Chuong gioi thieu (phan 1) ppt

Chapter The Environment and Sustainability Science Environmental Chemistry, 9th Edition Stanley E Manahan Taylor and Francis/CRC Press 2010 1.1 From the Sun to Fossil Fuels and Back Again Early 2000s have shown evidence of strain on Earth's support systems Shortages and high prices for fuel and materials in early 2008 • Leading to economic collapse Evidence of global warming • Glaciers melting • Loss of Arctic ice cap Stress and depletion of Earth's natural capital • Agricultural land depleted • Water sources limited • Wildlife habitat lost The Brief But Spectacular Era of Fossil Fuels • Began with coal in latter 1700s • Coal-fired steam engine as a source of power • Progressed to petroleum and natural gas • Petroleum supplies will become exhausted within decades • New supplies of natural gas are being found • Natural gas is an ideal fossil fuel for many applications • Not all coal can be used because of global warming potential Relative to the time of human life on Earth, the era of fossil fuels must soon end • How it ends and what replaces it will largely determine the welfare of humankind for centuries to come Back to the Sun for Energy, Fuel, and Raw Materials • Direct use for solar heating and solar voltaic power generation • Indirect use for wind, biomass, hydroelectric (solar-powered hydrologic cycle) Photosynthetically-Produced Biomass for Synthetic fuels • Fermentation of sugars to ethanol • Chemical conversion of lipids to synthetic diesel fuel • Chemical conversion of biomass to CO and H followed by chemical synthesis of hydrocarbons and alcohols Several abundant sources of biomass • Crop byproducts such as corn stover • Dedicated crops such as hybrid poplar or corn stover • Highly productive algae, which may even be grown in brackish water 1.2 The Science of Sustainability Sustainability or sustainable development is an economic and industrial system that meets the needs of the present without compromising the ability of future generations to meet their own needs (Bruntland Commission 1987) • Maintenance of Earth’s ability to maintain an acceptable level of human activity and consumption over a sustained period of time Nobel-level breakthroughs required to achieve sustainability (Chu, 2009) Solar energy capture and conversion to electricity to improve several-fold Improved electric batteries • Capture and store electricity from intermittent renewable sources • Practical driving range in electric vehicles Improved crops to convert more solar energy to biomass chemical energy • Now less than 1% • Genetic engineering should improve several-fold Environmental Science The science of the complex interactions that occur among the terrestrial, atmospheric, aquatic, living, and anthropological systems that compose Earth and the surroundings that may affect living things Green Science and Technology The practice of sustainable science and technology Green Chemistry The practice of inherently safer and more environmentally friendly chemical science Green Engineering Engineering practiced in a sustainable and environmentally friendly manner Environmental chemistry has developed as a positive force for a clean environment • Revealing problems such as by pollutant analysis • Measures to control pollution • Foreseeing problems before they develop • Appropriate action to forestall environmental problems • Support of other disciplines such as industrial ecology and green chemistry employed in environmental improvement Toxicological chemistry relates the chemical nature of substances to their adverse effects on organisms 1.4 WATER, AIR, EARTH, LIFE, AND TECHNOLOGY Much of environmental chemistry deals with the interchange of materials among water, air, earth, and biological systems and the effects of technology thereon See Figure 1.2 (next slide) Biogeochemical cycles describe the interchange of matter and energy among the various environmental spheres • Effects of organisms • Effects of humans (technology) 10 19 1.6 ENERGY AND CYCLES OF ENERGY Earth receives solar energy at 1,340 watts/meter at the top of the atmosphere • Enormous amount of incoming energy largely in visible region of the electromagnetic spectrum • Must re-radiate this energy to outer space as longer-wavelength infrared radiation 20 Light and Electromagnetic Radiation Electromagnetic radiation carries energy through space at 3.00 x 10 meters/second (c, speed of light) In order of shortest wavelength (more energetic) to longer wavelength (less energetic): • gamma>X-rays>ultraviolet>visible>infrared Characteristics of wavelength (λ, meters), amplitude, and frequency (ν, s Hertz) • νλ = c Energy: E = hν where h is Planck’s constant Dual wave/particle nature of electromagnetic radiation -1 or 21 Energy Flow and Photosynthesis in Living Systems Figure 1.3 Energy conversion and transfer by photosynthesis 22 1.7 HUMAN IMPACT AND POLLUTION Pollutant: Substance in greater than natural concentration that is detrimental Contaminants cause deviations from normal concentration but are not pollutants unless they have adverse effects 1.8 CHEMICAL FATE AND TRANSPORT Interchanges of contaminants released from the anthrosphere among various segments of the other environmental spheres and illustrations of pathways involved in chemical fate and transport 23 24 Fate and transport of contaminants controlled largely by • Physical transport: Movement without reacting or interacting with other phases • Reactivity: Including chemical or biochemical reactions or physical interactions with other phases 25 Three Major Environmental Compartments Considered in Chemical Fate and Transport 26 Physical Transport (1) Advection: Movement of masses of fluid that simply carry pollutants with them • Vertical advection of air or water is called convection (2) Diffusive transport: Molecular diffusion, the natural tendency of molecules to move from regions of higher to lower concentrations • Also called Fickian transport • Approximated by turbulent mixing such as in flowing water 27 Reactivity • Chemical reactions • Biological uptake • Binding to and release from surfaces Two broad categories of reactivity (1) Chemical reactions (2) Interphase exchange • In water, binding of soluble species to suspended particles • In air, includes evaporation and condensation of species • Includes biological processes 28 Illustration of the Mass Balance Relationship for a Pollutant with Respect to a Specified Compartment of the Environment Steady state applies when there is not net change of mass of pollutant within the control volume 29 Distribution Among Phases • Partitioning between major compartments • Partitioning between phases within a compartment • Partitioning between water and a solid depends upon a substances solubility or hydrophilicity • Partitioning between water and air depends upon vapor pressure Sorption • Adsorption onto material surface • Absorption within body of material 30 1.9 CHEMICAL FATE AND TRANSPORT IN THE ATMOSPHERE, HYDROSPHERE, AND GEOSPHERE Pollutants in the Atmosphere • Volatile organic compounds transported in atmosphere • Partitioning between air and atmospheric particles Pollutants in the Hydrosphere • More hydrophilic compounds tend to stay in water • Soil water partition coefficient, Kd, where Cs and Cw are concentrations on solids and in water, respectively • Partitioning of organics onto solids depends upon organic fraction of solids Pollutants in the Geosphere • Transport of contaminants depends upon porosity, nature of geospheric solids, nature of contaminants 31 1.10 ENVIRONMENTAL MISCHIEF AND TERRORISM Chemistry can be used for harmful acts • Explosives, corrosives, and otherwise damaging substances • Toxic substances Chemistry can be used to combat terrorism • Instruments to detect harmful substances • Protective materials Some environmental incidents have resembled terrorist attacks • 1984 Bhopal, India, release of methyl isocyanate that killed 3,500 • 2003 release of toxic hydrogen sulfide with natural gas that killed over 200 in China Measures that are good practice of environmental chemistry tend to reduce terrorist threats 32 Protection Through Green Chemistry and Engineering Green chemistry is safe and sustainable chemistry • Avoids hazards that can be used to harm • Reduces vulnerability such as interruption of materials supplies • Avoids use, generation, or storage of hazardous substances • Avoids severe conditions that may pose hazards • Carefully monitor conditions for trouble 33 1.11 ENVIRONMENTAL FORENSICS Environmental forensics deals with the legal and medical aspects of pollution Important in several areas • Health effects • Legal liabilities • Determining responsibilities for terrorist attacks • Assessment of hazardous waste sites • Suitability of sites for brownfields restoration Important aspects regarding environmental incidents • Source • Timing • Extent ... Major Environmental Compartments Considered in Chemical Fate and Transport 26 Physical Transport (1) Advection: Movement of masses of fluid that simply carry pollutants with them • Vertical advection... • Biological uptake • Binding to and release from surfaces Two broad categories of reactivity (1) Chemical reactions (2) Interphase exchange • In water, binding of soluble species to suspended