Introduction Essays (2419 words) - Air Pollution, Exhaust Gas

Introduction Air pollution is nothing new. Ever since the discovery of fire, less-than-desirable substances have been vented into the air. One of the first air-pollution regulations dates back to the fourteenth century, when King Edward I banned the burning of sea coal in lime kilns. U.S. air-pollution regulations have their roots in British Common Law. But regardless of those efforts, air pollution continues to be a serious local and world-wide problem. Pollution is the pressure within the air of one or more substances that are harmful to human health, welfare, animal or plant life, or property. In the past with air pollution we included mainly the outdoor pollutants, although in recent years this is not the case. Today we separate pollutants in to two categories. Primary pollutants, because they come directly from various sources, and secondary which are by-products of chemical interactions of the primary pollutants within the atmosphere. Particulates Although air pollution might be thought of as unwanted gases in the atmosphere, two of five primary pollutants are really solid substances called particulates. Soot has always been a sure indicator of a polluted atmosphere, but other than soiling and a negative psychological effect, soot can't settle into the lungs and cause serious diseases. Thick ,black smoke coming out of a stack is that what we think causes the pollution, but what really creates the damage is what we can't see. Particles like this are called suspended particles. They come from many incomplete burning and can consist a variety of substances. The most harmful type of particulate is so small that that it is microscopic. All the particulates are harmful for several reasons. When inhaled, they can damage the interior of the lung; they can also be poisonous. Sometimes gases will glue to their surfaces and in a process called adsorption they can reach the lungs. All these particles are mainly products of combustion. The major sources include industrial processes, power plants that are both coal and oil-fired, residential heating, and transportation. But coal burning is the greatest source. Table 1 below shows estimates of U.S. particulate emissions from various sources. TABLE 1 National U.S. Emissions Estimates-1990 (Million metric tons/year) SOURCE PARTICULATES SULFUR OXIDES CARBON MONOXIDES Transportation Highway 1.3 0.6 30.3 Aircraft 0.1 0 1.1 Rail&Sea 0 0.3 1.9 Off-Highway equipment 0.1 0.1 4.4 TOTAL 1.5 1 37.7 Stationary fuel combustion Electric utilities 0.4 14.2 0.3 Indusrial furnaces 0.3 2.3 0.7 Commercial 0 0.4 0.1 Residential 1 0.3 6.4 TOTAL 1.7 17.2 7.5 Industrial processes 2.8 3.1 4.7 Solid waste disposal 0.3 0 1.7 Miacellaneous Forest fires 1.1 0 8.1 Other burning 0.1 0 0.6 Misc. Organic solvents 0 0 0 TOTAL 1.2 0 8.7 OVERALL TOTAL 7.5 21.3 60.3 Only 13% of the total is generated by transportation. Industrial sources account for nearly three times as much as 37%. Fires account for just about as much particulate emissions as transportation. That amount is matched by combustion from sources, which include the generation of all heat and electricity. Emissions When coal was the main source to generate energy, power plants and homes accounted for much greater contribution. The switch to oil and nuclear power has lowered those concentrations, but it hasn't been without its own problems. In addition to health-related problems, particles can damage materials through corrosion and erosion, as well as soiling. Particles can also impact the weather, through changes in visibility, and even in enhancing precipitation. Studies around major urban areas show an increase in precipitation and in thunderstorms with hail downwind from downtown areas. The weather modification is localizes but definite, and may be related to an increase in the large condensation nuclei that the particles provide. Lead particulates are brutal primary pollutant. Their presence in the atmosphere has diminished sharply during the past 29 years. Since 1975, the concentration of lead has decreased by more than 90%, which can be directly linked to the elimination of lead from gasoline. The following table shows that huge drop. TABLE 2 Gas Another primary group of pollutants consists of the surfur oxides(Sox), and the major contributor is SO2, a sulfur dioxide. This is generated whenever sulfur is burned, most often where fuel with a high sulfur content is used. Coal can have very high sulfur concentrations, as can some oil. Overall, coal and oil are the major sources for sulfur oxide pollution. The vast majority of this type of air pollution comes from generation of

Review Essay - Uses a Documentary Review Essay Sample

Review Essay - Uses a Documentary Review Essay SampleIf you want to be an instructor or lecturer, a documentary review essay sample is an important aspect of your toolbox. If you are planning to teach a class on film theory or film history or on film and media, then you need a piece of this good-quality writing to help you get your message across.There are many reasons for writing this type of essay, and the quality of the writing is very good indeed. It will look professional, be clear and concise, and will build up a sense of self-confidence for you. Your written material will also be useful for reference in the coursework.The first thing you need to do is to decide what subject you wish to cover. Most essays on film history, for example, are based on some more recent event. You need to think about what will be appropriate for your audience. You also need to decide whether you want to write a thesis or a case study, and which form you should choose.Many teachers feel that a thesis or case study is better suited to a student who has a long way to go before they can begin to write an essay. If you are struggling with this, you could look at looking at a thesis. However, if you have the right attitude and the idea is right, then a review essay is the right choice for you. When you are teaching this type of course, you will always have topics that come up, so having something in the bag that you can always refer to is a big advantage.Once you have decided what subject you want to use, then you need to look at what style of essay you are going to use. A review essay needs to be written using a variety of styles. It will probably be best to start by reading through some of the best essays available. This will give you an idea of what you are going to be working with and help you avoid making a similar mistake.The next step in the process is to think about the style that you are going to adopt for your final decision. You should try to pick a style that is as close to the style you would be using as possible. The problem with this is that there is no one style that is correct. There are many styles and you will need to use one that best fits the needs of your students.Once you have decided on the style, the next step is to think about the subject matter you will cover. Many reviewers make a comparison between film and literature, so if you have a book on film, you will want to do a comparison with a review essay. To make sure you make the most of your essay, it is advisable to read as much as you can to get an idea of the subject and the importance of the work you are going to cover.You may want to do some research about the review yourself, or you may want to have someone else do this, but the final decision will depend on what you feel comfortable with. If you think you might need a piece of guidance before you start, then you can take a look at a basic guide to writing review essays. This will ensure you get started on the right foot and ma ke sure you have all the answers to your questions.