are generally thought of as satisfactory. When AQI values are above 100, air quality is considered to be unhealthy-at first for certain sensitive groups of people, then for everyone as AQI values get higher. Indoor Air Quality Indoor air quality (IAQ) is important because people generally spend most of their time indoors. Indoor air contaminants include: –combustion products (especially tobacco smoke) –radon –asbestos –formaldehyde –lead –biological substances Environmental tobacco smoke (ETS), which contains more than 40 carcinogenic compounds, causes thousands of lung cancer deaths each year in nonsmoking adults Asbestos, a mineral fiber used as insulation and as a fire retardant in buildings. It has been banned from Saudi Arabia. –It can cause lung cancer if very small airborne asbestos fibers are inhaled. Formaldehyde, a colorless gas that comes from certain building materials and household products. –can cause eye and throat irritation (and maybe cancer) Radon, a naturally occurring colorless, odorless, radioactive gas, can enter buildings through porous soil and rock fissures at basement walls and floors. –It can be a cause of lung cancer if inhaled for long Periods Radon is a colourless, odourless, tasteless radioactive gas. Radon comes from the natural breakdown of uranium in soil, rock and water. It is the second leading cause of lung cancer in the United States. Radon can enter homes and buildings through cracks in floors, walls or foundations. Radon gas that seeps out of soils can decay inside the buildings Radon can also be in water supplies, especially well water. Testing is the only way to know if indoor areas have elevated radon levels. Indoor Air Quality Proper infiltration and ventilation (air exchange) is necessary to minimize levels of indoor air pollutants. Indoor Air Quality (IAQ) is a component of the LEED green building certification credits related to indoor environmental quality. Air Pollution Control Air pollution control strategies include: –Complete source shutdown –Source location (or air zoning) –Fuel substitution –Process changes –Enforcement of emission standards for specific sources Several types of air cleaning devices can trap air pollutants before they are emitted into the atmosphere Control of Particulate Matter Particulate matter control equipment includes: –Gravity settlers –Cyclones –Electrostatic precipitators –Fabric filters –Wet scrubbers The selection of control equipment depends on the range of particulate sizes, flow rates, temperatures of the carrier gas, costs, and other factors. One of the most efficient of these devices for removing suspended particulates is the fabric filter (or baghouse) Dust separates due to centrifugal action. - Good for large particle sizes. Dust collection efficiency between 90% to 95% Baghouse (Fabric filters) Uses cloth as filters. During operation, dust and other particles too large to pass through the bags accumulate on the bags' surfaces and form a layer known as a dust cake (which thickens and slows the rate that gas can enter the bags). A rod, driven by a motor, shakes the bag in a horizontal direction to remove the dust cake. Normal operation of the baghouse temporarily ceases during this time. Wet scrubbers Wet scrubbers remove dust particles by capturing them in liquid droplets. The droplets are then collected.\ Electrostatic precipitators 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 can easily remove fine particulate matter such as dust and smoke from the air stream. This device is used in cement plants. Gaseous air pollutants Gaseous air pollutants can be controlled using either absorption or adsorption processes. Absorption involves the transfer of a gaseous pollutant into a contacting liquid. Adsorption involves attracting and trapping gas molecules onto the surface of a solid (e.g., activated carbon) Wet scrubbers can be used for gas absorption, as well as packed scrubber towers. Activated carbon can be used to adsorb certain gaseous air pollutants Catalytic converters Emissions from the internal combustion engine, which is a major mobile source of air pollutants, are controlled by positive crankcase ventilation systems and catalytic converters. Solid Waste Management Solid Waste Waste is a human-derived word. Materials are considered a waste when owners and society believe they no longer have value. Any non-liquid material that is thrown away or discarded as useless and unwanted is considered to be solid waste Solid waste can host rodents and insects, which may act as vectors of infectious diseases such as typhoid, plague, and dysentery. Effect of Improper Solid Waste Disposal There is connection between improper solid waste disposal and public health. Improper disposal of solid waste can cause serious environmental or ecological damage. – Air pollution can result from inadequate solid waste incineration – Soil contamination – Surface water and groundwater pollution, can be caused by the disposal of solid waste in improperly built landfills. Sources of Solid Wastes Municipal solid waste (MSW) – The term municipal solid waste is generally used to describe most of the nonhazardous solid waste from a city, town, or village that requires routine or a periodic collection and transport to a processing or disposal site. Industrial solid waste – Wastes arising form industrial activities – Some of industrial waste is classified as hazardous waste Agricultural solid waste Mining solid waste Solid Waste Management requires an understanding of waste generation, storage, collection, transport, processing, and disposal Objectives of Proper Management of Solid Wastes Proper management of solid wastes has five main objectives: 1. Follow the pollution prevention hierarchy, which prefers source reduction and recycling over treatment and disposal. 2. Protect public health. 3. Protect the environment (including biodiversity) and view the waste material as a resource. 4. Address social concerns (equity, environmental justice, aesthetics, risk, public preferences, recycling & renewable energy). 5. Minimize economic, social, and environmental costs. Types of Municipal Solid Waste Garbage contains putrescible or highly decomposable food waste, such as vegetable and meat scraps. Rubbish contains mostly dry, non-putrescible material, such as glass, rubber, metal cans, and lowly decomposable or combustible material, such as paper, textiles, or wood objects. Trash includes bulky waste materials that generally require special handling and is therefore not collected on a routine basis. An old couch, mattress, television, or refrigerator and even a large uprooted tree stump are examples of trash items. Quantities of MSW Information regarding the weight, volume, and the composition of the MSW is important for the proper planning, design, and operating of collection and disposal facilities. In Saudi Arabia, about 15 million tons of MSW/year. (1.5-1.8) kg are generated per person every day. The actual number will vary for each community depending on: 1. The time of year 2. The location 3. Commercial and industrial activities In Saudi Arabia:* Recycling rate ranges from 10-15% (low rate). Recycling activities are mostly manual and labor intensive. Composting is also gaining increased interest in Saudi Arabia due to the high organic content of MSW (around 40%). MSW Management Strategy (3 main components) 1- Source reduction (waste prevention) includes: - reuse of products on-site - packaging to reduce their quantity - on-site composting of garden trimmings 2- Recycling - off-site recovery and processing for reuse - off-site composting 3- Energy recovery 4- Treatment 5- Disposal - incineration - landfills Solid Waste Collection Solid waste Collection includes: o Temporary storage and containerization o Transfer to a collection vehicles o Transport to a processing facility or disposal site About 2/3 of the total cost for MSW management is needed for waste collection - it is labor intensive If source separation is applied, the recyclable material (e.g. Plastic, Paper, … etc.) can be collected separately from non-recyclable garbage and rubbish. Transfer stations solid wastes from individual collection trucks are consolidated into larger truck, economical way to transport the solid waste over the long-haul distance to the processing and disposal site. Compost and Composting Compost: a combination of Composting: Natural process of decay decomposed plant and animal to change organic wastes (i.e., grass materials and other organic clippings, food scraps, and leaves) into materials that are recycled into a a valuable, humus-like material known rich black soil. as compost. Solid Waste Processing The purpose of MSW processing is to: – Reduce the total volume and weight that needs final disposal, – Improve its handling characteristics, and – Recover natural resources and energy for reuse. The commonly used processes for MSW includes: – Sorting and separating – Shredding – Pulverizing – Baling – Composting – Incineration Shredding (cutting and tearing) or pulverizing (crushing and grinding) can achieve size reduction of solid waste. Baling involves compaction of the waste into the form of rectangular blocks, which are wrapped with steel wire to retain their shape during handling Composting is a biological process that allows the organic portion of MSW to decompose under controlled conditions, transforming the waste into a potentially beneficial material called compost (humus) compost can enrich and improve soil properties for agricultural use. Recycling involves separating out and reusing the components of the MSW stream that have some economic value, including metals, paper, glass, and plastic (Aluminum has the highest recycling value). Separation can be done at the source or at a centralized waste processing plant Incineration (MSW Combustion with Energy Recovery) Incineration: Complete combustion using excess oxygen MSW combustion typically reduces the volume of wastes by 90%. MSW combustion produces flue gases with high temperature, and the thermal energy can be used to raise steam to drive a turbogenerator to produce electricity. While older waste incineration plants emitted high levels of pollutants, new technologies have significantly reduced this concern Sanitary Landfill Ultimately, a portion of the MSW stream is disposed of in a sanitary landfill, which is a carefully planned and engineered facility. The key characteristics that distinguish landfills from old-fashioned "dumps" are as follows: – Waste is placed in a suitably selected and prepared site in a carefully prescribed manner. – Waste material is spread out in layers and compacted with appropriate heavy machinery. – Waste is covered each day with a layer of compacted soil In addition, all landfills are deigned to prevent groundwater pollution by the leachate (polluted liquid) seeping out from the bottom of the landfill. Landfill is generally the most economical alternative for MSW disposal, although It has become increasingly difficult to find suitable sites for new landfills. Sanitary Landfill site selection The most important factors in landfill site selection are: 1. Volume capacity 2. Accessibility 3. Hydrogeological condition Accessibility refers to the ease with which collection or transport vehicles can reach the disposal area without causing a public nuisance or hazard. Local geology and hydrology (hydrogeology) have a direct influence on the possibility of water pollution Modern landfills are also called containment landfills because they are constructed with bottom liners. The liners confine the leachate and prevent it from mixing with groundwater. Hazardous Wastes MSW is not generally considered to be hazardous, but certain types of commercial or industrial wastes are characterized as hazardous waste that can cause immediate and direct harm to people or the environment if disposed of improperly. Hazardous Waste is defined as a solid waste that may cause or significantly contribute to an increase in mortality or an increase in serious irreversible or incapacitating reversible illness; or pose a substantial potential hazard to human health or the environment when it is improperly treated, stored, transported, or dispose of. This hazardous waste typically requires transport, processing, and disposal methods that are different from those required for nonhazardous MSW. Noise Pollution and Control Sounds and Noise Sound is a pressure variation(wave) that travels through air and is detected by the human ear. Noise is unwanted and potentially harmful sound. Noise is perhaps one of the most undesirable by-products of a modern mechanized lifestyle. Noise is a pollution problem that affects human health and well-being and that can contribute to a general deterioration of environmental quality. It takes energy to produce all sound, so, in a manner of speaking, noise is a form of waste energy. Not all sound is noise. What may be acceptable to one person may be noise to another Noise from highway traffic, construction activities, and other sources in the community is of special concern to environmental engineers. Noise can have impacts ranging from temporary public or personal nuisance to permanent hearing loss in individuals. Excessive noise pollution (undesirable and unwanted sound) can have harmful effects, ranging from: – physical damage to the ear; – temporary or permanent hearing loss; – physiological effects of raising blood pressure and pulse rates; – causing stress; Irritability and anxiety Basics of Sounds Sound energy is produced by mechanical vibrations of a sound source. We can’t measure acoustic energy very well, but we can measure sound pressure well. Sound pressure is a surrogate for acoustic energy. The vibrations are transmitted or carried away from the source in the form of sound waves. Sound waves can be transmitted through solids, liquids, or gases, but they cannot be transmitted in a vacuum, where there is no medium or material to transmit the vibrations The physical characteristics of sound waves are wavelength, frequency, and amplitude. – Wavelength is the distance between air pressure peaks (or valleys) – Frequency or pitch is the number of wavelengths that passes a fixed point in 1 sec. – Amplitude of the sound wave is the height of the air pressure peaks (i.e., above the average air pressure) measured in decibels (dB). A single wavelength is called a cycle, and the frequency is expressed in terms of cycles per second (cps). The term "hertz" (Hz) is often used for frequency, where 1 Hz = 1 cps. The relationship among the three characteristics is v=λXf where v is the speed of sound in m/s, λ is wavelength in m per cycle, and f is the frequency in Hz (or cps). The speed of a sound wave v in air is about 340 m/s. Human perception of sound includes its loudness (amplitude) and pitch (frequency). Loudness is related to the amplitude of the wave aswell as other factors. Pitch is a function of the frequency of the wave that produces it. The human ear can detect sounds in the frequency range of about 20 to 20,000 Hz The average atmospheric pressure is about 1 bar, and an average person can typically detect a sound with amplitude as small as 0.0002 μbar. The human ear can perceive sound pressures as high as 10,000 μbar before ear damage occurs. The audibility of a sound depends on both frequency and amplitude. Sound Pressure Level (SPL) A decibel is essentially a ratio of two pressures; logarithms are used to convert the range of the ratios into more manageable and convenient numbers. The magnitude of volume or a sound expressed in decibels is called a sound pressure level (SPL). An SPL is defined mathematically as 164 ‫قانون ص‬ SPL= sound pressure level, dB P = RMS sound pressure, μbar (RMS = Root Mean Square) Po = reference pressure (0.0002 μbar, is the hearing threshold or lowest audible sound pressure) Decibel scale is used for noise measurement, and sound pressure levels (SPLs) are expressed in terms of decibels (dB). An SPL = 0 dB is the lowest audible sound, and an SPL of 140 dB just exceeds the human threshold of pain. The decibel (dB) scale is used to measure noise levels A-weighted decibels (dBA) In the A-weighted system, the decibel values of sounds at low frequencies are reduced, compared with unweighted decibels, in which no correction is made for audio frequency. Two sound levels of equal dB level but of different frequencies have different dBA levels; the lower frequency sound has the lower dBA level This correction is made because the human ear is less sensitive at low and high audio frequencies, especially below 500 Hz, and above 6 kHz audio frequencies The A-weighting filter The A-weighting filter, filters out the low-frequency and very high-frequency sounds, where the human ear is less efficient and measures the sound level in A-weighted decibels, or dBA. Using dBA level helps to match the meter readings with the sensitivity of the ear and with average person’s judgment of the relative loudness of various sound. The ‘A’ weighting filter covers the full frequency range of 20 Hz to 20 kHz Noise Standards: Criteria level There are two factors determines how hazardous noise is: Intensity (loudness) measured in dBA Time of exposure measured in hours and minutes OSHA = Occupational Safety & Health Administration Combined Noise In many instances it is necessary to predict what the combined sound pressure level will be when two or more nearby noise Sources act at the same time. Noise Control Noise can be controlled in four fundamental ways: – protect the recipient – increase the path length – block the path – reduce the noise at the source Earplugs or earmuffs protect recipients by as much as 40 dBA. One of the best, but often overlooked, methods of noise source reduction is regular and thorough maintenance of operating machinery. Sound levels also drop significantly with increasing distances from the noise sources, so increasing path lengths between sources and recipients offers a passive means of control. If path length from a point source is doubled, for example, the intensity of the noise reaching the recipient is one fourth of the original intensity. Sound levels from line sources (e.g., highways) decrease 3 dBA for each doubling of the distance from the source. In industrial plants, noise reduction can be achieved by enclosing machinery in acoustic absorbing materials and by using absorbent mounts and pads Reducing noise levels from construction sites include Barriers to block noise and restriction of hours of construction activity Proper highway planning and design are essential for controlling traffic noise. Lower speeds, depressed roadways, and construction of vertical wall barrier are methods used to control of traffic noise. Most of automobile traffic noise comes from the movement ofthe vehicle tires on the pavement and wind resistant. The path of traffic noise can also be blocked by the construction of vertical walls or barriers along the highway Relationship between the sound level and distance from a line source The relationship between the sound level and distance from a line source (e.g. highways) can be written as follows: 171‫قانون ص‬ SLA = sound level at distance DA from the source SLB = sound level at distance DB from the source Environmental Impact Assessment Environmental impact assessment (EIA) is the process of determining and evaluating the effects that a proposed action would have on the environment before the decision is taken on whether or not to proceed with it. Environmental impact statement (EIS) is the most common name given to the printed report which documents the results of the EIA process for consideration by decision makers. (Several names are also used, including environmental impact report and environmental review). Use and Misuse of EIA A basic objective of an environmental study is to anticipate any potential impacts, adverse or beneficial, of a proposed construction project on the environment. This is done so that measures can be taken to minimize or eliminate the harmful impacts when the project is implemented. It is supposed to be objective and unbiased, and it is meant to neither promote nor block the implementation of a proposed project.

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