Water Quality Indicators Lab

Transcription

1 Water Quality Indicators Lab Introduction Water is an essential resource for all life forms. In fact, water is the main component in cells and it composes up to 60 to 70 percent of the weight of living organisms. It is used for almost every activity in today s world. Water often seems to be available in an almost endless supply, but as the human population grows and the world becomes more industrialized, more and more is being used. With this increased use of water, a problem arises: the water becomes polluted and contaminated. The amount of water available, its distribution, and its quality are critical issues that affect every organism. Hypothesis In the table below, make predictions about the quality of the different water sources for each indicator. DO: Chlorine: Phosphate: Nitrate: ph: Acid, Bacteria: Suitable for Safe or Safe or Safe or Neutral, or Safe or Organisms, Unsafe Unsafe Unsafe Base Unsafe Yes or No Bottled Water Tap Water Creek Water Materials bottled water creek water tap water test tubes TesTabs (various chemical tablets used to test different indicators) Procedure 1. At each lab station, read the Background information about each water quality indicator. 2. For each water sample, compare the color of the water sample to the colors on the Color Card. 3. Record the value in the appropriate part of the data table. Each value should be recorded in parts per million (ppm). Note: if the color of the water sample appears to be between two values, then record the range in the table. 4. If your station has Mystery s, then compare the Mystery to the colors on the Color Card. Record the value(s) in the data table. 5. Based on the value of the Mystery sample, try to predict what it is. Record your prediction in the data table. 6. Look in the envelope to identify the Mystery. Record the substance in the data table. 7. Clean up the station. Return the Mystery card to the envelope. 8. Answer the questions for your station.

2 Date pg. Station 1 Chlorine Chlorine is not naturally found in water at any significant levels. In order to make sure water is safe to drink, chlorine is added to the water at water treatment plants to kill disease producing bacteria. Chlorine levels in tap water are safe for humans to drink. Large levels of chlorine introduced to streams, lakes, rivers, and ponds can be harmful and possibly fatal to aquatic organisms. Drinking water usually has less than ppm (parts per million). Most aquatic organisms cannot survive in water with chlorine levels above 0.37 ppm. Data Table 1 Chlorine Level (ppm) : 1. How do the chlorine levels vary between the bottled, tap, and creek water samples? 2. Why does the tap water sample have a higher chlorine level than the bottled water sample? 3. Explain whether or not aquatic life could survive in the creek water based on its chlorine level. Station 2 Phosphate Usually, phosphate is found naturally in water and is a necessary element for plants and animals. It can come from human waste, animal waste, and industrial waste. Detergents (dish and laundry) and agricultural fertilizers are a large source of phosphate. Phosphate is a nutrient that acts as a fertilizer for aquatic plants. When nutrient levels are too high, plants and algae grow out of control and create water quality problems. When large amounts of plants die and rot, oxygen levels drop and the area may eventually become an unfit habitat for fish, animals, and insects that used to live there. Phosphate levels higher than 0.03 ppm may lead to increased plant growth.

3 Data Table 2 Phosphate Level (ppm) : 1. How do phosphate levels vary between the bottled, tap, and creek water samples? 2. What can explain the phosphate level in the creek water sample? 3. Would the creek water be a suitable environment for aquatic plants? Aquatic animals? Explain your answers. Station 3 Nitrate Nitrate is one of the main ingredients in fertilizer and is used to increase production of healthy, green grass and plants. If more fertilizer is applied than can be used by the plants, the extra nitrate is washed out of the soil and into nearby rivers when it rains. Nitrate can also enter water from leaking sewage systems, animal wastes, and car exhaust. Unpolluted water usually has a nitrate level below 4 ppm. Nitrate levels above 10 ppm may be unfit to drink, and high levels of nitrate can poison and suffocate young babies by depriving them of oxygen. Data Table 3 Nitrate Level (ppm) :

4 1. How do nitrate levels vary between the bottled, tap, and creek water samples? 2. Would the creek water sample be considered polluted or unpolluted? Explain your answer. 3. If a water sample were taken at a stream next to a large farm, how do you think the nitrate level would be affected? Explain your answer. Station 4 Dissolved Oxygen The presence of oxygen in water is a healthy sign and is one of the most important indicators of the overall health of a body of water. Water with consistently high levels of DO (6 ppm or more) typically supports the most diverse biological ecosystems. Water with consistently low DO (below 3 ppm) is extremely stressful to aquatic organisms and may only support a few types of organisms. DO levels below 2 ppm will not support fish life. Most DO enters water from the atmosphere. In nature, waves and wind whip up the water and mix it with oxygen in the air. Aquatic plants add oxygen to water during photosynthesis. Data Table 4 Dissolved Oxygen Level (ppm) Suitable for Life? 1. How do the dissolved oxygen levels vary between the bottled, tap, and creek water samples? 2. Which sample(s) would support a wide range of aquatic life? Explain your answer. 3. If a sample were collected several miles downstream, how do you think the dissolved oxygen levels would compare to the creek water? Explain your answer.

5 Stations 5 ph The ph test is a standard test used during water analysis; a ph value tells us how acidic or basic things are. The ph scale ranges from 0 (very acidic) to 14 (very basic), and a ph of 7 is neutral (neither acidic nor basic). Normal precipitation may have a ph as low as 6. The ph of water is critical to aquatic life. Most organisms are used to living in water with a specific ph and may die if ph levels change even slightly. Most organisms require a range of ph from 6.5 to 8.2. Data Table 5 Acid, Neutral, ph Level or Base 5. Mystery : : 1. How do ph levels vary between the bottled, tap, and creek water samples? 2. Explain whether or not aquatic organisms could live in the creek where the water sample was taken. 3. Could either of the Mystery s support life? Explain your answer. Station 6 Bacteria (coliform) Coliform bacteria are usually harmless bacteria that live naturally in the intestines of warm-blooded animals (including humans) and help the body function properly. Coliform bacteria are found in human and animal feces but do not usually occur elsewhere. Although coliform bacteria are typically harmless, they are found with other types of harmful bacteria, so coliform bacteria are used as an indicator of sewage or fecal contamination. Bodies of water can become contaminated with coliform bacteria from damaged sewer lines, stormwater runoff containing pet waste, and animal waste from animals that live in the area.

6 Data Table 6 ****DO NOT TOUCH THESE VIALS**** Bacteria + or 1. How do bacteria results vary between the bottled, tap, and creek water samples? 2. Would you expect to get a positive test result for the tap water sample? Explain your answer. 3. What could explain the presence of bacteria in the creek water sample (whether or not the result is positive)? Complete the table. Water Quality Indicator Safe Levels / Level Needed to Support Life Water Quality Information Sources (Where do these chemicals come from?) Effects of Unsafe Levels chlorine phosphate nitrate dissolved oxygen ph bacteria (coliform)