Water Temperature and Oxygen Saturation in Relation to Barometric Pressure

 

 

Michele Durocher

Frances Quintanilla

10/30/98

 

 

 

 

 

 

Abstract

 

The purpose of our experiment was to test theoretical values of dissolved oxygen in a given body of water versus atmospheric pressure and compare them to actual data we gathered for dissolved oxygen based on temperature and atmospheric pressure. We traveled to the Jackson Park lagoon near Alverno College, to measure dissolved oxygen and water temperature with the YSI-85 instrument. In addition, we referred to the Milwaukee Journal Sentinel to gather barometric pressures for the days that we measured the dissolved oxygen and water temperature in Jackson Park lagoon. Our results indicated that our measurements did not coincide with the theoretical values. We concluded that an abundance of algae growth and the amount of ducks that frequent the pond (fecal matter) were contributing factors for the low oxygen levels.

 

Keywords: water quality, dissolved oxygen, water temperature, atmospheric pressure, and algae

 

Introduction

Dissolved oxygen levels increase as temperature decreases, but barometric pressure effects the levels also (Eaton et al, 1995). The pressure essentially "pushes" oxygen into the water. Temperatures that fluctuate and varying pressures effect the levels of oxygen in water. Our purpose was test Jackson Park lagoon over a period of 4 weeks for dissolved oxygen, temperature, and barometric pressure. These results were then compared against a chart that gave the theoretical values for the oxygen levels based on temperature and barometric pressure (USGS, 1994). Our hypothesis was the data that we collected would be lower than the theoretical values (see the next page). We based our theory on the fact that there was a lot of plant life, such as algae, and several species of animals (birds) that use and habituated the lagoon during our tests.

 

Methods

The area where we collected our data was the Jackson Park Lagoon. For dates and times regarding our collection please refer to the results on page number five. We took five measurements at the above location.

Our methods included using a YSI-85 to measure temperature of the water, which also measured dissolved oxygen at the same time. Field operation of the instrument included calibration for oxygen, then measuring dissolved oxygen (Shelton 1994). To

 

 

 

 

 

Table 1 contains the theoretical values of dissolved oxygen in relation to water temperature and dissolved oxygen. We used this chart to compare our actual data gathered regarding dissolved oxygen values in relation to water temperature and atmospheric pressure at Jackson Park Lagoon (USGS, 1994)

 

Table 1: Dissolved Oxygen Values in relation to Water Temperature vs. Atmospheric Pressure

[Solubility of dissolved oxygen is in mg/L. mm/Hg, millimeter of mercury;

C, degree Celsius]

___________________________________________________________

Water Atmospheric pressure (mm/Hg)

Temp -----------------------------------------------------------------------------------------

(C) 760 740 720 700 680 660 640 620 600 580

___________________________________________________________

0.0 14.6 14.2 13.8 13.4 13.0 12.7 12.3 11.9 11.5 11.1

2.0 13.8 13.4 13.1 12.7 12.3 12.0 11.6 11.2 10.9 10.5

4.0 13.1 12.7 12.4 12.0 11.7 11.4 11.0 10.6 10.3 10.0

6.0 12.4 12.1 11.8 11.4 11.1 10.8 10.4 10.1 9.8 9.5

8.0 11.8 11.5 11.2 10.9 10.6 10.2 9.9 9.6 9.3 9.0

10.0 11.3 11.0 10.7 10.4 10.1 9.8 9.5 9.2 8.9 8.6

12.0 10.8 10.5 10.2 9.9 9.6 9.3 9.0 8.8 8.5 8.2

14.0 10.3 10.0 9.7 9.5 9.2 8.9 8.6 8.4 8.1 7.8

16.0 9.8 9.6 9.3 9.1 8.8 8.5 8.3 8.0 7.7 7.5

18.0 9.4 9.2 8.9 8.7 8.4 8.2 7.9 7.7 7.4 7.2

20.0 9.1 8.8 8.6 8.3 8.1 7.8 7.6 7.4 7.1 6.9

22.0 8.7 8.5 8.2 8.0 7.8 7.5 7.3 7.1 6.8 6.6

24.0 8.4 8.2 7.9 7.7 7.5 7.2 7.0 6.8 6.6 6.3

26.0 8.1 7.9 7.6 7.4 7.2 7.0 6.8 6.5 6.3 6.1

28.0 7.8 7.6 7.4 7.2 7.0 6.7 6.5 6.3 6.1 5.9

30.0 7.5 7.3 7.1 6.9 6.7 6.5 6.3 6.1 5.9 5.7

 

 

calibrate the instrument we used clean water to wet the sponge in the probe storage area, and poured off excess. Then we followed proper instructions to measure dissolved oxygen (DO). We then submerged the tip of the instrument in the water and moved it at about a rate of one foot per second, to get the proper reading on the instrument.

In addition, we obtained barometric pressure data from the weather section included daily with Milwaukee Journal Sentinel on the days that we took our measurements. Because weather reports in the newspaper are reported in inches of mercury, we had to convert all of the given data in inches of mercury to mmHg to correspond with the above theoretical data table.

Results

Table 2*:

Date

Time

MmHg

Temperature (C° )

% Oxygen Saturation

7-Oct

10:30

765

16

6.15

14-Oct

10:30

762

13.1

4.5

21-Oct

10:30

771

12.4

5.75

30-Oct

10:30

762

12.1

6.27

3-Nov

10:30

769

10.1

7.7

*Refer to meta-data sheet for actual data concerning inches of mercury.

 

 

Discussion

The data represented by the table regarding atmospheric pressure, temperature and percent oxygen saturation does not seem to hold any specific patterns. Unfortunately, our atmospheric pressure is above the theoretical values given in the table. We did infer that if the table continued to our values the dissolved oxygen would still continue upward. The percent oxygen saturation decreased at first and then proceeded to increase. The atmospheric pressure on the other hand, stayed mostly at thirty with minor fluctuations. The temperature continued downward, and we expected that due to the decreasing air temperature.

However, the percent dissolved oxygen in relation to air pressure and temperature at Jackson Park lagoon is still lower than the theoretical values chart given on page 4. The results that we saw coincided with our hypothesis that the dissolved oxygen levels would be lower than the theoretical values. We believe that many factors affect how well a body of water can hold oxygen and to what extent. Over growth of algae, evident by opaque water, contributes to this factor. As the algae population becomes more dense, the dead algae sinks to the bottom and becomes food for bacteria that live on the bottom. Bacteria that feed on the algae require oxygen for their metabolism. If more algae sinks to the bottom, then there is more food for the bacteria, thus creating a growing population of bacteria utilizing the oxygen (USGS, 1994). It has been shown that dissolved oxygen in water is related to algal growth dynamics (Lee, Wong. 1997). Also contributing to this factor is that sunlight can not penetrate to deeper depths thus limiting photosynthesis. The combined factors led to us having low levels of dissolved oxygen in the Jackson Park lagoon.

Although we did not test for nitrogen concentration in the lake, it may have been a good idea. We feel that in the future we would like to consider this variable in relation to dissolved oxygen, as well as, the atmospheric pressure because of the many species that frequent the area. Many ducks and geese use the lagoon as a "wayside" on their migratory path south for the winter. We believe that measuring nitrogen in relation to dissolved oxygen would be an interesting experiment.

Camp, Thomas. 1963. Water and its impurities. Rienhold Publishing. NY. 290-94

Colinvaux, P. 1993. Ecology 2. John Wiley & Sons. NY. 552.

Eaton, A.; Clesceri, L.; Greenberg, A. 1995. Standard methods for the examination of water wastewater. United Book Press. MD.

Shelton, Larry R. 1994. Us Geological Survey: Field guide for collecting and processing stream-water for the National Water Quality Assessment Program. 38-42. Available URL: water.wr.usgs.gov/pnsp/perst.rep/sw-t.html

Lee, J.H.W.; Wong, P.P.S. 1997. Water quality model for mariculture management. Journal of Environmental Engineering. 123:1136-1142.