Soil pH Along the Kinnickinnic River and Lake Michigan

Erica Isaacson and Debora Hernandez

November 8th, 2012

 

Abstract

We tested the pH difference of soil from Lake Michigan and from the Kinnickinnic River. We hypothesized the soil near the lake will have a higher pH level than the soil near the river. In our experiment the pH of the soil by Lake Michigan was not significantly different (P = 0.0811) than the pH of the soil by the Kinnickinnic River.

Keywords: soil pH, Kinnickinnic River, Lake Michigan

Introduction

To determine whether the pH of the two different types of soil is acidic, basic, or neutral, one would need to measure the molar concentration of hydrogen ions in a solution. The pH scale ranges from 0 to 14. 0 to 6 is considered to be acidic meaning the substance has a high concentration of hydrogen ions. The indicator of having a neutral pH is when the pH is at a 7. A pH of 8 to 14 is considered to be basic meaning it has a low concentration of hydrogen ions. We hypothesized that the soil near the edge of Lake Michigan will have a higher pH than the soil near the Kinnickinnic River because waves of lake water wash up on the shore and sink into the soil near it. Rainwater can be a factor on the soil pH because it has an acidic property but environmental CO2 affects the acidity of rainwater and it also gets its acidic properties from pollution (Huo et al, 2012). Since rainwater has a more of an acidic pH the soil near the river would be more acidic because rain is one of the few factors the river has affecting the pH of the soil surrounding it. Although it rains by the lake, the water contains a constant level of basic properties. Since the water washes up onto the shore, the soil along the lake becomes basic. In addition to rainwater, soil pH can also vary because of the different nutrients found in soil such as zinc, iron, aluminum, magnesium, nitrogen, potassium, and calcium in order for vegetation to grow, and for photosynthesis of plants to occur (Boul, 1995). Many nutrients have acidic properties causing the soil around vegetation to have a lower pH.  Since the river has a higher amount of vegetation near the edge compared to the lake, the soil pH around the river will contain more acidic properties.  When studying pH at Lake Michigan, Young, Moon, and Choi (2012) found that pH increased because of neutralization of the alkaline soil caused by coniferous trees.  This study shows that the lack of pine trees around the lake causes the soil to develop more basic properties.  

Materials and Methods

On Tuesday October 30th, 2012 at 1300 hours we drove to Jackson Park on 3500 W. Forest Home Ave, Milwaukee, WI to collect ten samples of soil near the Kinnickinnic River.  Using a Westcott® meter stick, we started one meter from the edge of the river, collected sample number one, and put it in a plastic bag. Then, we measured one meter from sample number one continuing down the edge of the river to collect sample number two.  To collect the next eight samples we used the previous stated steps, continuing to measure one meter from the previous sample taken and one meter from the edge of the river.  We put each sample in numbered plastic bags. We then drove to Bradford Beach 2400 N. Lincoln Memorial Dr. Milwaukee, WI at 1430 hours to gather ten different data samples. We started one meter from the receding shoreline to collect sample number one. Using the same sample collecting process as the Kinnickinnic River, we gathered the next nine samples at Lake Michigan and put all the samples into individual bags. To test the pH of the soil samples for both sites we used a LaMotte soil test kit.  We carried the soil from the areas near Lake Michigan and Kinnickinnic River, and placed them in the kit to compare the pH of the two different soil types.  The equipment needed to do a pH test on soil is a test tube, pH Indicator Solution, soil, 0.5/g spoon, test tube cap, and pH color chart. We filled the test tube to line four with pH Indicator Solution, which was the designated line in the instruction manual to determine soil pH. We then took three 0.5/g scoops of soil and poured it into the test tube. We caped it, and shook it for a minute. We then let the test tube stand for 10 minutes and then matched the color of the soil solution to the pH color chart. Finally, we recorded data and continued to test the remaining of the soil samples. At the end we had 10 trials for each location that totaled to 20 trials of both locations.  The statistical tests we used to determine the statistical difference between the two testing sites was the T-test using type 3 with two tails, calculated in Microsoft Excel 2009.

Results

There was no significant difference between the soil pH of Lake Michigan and the pH of the soil from the Kinnickinnic River (Fig. 1, P = 0.0811).  However, the average pH for the soil near Kinnickinnic River (Mean = 7.7, S.E.= 0.483) was lower than the soil pH near Lake Michigan (Mean = 8, S.E.= 0.0).

P-value = 0.0811
 
 

    Figure 1. (Mean+/-S.E.) pH of soil one meter from Kinnickinic River and one meter from Lake Michigan.

Discussion

Soil pH in this experiment did not show a significant difference between the soil near the Kinnickinnic River and Lake Michigan. Our results refuted our hypothesis that the soil near Lake Michigan will have a higher pH level than the soil near the Kinnickinnic River. One reason why our hypothesis was refuted could be because we didn’t consider that it rains everywhere, so the rainwater might have affected both the soil of lake and river. Rainwater can leach down into the soil or become absorbed by vegetation around it causing the pH of the soil to stay higher at the river (Huo et al, 2012).  Other researchers, such as Wood and Lawrence, studied the Costa Rican rain forest, and found soils that were drier had a higher pH value than those that were wet.  When wet microbial cell walls get broken down and release phosphorus, which is acidic making wet soil to have a lower pH (Wood & Lawrence, 2008).  This may be one reason explaining why the soil near the river had a high pH value, and resulted in not having a significant difference to the soil near the lake. 

If this experiment were to be tested, again some changes would need to be made in order to improve it.  One change would be to test the pH of soils when they are wet, since wet soils tend to have a lower pH than drier soils.  This factor could yield in a significant difference between the soil near the lake and the river.  A limitation to this would be in knowing how much water we would add to the river soil, so that both types of soil will have the same amount of moisture.  We think it also might be beneficial to test soils during the same time of the day.  In addition, testing the pH at the sites rather than bringing them back to school to test could have affected the pH of the samples. This might be helpful to see how much temperature affects the pH of soil.  A limitation to this would be each person performing the experiment, which is a risk for human error to occur when collecting data.

Literature Cited

Boul, W.S.  (1995). Sustainability of Soil Use.  Annual Review of Ecology and Systematics. Vol. 26: pp. 25-44.  Retrieved on October 15, 2012 from: JSTOR database.

Huo, M, Sun, Q, Bai, Y, Li, J, Xie, P, Liu, Z, and Wang, X. (2012). Influence of airborne particles on the acidity of rainwater during wash-out process. Atmospheric Environment. Vol. 59: pp.192–201. doi: 10.1016/j.atmosenv.2012.05.035 Retrieved on October 15, 2012 from: Science Direct Database.

Wood, T., & Lawrence, D. (2008). No short-term change in soil properties following four-fold litter addition in a Costa Rican rain forest. Plant & Soil, 307(1/2), 113-122. doi:10.1007/s11104-008-9588-2.

Young, Moon, C., & Choi, Y. D. (2012). Structure, Species Composition, and Soil Characteristics in a Chronosequence of Jack Pine (Pinus banksiana Lamb.) Stands on the Southern Shore of Lake Michigan. American Midland Naturalist, 168(2), 408-426.