The Difference in pH of Lakes and Ponds in the Milwaukee Area

Miranda Petrick and Carina Macorncan

Abstract

We tested the difference in pH in the water of Lake Michigan and ponds in the Milwaukee area. We recorded the pH levels of eight sites at Lake Michigan and eight ponds across Milwaukee, There was a significant difference between the pH level in the lake and ponds We found that the lake was more acidic than the ponds (P=0.002).

Keywords: pH, lake, ponds, acidic, neutral

Introduction

pH is one of the many characteristics that are helpful in determining the quality of water for living. pH is a measure of whether water is acidic or basic (Stevens, 2009). pH in this case measures the concentration of hydrogen ions in a chemical solution to determine the solution's relative acidity or alkalinity (WDNR, 2010). In Wisconsin, bodies of water have a pH that ranges from 4.5 to 8.4 (WDNR, 2009). pH can vary in bodies of water depending on a variety of factors. One of the factors varying pH is the plant life surrounding the body of water because plants use photosynthesis and respiration as processes of energy.

Plants and other vegetation depend on photosynthesis and respiration for survival, these both can change the amount of CO₂ in the water. When the plants use solar radiation, water and CO₂ to produce sugar and oxygen, it results in a reduction of acidity and an increase in pH (WDNR, 2009). The connection between pH and photosynthesis is that the vegetation creates a higher pH level. Here, we can infer that because of the greater surrounding vegetation in ponds they will be less acidic than the lake.

Acid rain can lower the pH because of carbon dioxide in the air dissolving in water to produce a weak carbonic acid solution (WDNR, 2009). Filtering water and debris from waste in water can also change pH. We hypothesized that the pH level in the lake will be more acidic while the ponds will be less acidic.

Methods and Materials

On October 30, 2011 between approximately 1300 hours and 1500 hours we conducted our study in Milwaukee, Wisconsin. It was approximately 6 degrees Celsius during the fall season and was windy and rainy. To start we drove the following eight different parks to test the pH of the ponds: Jackson Park, McCarty Park, Greenfield Park, Whitnall Park, Wilson Park, Scout Park, Humboldt Park and Mitchell Park. We relied on the direction of a Garmin© global positioning system to get us to our locations. We took three samples at each pond with pH strips and then recorded our data in a notebook. To determine our sites at each pond we chose an area with the least amount of visible leaf litter and easy access to test the water. To test the lake water we chose a starting point along Bradford Beach. Our test sites were chosen based on accessibility to the water. We then measured the pH every twenty meters of the lake for a total of eight sites and measured each site three times. After measuring the pH we recorded our data and then used the average of the three samples taken at each site to construct a graph. The data was analyzed using a 1-tailed, type 2 T-test on Excel © for Windows 2007©.

Results

There was a significant difference between the pH levels in the lake and ponds (Fig. 1, P=0.002).The results show that the pH of the ponds was more basic than the pH of the lake. The mean pH of the ponds was 5.9 with a standard deviation of 0.34. The mean pH of the lake 4.9 was with a standard deviation of 0.79.

Figure 1. Mean (+/- S.D.) of pH in water of ponds and lake.

Discussion

Our data supported our hypothesis that the pH level in lake water will be more acidic while the pH level in pond water will be less acidic. The difference between the two groups was significant (P value= 0.002). If we were to repeat this experiment again we would use a different tool to read pH. Our interpretations of the color could have been inaccurate and we feel that if we used a pH meter with electronic readings it could be more accurate because it has a broader range. Also, we would like to test different bodies of water across the world to compare the pH levels. We would test water from different rivers, streams and oceans.

There might be some limitations to this study like the pH strips. We found that it was difficult to read the exact measurements of color on the pH strips so this could be one possible influence on error. Another factor that could have affected the pH levels was weather, the day of the experiment it was raining. Acid rain can affect the pH making it much higher than normal. This acid rain can be a result of pollutants from motor vehicles, chemical plants and other factories (Shea, 2008). If a body of water becomes more acidic, there is a chance that only certain organisms will be able to survive. This can cause a loss in species diversity and reproductive success (WDNR, 2009). Finally, the day of the experiment was very windy which could have blown any rain into the ponds or lakes that may have been somewhat acidic resulting in a change in pH.

Literature Cited

Shea, S. (2008). acid Rain, Rain Go Away: Some Adirondack lakes are showing promising signs of recovery. New York State Conservationist, 62(5), 12-17. Retrieved from EBSCOhost.

Stevens, R. (2009). Fish Pond Water Quality: As Simple as Chemistry 101. Retrieved from http://noble.org/AG/Wildlife/Fish-Pond-Water/index.html

Wisconsin Department of Natural Resources. (2009).pH-acidity-understanding lake data. Retrieved from http://dnr.wi.gov/lakes/publications/under/acidity.htm

Wisconsin Department of Natural Resources. (2009). Carbon dioxide-understanding lake data. Retrieved from http://dnr.wi.gov/lakes/publications/under/carbondi.htm

Wisconsin Department of Natural Resources. (2010). Acid rain in Wisconsin. Retrieved from http://dnr.wi.gov/air/aq/global/acidrain.htm