色彩與環境化學 『從原子到宇宙』課程第七週 胡維平 國立中正大學化學暨生物化學系 11/01/2012 Colors and Molecular Spectra 鹵素 染料 硫晶體 PbMoO4 MnCO3 Chromium Compounds Richard Megna/Fundamental Photographs Chemistry of Vision 環境化學 The Future of the Earth ? Properties of Our Atmosphere 2009, Prentice-Hall, Solar Radiation The atmosphere is the first line of defense against radiation from the Sun. 2009, Prentice-Hall, Composition of the Atmosphere • Because of the great variation in atmospheric conditions, the composition of gases in the atmosphere is not uniform. • Lighter gases tend to rise to the top. 2009, Prentice-Hall, Composition of the Atmosphere • Near the Earth’s surface, about 99% of the atmosphere is composed of nitrogen and oxygen. • Oxygen has a much lower bond enthalpy than nitrogen, and is therefore more reactive. 2009, Prentice-Hall, Outer Atmosphere • The Sun emits a wide range of wavelengths of radiation. • Remember that light in the ultraviolet region has enough energy to break chemical bonds. 2009, Prentice-Hall, Ozone • Ozone absorbs much of the radiation between 240 and 310 nm. • It forms from reaction of molecular oxygen with the oxygen atoms produced in the upper atmosphere by photodissociation. O + O2 O3 2009, Prentice-Hall, Ozone Depletion In 1974 Rowland and Molina discovered that chlorine from chlorofluorocarbons (CFCs) may be depleting the supply of ozone in the upper atmosphere by reacting with it. 2009, Prentice-Hall, Chlorofluorocarbons • CFCs were used for years as aerosol propellants and refrigerants. Freon 11: CCl3F, Freon 12: CCl2F2 • They are not water soluble and are quite unreactive. • The C—Cl bond is easily broken, though, when the molecule absorbs radiation with a wavelength between 190 and 225 nm. • The chlorine atoms formed react with ozone: Cl + O3 ClO + O2 2009, Prentice-Hall, Inc. Adopted from “UV Photolysis of ClOOCl and Ozone Hole” by Jim J. Lin, Andrew F Chen, Yuan T. Lee, Chemistry, An Asian Journal, submitted. Air Pollution • Two main sources: Transportation Production of electricity • Combustion of petroleum produces CO, CO2, NO, and NO2, along with unburned molecules from petroleum. 16 Nitrogen Oxides (Due to Cars and Trucks) • • • At high temperatures, N2 and O2 react to form NO, which oxidizes to NO2. The NO2 breaks up into nitric oxide and free oxygen atoms. Oxygen atoms combine with O2 to form ozone (O3). Radiant energy NO2 (g ) NO(g ) O(g ) O(g ) O2 (g ) O3 (g ) 17 Sulfur Oxides (Due to Burning Coal for Electricity) • • Sulfur produces SO2 when burned. SO2 oxidizes into SO3, which combines with water droplets in the air to form sulfuric acid. S(in coal) O2 (g ) SO2 (g ) 2SO2 (g ) O2 (g ) 2SO3 (g ) SO3 (g ) H2O(l ) H2SO4 (aq ) Copyright © Cengage Learning. All rights reserved 18 酸雨 • High acidity in rainfall causes corrosion in building materials. • Marble and limestone (calcium carbonate) react with the acid; structures made from them erode. Sulfur • Sulfur dioxide is a by-product of the burning of coal or oil. • It reacts with moisture in the air to form sulfuric acid. • It is primarily responsible for acid rain. 2009, Prentice-Hall, 煤除硫化 • SO2 can be removed by injecting powdered limestone which is converted to calcium oxide. • The CaO reacts with SO2 to form a precipitate of calcium sulfite. 2009, Prentice-Hall, Carbon Monoxide • Carbon monoxide binds preferentially to the iron in red blood cells. • Exposure to significant amount of CO can lower O2 levels to the point that loss of consciousness and death can result. 2009, Prentice-Hall, Photochemical Smog • These nitrogen oxides are just some components of photochemical smog. • Ozone, carbon monoxide, and hydrocarbons also contribute to air pollution that causes severe respiratory problems in many people. • government emission standards for automobile exhaust have become continually more stringent. Hybrid Car Water Vapor and Carbon Dioxide • Gases in the atmosphere form an insulating blanket that causes the Earth’s thermal consistency. • Two of the most important such gases are carbon dioxide and water vapor. Water Vapor and Carbon Dioxide • This blanketing effect is known as the “greenhouse effect.” • Water vapor, with its high specific heat, is a major factor in this moderating effect. • But increasing levels of CO2 in the atmosphere may be causing an unnatural increase in atmospheric temperatures. 2009, Prentice-Hall, Chemical Processing Plants Solvents such as supercritical CO2 are great “green” alternatives. Simon Fraser/SPL #S4644E 什麼是優養化 (Algal bloom)? 「優養化」是指水中的氮、磷等營養元素不斷增加 (PO42-, NO3-),造成水中藻類大量繁殖,藻類耗用水中溶氧量,造成 水棲生物、魚類、蝦蟹缺氧、死亡,動物屍體又會惡化水體, 惡性循環下,「優養化」就不斷加遽。 自然界中,氮、磷是稀有的成分,但是近年水庫上游因人為開 發,在山坡地種植蔬果,噴撒農藥、肥料,或是人為排放的廢 水、洗衣粉,都含氮、磷,才加速水庫優養化。