Students measure the dissolved oxygen content of water from several natural sources as well as the change in solubility with temperature. As will be seen, the probe contributes signif icantly to the oxygen dynamics. This experiment will sketch out the procedure for determining the dissolved oxygen do levels in water samples obtained from the charles river. Ap sample lab 12 dissolved oxygen biology junction. This experiment uses the azide modification of the iodometric winkler titration method. Like land animals, fish and shellfish require oxygen to survive. The minimum do level of 4 to 5 mgl or ppm is desirable for survival of aquatic life. The determination of dissolved oxygen content in water serves as the basis of bod test. However, the pipe material is dissolved by the formation of iron carbonate feco 3. Referencesfor more information hach company h 2 o university. Oxygen, a colorless, odorless, tasteless gas essential to living organisms, being taken up by animals, which convert it to carbon dioxide.
Techne range of do2 dissolved oxygen meters by jenway model 970 is a low cost hand held unit that is rated ip65 for portable use. The model 9200 dissolved oxygen meter is designed and constructed to resist the harshest of field, laboratory and industrial environments. In summer and fall, when the water temperature is high, the dissolvedoxygen concentration is often lower. Analyze the effects of various factors on the level of dissolved oxygen in a water sample e. Dissolved oxygen unit conversions at 21 celsius 70 f and 1 atmosphere 760 mmhg dissolved oxygen is usually reported in milligrams per liter mgl or as a percent of air saturation.
Dissolved oxygen and primary aquatic productivity laboratory 12 introduction dissolved oxygen levels are an extremely important factor in determining the quality of an aquatic environment. Pdf after performing this experiment, the student shall be able to. The two methods of dissolved oxygen measurement we will describe are the winkler titration method with azide modification and the membrane electrode. In winter and early spring, when the water temperature is low, the dissolved oxygen concentration is high. Temperature, ph and dissolved oxygen in this investigation, students will measure the air temperature, and the temperature, ph and dissolved oxygen of the water at their monitoring site. Dissolved oxygen gets into the water by diffusion from the atmosphere, aeration of the water as it tumbles over falls and rapids, and as a waste product of photosynthesis. You probably know that the air you breathe is not pure oxygen. In this demonstration, one student is showing his peers how to conduct the do test and read the results using comparison samples. We also predict that all of our experimental variables will contain more dissolved oxygen than our control, the distilled water. Oxygen forms compounds by reaction with practically any other element. In general, the concentration of dissolved oxygen in the water is broad. Experiments to show, 1 that various species of pond fish can live in water with a stratum of pure oxygen over the water, and 2 that they can stand a sudden transition from water with a low oxygen content to water of a relatively high oxygen content and the reverse. Determine the level of dissolved oxygen in a sample of water using winklers method. Allow the probe to stay submerged for 2 minutes, then repeat steps 57.
Maximum dissolved oxygen concentration saturation table. As the condensate is replenished, the pipes continue to corrode. Massachusetts institute of technology department of chemistry. Pdf knowledge of the dissolved oxygen o2 concentration in seawater is. Learn how to measure dissolved oxygen content using the winkler. Dissolved oxygen do levels in environmental water depend on the physiochemical and biochemical activities in water body and it is an important useful in. A dissolved oxygen tension of 100 % corresponds to a solution where the oxygen partial pressure is in equilibrium with air, that is, an oxygen saturated solution. Terrestrial environments hold over 95% more oxygen than aquatic environments. Biochemical oxygen demand, or bod, measures the amount of oxygen consumed by microorganisms in decomposing organic matter in stream water. The concentration of dissolved oxygen can be readily, and accurately, measured by the method originally developed by winkler in 1888 ber. Explain to students that they will be conducting an experiment to test the effect of increasing temperature on the concentration of dissolved oxygen found in water.
Langdon and others published determination of dissolved oxygen in seawater by winkler titration using the amperometric technique find, read and cite all the research you. Now imagine that a source of oxygen demanding wastes, such as feed lot. Candona subtriangulata has the highest minimum oxygen requirement of 5. For large deviations, the probe tends to respond faster for up responses than for down responses, lee and tsao, 1979. Measuring dissolved oxygen environmental measurement.
Water research center dissolved oxygen in water, streams. The concentration of dissolved oxygen, do, in an aquatic environment is an important indicator of the environments water quality. The mean requisite for dissolved oxygen by ostracodes falls within a very narrow margin of 7. Aquatic organisms for respiration obtain the oxygcn from water, where it remains in dissolved form. Find out about the winkler method for determining the dissolved oxygen content of water and plan an experiment to find the amount of oxygen in a sample of water.
Dissolved oxygen do determination measures the amount of dissolved. Knowledge of the dissolved oxygen o2 concentration in seawater is often necessary in environmental and marine science. Principle of analysis the chemical determination of oxygen concentrations in seawater is based on the method first proposed by winkler 1888 and modified by strickland and parsons 1968. Oxygen and fish behaviour how fish behave fish behavior. Students will explore the role of plants in the conversion of light energy into chemical energy. When oxygen is present, ferrous carbonate and bicarbonate decomposes. Oxygen enters the water from the air through rain, turbulence and wind, and through the photosynthesis of aquatic plants. Nov 25, 2014 cartoon, actual experiment then chemical calculation and explanation. Distilled water contains no organisms, is stagnant, and is kept at room temperature. Determine the level of dissolved oxygen in a sample of water using winklers.
Dissolved oxygen can also be determined with precision using oxygen sensitive electrodes. Geological survey twri book 9 4 do xthe amperometric method section 6. Determination of dissolved oxygen in sea water by winkler. This oxygen can be produced by the photosynthesis of aquatic plants and algae, or it.
Fill the given water sample in a glassstoppered 300ml bod bottle. Winklers method involves the oxidation of manganeseii hydroxide by the dissolved oxygen to form manganeseiii hydroxide. All of these physical factors, along with oxygen concentration, work together to increase diversity in aquatic habitats. Determination of dissolved oxygen in polluted waters huscap. At 4,000 meters in elevation,000 feet, the amount of dissolved oxygen in water is less than twothirds what it is at sea level. Andersen demonstrates the azidewinkler method of dissolved oxygen analysis. Be careful to avoid contact of the sample with air.
The determination of dissolved oxygen by the winkler. Dissolved oxygen is a key indicator of water quality as high dissolved oxygen is necessary to support life. Fourth grade lesson testing for dissolved oxygen betterlesson. Determination of dissolved oxygen the classical method for the determination of dissolved oxygen in aqueous solutions is known as the winkler method. Dissolved oxygen and primary aquatic productivity laboratory 12. It is not the oxygen that is part of the water molecule but rather oxygen gas. Minimum do requirements organism minimum dissolved oxygen mgl trout6. This lesson focuses on the importance of dissolved oxygen to a healthy aquatic ecosystem and how dissolved oxygen in water can be increased.
Dissolved oxygen probe tech tips with vernier duration. As this experiment reaches the endpoint, it will take only one drop of the titrant to. Dissolved oxygen do levels in environmental water depend on the physiochemical and biochemical activities in water body and it is an important useful in pollution and waste treatment process control. The effect of high concentrations of dissolved oxygen on.
Dissolved oxygen sensors there are two primary types of dissolved oxygen sensing technologies available. Dissolved oxygen concentration is reported in units of mgl, or milligrams per liter mgl is also referred to as parts per million ppm because a liter is grams of fresh water, and a. Pdf determination of dissolved oxygen in seawater by. Dissolved oxygen do is a measure of how much oxygen is dissolved in the water the amount of oxygen available to living aquatic organisms. Dissolved o2 measuring dissolved oxygen inside an active photosynthetic system after the ten minute period, shake the darkexposed glass container, open the cap and measure the dissolved oxygen with the probe as in step 1. Have students discuss whether warm water or cool water holds more dissolved oxygen. Cel212 environmental engineering second semester 2011. Dissolved oxygen environmental measurement systems. Cold water can hold more dissolved oxygen than warm water.
After performing this experiment, the student shall be able to. Understanding the chemistry of dissolved oxygen do measurement. Oxygen is a key component in cellular respiration for both aquatic and terrestrial life. Dissolved oxygen is necessary for the metabolic processes of almost every organism. What is biochemical oxygen demand and why is it important. A source of do is atmospheric oxygen infiltrate water body when dissolved oxygen in water is not. In fact, it is mostly nitrogen gas n2 with oxygen gas o2 dissolved in it. Dissolved oxygen the amount of oxygen dissolved and freely available in water is one of many measures of water quality, but an important one for aquatic life. Dissolved oxygen and aquatic primary productivity by. As the amount of dissolved oxygen drops below normal levels in water bodies, the water quality is harmed. Exploring photosynthesis measuring dissolved oxygen from. The amount of oxygen found dissolved in given water at a given temperature and pressure is known as the dissolved oxygen. A relevant experiment for the introductory laboratory journal of chemical education. Dissolved oxygen sensor dissolved oxygen tension is measured with a probe in the reactor liquid.
Dissolved oxygen is used as an indicator of the health of a water body, where higher dissolved oxygen concentrations are correlated with high productivity and little pollution. Waters with higher dissolved oxygen have ecosystems. Dissolved oxygen the dissolved oxygen do is oxygen that is dissolved in water. Organisms absorb the oxygen through structures such as gills or their skin. Healthy water should generally have dissolved oxygen concentrations above 6. April 12, 2017 2 quality control all dissolved oxygen meters will be maintained and operated in accordance with the manufacturers instructions and the sesd operating procedure for equipment inventory and management sesdproc108. Dissolved oxygen levels below 2 or 1 ppm will not support fish. Dissolved oxygen values shown in the table represent saturation for the corresponding temperature. In this experiment, you will use a dissolved oxygen probe to measure the concentration of dissolved oxygen in water.
Dissolved oxygen do refers to oxygen dissolve in water molecules state, do is vital for all higher aquatic life b. Measurement of dissolved oxygen as a determination of media. Calculation of oxygen capacity diffused aeration coarse or. Oxygen from the atmosphere is mixed into the water through diffusion. Oxygen gas dissolved in water is vital to the existence of most aquatic organisms. This lesson also illustrates how controlled experiments are prepared and conducted.
Dissolved oxygen in the aquatic habitat is an important requirement for survival. This method is based on the reaction between oxygen and a suspension of manganeseii hydroxide in a strongly alkaline solution. Pour the bottle contents down the drain when complete. For the determination of dissolved oxygen content in water by winkler method experiment. The procedure was first written up by a graduate student in 1888. Measuring dissolved oxygen environmental measurement systems.
Page 1 indian institute of technology delhi department of civil engineering cel212 environmental engineering second semester 20112012 laboratory experiment 6. The ph of the condensate is increased by reduction in the amount co 2 in solution. Two liters of untr eated deionized water were helium sparged and the dissolved oxygen was. A dissolved oxygen sensor can be used in the lab or in the field. In practice, most sensors do not measure the oxygen concentration but the dissolved oxygen tension, a quantity proportional to the oxygen partial pressure. Cel212 environmental engineering second semester 20112012. Place the cap on the bottle and shake it vigorously for 30 seconds.
Plan your 60minute lesson in science or human impact on earth with helpful tips from meredith gannon. Since the dissolution of air in water is an precipitate of mn oh2. Investigating the dissolved oxygen content of water. The determination of dissolved oxygen by the winkler method. A video of a student testing for dissolved oxygen can be found here. Dissolved oxygen is the oxygen present in water available to aquatic organisms. Dissolved oxygen in a stream may vary from 0 mgl to 18 mgl. Procedure for determination of dissolved oxygen in water.
Dissolved oxygen experiments like all animals, fish breathe oxygen. This is then reacted with iodide ions to liberate iodin e. A dissolved oxygen meter, water quality sonde or data logging system can be used to record measurement data taken with a do sensor. These all contribute to a lower dissolved oxygen concentration. Do sensors can be designed for biochemical oxygen demand bod tests, spot sampling or longterm monitoring applications. Predict the effect of water temperature on aquatic life. The dissolved oxygen concentration of seawater is defined as the number of milliliters of dioxygen gas o2 per liter of seawater ml l 1. Exploring photosynthesis measuring dissolved oxygen from aquatic plants lesson overview through this lesson, students will explore the process of photosynthesis by aquatic plants. This experiment was to determine the length of time required for helium sparging to reduce the dissolved oxygen level to the experimentally determined equilibrium level and below. In a healthy body of water such as a lake, river, or stream, the dissolved oxygen is about 8 parts per million. Similarly, oxygen is found dissolved in most water, especially where there is agitation on the surface. Study the effect of temperature on the amount of dissolved oxygen in water.
Some organisms, such as salmon, mayflies, and trout, require high concentrations of dissolved oxygen. Dissolved oxygen levels are an extremely important factor in determining the quality of an aquatic environment. Determination of dissolved oxygen by winklers method. All the gases of the atmosphere are soluble in water to some degree. If you have already obtained the dissolved oxygen results in the field, send the data sheets to your sampling coordinator. The winkler method is a technique used to measure dissolved oxygen in freshwater systems. Understanding the chemistry of dissolved oxygen do. A student laboratory experiment journal of chemical education. The amount of dissolved oxygen in a stream or lake can tell us a lot about its water quality. Mar 05, 2018 measurement of dissolved oxygen in water sample duration.
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