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    Western Australia Branch Bayliss Youth Lecture Chemistry and the Environment

    Patrick J. Garnett
    Edith Cowan University

    Tribute to Sir Noel BaylissI would like to begin by paying tribute to Sir Noel Bayliss who was Professor of Chemistry at the University of Western Australia during my time as an undergraduate and postgraduate student in the 1960s. Sir Noel's contribution to Chemistry in this State is immense. During his time as Professor of Chemistry he developed the School of Chemistry into one of the most respected research and teaching schools in the country. Thank you, Sir Noel, for your contribution to Chemistry and for the opportunities you provided to students of several generations.IntroductionIncreasing awareness of environmental issuesThe past two decades have witnessed an astonishing growth in public awareness of environmental issues. Several factors have contributed to this increased interest in the environment.

    1. The American space missions of the 1960s and 1970s and the accompanying T.V. pictures beamed back to Earth showing the planet as a tiny living sphere in the immensity of space;
    2. The influence of authors and conservationists such as Rachel Carson, Paul Ehrlich and David Suzuki who have graphically described the effect of human impacts on the environment;
    3. A series of increasingly serious global and local environmental issues such as
      • acid rain
      • photochemical smog
      • the greenhouse effect
      • ozone depletion
      • eutrophication of wetlands and waterways
      • encroaching salinity
      • acute pollution episodes e.g. Exon Valdez, Bhopal, Chernobyl.

    Understanding the environmentTwo disciplines which are central to our understanding of the environment and the human impacts upon it are Ecology and Environmental chemistry. Ecology is the study of living things in relation to their environment. Environmental chemistry refers to the composition of and the chemical processes which take place in the biosphere, atmosphere, hydrosphere and lithosphere.

    This paper focusses on the chemistry of our environment, particularly the hydrosphere and the atmosphere. By better understanding the chemical nature and processes within the environment, we should be able to solve some of the present problems with which we are faced and learn to live and function in a manner which is more harmonious with nature and which is sustainable for future generations.

    Elemental distributionI would like to start by going back to the beginning, to the basic building blocks of matter - the elements, and to the beginning of the Universe.

    The Periodic Table includes the symbols of all the elements which make up the Universe. Of the first 92 elements, 90 occur naturally on the Earth while elements 93 to 106 have been synthesised in the laboratory.

    Elemental abundances in the Universe, the Earth and its crust differ quite markedly. Within the Universe hydrogen and to a lesser extent helium are by far the most abundant elements. Indeed, most scientists believe that shortly after the Big Bang which seems to have marked the beginning of the Universe as we know it, virtually all the mass of the Universe existed as hydrogen. Gradually over the 10-20 billion years since that time some of the hydrogen has undergone a complicated series of nuclear reactions in the stars to form the heavier elements from which the Earth and other planets are formed.

    In the lower temperature, less hostile conditions which prevail on Earth the elements and their constituent atoms are no longer subject to the transmutation processes which occur in the stars. As a result the elemental composition of the Earth is essentially fixed. While chemical processes can alter the arrangements of the elemental atoms into different combinations and compounds the actual abundances of the elements in the Earth can be considered as fixed. 

    Environmental cycles

    Although the percentages of each element on the Earth are fixed, atoms of the elements are constantly recycled by the various chemical, biological and physical processes through which the biosphere and the environment function on our living planet. This recycling of atoms of the elements can be represented using environmental cycles. These show the distribution of an element in various reservoirs and the movement of the element between reservoirs. Environmental cycles have been developed for several elements including carbon, nitrogen, oxygen, phosphorus and sulfur.

    Carbon cycle

    The major carbon reservoirs and the processes by which carbon moves between these reservoirs are shown in Figure 2.

    Major reservoirs include the atmosphere, plants, dead organic matter, dissolved carbon in oceans, sediments and fossil fuels.

    Processes by which carbon moves between these reservoirs include photosynthesis, respiration, decomposition, fossil fuel combustion, dissolving and precipitation. Chemical equations representing these processes are shown below. 

     Human impacts can profoundly affect the rate of movement of elements between reservoirs and produce significant effects at both the local and global levels. These changes may distort the balanced processes which normally occur in natural systems. For example, human activities such as the combustion of fossil fuels and deforestation are thought to contribute to an increase in CO2 inputs to the atmosphere of about 7 billion tonnes per year. Of this about 4 billion tonnes per year is being taken up by increased amounts dissolved in the oceans and in the Earth's biomass, resulting in a net gradual build up of about 3.5 billion tonnes per year in the atmosphere.

    Water and aquatic systems
    The hydrosphere is of crucial importance both in the natural environment and as the source of the water which is essential for our daily needs. Water quality is important both in sustaining natural ecosystems and in relation to the supply of drinking water which we all take for granted.

    Similar to the elemental cycles described previously, water pass€es through a natural cycle known as the water or hydrologic cycle (Figure 3). The water cycle, like the elemental cycles, is powered by the sun which provides the energy required for evaporation and air transport processes.

     Water in natural freshwater systems (lakes and rivers)
    Liquid water in natural systems is virtually never pure. This is because water is an excellent solvent. It dissolves gases from the air and, because of its polar nature, it also dissolves ionic salts as it makes its way in rivers or underground systems towards the sea.

    Dissolved gases
    Gases dissolved in water because of its interaction with the atmosphere include nitrogen, oxygen and carbon dioxide.

    Oxygen
    The presence of dissolved oxygen is of crucial importance in natural systems as it is critical to the sustainability of aquatic life. The level of dissolved oxygen depends on the temperature, the stability of the water system, and the rates of photosynthesis and respiration. The solubility of oxygen, like other gases, decreases as the temperature increases.

    Dissolved oxygen is needed by aquatic plants and animals so that respiration and decomposition processes can take place. The level of dissolved oxygen or D.O. is a useful indicator of water quality in aquatic ecosystems. If the D.O. level falls to less than about half of that needed to saturate the water then the water quality is likely to be poor. This may be the result of high levels of organic matter such as plant and animal wastes which use up the dissolved oxygen as they are oxidised. If the D.O. gets too low this can result in the death of plants and animals and lead to anaerobic decomposition products such as methane, ammonia and hydrogen sulfide.

    Carbon dioxide
    Carbon dioxide from the atmosphere dissolves quite readily in rain, seawater and freshwater. When it dissolves carbon dioxide forms carbonic acid which behaves as a weak acid.CO2 + H2O ⇌ H+ + HCO3-

    HCO3- ⇌ H+ + CO32-

    This explains why rainwater and distilled water which has been exposed to the atmosphere has a pH of about 6, whilst that of pure water is equal to 7. Carbon dioxide is essential for photosynthesis by aquatic plants and also plays an important role in the formation of limestone deposits, caves and cave formations.

    Dissolved Salts
    Some of the ions which occur most commonly in natural aquatic systems are

    • sodium ion, Na+
    • potassium ion, K+
    • calcium ion, Ca2+
    • magnesium ion, Mg2+
    • chloride ion, Cl-
    • sulfate ion, SO42-
    • hydrogencarbonate ion, HCO3-

    The total concentration of soluble salts can be determined by boiling off all the water from a sample and weighing the residual mass of solid. A quicker and simpler method is to measure ihe conductivity of the sample and to use this as an estimate of total soluble salts.SalinitySalinity levels are usually expressed as the concentration of soluble salts expressed in mg/L or ppm. Salinity levels are classified as shown in Table 1.

     In Western Australia and in many other parts of Australia salinity is a considerable problem in agricultural areas. This is a result of excessive forest clearing in the past. As a consequence the water table has risen in these areas, mobilising the salt and resulting in saline seeps and increased stream salinity.

     Increased salinity decreases the amount of useful land available for agriculture. Increased stream salinity decreases the amount of good drinking water available. Various techniques are now being used in an attempt to reduce this problem including reduced clearing and reafforestation.

    Water hardness
    In water samples where the concentrations of Mg2+, Ca2+, SO42- and HCO3- are high the water is said to be "hard". Usually water is considered to be hard when the concentration of these or similar salts is greater than the equivalent of 200 mg/L of CaCO3. In hard water, soaps are much less effective than in soft water because thd dissolved salts form a scum or precipitate with the soap.Ca2+ + 2C17H35COO- → Ca(C17H35COO)2(s)

    As well, scale formation in kettles and boilers can be a significant problem when used with hard water.

    Dissolved nutrients
    Healthy natural aquatic systems must contain sufficient "nutrients" to support plant growth. The most important of these are
    • nitrate ion, NO3-
    • ammonium ion, NH4+
    • phosphate ion in its various forms, PO43-

    While these species are essential to support plant growth in aquatic ecosystems, high levels of nutrients resulting from sewage outlets, animal wastes (eg. piggeries), excessive application or run-off of fertilisers, and the over-use of phosphate-containing detergents can lead to the serious problem of eutrophication. High nutrient concentrations stimulate algal growth, sometimes resulting in the formation of algal blooms. Enhanced algal growth reduces the ability of light to penetrate the system and increases the oxygen demand of the system. Lower level plants may die causing the dissolved oxygen levels to fall further as the dead plants decompose. With reduced levels of dissolved oxygen the system is less able to support higher forms of life which may result in the death of various aquatic organisms including fish. In addition, decomposition in the absence of oxygen tends to occur through the activity of anaerobic bacteria leading to the formation of unpleasant by- products such as methane (CH4 , hydrogen sulfide (H2S) and ammonia (NH3).

    Algal blooms may include macroalgae; a range of microalgae including green algae and the notorious blue-green algae; diatoms; and dinoflagellates. The effects of algal blooms include deoxygenation (with resultant deaths of bottom animals and fish), decreasing aesthetic appeal (formation of scum and unpleasant odours), threat to water supplies (unpleasant taste and organic load), and the possible release of toxins (threat to wildlife, stock and human health).

    Some recent examples of the problems of eutrophication have occurred in

    • The Murray-Darling River system in the Eastern States;
    • The Peel-Harvey Estuary at Mandurah - leading to the Dawesville Cut;
    • The upper reaches of the Swan River.

    Considerable efforts are now underway to minimise these problems by improved catchment management involving reduced fertiliser use and the better management of animal waste and sewage.

    Water for drinking
    Clearly the supply of good quality drinking water is of great importance to modern societies. In Western Australia our drinking water comes from three major sources:
    • Hills dam storage;
    • Unconfined groundwater aquifers e.g. Gnangara and Jandakot Mounds;
    • Confined artesian water e.g. Leederville and Yarragadee Formations.
    The water that is supplied to us has to conform to certain standards adopted by the Water Authority of W.A. and based on NHMRC and WHO standards. These standards relate to colour, turbidity, odour, pH, coliforms (microbiological contaminants), and the total concentration of soluble salts. Most of the water we currently drink is less than 500 mg/L total soluble salts with sodium chloride being the major dissolved salt.

    Treatment of Hills storage water
    Hills storage water is of good quality and is only chlorinated and fluoridated before being distributed throughout the community.

    Chlorination involves treatment with chlorine (Cl2), a greenish yellow gas which is a strong oxidising agent, an algicide and bacteriocide. It is used to destroy potential pathogens and also to prevent the growth of algae in water pipes. Sufficient chlorine is usually added to provide a residual minimum of 0.2 to 0.5 mg/L or ppm.

    Chlorine is also used in swimming pools for the same reasons. In household pools instead of using chlorine gas which is dangerous and quite difficult to handle it is common to supply chlorine in some other form such as

    • calcium hypochlorite (white powder) - Ca(ClO)2
    • sodium hypochlorite (solution) - NaClO
    • sodium dichloroisocyanurate (white powder) - NaCl2C3N3O3.2H2O
    In home swimming pools it is usual to try and maintain a chlorine level of 2 ppm in order to destroy the bacterium responsible for the potentially deadly amoebic menengitis.

    Sodium hexafluorosilicate (Na2SiF6) or fluorosilicic acid (H2SiF6) is added in small amounts to our water supply to provide concentrations of about 1 ppm of fluoride ion (F-). At these levels the fluoride is built into the dental enamel in children's teeth which are consequently much more resistant to dental decay.

    Treatment of groundwater
    Groundwater usually undergoes a more comprehensive treatment to remove colour (iron and humic acids) and unpleasant odours such as hydrogen sulfide. CSIRO has been particularly active in the development of groundwater treatment systems. The Sirofloc Process is one method used in the treatment of groundwater. In this process magnetite (FeO.Fe2O3) is added to the water and absorbs the humic acids responsible for the colour. The magnetite is then collected magnetically leaving clear water behind.

    The atmosphere
    The atmosphere plays a vital role in making the Earth habitable for plant and animal life. The atmosphere:
    1. Maintains the Earth at an average temperature of 15°C compared with a temperature of -18°C if the Earth had no atmosphere;
    2. Shields the Earth's surface from potentially harmful ultraviolet radiation;
    3. Provides CO2 for photosynthesis;
    4. Provides O2 for respiration;
    5. Provides a medium for the hydrologic cycle;
    6. Pressurises the environment.

    The atmosphere is generally considered to have four major regions which are identified by temperature discontinuities between these regions. The regions are as follows:
    1. Troposphere - up to about 15 km and containing the Earth's weather systems;
    2. Stratosphere - 15-50 km and containing the ozone layer
    3. Mesosphere - 50-85 km;
    4. Thermosphere - >85 km.

    I will briefly describe four environmental issues which relate to the atmosphere and comment on the chemistry associated with them. Three of these, acid rain, photochemical smog and the greenhouse effect relate to the troposphere while the fourth, ozone depletion, is associated with the stratosphere.

    Composition of dry, pure air in the troposphere
    The composition of dry, pure air
    * by volume is as follows:
    CO2 0.03%
    N2 78.1%
    O2 21.0%
    Ar 0.9%
    * Water (H2O) can make up to about 5% of the atmosphere.
    * The atmosphere contains traces of other gases.

    Acid rain
    Normal rain is slightly acidic and has a pH of about 6 due to the presence of dissolved CO2.

    Rain is usually described as acid rain if it has a pH lower than 5. The worst examples of acid rain are probably those in Western Europe and the North East of the United States. These occur in and adjacent to densely populated and highly industrialised regions in these continents. In some areas rain with a pH of 4 is quite common and rainfall events with a pH close to 2 have occurred. In Australia rain with a pH of 3.6 has been recorded in the lower Hunter Valley near Sydney.

    Acid rain is usually the result of rain dissolving

    • sulfur oxides - SO2 and SO3
    • nitrogen dioxide - NO2

    The rain becomes a dilute solution of various acids such as sulfurous, sulfuric and nitric acids.

    Human outputs of sulfur oxides into the atmosphere are usually the result of burning fossil fuels (eg. oil and coal) in electric power stations and the smelting of sulfide ores in smelting plants.

    S(in fuel) + O2 → SO2
    MS(sulfide ore) + 3/2O2 → MO + SO2
    2SO2 + O2 → 2SO3

    Human outputs of nitrogen oxides are usually the result of high temperature internal combustion processes such as those found in motor cars. These bring about the reaction of atmospheric N2 and O2:

    N2 + O2 → 2NO
    2NO + O2 → 2NO2

    When dissolved in water these sulfur and nitrogen oxides produce acids as illustrated below:

    SO2 + H2O → H2SO3
    SO3 + H2O → H2SO4
    4NO2 + 2H2O + O2 → 4HNO3

    Acid rain can have the following effects:

    1. Make soils, surface waters and takes acidic with resulting damage to aquatic plants and animals including fish;
    2. Damage plants including crops and forests;
    3. Corrosion of metal and stone (especially limestone/marble) buildings.

    A lot of research has been undertaken to reduce the emissions of sulfur oxides and nitrogen oxides into the atmosphere. For sulfur oxides these include reducing the sulfur content of fuels and removing sulfur oxides from atmospheric emissions. In electricity generating power stations tall chimney stacks are often used with the aim of dispersing SOx emissions over a wider area. While this may reduce an acute local problem such pollution may inadvertently be spread to other regions as has occurred in western Europe and the United States.

    With regard to nitrogen oxide pollution research has focused on improving technology to reduce the amount of nitrogen oxides produced as a side-effect of the combustion of fossil fuels.

    Photochemical smog
    The formation of photochemical smog or Los Angeles smog is a phenomenon of large modern cities. Such smog is associated with a brown haze, reduced visibility, eye and bronchial irritation, damage to plants and animals, and deterioration of materials.

    The requirements for the formation of photochemical Smog are intense sunlight (containing some ultraviolet light), stagnant air (possibly resulting from a temperature inversion), nitrogen oxides and unburned hydrocarbons from automobile emissions.

    A simplified reaction scheme for the formation of photochemical smog is set out below:

    1. Production of nitrogen oxides.
    N2 + 02 → NO
    2NO + 02 → 2NO2

    2. Absorption of ultraviolet light by NO2 to form atomic oxygen and ozone.
    NO2 + hv → NO + O
    O2 + O → O3

    3. Reactions of hydrocarbons with atomic oxygen and ozone to form various organic free radicals.
    Hydrocarbons + O → R* + ROO*
    Hydrocarbons + O3 → R* + ROO*

    4. Formation of aldehydes, peroxyacyl nitrates etc.
    e.g. CH3CHO (ethanal), CH3COOONO2 (peroxyacetyl nitrate)

    The release of hydrocarbons and initial formation of NO and NO2 is followed later in the day by increasing levels of ozone and other oxidants. A diagram of the variations in the concentrations of the various pollutants in photochemical smog during the day is shown in Figure 4. 

     Increasingly on still summer days in Perth, as in Sydney and Melbourne, we are seeing the beginnings of a photochemical smog problem. This is mainly the result of the extremely high dependence of city dwellers on the use of cars. The development of an improved public transport system and the use of various incentives and disincentives will be essential components of the city's approach if it is to avoid a significant photochemical smog problem in the future.

    Ozone depletion
    In the stratosphere the critical species is ozone, 03. This triatomic form of oxygen is very reactive at ground level where it reacts with many other substances. In the stratosphere it has a much longer lifetime due to the rarer atmosphere at these altitudes.

    A graph of ozone concentration with altitude, (Figure 5) shows a maximum of about 10 ppm at an altitude of about 85 km. As previously mentioned, this "ozone layer" plays a critical role in filtering potentially harmful ultraviolet rays from solar radiation and preventing them from reaching the Earth's surface.

    Within the stratosphere ozone is produced and consumed according to the so-called Chapman mechanism which maintains ozone levels at a more or less steady state. The reactions in a simplified Chapman Cycle are as follows:

    Production:

    O2 + hv → 2O
    O3 + O → O3

    Decomposition:

    O3 + hv → O2 + O
    O + O → O2

    The decomposition reactions can be catalysed by a variety of species such as HO*, NOx and Cl*.

    As early as 1974 some scientists were warning of the potential threat which CFCs posed for the ozone layer. However the first definitive evidence was provided by British scientists who reported significant declines in ozone over the Antarctic in 1985. Debate ensued as to the cause of this decline; increased NOx levels, CFCs and changing atmospheric transport processes all being mentioned as possible causes.

    A crucial NASA Airborne Antarctic Ozone Experiment conducted in spring 1987 shed considerable light on this debate. This experiment involved about 150 scientists, ground and aeroplane-based laboratories. The experiment involved analysing stratospheric chemical species as a function of latitude. The graph in Figure 6 shows that ozone levels as a function of latitude were almost a mirror image of ClO levels and clearly implicated chlorine as part of the ozone depletion problem. This chlorine is thought to arise from the photochemical decomposition of CFCs as they diffuse to higher altitudes in the atmosphere. 

     The reason that ozone levels fall so drastically over the Antarctic during Spring seems to result from the peculiar meteorological conditions which exist at this time. Air in the so-called polar vortex is stagnant during winter and early spring. This very cold air produces stratospheric clouds containing ice particles which seem to play a critical part in the catalytic decomposition of the ozone. As a result of the NASA experiment governments around the world are now moving quickly to phase out the use of CFCs in its various applications. A series of international agreements starting with the 1987 Montreal Protocol has now brought forward the phasing out of most CFCs in industrialised countries to 1995. Despite this phasing out it is predicted that it will take the best part of a century for atmospheric chlorine levels to decrease to their 1970 levels.

    Greenhouse effect
    The Earth receives energy from incoming solar radiation and itself radiates energy back into space. Some of the energy radiated back into space as infrared radiation is trapped in the atmosphere resulting in the Earth being warmer, (average about 15°C), than it would be if it had no atmosphere of its own, (about -18°C).Thus the Earth has a natural greenhouse effect which is due to the presence of water and carbon dioxide molecules in the atmosphere. These are the molecules in the atmosphere which are most responsible for trapping the infrared radiation.

    Within the Earth's atmosphere several gases are increasing in concentration which have the potential to increase the Earth's natural greenhouse effect and produce global warming. These include carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and ozone.

    These gases are produced as follows:

    • Carbon dioxide from combustion of fossil fuels;
    • Nitrous oxide from combustion processes and fertiliser use;
    • Ozone in photochemical smog;
    • CFCs from air conditioning units, use as refrigerants, foaming agents, and solvents;
    • CH4 from enteric fermentation by ruminants (flatulent sheep and cows!) and anaerobic methanogenesis in rice paddy fields and landfills.
    Table 2 shows the changes in concentrations of some major greenhouse gases from preindustrial times to the present and projected to the year 2050 assuming continued commitment to the use of fossil fuels.

     Figure 7 show the changes in carbon dioxide over the last 30 years.

     The evidence is quite clear that anthropogenic (human) activities are changing the composition of the atmosphere. Changes to the major atmospheric components, nitrogen and oxygen, are insignificant. However the relative changes in the concentrations of the minor atmospheric constituents is quite marked. For example, carbon dioxide levels are projected to increase to about 600ppm by the middle of the next century.

    The effect of these changes in the levels of the minor atmospheric components is difficult to predict with certainty. Scientists are using computer models called General Circulation Models (GCMs) which consist of extremely complicated mathematical equations used to predict winds, temperatures, pressures, cloud cover and precipitation as changes in atmospheric composition take place.

    These models are both complex and crude. The models contain huge amounts of information but are crude in that one datapoint represents a 500km square grid on the Earth's surface. The different models may consider four, nine or 15 vertical levels in the atmosphere. There are enormous problems in trying to cope with the complexities of atmospheric circulation patterns, the interaction of ocean and atmospheric dynamics, and feedback processes associated with clouds, the biosphere and the Earth's surface albedo.

    The postulated consequences of changes in the Earth's atmosphere vary from model to model and there is presently a vigorous and vitriolic debate on the extent of the changes which are likely to take place. The models are tending to suggest the following changes:

    • Temperature increases of the order of 2-4°C;
    • Increased but uneven rainfall (10%);
    • Rising sea levels (10 - 80 cm);
    • Poleward shift of climatic zones;
    • Increased frequency of extreme weather events;
    • Threat to some ecosystems due to the rapidity of climatic change.
    With these quite serious predictions it is appropriate to ask what evidence is available concerning changes which have already taken place. This is very difficult to establish, particularly because of the large natural variations which take place in the Earth's weather systems.

    While there is no doubt that the atmosphere's composition is changing there is considerable debate over the extent to which climatic change is or is not currently taking place. One extensive study concluded that temperatures had increased by about 0.5°C over the past century but this result has been questioned. The IPCC panel concluded that sea levels have increased by 10-20cm over the same period but once again there is discussion over the validity of this claim. Thus there are competing views on the extent to which we are already seeing climatic changes associated with changing atmospheric composition.

    The difficulty of policy setting in this climate of uncertainty is clearly a dilemma for decision makers. The two extremes in position can be summarised as follows:

    1. Policy makers must wait for greenhouse science to get better. It is premature to make policies based on fragile data especially as the economic consequences could be severe.
    2. Uncertainty should not be used as an excuse for inaction especially as the longer action is delayed the greater the extent to which the Earth will be committed to irreversible greenhouse effects.
    It is likely to be several years before we have sufficient evidence to confidently predict the climatic consequences of changing atmospheric composition. At a political level the emerging policy is what has been called a policy of "no regrets" or "spreading your bets". This means taking action which even now makes sense for environmental and economic reasons but avoiding the more difficult decisions which may need to be made if the most extreme predictions from greenhouse warming eventuate. Current action includes a range of measures aimed at reducing greenhouse gas emissions through a variety of mechanisms such as increased energy efficiency, preferred use of natural gas and improved land management practices.

    The challenge
    With the current and emerging environmental problems which confront the Earth it would be easy to become pessimistic. There are however reasons to be optimistic. International agreements such as the Montreal Protocol, the Toronto Conference on Climate (1988) and the Earth Summit (1992) are encouraging signs of the ability of different nations to work together to solve international environmental problems. The continuing challenge is to:
    • Encourage and promote global cooperation on environmental issues;
    • Achieve population stabilisation;
    • Plan for sustainable economic development;
    • Develop and promote the use of alternative forms of energy and energy efficient technology;
    • Encourage everyone to make an individual commitment to the environment.

    I would like to issue a challenge to everyone here tonight to commit themselves over the next five years to tackle one significant issue relating to the environment. This might mean encouraging your local Council to develop an improved recycling policy, increasing energy efficiency in your own home or school, training as a more environmentally aware architect, or undertaking research into the development of renewable energy technologies.


    Good Luck!

    THE CHEMISTRY OF CROISSANTS
    Basic Aerosol Technology
     

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