Diploma of Environmental Monitoring & Technology Study module 1 Introduction to air pollution MSS025009A Air pollution monitoring Completion Record Student name Type your name here Available marks 63 Final mark Marker to enter final mark Completion date Marker to enter date. cffet.net/env APM Study module 1 – Introduction to air pollution MSS025009A INTRODUCTION 2 The definition of air pollution 4 THE ATMOSPHERE 5 Stratification of the Atmosphere Factors Likely to increase the Levels of Air Pollution The Protection of the Environment Operations Act 7 8 8 MAJOR SOURCES OF AIR POLLUTANTS 9 Transportation-Combustion Sources Stationary (Industrial) Sources Fugitive Emissions and Other Sources 10 11 15 HEALTH EFFECTS OF AIR POLLUTION 16 Effects of Air Pollution on Human Health Interactions between pollutants and synergism Susceptible parts of the Human Body Effects of specific chemicals 16 16 17 17 ENVIRONMENTAL EFFECTS OF AIR POLLUTANTS 21 EFFECTS OF AIR POLLUTANTS ON BUILDINGS AND MATERIALS 22 ASSESSMENT TASK 24 ASSESSMENT & SUBMISSION RULES 28 Answers Submission Penalties Results Problems? 28 28 28 28 28 RESOURCES & REFERENCES 29 References Resources Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 29 29 Page | 1 APM Study module 1 – Introduction to air pollution MSS025009A Introduction The Earth is surrounded by an envelope of gases which provide many functions including, protection from harmful radiation, moderating the surface temperature and providing a medium (which we call air) that allows organisms to exchange gases in order to survive (breathing). Any substantial change in the nature or contents of the atmosphere has a direct consequence on how well the atmosphere performs these tasks. Air is of fundamental significance to our existence. If the quality of the air we breathe is degraded then our health will directly suffer and our standard of living decrease. This is one of the great paradoxes of modern society. In general the higher the degree of sophistication of society (some might call this civilisation), the lower the quality of the air that they are exposed to. Indeed the lifestyle and extent of civilisation of societies on the Earth directly relate to the type of atmospheric degradation which is present. Historically air pollutants of greatest concern have been total suspended particulates (TSP), and oxides of sulfur, but as our processing industries become more sophisticated the list of significant pollutants grows. Now we commonly include oxides of nitrogen and photochemical oxidants (smog & ozone) as routine pollutants, and often include particulate lead, asbestos, mercury, sulfuric acid and many others that require careful monitoring. Concern over the atmospheric concentrations of substance not normally considered pollutants have also become much greater in the latter part of the twentieth century. A good example of this is CO2. The levels of this gas have increased by as much as 5% over the last two decades of the twentieth century. Most of this is thought to be due to the combustion of fossil fuels. This has been targeted as a major environmental problem by most of the world’s nations and strategies have been put in place to reduce the amount being discharged into the atmosphere. It is expected that the levels of CO2 in the atmosphere will peak around 2040 – so the problems associated with degradation of the atmosphere in general will take a long time to fix. This needs to be considered by nations that are emerging as economic powers. The Earth’s atmosphere has never been completely pure. It has always contained waste materials from many natural sources such as bushfires, decay from plant and animal life, and windblown dust particles to mention a few sources. Pollutants also arise from unexpected natural sources. For example rainforests are regarded as essential for the health of the atmosphere in that they remove CO2 and replace it with O2. For this reason they are thought of as the Earth’s lungs (along with ocean phytoplankton). Rainforests and other types of forests also produce natural hydrocarbon products however, which can undergo photochemical oxidation to produce pollutant haze – which we would term air pollution. This formation of wastes is Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 2 APM Study module 1 – Introduction to air pollution MSS025009A part of the cycling and recycling of matter in natural ecological systems. Wastes released into the atmosphere are diluted and dispersed in the air, and are processed and recycled through a variety of natural physical, chemical and biological mechanisms. For example, many particles of waste are removed by settling or are washed out by rain. Many gaseous wastes are oxidised to form particles, which then settle out or are washed out while others are converted to other gases in the atmosphere or absorbed by plants or other soil microorganisms. In this way the atmosphere is continually cleaned of these substances. Atmospheric problems are made worse when weather conditions such as a lack of rain or wind cannot disperse pollutants. This not only holds them in the air, increasing human exposure, but also allows them to undergo chemical reactions to produce secondary pollutants that are often far more dangerous than those substances from which they were made. The residence time of waste products in the atmosphere before they are broken down or brought back to the ground varies between a few hours and many years. Air pollution problems occur whenever any of these normal functions of the atmosphere are disturbed or overloaded. Indeed natural pollutants may pose a serious threat to air quality when they are generated in large amounts near human settlements. Examples of this include dust storms, bush fires and volcanic eruptions. Natural pollution generally has a low impact on human wellbeing as the levels of pollutants associated with most natural pollutants are relatively low, the sources are generally well separated from large human populations and natural forces responsible for the pollution occur at infrequent intervals. One major exception to this rule is the biogenic emission of photochemically active hydrocarbons such as isoprene, -pinene and other terpene molecules. These natural hydrocarbons play a major role in the formation of photochemical smogs, and are major contributors to haze. This is especially a problem in Australia where heat produces large amounts of eucalyptus haze from gum trees. This does not mean that pollution from man-made sources is not a problem. A closer look at air pollution will show that dispersal of pollutants is a very important consideration – as the atmosphere is not homogeneous. This means that pollutants tend to concentrate in specific areas – most of which are near where large human populations reside. This means that pollutant levels around residential areas are often much greater than would be expected in ambient air. Natural sources on the other hand are in general more evenly spread, but there are exceptions such as extremely high levels of dust and acidic gases associated with volcanic activity. Man's activities (also called anthropogenic) release heat, gases, aerosols and other wastes into the atmosphere. These are particularly significant in that our wastes are discharged in Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 3 APM Study module 1 – Introduction to air pollution MSS025009A such high concentrations that we overload the natural dispersal, dilution and recycling systems on a local, regional and global scale which causes damage to plants, animal life, and materials. The ecological systems themselves are degraded, and the services they provide are reduced. In addition to this overload due to increased concentrations of waste products in particular areas, we are now releasing quantities of new or previously rare substances into the environment. Very little is known about the dispersal processes and the passage through ecological systems of these substances. Many are resistant to degradation, some are cumulative and harmful. The definition of air pollution Air pollution is not an easy thing to define. The World Health Organisation defines air pollution as; “Air is polluted when one or several pollutants are present in the atmosphere at such a concentration and for so long a time that they are harmful to man, animals, plants or material property, cause harm or reduce well-being or disturb appreciably its application”. Whilst this is fairly complete in its cover, it is also very complex – hence simpler definition are often used. The definition of air pollution for legal purposes is defined in the NSW Protection of the Environment Operations Act as; “any deviation from the natural combination of gases in our atmosphere”. What this definition fails to mention is that the natural combination of gases in our atmosphere must be taken as dry air at sea level. This is necessary as it is not possible to quantitatively define pure air because it will change according to altitude and location. This also means that theoretically air pollution can also arise from the removal of gases from the atmosphere. Neither of the definitions listed above completely cover other factors that we might also call pollution such as the release of energy, radiation, odour or noise. Most air pollution concerns are associated with ambient air, that is air that is outdoors and free flowing – hence most control programs focus on ambient air pollution, but significant pollution now occurs in occupational environments which are indoors. Especially important here are the effects of cigarette smoke which may contain large amounts of carbon monoxide and extremely toxic polycyclic aromatic hydrocarbons. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 4 APM Study module 1 – Introduction to air pollution MSS025009A The Atmosphere The Earth’s atmosphere is approximately 160 kilometers deep, but 95% of its air mass lies within 20 kilometers of the surface. Moving up from the earth’s surface the density of the atmosphere decreases rapidly and the air “thins”. Hence the atmosphere is neither uniform, nor static in nature. Its characteristics vary widely with altitude, season, location and solar flare activity. Air within a few kilometers of the earth’s surface will typically contain the components shown in table 1.1. The most obvious conclusion that may be drawn from this table is that the pollutants with which we have the most problems make up an extremely small part of the atmosphere. Figure 1.1 shows sulfur dioxide to be the air pollutant produced in the greatest amount by a long way, yet it forms an insignificant proportion of the atmosphere (a fortunate thing from our point of view). The figures in Table 1.1 are distorted somewhat by the fact that in polluted city areas these % concentrations will change markedly for some pollutants. A few other important facts should be stated about the data in Table 1.1. The concentrations of nitrogen, oxygen, argon, neon, helium, krypton, hydrogen and xenon remain essentially constant. These gases are fairly inert and play little or no role in atmospheric chemistry. Element Total Mass in the Atmosphere (x1012 tonnes) % (by volume) in the atmosphere nitrogen 78.08 3900 oxygen 20.95 1200 argon 0.934 67 carbon dioxide 0.035 2.5 Neon 0.0018 0.065 Helium 0.00052 0.004 Methane 0.00015 0.005 Krypton 0.0001 0.017 Carbon Monoxide 0.00001 0.0006 Ozone 0.000002 0.0003 Nitrogen Dioxide 0.0000001 0.000013 Sulfur Dioxide 0.0000001 0.000018 water 0.1 – 5 (normal range 13) Varies according to location Table 1.1 – Typical constituent concentrations of the atmosphere Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 5 APM Study module 1 – Introduction to air pollution MSS025009A Even though it is the most abundant gas, nitrogen has little effect on major atmospheric processes or to the sustenance of life forms. It does however, serve as a precursor for other species such as NO3-, as well as amino acids and nucleic acids (amongst others) which are essential for life. Nitrogen reacts with oxygen – the second most abundant gas in the atmosphere to form oxides of nitrogen (NOx). These include NO, NO2, N2O4 and N2O. The NOx compounds in the atmosphere are found in trace levels and their concentration varies with place and time of day. Nitrous oxide (N2O) was thought to remain constant in atmospheric concentration, but synthetic fertiliser compounds containing nitrogen have been found to increase the amount of nitrification by soil bacteria, which has in turn increase the amount of N 2O being generated by natural sources. As the great majority of species on Earth use an oxidative metabolism, it comes as no surprise that oxygen is the most important atmospheric gas for the nurturing of life. Its significance as an atmospheric gas goes far beyond sustaining life however. Oxygen is also present in the atmosphere as ozone (O3), which exists in high concentrations in the upper atmosphere and acts as a heat and radiation shield for the planet – maintaining fairly constant temperatures that allow life to exist. At 0.035%, the concentration of carbon dioxide in the atmosphere is very low compared to molecular oxygen or nitrogen. It is still of enormous significance however as it is the raw material used by plants for carbon fixation to produce the compounds used for energy by almost all forms of life. It is also a significant greenhouse gas – which serves to keep the planet warm. Water vapour is the most variable of all atmospheric components (varies from 0.1 – 30,000ppm), but it is also of huge significance. Water rapidly changes phase from liquid to gas or solid in response to atmospheric conditions. This means that it allows the transport of energy around the planet. Water vapour also condenses to form clouds that are responsible for the Earth’s albedo – the ability of the Earth to radiate sunlight back into space – which is another factor in controlling the Earth’s surface temperature. The atmosphere also contains trace gases produced from biological or geological processes. These include ammonia, methane, hydrogen sulfide, carbon monoxide and sulfur dioxide. Ammonia, methane and hydrogen sulfide are primarily produced by bacterial decomposition, whilst carbon monoxide and sulfur dioxide are produced mostly by geological processes. To help understand the significance of air pollutants requires an analysis of what a person breathes. The average person breathes 20,000 litres of air per day, 995 of which is nitrogen or oxygen. The other 1% is a mixture of gases and particulates, many of which might be termed Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 6 APM Study module 1 – Introduction to air pollution MSS025009A pollutants. This means that we breathe as much as 200litres of pollutants per day! Stratification of the Atmosphere As we move away from the Earth’s surface the temperature drops (as well as the pressure). This causes stratification – or layering of the atmosphere The lowest layer of the atmosphere is known as the troposphere, and extends to an area of between 10 and 16 kilometres above the earth. This is where our weather and almost all of our pollution problems occur. Its composition fairly homogeneous due to the weather producing circulating air masses that allow constant mixing. 95% of the atmosphere’s air mass is found in the troposphere. The upper troposphere has a temperature of -56ºC. At the top of the troposphere is the tropopause layer. It serves as a barrier to prevent water vapour rising much higher as it causes ice formation. Water vapour cannot pass through it. If it did, it would photodissociate in contact with ultraviolet radiation, and the hydrogen would be lost to space. The tropopause separates the stratosphere from the troposphere. Above the tropopause layer is the stratosphere, between 10 and 50 km above the earth.. Moving up in this layer we find the temperature rises, and may reach up to -2ºC., The ozone layer is within the stratosphere, and reaches levels of up to 10ppm in the middle of the stratosphere. The stratosphere can reach temperatures of up to -2C due to the absorption of ultraviolet radiation by the ozone. The mesosphere is above the stratosphere, covering an area of between 50 and 85km above the earth. At 85km the temperature is -92C. Above the mesosphere is an area called the exosphere where molecules and ions can be lost to space. An area extending far into space is called the thermosphere, an area of high temperatures (1200C) due to the absorption of radiation from space. Figure 1.1 – The layers of the atmosphere Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 7 APM Study module 1 – Introduction to air pollution MSS025009A Factors Likely to increase the Levels of Air Pollution Certain conditions help make air pollution worse. Basically these are factors which prevent air circulation, and concentrate air effluent into areas. Examples of these include; calm conditions low level emission sources temperature inversions high buildings and narrow streets By contrast other conditions are known to lower air pollution levels in general. These are those conditions that encourage circulation or remove pollutants from the atmosphere. Examples include; windy or turbulent conditions high levels of vegetation high level emission sources such as smoke stacks rain The Protection of the Environment Operations Act This act specifies all legal requirements for the control of air pollution in NSW. It attempts to reduce air pollution by prescribing standards for emission of pollutants. These are generally linked to accepted world health standards used in other countries. Some premises are licensed under the act to pollute. This does not mean that air pollution is encouraged, rather it is a means of controlling emission from major sources such as power stations etc.. These premises are charged a fee for a licence to discharge pollutants, the levels of which are carefully monitored. Any contravention of the licence means that the company responsible will be charged in the Land & Environment Court and generally fined. Accepted Levels of Major Air Pollutants These vary significantly from country to country, so the values listed in Table 1.2 should only be used as guidelines. For the most up to date information on accepted pollutant levels you should consult the NSW EPA. Air Pollutant CO NO2 Acceptable Level 1 hour ave. 30ppm (60ppm detrimental) 8 hour ave. 9ppm (20 ppm detrimental) 1 hour alert level 150ppm 1 hour ave. 0.12ppm (0.25ppm detrimental) 8 hour ave. 0.06ppm (0.15 ppm detrimental) Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 8 APM Study module 1 – Introduction to air pollution NH3 HNO3 SO2 H2S Photochemical oxidants (as O3) Respirable particles 2.5um PM10 Respirables Atmospheric Lead Benzo[]pyrene Benzene Fluorine MSS025009A 1 hour alert level 0.50ppm 1 year 0.03ppm Ground level conc. 0.83ppm (0.6 mg/m3) Ground level conc. 0.067ppm (0.17 mg/m3) 1 hour ave. 0.20ppm (0.34ppm detrimental) 8 hour ave. 0.06ppm (0.11 ppm detrimental) 1 day ave. 0.08ppm 1 year ave. 0.02ppm 1 hour alert level 0.50ppm Ground level conc. 0.0001ppm (0.00014 mg/m3) 1 hour ave. 0.10ppm (0.15ppm detrimental) 4 hour ave. 0.08ppm (0.15ppm detrimental) 8 hour ave. 0.05ppm (0.08 ppm detrimental) 1 hour alert level 0.25ppm 24 hour ave. 25 ug/m3 (240mg/m3 detrimental) 1 year ave. 8 ug/m3 (80mg/m3 detrimental) 1 day ave. 50g/m3 3 month ave. 1.0 g/m3 1 year ave. 0.50g/m3 1 year ave. 5.0ng/m3 1 year ave. 10.0ng/m3 Ground level conc. 0.033ppm (0.067 mg/m3) Table 1.2 – Accepted levels of major air pollutants. See the following website for details; http://www.environment.gov.au/resource/national-standards-criteria-air-pollutants-1-australia Major Sources of Air Pollutants The number of different types of pollution sources in modern society is almost endless. Hence in this chapter we will look at only the most significant sources of air pollutants. For convenience pollutant sources can be grouped into mobile or transportation sources, and stationary sources. Approximately 50 - 70% of all air pollution arises from transportationcombustion sources, 15-25% from heavy industrial stationary sources and as much as 25% from other stationary sources. Table 1.2 lists the major sources of pollution in the USA during the late 1980’s. It provides estimates of the amounts emitted of the five most significant air pollutants. Levels in Australia will vary somewhat, but as our social demographics are similar to the United States these are also a good estimate of the approximate break up of pollutants sources. Note however that the total amount emitted in Australia will be far less than those in the USA. One pleasing aspect is that there has been a significant reduction in the amounts of CO and hydrocarbons when compared to the previous decade, whilst the levels of other pollutants Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 9 APM Study module 1 – Introduction to air pollution MSS025009A has been steady or shown only a slight increase. Emissions (106 tonnes / year) Source CO Particles H/C’s NOx SOx Total % 40.7 7.2 1.4 1.8 6.0 2.3 8.4 10.3 0.9 16.4 57.4 38.0 44.9 29.7 Industrial Processes 4.7 2.5 8.3 0.6 3.1 19.2 15.0 Solid waste disposal 1.7 0.3 0.6 0.1 0 2.6 2.0 7.1 61.4 48.0 1.0 7.0 5.5 2.4 19.6 15.3 0.1 19.5 15.3 0 20.4 15.9 10.6 127.8 8.3 Transport Stationary fuel combustion Miscellaneous Total % 100 Table 1.2 – Estimated emission of 5 primary pollutants in the USA Transportation-Combustion Sources There are many different types of transportation sources, not all of which are significant sources of pollution. Unfortunately the most important transportation sources at present are major polluters. Motor vehicles are a very significant source of pollution. They produce many different pollutants including carbon monoxide, carbon dioxide, hydrocarbons, oxides of nitrogen, lead particulates and even small amounts of oxides of sulfur. Motor vehicle exhaust accounts for 40% of all hydrocarbon air pollutants and 90% of all nitrogen dioxide. Additionally the pollutants from motor vehicles can react in the atmosphere to form different and even more reactive (and dangerous) pollutants such as photochemical smog. Many trucks run on diesel fuel. Whilst this is more economical it is also a source of very dangerous hydrocarbons and is a major source of the extremely carcinogenic polycyclic aromatic hydrocarbons (PAH’s). Lead is rapidly decreasing in significance as a pollutant from motor vehicles as more and more use unleaded fuels. IN the USA the introduction of unleaded fuel in 1978 produced a reduction in atmospheric lead over the next decade of 94%. A similar reduction is expected in Australia. Additionally vehicles running on unleaded fuels emit lower levels of oxides of nitrogen and sulfur as the catalytic converters in the exhaust systems help to reduce these. Aircraft and trains are less significant sources of pollution compared with road transport vehicles. Aircraft run on kerosene, which is burnt fairly efficiently, but as they fly very high in the atmosphere the pollutants – most of which are hydrocarbons – are spread and diluted in the upper atmosphere. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 10 APM Study module 1 – Introduction to air pollution MSS025009A Many trains now run on electricity, and hence contribute very little to air pollution. The discharge associated with high voltage electrical cables used to power them can however, give off ozone, which is very toxic and a powerful oxidising agent. Despite this electric trains are probably the most environmentally friendly forms of mass transport systems available in modern society. Stationary (Industrial) Sources Again these are many and varied in nature. Some of the more important sources include furnaces - and their combustion of carbonaceous fuels boilers ovens and dryers process systems which produce volatile chemicals, gases, etc Solvent Evaporation Solvent evaporation can come from solvent-based paints, leaking pipe joints, maintenance work involving the dismantling of pumps or breaking of pipelines, spills, unloading /loading procedures and contaminated ground. Solvent vapour is an important part of photochemical pollution (see photochemical smog). Stack emissions The emission of waste gases, fumes, vapours and smokes to the atmosphere are usually by the use of a smoke stack or chimney. A backyard incinerator, or even a whole city or industrialised area could also be thought of as a stack emission to the atmosphere. Although such emissions are usually the waste products of combustion, many waste solvent vapours are vented to the atmosphere in this manner. The stack emission becomes a plume in the atmosphere. The plume is an area of concentrated waste emissions that slowly become diluted with the other atmospheric gases. How this dilution happens will depend on a number of factors: Nature of the waste emission Toxic emissions will need to be very dilute if they are allowed to be vented to the atmosphere. Volume of the waste Is the emission constant or only at certain times in the process. For example, pottery kilns will only vent waste products when the kilns are operating. Coal-fired electrical generating plants will vent waste products all the time. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 11 APM Study module 1 – Introduction to air pollution MSS025009A Local topography Many cities in the world are located in delta areas surrounded by hills or mountains. Melbourne, Sydney, Los Angeles and Mexico City are examples of cities located in delta areas. During periods of low wind and cooler temperatures, these cities suffer from photochemical smog. Prevailing climate The direction of prevailing winds is important with stack emissions. The area the wind takes the emissions may be affected by photochemical smog, acid rain or fallout of pollutants. Queenstown, in the south-east of Tasmania is a famous example of the effect of stack emissions. The smelter emissions created a "fan" of bare hills in the direction of the prevailing wind. This fan continues for some miles beyond Queenstown. Emissions from aluminium smelters also are linked with fluorine damage to plants and animals in a "fan" made by the prevailing wind. The Existing Atmosphere In very polluted cities, the introduction of more stack emissions may not be desirable. Large coal-fired electrical plants are built in country areas, where the waste gases can be vented to clean air. If these plants were built in urban areas, the photochemical smog will be much worse. If photochemical smog is already a problem, the introduction of more waste gases must be done carefully, or where possible avoided entirely. Any new waste gases may react strongly with the photochemical smog. An example would be sulfur dioxide. The effects of plumes are considered local within 500 metres of the stack, and regional beyond this. Plume behaviour The mixing or dispersion of the waste gases and products into the atmosphere is called plume behaviour. In stable air, and where the vertical movement of the plume is slow, a fanning plume is produced. This wide, shallow, spreading plume is very common after calm clear nights. A temperature inversion limits the rise of the plume into the upper atmosphere. The following diagram shows normal air movements, and a temperature inversion. A layer of warm air limits the rise of the plume into the upper atmosphere, and creates a higher concentration of polluted air at lower levels. This plume exists for several hours. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 12 APM Study module 1 – Introduction to air pollution MSS025009A Figure 1.2 - A Fanning Plume In windy conditions the plume can swirl up and down. This is a looping plume, and is common in the afternoon. Moderate and strong winds are formed on sunny days creating unstable conditions. This plume exists for several hours. Figure 1.3 – A Looping Plume With moderate winds and overcast days, the plume may become a coning plume. This plume is wider than it is deep, and is elliptical in shape. This plume exists for several hours. Figure 1.4 – A Coning Plume Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 13 APM Study module 1 – Introduction to air pollution MSS025009A The fumigating plume is short-lived (fraction of an hour), but reaches the earth's surface. Fumigating plumes occur when the conditions move from stable to more unsettled. A fanning plume might have developed overnight under stable conditions. As the day heats up, unstable air is produced. This unstable air affects the fanning plume, causing the plume to move vertically up and down. These plumes can cause localised pollution. Fumigating plumes become looping or coning plumes as the air conditions stabilise. Figure 1.5 – A Fanning Plume Where the plume is above the inversion layer, it becomes a lofting plume. Normal wind direction and speed will disperse the plume into the atmosphere without effect from ground warming or cooling. Figure 1.6 – A Lofting Plume A number of factors are used to establish the amount of stack emission allowed, and its concentration to the atmosphere. These include: smoke stack (chimney) height, local topography, temperature, emission rates, Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 14 APM Study module 1 – Introduction to air pollution chemical reactivity, and existing air pollution problems MSS025009A Increasing the height of smoke stacks results in the emission of pollutants higher up in the atmosphere. In theory this means that the pollutants will be more diluted by the atmosphere if and when they return to the ground – hence the effect on those closer to the stack is decreased compared to if the emission occurred at a lower height, or at ground level. Whilst this is true it also means that the pollutants are spread over a much greater area with taller stacks, and more individuals may be affected. In general however, higher stacks allow emission of higher levels of pollutants. Some types of topography harbour pollutants better than others. In general areas in low valleys surrounded by mountains, with little wind are not conducive to natural removal of pollutants. Hence lower pollution levels can be tolerated in these areas. By contrast open flat areas with high levels of prevailing wind allow rapid dispersal of pollutants. High temperature emissions will rise to a higher level into the atmosphere. This may mean that the pollutants will go up into the atmosphere, away from the local area under most conditions, whilst low temperature emissions may fall rapidly, and blanket the area surrounding the stack. High rates of emission or emission of highly toxic or highly reactive species require lower limits to be set on the emission source. Fugitive Emissions and Other Sources Fugitive emissions are those which escape from a process rather than being discharged. These often have serious consequences because their levels are not monitored and they are untreated when entering the atmosphere. There are many sources of fugitive emissions including: industrial sources (particulate fluorides from aluminium smelters) small business (e.g. dry cleaning) agriculture (e.g. dust from ploughing) natural sources (e.g. volcanoes, forest fires) Often fugitive emissions are the result of poor maintenance of plant and equipment and can be eliminated by standard operating procedures that involve timed maintenance and quality control checks, but some are almost impossible to control (such as those from natural sources). An example of the former is the particulate and gaseous fluoride emissions from aluminium smelting. These are emitted unintentionally when the casting areas of aluminium potlines are opened or incorrectly sealed. Standard operating procedures that ensure that the casts are sealed greatly reduce the problem. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 15 APM Study module 1 – Introduction to air pollution MSS025009A Health effects of air pollution There have been many reports of death, illness and environmental damage caused by air pollution. This chapter describes the more important effects of major air pollutants and explains how they interact with each other and the environment. Effects of Air Pollution on Human Health In general specific sections of the public are most affected by air pollution. Those individuals already suffering from diseases of the cardiorespiratory system such as asthmatics and smokers are far more likely to be affected than those individuals who are healthy. Pollutants generally act on the surfaces of the respiratory system, causing chronic respiratory and cardiovascular disease. They may also alter important body functions such as oxygen exchange in the lungs, or oxygen transport in the blood. Irritant pollutants may lead to irritation and long term damage to eyes, nose, throat and other wet surfaces of the body. Deposition of particulate matter in the alveoli of the lung is quite serious as removal can be slow. Soluble particles will be transferred to the blood. One of the most important particles man encounters in the atmosphere is H2SO4, which irritates the mucous membranes and leads to bronchial constriction. Most of the gaseous effects are more acute than chronic (as opposed to the particulate pollutants). SO2, O3 and NO2 are all pulmonary irritants, and may lead to congestion, oedema and even haemorrhage. NO, H2S and CO are asphyxiant gases. These combine with haemoglobin molecules to prevent oxygen transfer around the body. These molecules bind far more successfully to haemoglobin than does O2. Many of the organic gas pollutants such as acrolein (1-propenal) as well as those gaseous pollutants mentioned above produce eye irritation. Other chronic diseases related to air pollution include lung cancer, emphysema, chronic bronchitis and asthma. In addition air pollution can have serious effects on acute diseases such as the common cold. In the following sections each major pollutant’s specific effects on human health and is examined. Synergistic effects are also considered. Interactions between pollutants and synergism Ambient air is a complex mixture of gases and particulate matter. In such a mixture it is likely that there will be interaction between the components to modify the physiological effects of others. This may occur in several ways. For example, one pollutant may affect the site of deposition of another as is the case with sulfur dioxide. Due to its great solubility in water, sulfur dioxide is normally be removed in the upper respiratory system – where it has a corrosive effect. When sulfur dioxide is adsorbed/absorbed onto particles, it can however, be transported deep into the pulmonary Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 16 APM Study module 1 – Introduction to air pollution MSS025009A system, where irritation and corrosion may occur. Thus, the particles may amplify the effect of sulfur dioxide. Also, harmful aerosols such as sulfuric acid can be produced by the interaction of gaseous pollutants in the warm moist environment of the lung. Interaction between pollutants may result in effects that may be additive, synergistic, or antagonistic. Additive effects are those which occur when the exposure to several pollutants produces an effect equal to the sum of the effects of the pollutants acting alone. Synergistic effects are those where the sum of the effects of two or more pollutants is greater than the combined effect. Antagonistic effects refer to the situation where one pollutant lessens the effect of another pollutant. The great majority of pollutant effects are additive. Susceptible parts of the Human Body All forms of air pollution (gases, liquids and particulates) can damage human health. There are three main routes by which they enter the body: absorption through the skin ingestion, and inhalation Of these the latter is by far the most important as we exchange large amounts of atmospheric gas every day through our lungs. All forms of air pollutants can enter the lungs, but at this point it is probably appropriate to describe the structure of the human respiratory system, which allows us to exchange air with the atmosphere. All of the air passages have a coating of mucus and are also lined with tiny branch like structures called cilia, which constantly move in an upward fashion to remove any solid material that enters the lungs. Injury to the respiratory tract occurs when chemicals enter the lungs and cause direct damage to the lung tissue, or when the lungs trap material and allow it to be transferred to the bloodstream where it may affect any organ in the body. Effects of specific chemicals Carbon Monoxide High levels of carbon monoxide are a major concern since the gas preferentially and irreversibly binds to haemoglobin in the blood forming carboxyhaemoglobin. The net effect is thus a reduction in the blood's capacity to carry oxygen. Carbon monoxide has a higher affinity (200 times greater) for haemoglobin than O2, and also tends to remain more tightly bound. Reduction in the levels of CO in car emissions have been associated with changes in the Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 17 APM Study module 1 – Introduction to air pollution MSS025009A design of the exhaust system, whereby oxidation catalysts, such as Pd and Ru, promote further reaction with excess air to carbon dioxide. Uncontrolled emissions average 3.5% CO: current design rules limit emission to 1.0%. Under specified testing procedures, this is equivalent to 24.2 g/km. Sulfur Compounds Sulfur compounds include the very corrosive sulfur dioxide and sulfur trioxide, and hydrogen sulfide. Sulfur dioxide and sulfur trioxide produce very similar effects as both are very corrosive, whilst hydrogen sulfide produces similar effects to CO in that it can lead to anoxia when present in high concentrations – a situation which is very rare in ambient air. Sulfur Dioxide and Particulates Analysis of the effects of sulfur dioxide are complicated by the fact that it is often associated with particulate pollutants – so the direct effects of each individual pollutant are difficult to separate. They are often produced by a common source, such as the combustion of coal, hence high SO2 levels are often associated with high particulate matter levels often forming sulfate aerosols. Sulfate aerosols present a more significant threat to health than do sulfur dioxide emissions alone. These are produced when acidic particles are formed by the reaction of water with ash and SO2, to give SO42- and H+. Particles from aerosols are just the right size to be retained in the lungs so cause maximum physiological damage. Sulfur Dioxide Sulfur dioxide in the atmosphere has its primary effect on the respiratory tract, producing irritation and difficulty in breathing. It affects most strongly those people who already have respiratory problems. Children are known to suffer increased frequency of infection upon prolonged exposure to sulfur dioxide – but true long term effects of exposure are not well understood. Because of its solubility in water, SO2 is almost entirely removed in the mouth, throat, and nose through normal breathing. Less than 1% of inspired SO2 reaches the lung tissue (alveoli). Although exposure of the lower airways and alveoli to SO2 increases considerably during exercise, the principal effect of SO2 exposure is to alter the mechanical function of the upper airway. Oxides of Nitrogen Nitric oxide is a relatively non-irritating gas and is thought to pose little threat to health at normal ambient levels. Its importance lies in the fact that it is rapidly oxidised to NO 2, a gas Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 18 APM Study module 1 – Introduction to air pollution MSS025009A of much greater toxicity. Whilst SO2 is rapidly absorbed in the fluids in the upper respiratory tract, NO 2 is less soluble and generally penetrates deep into the lung leading to tissue damage. Exposure to acute high levels leads to effects such as pulmonary oedema. The lowest NO2 exposure level shown to cause physiological change is 0.5ppm at which adverse effects included the destruction of cilia, alveolar tissue disruption, and obstruction the respiratory bronchioles. Exposures at higher levels can lead to severe tissue damage. Minor respiratory problems are caused by brief exposures at levels below 5ppm. At levels below 100ppm, exposure leads to prolonged, but non-fatal inflammation of lung tissue. Higher levels are generally toxic. There is also evidence that NO2, can damage respiratory defence mechanisms, allowing bacteria to proliferate and invade lung tissues. Another health problem linked to nitrogen oxides is that they are precursors for pollutants that form photochemical smog. Hydrocarbons Most hydrocarbons are relatively nontoxic at the ambient levels found in normal atmospheres. They are however key reactants in photochemical smog formation. Where they undergo complicated reactions in the atmosphere with O2, O3, NOx, SOx and other components to form photochemical smog (see following section) which is very deleterious to human health. They reduce visibility, have unpleasant odours and cause skin and eye irritation at higher levels. Some are carcinogenic, such as benzo[]pyrene. Hydrocarbon air quality standards are not based on the health effects of hydrocarbon chemicals, but rather an attempt to reduce photochemical smog formation. Ozone & Photochemical Smog Ozone is one of the most toxic pollutants regulated under ambient air quality standards. It may cause significant physiological and pathological changes in both animals and humans at exposure concentrations that are within the range of those measured in polluted ambient environments. O3 may cause significant lung function changes even with exposures in the 0.10-0.40ppm range of for 1-2 hours The changes are transient; and lung function appears to return to normal after the exposure is stopped. Lung function changes are concentration dependent and increase with increasing depth of breathing. Such changes have been reported for healthy adolescents and young adults. There is no evidence, however, that smokers, older adults (over 55), asthmatics, or individuals with chronic obstructive lung disease are more responsive to O3 exposures. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 19 APM Study module 1 – Introduction to air pollution MSS025009A Particulate Matter Particulate matter exhibits toxic effects due to the direct irritant action of particles (such as sulfuric acid) and substances that are readily adsorbed to the large surface area of small particles. The concentration of adsorbed substances may be considerably greater than in the ambient atmosphere. Adsorbed substances of particular concern include SO x, polycyclic aromatic hydrocarbons (PAH), and heavy metals such as lead, cadmium, zinc and mercury. The PAH and heavy metals tend to predominate in the small respirable particles. The health consequences of atmospheric particulate matter depend on its ability to penetrate respiratory defence mechanisms. These are adequate to remove inhaled particles in excess of 10m, but particles smaller than can enter and be deposited in the respiratory system. These are described as "inhalable particles". Particles less than 2.5m are called "respirable"; they can enter pulmonary tissue and be deposited there. Particles larger than 2.5m are removed in the upper respiratory system. Lead Depending on the level of exposure, individuals may develop symptoms of acute or chronic lead poisoning. The most affected organs are the blood, the brain, the kidney, the nervous system and the reproductive system. Symptoms of acute lead poisoning include shock, anaemia, nervousness, and irreversible kidney and brain damage. Lead has been shown to interfere with the maturation and development of red blood cells. It does so by inhibiting enzymes involved in haemoglobin synthesis. Blood lead is much higher in smokers than non-smokers. Atmospheric lead does not lead to acute intoxication, but rather is a chronic problem. Asbestos The name asbestos refers to number of minerals which are compressed together to form fibrous materials. Particulate asbestos is a considerable community health problem due to its past use as a construction and insulating material. Medical evidence suggests that inhalation of the fibres causes the lung disease asbestosis – which is characterised by scarring of the lower lungs and lowered breathing function. It is a common disease in those exposed to asbestos for long periods. Some forms of asbestos are responsible for causing lung cancer and mesothelioma (cancer of the lining of the body cavity). Asbestos fibres are chronic toxins with very long latency periods. Once the fibre is inhaled it has the potential to cause cancer for the rest of the individual’s life. It is estimated that Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 20 APM Study module 1 – Introduction to air pollution MSS025009A between 25-50% of all individuals have asbestos in their bodies. Fluoride Gaseous fluorides damage vegetation and if ingested in sufficient quantities the bones and teeth of animals eating these plants. Environmental Effects of Air Pollutants When developing standards for the assessment of air pollution the emphasis has always been on controlling the effects on human beings, with all other effects being treated as of much lesser importance. Air pollutants do have significant effects on plants, buildings and other animals and these should also be considered when developing standards to assess environmental harm from air pollution. Plants are often the first to show damage associated with increased ambient levels of air pollution. The effects of SO2, HCl and HF have been reported as early as the middle of the 19th century. The most severe damage seems to have been associated with high levels of SO2 and heavy metal particulates associated with mining and smelting, but many other pollutants such as NO, Cl and NH3 are now known to cause direct toxic effects on plant tissue. The problems of acid rain and photochemical smog were first suggested as major environmental problems by their actions on plants. Air pollutants may injure plants in several ways– with some effects being subtle, but others clearly visible. Visible effects normally involve identifiable changes in the leaf structure such as chlorophyll destruction (chlorosis), tissue death (necrosis) and pigment formation. Subtle effects include inhibition of growth and lowered rates of photosynthesis. Plant tissue damage may be either acute or chronic. Acute exposures to high levels of pollutants generally lead to necrosis. Chronic injuries result from intermittent or long term exposures to lower levels of pollutants, with chlorophyll destruction or chlorosis being the most common symptoms of injury. Different pollutants produce differing symptomatic effects on plants and this can be used as an indicator as to the possible presence raised levels of certain pollutants. These are discussed in more detail in the paragraphs below. Particulate Materials Particulate dusts may cause injury to vegetation both directly and indirectly. Direct effects such as those for cement kiln dust include a variety of plant responses, such as; reduction in yield and growth without visible injury, Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 21 APM Study module 1 – Introduction to air pollution increase in disease incidence, severe injury to leaf cells, suppression of photosynthesis, and death of trees. MSS025009A The injury may result from the deposition of a thick crust that suppresses photosynthesis and/or alkaline toxicity when alkaline solutions are produced when dusts are present in free moisture. Ecological studies of forest communities affected by the deposition of limestone dusts have shown significant changes in tree growth and species composition. Changes in dominant tree species and the decrease in herbaceous vegetation are particularly evident. There are indirect beneficial effects from soil neutralisation by alkaline dusts. Atmospheric aerosols near urban areas may significantly elevate lead levels in both soil and vegetation. The uptake of lead by roadside plants results in no apparent visible injury. Heavy metal aerosols generated by nonferrous metal smelters may, however, have significant plant effects. The severe devastation of vegetation and denudation of the landscape around smelters is likely due to aerosol-derived heavy metal contamination of the soil and subsequent accumulation of phytotoxic levels by plants. There is evidence of this in the hills around Queenstown in Tasmania. This heavy metal problem is exacerbated by high concentrations of SO2, which occur simultaneously with metal aerosol emissions. Growth of vegetation around smelters that have ceased operation is still suppressed for many years after their closure Acid Deposition Acidic particles which fall onto plants or soil in which they grow can cause significant changes in plant wellbeing. These can result in necrotic lesions of the upper leaf surface, which is followed on subsequent exposures by tissue collapse on both surfaces. An indirect effect is the deposition onto soil, which affects soil pH. The effects here may be positive or negative depending on the makeup of the soil. Effects of Air Pollutants on Buildings and Materials Air pollution is renowned for soiling building surfaces, clothing and other articles. This is generally a result of smoke particles adhering to the surface in question, but there are many other more sinister effects. Air pollutants significantly affect many non-biological structures and materials. These effects cause economic losses in billions of dollars each year. Most important are effects on metals, carbonate building stones, paints, textiles, fabric dyes, rubber, leather, and paper. In Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 22 APM Study module 1 – Introduction to air pollution MSS025009A Western Europe, which is a repository for many monuments of history and fine works of art, air pollutant-induced damage has been incalculable. Because these cultural treasures are irreplaceable, their preservation from the destructive effects of airborne contaminants poses a significant challenge to scientists. Materials can be affected by both physical and chemical mechanisms. Physical damage may result from the abrasive effect of wind-driven particulate matter impinging on surfaces and the soiling effect of passive dust deposition. Chemical reactions may result when pollutants and materials come into direct contact. An example of this is the reaction of lead in older paint materials with sulfurous materials (particularly H2S) from air pollution to produce the unsightly lead sulfide black streaks on buildings. Metal Corrosion Metal corrosion in industrialised areas represents one of the most costly effects of atmospheric pollutants. Since corrosion is natural we tend not to recognise the role that pollutants play in accelerating this process. As the ferrous metals, iron and steel, account for about 90% of all metal usage, pollution-induced corrosion on these metals is of particular significance. The acceleration of corrosion in industrial environments is associated with high levels of atmospheric SO2 and particulate matter pollution is very significant. Oxidants, such as ozone, inhibit the effects of SO2 by producing a more corrosion-resistant product. Rubber and Fabrics Another important material damaged by pollution is rubber, which is attacked by ozone. This leads to cracking, which is an economically significant problem. Fabrics such as nylon are also affected by air pollution. These tend to disintegrate upon prolonged exposure to the air. Bleaching and discolouration may also occur. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 23 APM Study module 1 – Introduction to air pollution MSS025009A Assessment task This section provides formative assessment of the theory. Answer all questions by typing the answer in the boxes provided. Speak to your teacher if you are having technical problems with this document. Type brief answers to each of the questions posed below. All answers should come from the theory found in this document only unless the question specifies other. Marks shown next to the question should act as a guide as to the relative length or complexity of your answer. 1. Provide a definition for the term ‘air pollution’. Explain why it is difficult to define. [4mk] Click here to enter text. Assessor feedback 2. Which key piece of NSW legislation acts to control pollution from existing activities? [2mk] Click here to enter text. Assessor feedback 3. Briefly explain the following statement; “Although natural pollutants are far greater in volume than anthropogenic pollutants, it is anthropogenic pollutants that pose the greater harm to the planet” [5mk] Click here to enter text. Assessor feedback Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 24 APM Study module 1 – Introduction to air pollution MSS025009A 4. List four atmospheric conditions that are likely to help levels of air pollution low. [4mk] Click here to enter text. Assessor feedback 5. List four atmospheric conditions that are likely to help keep levels of air pollution low. [4mk] Click here to enter text. Assessor feedback 6. Identify four significant layers of the atmosphere. Which of these is most important for air pollution studies? Why? [6mk] Click here to enter text. Assessor feedback 7. Visit website 1 (found in the resources section on the last page) and list the six criteria air pollutants. Briefly discuss why you think these six pollutants are more important than all of the other chemicals in Table 1.2 above. [6mk] Click here to enter text. Assessor feedback 8. List three categories of pollutant sources. [3mk] Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 25 APM Study module 1 – Introduction to air pollution MSS025009A Click here to enter text. Assessor feedback 9. Briefly discuss what makes transportation the most detrimental source of pollution to ambient air quality? [4mk] Click here to enter text. Assessor feedback 10. Emissions from stationary sources can be diluted by several factors. Briefly list and describe three of these factors. [6mk] Click here to enter text. Assessor feedback 11. What is meant by the term ‘fugitive emission’? Provide an example of a common fugitive emission. [3mk] Click here to enter text. Assessor feedback 12. For three of the six criteria air pollutants, state the statutory limit and briefly explain the potential health consequences if these limits are exceeded. [6mk] Click here to enter text. Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 26 APM Study module 1 – Introduction to air pollution MSS025009A Assessor feedback 13. What are the potential health effects of pollutants (generally) on plants? How does this have an effect of the whole of the ecosystem? (note that this requires some prior knowledge of primary productivity ecology). [4mk] Click here to enter text. Assessor feedback 14. What are two significant effects of air pollutants on buildings and materials? Which chemical air pollutant would you claim to be the worst? [4mk] Click here to enter text. Assessor feedback 15. Of all the possible particulate air pollutants, mineral fibers are considered the worst for our health. What key type of fiber is the worst, and what health issue does it create? [2mk] Click here to enter text. Assessor feedback Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 27 APM Study module 1 – Introduction to air pollution MSS025009A Assessment & submission rules Answers Attempt all questions and tasks Write answers in the text-fields provided Submission Use the documents ‘Save As…’ function to save the document to your computer using the file name format of; Yourname-APM-SM1 email the document back to your teacher Penalties If this assessment task is received greater than seven (7) days after the due date, it may not be considered for marking without justification. Results Your submitted work will be returned to you within 3 weeks of submission by email fully graded with feedback. You have the right to appeal your results within 3 weeks of receipt of the marked work. Problems? If you are having study related or technical problems with this document, make sure you contact your assessor at the earliest convenience to get the problem resolved. The name of your assessor is located on Page 1, and the contact details can be found at; www.cffet.net/env/contacts Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 28 APM Study module 1 – Introduction to air pollution MSS025009A Resources & references Unless specified otherwise, the references and resources listed below are for interest only. You are not expected to purchase, download or otherwise read these resources unless the question you are answering specifically requests that you do so. Most of the resources here are either available from your campus library, or directly from the teacher. References Australian-Standards. (Various dates). AS/NZS 3580 Methods for sampling and analysis of ambient air (entire series). Canberra: Standards Australia. Bates, G. (2010). Environmental Law in Australia. Australia: LexisNexis-Butterworths. Baukal Jr, C. (2004). Industrial Combustion Pollution and Control. New York, USA: Marcel Dekker. Burden, F. E. (2002). Environmental Monitoring Handbook. McGraw-Hill Professional. Colls, J. (2002). Air Pollution. England: Talyor & Francis. Manahan, S. (2000). Environmental Chemistry. Boca Raton: Lewis Publishers. Manly, B. (2009). Statistics for environmental science and management. Boca Raton: Taylor & Francis Group. Schuenemeyer, J. E. (2011). Statistics for Earth and Environmental Scientists. New Jersey: John Wiley & Sons. Seinfeld, J. P. (2006). Atmospheric Chemistry and Physics: From Air Pollution to Climate Change, 2nd Ed. Hoboken, USA: John Wiley & Sons. Vallero, D. (2008). Fundamentals of Air Pollution, 4th Ed. Burlington, USA: Academic Press. vanLoon, G. W. (2011). Environmental Chemistry: a global perspective. New York: Oxford University Press. Workplace Health and Safety Act 2011. (n.d.). Workplace Health and Safety Regulation 2011. (n.d.). Resources Websites 1. http://www.environment.gov.au/resource/national-standards-criteria-air-pollutants-1-australia Chemical, Forensic, Food & Environmental Technology [cffet.net] Version 1.0 30/05/2016 Page | 29