Dissolved Oxygen by the Winkler Method

 

dissolved oxygen lab report

Jan 30,  · The Winkler Method is a technique used to measure dissolved oxygen in freshwater systems. 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. REPORT Explain the reaction involved in the determination of dissolved oxygen in water using Winkler methods. Establish the relationship: 10 ‐cm3 of mol dm3 sodium thiosulphate = 1 mg 0 2. Report ‐the result in mg dm3 and as percentage saturation (refer to the table attached) REAGENTS. Environmental Chemistry of Boston Harbor – IAP Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science.


Dissolved Oxygen lab by Maggie Danicek on Prezi


Dissolved oxygen levels are an extremely important factor in determining the quality of an aquatic environment. Dissolved oxygen is necessary for the metabolic processes of almost every organism. Oxygen levels in aquatic environments are very vulnerable to even the slightest change. Oxygen must be constantly be replenished from the atmosphere and from photosynthesis, dissolved oxygen lab report.

There are several factors that effect the dissolved oxygen levels in aquatic environments. Temperature is inversely proportional to the amount of dissolved oxygen in water. As temperature rises, dissolved oxygen levels decrease. Wind allows oxygen to be mixed into the water at the surface. Windless nights can cause lethal oxygen depletions in aquatic environments. Turbulence also increases the mixture of oxygen and water at the surface. This turbulence is caused by obstacles, such as rocks, fallen logs, and water falls, and can cause extreme variations in oxygen levels throughout the course of a stream.

The Trophic State is the amount of nutrients in the water. There are two classifications: oligotrophic and eutrophic. Oligotrophic lakes are oxygen rich, but generally nutrient poor. They are clearer and deeper than eutrophic lakes and are younger. Oxygen levels are constant. Eutrophic lakes are more shallow and nutrient rich. The oxygen levels constantly fluctuate from high to low.

Primary production is the energy accumulated by plants since it is the first and basic form of energy storage. The flow of energy through a community begins with photosynthesis.

The energy remaining after respiration and stored as organic matter is the net primary production, or growth. The equation for photosynthesis is as follows:. There are two ways to measure primary production, the oxygen method and the carbon dioxide method.

The oxygen method uses a dark and light bottle to compare the amount of oxygen produced in photosynthesis and used in respiration, dissolved oxygen lab report.

Respiration rate is determined by subtracting the dark bottle from the initial bottle. The carbon dioxide method places a transparent plastic bag over one sample and a dark plastic bag over the other. Each bottle is set up so that air is drawn through the enclosure and passes over carbon dioxide-absorbent material.

The amount of carbon under the dark bag is respiration, while the amount of carbon under the transparent bag is the amount of photosynthesis minus the amount of respiration. There are three main gases dissolved in aquatic environments: nitrogen, oxygen, and carbon dioxide. Altitude may affect the p value of the equation. Higher altitudes decrease the solubility of gases in water.

Temperature also has an affect, as temperature rises, solubility decreases. Salinity, the occurrence of various minerals in solution, also lowers the solubility of gases in water. The method used to determine the amount of dissolved oxygen in the water is the Winkler titrametric method. It involves a series of chemical reactions which ends with a quantity of free iodine equal to the amount of oxygen in the sample.

The iodine is dissolved oxygen lab report titrated with thiosulfate to find this quantity. The temperature and amount of light an aquatic environment receives greatly affects the dissolved oxygen levels, along with the amount of primary aquatic productivity. Dissolved oxygen lab report part of the lab required a sample bottle of water from a natural source, a BOD bottle, thermometer, dissolved oxygen lab report, mangonous sulfate, alkaline iodide, thiosulfate, a 2-mL pipette, sulfuric acid, dissolved oxygen lab report, a mL sample cup, a white piece of paper, starch solution, and a nomograph.

Part B required a sample bottle of water from a natural source, 7 BOD bottles, aluminum foil, 17 cloth screens, dissolved oxygen lab report, rubber bands, a light, thermometer, concavity slides, dissolved oxygen lab report, light microscope, mangonous sulfate, alkaline iodide, thiosulfate, a 2-mL pipette, sulfuric acid, a mL sample cup, a white piece of paper, starch solution, dissolved oxygen lab report, and a nomograph.

The sample bottle was filled completely so that there were no air bubbles in the bottle. A BOD bottle was filled with the sample water until it contained no air bubbles.

Eight drops of mangonous sulfate were added to the bottle. Next, eight drops of dissolved oxygen lab report iodide was added and the precipitate manganous hydroxide was formed.

The bottle was inverted several times and then allowed to settle until the precipitate was below the shoulders of the bottle. While the solution was settling, a 2mL pipette was filled with thiosulfate. A scoop of sulfuric acid was added, and the bottle was inverted until all of the precipitate dissolved. The sample turned a clear yellow. The cup was placed on a white sheet dissolved oxygen lab report paper so that the color changes could be observed.

The sample was then titrated with the thiosulfate. One drop of the titrant was added at a time until the color changed to a pale yellow color. A second sample bottle was filled from a natural source making sure there were no air bubbles.

Seven BOD bottles were filled completely with the sample with no air bubbles. The first bottle was labeled 1-Initial. The second bottle served as the dark bottle dissolved oxygen lab report was labeled 2-Dark. Bottle 2 was wrapped completely in aluminum foil so that it received no light. The other five bottles were wrapped in screens to produce the desired light intensity.

Bottle 3 had no screens, bottle 4 had 1 screen, bottle 5 had 3 screens, bottle 6 had 5 screens, and bottle 7 had 8 screens. The screens were held in place with rubber bands. Bottles were placed under a light source and left overnight. Bottle 1 was fixed by following the Winkler method. It was left at room temperature until the other samples were processed. A wet mount was observed under a light source, so that the different organisms present could be identified.

The next day, bottles were fixed by following the same method used on Bottle 1. The dissolved oxygen levels were determined in each of the seven bottles by titrating. The respiration data from Part B was converted to carbon productivity. The dissolved oxygen lab report was graphed with comparison to water depths.

As temperature goes up the solubility of oxygen in water goes down. They are inversely proportional. Would you expect to find a higher dissolved oxygen content in a body of water in winter or summer? Oxygen levels would be higher in the winter because the solubility of oxygen in water is higher at lower temperatures.

List and discuss three factors that could influence the dissolved oxygen concentration of a body of water. Salinity-The occurrence of various minerals in solution lowers the solubility of oxygen in water.

Do you think it would be wise to stock a pond with game fish if it had a dissolved oxygen content of 3ppm? Why or why not? It would not be dissolved oxygen lab report to stock a pond with an oxygen level of 3ppm with game fish because their optimal levels range from 8 to 15ppm.

A concentration of dissolved oxygen less than 4ppm is stressful to most forms of aquatic life. Each sample was given a certain amount of light by the use of aluminum foil and screen. Bottle 2 received no light, because it was covered with aluminum foil. Lake 2 would be more productive because there is more oxygen available in the lower layers than in Lake 1. Primary productivity is measured by the amount of dissolved oxygen available in the water.

This shows the amount of oxygen produced by photosynthesis and the amount used by respiration. The Part A experiment was affected mainly by human error and inexperience with the Winkler method. The sample may have been over exposed to the dissolved oxygen lab report or the dissolved oxygen lab report may have changed before the fixing procedure was finished.

The original Part B experiment performed was unsuccessful. There were substantially more decomposing bacteria than photosynthetic organisms in the water sample use, dissolved oxygen lab report. The initial dissolved oxygen level was only 0. The amount of oxygen was so low that it was unable to form the free iodine and could not be titrated.

This left no quantifiable data to use in graphs and tables. Temperature is inversely proportional to the solubility of gases in water. As temperature rose the dissolved oxygen levels should have decreased.

Part B of the lab was used to measure dissolved oxygen concentration, gross and net productivity, and respiration rate of the water samples. It also demonstrated the effect of light and nutrients on photosynthesis. In aquatic environments oxygen production and oxygen usage must be balanced to prevent anoxia. In the original experiment this balance was interrupted by the limiting of light by screens and aluminum foil.

The amount of respiration in all of the bottles exceeded the amount of photosynthesis occurring. This was due to the types of organisms present in the sample, which was mainly decomposing bacteria and protozoan.

The experiment was correct in its methods however the data received was not quantifiable. This absence of sufficient oxygen in the water samples is dissolved oxygen lab report indicator of poor water quality, which may require further investigation. Excess pollution or dumping of wastes into the water sample is a suspected cause of the poor water quality.

 

 

dissolved oxygen lab report

 

CEL Environmental Engineering Second Semester Laboratory Experiment 6: Dissolved Oxygen (DO) Objective: Determine DO content of a given sample Background: Dissolved oxygen (DO) levels in environmental water depend on the physiochemical and. Environmental Chemistry of Boston Harbor – IAP Lab 1: DETERMINATION OF DISSOLVED OXYGEN BY WINKLER TITRATION 1. Background Knowledge of the dissolved oxygen (O2) concentration in seawater is often necessary in environmental and marine science. Jan 30,  · The Winkler Method is a technique used to measure dissolved oxygen in freshwater systems. 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.