A Water Quality Field Study<br />By<br />Paul Eyler<br />Kenya Trimble-McCullough <br />Zelia McGaha<br />David Peacock<br />
Objectives<br />Primary TEKS – 8.11 B, 8.4 A-B<br />Subsequent TEKS – 8.1 A, 8.2 A-E, 8.3 A-C<br />In this experiment, you will:<br /><ul><li>Compare and contrast water quality between freshwater aquatic systems.
Use VernierLabQuestand probes:</li></ul>Use a Temperature Probe to measure water temperature.<br />Use a Conductivity Probe to measure the conductivity of water.<br />Use a pH Sensor to measure the pH of water.<br />Use a Dissolved Oxygen sensor to measure dissolved oxygen.<br /><ul><li>Make visual observations at the test sites of plant, animal, and insect life.
Draw a map of your location</li></li></ul><li>The Freshwater Biome<br />Freshwater is defined as having a low salt concentration (less than 1%). Plants and animals in freshwater regions are adjusted to the low salt<br />Ponds, lakes, streams, rivers, and wetlands<br />
Introduction<br />When finding water quality, there are many measurements that can be made. In this experiment, you will measure the water:<br />Temperature<br />Conductivity<br />pH<br />Dissolved oxygen <br />
Temperature<br />Water temperatures in streams can range from 0C in the winter to above 30C in the summer<br />Cooler water in a stream is generally considered healthier than warmer water<br />Problems generally occur when changes in water temperature are noted along one stream on the same day <br />Some sample data are listed in Table 1 <br />
Conductivity<br />Conductivity values in lakes and streams are typically found to be in the range of 100 to 500 µS/cm. Some sample data are listed in Table 1<br />In areas of especially hard water or high salinity, conductivity values may be as high as 1000 µS/cm <br />Drinking water usually has conductivity in the 50 to 1000 µS/cm range <br />Some sample data are listed in Table 2<br />
Conductivity is a measurement of the ability of an aqueous solution to carry an electrical current. <br />An ion is an atom of an element that has gained or lost an electron which will create a negative or positive state. <br />For example, sodium chloride (table salt) consists of sodium ions (Na+) and chloride ions (Cl-) held together in a crystal. In water it breaks apart into an aqueous solution of sodium and chloride ions. This solution will conduct an electrical current. <br />
There are several factors that determine the degree to which water will carry an electrical current:<br />the concentration or number of ions <br />mobility of the ion <br />oxidation state (valence) <br />temperature of the water<br />Used as a measure of the mineral or other ionic concentration. Conductivity is a measure of the purity of water or the concentration of ionized chemicals in water<br />
pH<br />The best pH range for most aquatic organisms is pH 6.5 to 8.2. The pH values of streams and lakes are usually between pH 7 and 8. Hard water will often have pH values between 7.5 and 8.5. <br />It is used to measure the acidity of liquids represented by a scale of numbers from 0 to 14. The pH of pure water is 7.0, which is neither acidic nor basic. When the pH is less than 7.0 it is identified as acidic; and at a pH greater than 7.0, it is considered basic or alkaline.<br />Aquatic organisms’ ability to survive is reduced if the pH of the water becomes greater than 9.0 or less than 5.0. The pH of water is very important in order to sustain a healthy aquatic ecosystem.<br />
The main factors that could affect pH are:<br />Dissolved mineral substances (e.g. hard water-pH greater than 7.0)<br />Aerosols and dust from the air<br />Man-made wastes (e.g. waste from mining operations)<br />Photosynthetic organisms (plants remove carbon dioxide CO2-increasing pH)<br />Underlying rock and soil type in a watershed determines the general pH of the system<br />
Dissolved Oxygen<br />The dissolved oxygen (DO) is oxygen that is dissolved in water. Therefore, DO analysis measures the amount of gaseous oxygen (O2) dissolved in water. <br />Oxygen gets into water by diffusion from the surrounding air, by aeration (rapid movement), and as a waste product of photosynthesis. <br />
Oxygen is a necessary element to all forms of life. DO is important to fish and other aquatic life. <br />Adequate dissolved oxygen is necessary for good water quality. Natural stream purification processes require adequate oxygen levels in order to provide for aerobic life forms. <br />As dissolved oxygen levels in water drop below 5.0 mg/l, aquatic life is put under stress. The lower the concentration, the greater the stress. Oxygen levels that remain below 1-2 mg/l for a few hours can result in large fish kills. <br />
When performing the dissolved oxygen test, only grab samples should be used, and the analysis should be performed immediately. Therefore, this is a field test that should be performed on site.<br />When doing this experiment, you might choose to compare water quality at two or more points on the same stream, in two or more different streams or lakes, or in a lake and a stream that runs into it.<br />