How can we reduce the amount of waste that is produced? And how can we close the loop by redirecting spent materials and products into programs of recycling? All of these questions must be answered through careful research in the coming years as we strive to keep civilization in balance with nature.
Alteration of long-established practices to enhance environmental protection can involve serious financial expenditures. The possibility that these costs could bankrupt local and even regional governments and put U.S. industries at a competitive disadvantage makes it imperative that the best possible science be brought to bear on environmental problems. It also places a premium on finding creative, environmentally beneficial alternatives to existing products and processes. In many instances, industries are finding unanticipated payoffs from process redesign; greater efficiencies save money as well as reduce pollution, and waste streams can sometimes be turned into useful products. In the long run, the benefits of investing in environmental protection will be recognized as environmental awareness grows around the globe.
Since the time 3,000 years ago when Homer noted the smell of ozone created by lightning, people have been fascinated by the chemical behavior of the atmosphere. New techniques of analytical chemistry have fostered a rapid pace of discovery and understanding over the past few decades, allowing separation, identification, and quantitative measurement of chemical species at ever more sensitive levels. Other than nitrogen, oxygen, argon, and water vapor, all other components of air have average atmospheric concentrations below 0.1 percent of the total. Between 0.1 and 0.0001 percent, five more chemical species are added: carbon dioxide, methane, helium, neon, and krypton. Now that modern instruments have lowered these detection limits by up to a factor of 1 trillion during recent years, we know of many other substances whose atmospheric chemistry is both scientifically fascinating and globally important. At least 3,000 different chemical species have been identified in the atmosphere, and more than 50 of these have been detected in locations as remote as the South Pole.
Coal-burning power plants, as well as some natural processes, deliver sulfur compounds to the stratosphere, where oxidation produces sulfuric acid particles that reflect away some of the incoming visible solar radiation. In the troposphere, nitrogen oxides produced by the combustion of fossil fuels combine with many organic molecules under the influence of sunlight to produce urban smog. The volatile hydrocarbon isoprene, well known as a building block of synthetic rubber, is also produced naturally in forests.