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Standing at our deck rail, I look down at the creek below. It is picturesque at any season. In the spring and summer, flowers grow on the bank, trees of several different species stand straight and proud. In the fall when the leaves turn crimson, orange, and gold, my creek looks royal. Even in the winter when the leaves are gone and the trees are bare, the water still looks peaceful and tranquil. After living here half my life, I do not always notice the Dunkin Doughnut cups, soda cans, Styrofoam containers, and other litter strewn on the banks. But it is there, a sad reminder of human neglect of the environment. Standing on the bank looking into the water, I can see the glint of a metal soda can squashed and lying on the creek's bottom. I have many memories of the creek. When I was younger, my friend and I would eagerly pull on rubber boots and splash into the creek and follow it downstream. Sometimes we would sit on the big rocks in the middle. On Earth Day the neighborhood would gather to clean the banks and stream bottom, clear out brush, and plant flowers. I remember the time a gasoline truck spilled its contents into the water, causing the firemen to evacuate the neighborhood. They were afraid the gasoline would ignite and explode. However, for the years I have lived by it, I cannot remember a time when it contained aquatic life. Although further downstream there were some fish, there were never any fish swimming or frogs sunning on the banks near my house. All signs of a healthy aquatic environment were and are nonexistent. At the beginning of my block, Mill Creek emerges from underneath the city of Philadelphia. When it rains, torrents of water and trash from the storm sewers dump into the creek. Some of the house sewage pipes drain into the creek. The Philadelphia Water Department has been working on correcting this but has not yet succeeded. Sometimes the creek rises over its banks and floods the yard. Afterward we can tell how far it came by the line of litter in the grass. During all types of weather, however, human feces and sewage are also dumped into the creek. Though not always apparent, they sometimes turn the creek from blue to brown, and produce an unpleasant odor. These unwanted additions to the creek repulsed me, yet I desired to find out how polluted the creek really was. In the Clean Water Act of 1972, standards were put in place for treating municipal waste or sewage (Smith, p. 8). Even though the Act doubled the number of bodies of water that were safe for fishing and swimming, today 40 percent of the nation's waterways remain unclean for these uses. In Pennsylvania, roughly 25 percent of the water remains polluted (Cooper, p. 955-956). My creek is part of that 25 percent. I wanted to find out how polluted it really was. |
At the start of my project, I borrowed a water-testing kit from my high school. I also obtained access to a probe that would precisely measure the amounts of dissolved oxygen in the creek. Examining the equipment, I noticed that most of the tests would at best give me an estimate of the amount of that substance present in the stream. I was greatly disappointed that the test for fecal-coliform bacteria, which shows the presence of fecal content in the creek, would only give me a positive or negative reading. Researching online at a community Web site about our creek, I found a table showing the fecal-coliform bacteria content at different locations between the years of 1998 and 2001. I was amazed to find that in the short distance the creek traveled from its emergence from underneath the city, very close to my backyard, to about a mile downstream, the fecal-coliform bacteria count ranged from more than 200,000 colony counts per 100 milliliters (cfu) to 260 (Rudin chart). I began to wonder if other tests would also vary if tested at different locations as the creek traveled further away from the city. Mainly, I wondered if there was a connection between fecal-coliform bacteria levels and dissolved oxygen levels in the water. I didn't have the instruments to test bacteria levels, but I could use the oxygen probe and the data from the prior tests. I decided to go ahead and do all the tests but to focus on the connection, if any, between fecal-coliform bacteria and dissolved oxygen content. I also wanted to find out what factors were preventing the creek from supporting aquatic life.  Site 1: the creek behind Anna's house. Before I began testing, I researched the importance of dissolved oxygen in water. It is important in water because it affects the ability of aquatic life-forms to live in water. The oxygen gets into the water by several methods: diffusion from the surrounding air, rapid movement (which is also known as aeration), or as a waste product of photosynthesis. If the dissolved oxygen level in the water is too high, fish and other aquatic invertebrates can suffer from a disease in which burgeoning gas bubbles in their blood vessels block their blood flow. However, this condition is rare, and the oxygen level would have to be extremely high. On the other hand, if the level of oxygen drops too low, below 5.0 ppm (parts per million), aquatic life is put under stress—stress that increases as the oxygen levels drop. If the oxygen level is lower than 1-2 ppm for a long period of time, large numbers of aquatic organisms may die (Dissolved Oxygen, par. 1-4). |
        
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