Nitrate Levels (ppm) in Southeastern Wisconsin Lakes and Ponds

By: Tammy Berger and Erica Livermore

 

 

Abstract:

 

            We tested whether the nitrate concentration would be higher in ponds rather than in lakes in Southeastern Wisconsin since ponds have a smaller amount of water than lakes.  We used a nitrate electrode and meter for our detection.  Our results showed no significant difference in the concentration of nitrate between lakes and ponds in Southeastern Wisconsin. Our P-value was 0.876.

Keywords: Lakes, Ponds, Nitrate, Eutrophication, Nitrogen

 

 

Introduction:

 

Nitrogen is an essential nutrient for all living things. Nitrogen allows plant and animal cells to create amino acids and proteins. Nitrogen is found in the atmosphere in the gas form N2. The nitrogen is converted by plants and animals in forms that they can use through nitrogen fixation (Rice University, 2000). The N2 form of nitrogen comes from lightning and from soil microbes (Moffat, 1998). Nitrogen is also found in rain, snow, fog, water runoff, soil (University Corporation for Atmospheric Research, 2003) and in animal and human waste (Environmental Literary Council, 2006).

            Nitrates are the NO3 form of nitrogen. Nitrates are inorganic and can be formed naturally from decaying plants and animals (University Corporation for Atmospheric Research, 2003). Nitrates allow plants to grow and aids in their reproduction. Nitrogen is called a limiting nutrient because when it is naturally occurring there is not an abundant amount. Aquatic plants and algae use the available nitrogen to grow and reproduce, but once the nitrogen is used the plants and algae begin to die. Therefore, the nitrogen is a limiting nutrient (University Corporation for Atmospheric Research, 2003).

            Nitrogen levels have increased due to human activity. With the added pollution and invention of fertilizers, nitrates are abundant and are causing problems in our area lakes, streams, and ponds. Nitrates are also found in fossil fuels. There is an over abundance of nitrates entering our area water ways (Water Watch, 2006). Another aspect that influences nitrate levels is poorly functioning or poorly located septic systems, and industries (Kevern, 1996).

When nitrates are added to lakes, ponds, and streams the lakes will experience rapid growth. With the added nitrates, the plants and algae thrive and continue to grow. This process is called eutrophication. This can reduce water clarity, water quality, and can kill other organisms in the water (University Corporation for Atmospheric Research, 2003). When excessive plant and algae growth occurs, the oxygen level in the lake depletes. When the algae and plants start to die off, there is an overabundance of decay occurring. As they decay the oxygen levels in the lake deplete because bacterial and other microorganisms that aid in the decaying process use the oxygen. This causes death in other organisms living in the lake, pond, or stream, because they need the oxygen to survive (Moffat, 1998). The abundance of algae that grow due to the availability of nitrates in the water also blocks the sun from reaching other organisms that may be living below the water surface. This can cause other organisms to die because they may be dependent on the sun for their necessary processes (Environmental Literacy Council, 2002).  The over abundance of aquatic plant life is usually seasonal. This is dependent on when farmers are fertilizing fields and when people are fertilizing lawns near water ways (Moffat, 1998). The hypothesis that we tested was ponds will have a higher concentration of nitrates parts per million, and lakes will have lower nitrate levels parts per million. We tested this hypothesis because we thought that the size of the body of water would have an impact on the nitrate levels that were in the sites that we tested.

 

Materials and Methods:

            On October 9, 2006 and October 16, 2006, between the hours of 11:00am and 5:30pm we drove around to ten different locations throughout Southeastern Wisconsin.  Our stops included South Shore Park in Milwaukee, Pewaukee Lake in Pewaukee, Mukwonago Pond in the Vernon Wildlife Area of Mukwonago, Glendale Road Pond in Waukesha, Heyer Elementary Pond in Waukesha, Minooka Park Pond in Waukesha, Mill Pond in East Troy, Booth Lake in East Troy, Big Muskego Lake in Muskego, and Wind Lake in Wind Lake. 

Using the Orion nitrate electrode model number 93-07 and the Orion meter model 290A, we measured the concentration of nitrate at each site.  After inserting the electrode cable into the meter, distilled water was used to clean the electrode and then it was shaken dry.  The sensing module was then attached to the electrode by screwing it on counter clockwise.   The outer body was filled with Optimum Results F filling solution, Orion Cat. No. 900046, to just below the fill hole.  The sensing module was then grasped and shaken vigorously to ensure no bubbles were on the inner surface. 

The sensing module was taken out to two meters using the Keson 50 Meter graduated metric 2 sided tape measurer, from the shoreline of each testing site and placed into the water.  The Orion meter was turned on and its mode changed to concentration for a reading.  After the numbers had stopped fluctuating a measured reading was taken and written down.  The Optimum Results F filling solution was then let out of the Orion nitrate electrode by unscrewing the sensing module.  The Orion nitrate electrode and sensing module were then rinsed with distilled water thoroughly and dried off.  Our data was then analyzed using Microsoft Excel Spreadsheet.    

 

Results:

 

            The mean nitrate levels in the five lakes that we tested were 2.00435 ppm.  The mean nitrate levels for the five ponds tested were 1.7176 ppm.  A T-test was preformed and this showed that we had a P-Value of 0.876, which means that there was not a statistically significant difference between the nitrate levels in the lakes and the ponds that were tested (Figure 1).  Our lowest nitrate reading in (ppm) was Wind Lake, which had an average nitrate level of 0.04025 ppm.  Booth Lake had the highest nitrate level out of all of the lakes and ponds that were tested.  The average nitrate level in Booth Lake was 8.38 ppm (Table 1, Figure 2). This data does not support our hypothesis.

 

Table 1: The data collected in ppm at the ten test sites and statistical tests 

Lake Michigan

Pewaukee

Lake

Booth

Lake

Big

Muskego

Lake

Wind

Lake

Mukwonago

Pond

 

Glendale

Pond

Hyer

Elementary

Pond

Minooka

Pond

Mill

Pond

0.295

0.3735

8.38

0.933

0.04025

0.2

0.1185

1.9345

2.39

3.945

 

Standard Deviation

Lakes

Ponds

 

3.578964295

1.606292992

P-Value

0.875954398

 

 

 

 

Figure 1: The average nitrate levels (ppm) of the five lakes and five ponds that were tested.

 

 

Figure 2: The nitrate levels (ppm) for each site tested.

 

 

Discussion:

 

            The nitrate level in lakes versus the ponds tested was not statistically significant and did not support our hypothesis.  There are many factors that may have contributed to our results.  One factor that could have contributed to the results that we received is the season that we preformed testing.  If we would have tested in the peak of spring and summer, around June our results may have looked much different.  Our nitrate readings could possibly be higher due to heavy fertilizing of crops, and fertilizing of lawns.  With the more prevalent amount of fertilizers in the soil, the water from the fields and lawns would runoff into the waterways.  Some of the lake homes are only occupied in the summer.  The amount of fertilizers that are used on the lawns would decrease when people leave to go back home.  Also, people fertilize in the summer and not in the winter due to the climate, that we inhabit.  The grass and fields are covered with snow in the winter.

            Pewaukee Lake has some people that occupy their homes year round, but a majority of the homeowners are only there for the summer season.  This could be a reason why the levels were low in this lake.  There is a farm field across the street from the area from the test site.  The property is on the hill that slopes downward from a farm field.  During the spring and early summer we would expect the nitrate levels could be higher due to water runoff from the farm field.

            Heyer Elementary School Pond is located next to a soccer field.  The nitrate levels seemed to be higher in this pond (Figure 2).  This could have been a result of fertilizer that was used on the soccer field. Minooka Pond is located in a park.  The nitrate levels in this pond were also higher than others tested (Figure 2).  The higher level of nitrates could be occurring due to fertilization of the grassy areas of the park. Another factor that could be contributing to the nitrate level was animal feces. There were a lot of geese in the area when the tests were taken. This was also true at the Heyer Elementary School test site.

            Farm fields surrounded the Mukwonago pond. However, the nitrate levels averaged 0.2 ppm (Figure 2). We expected the levels to be higher because it was in an agricultural area. The reason that the nitrate levels could have been lower is because it is not really the season for farmers to be fertilizing the land. The pond is located on the Vernon Wildlife area. There may be more restrictions about fertilizers used by farmers because it is located on protected land. The DNR was testing the water on the same day in which we were. We did not have an opportunity to ask them what they were testing for but we are wondering if they were testing because they have regulations that promote good water quality.

            Mill pond is located in the township of East Troy. It is located directly across from a doctor’s office and behind the doctors office there is Buell industries.  Buell industry builds motorcycles.  Mill pond’s nitrate levels averaged 3.945 ppm (Figure 2).  We think this is due to the factory being located across the street. Booth Lake is also located in East Troy.  It had the highest average nitrate level at 8.38 ppm (Figure 2) out of all of the ponds and lakes that were tested.

 Booth Lake is highly populated with houses. The septic systems of these houses may be older than other lake homes. There may be more human wastes entering the lake. Another factor that could be contributing to the high level of nitrates is that Booth Lake may have experienced a large algae bloom.  Now that the algae are dying, they are emitting nitrates.  The lake was greener in color, which makes us come to the assumption about the algal growth for that year.

            When we took readings at Wind Lake, we took them at a boat launch. The lake seemed to be quite populated but the nitrate levels were averaged to be .04025 ppm (Figure 2).  The amount of a nutrient in a lake may also depend on the depth of the water (University of Washington, 2000). Wind Lake has a mean depth of 10 meters and a maximum death of 50 meters (Department of Natural Resources, 2002). Since the lake is very deep this may contribute to the level of nitrates in the water. Booth Lake is a shallower lake. The maximum depth is 24 meters and the mean depth is 12 meters (Department of Natural Resources, 2002).

 Lake Michigan’s mean depth is 85 meters and the maximum depth is 281 meters (National Oceanic and Atmospheric Administration, 2006).  When we tested the nitrate levels for Lake Michigan they were averaged to .295 ppm (Figure 2).  This could be due to the size of the lake.  The site at which we tested was a marina.  There were very few homes located on the lake in this area.  However, across the street were residential homes.  There were no agricultural fields near the test site.  This could be a contributing factor to the levels of nitrate that were found in Lake Michigan.

Big Muskego Lake had nitrate levels that averaged .933 ppm (Figure 2).  The lake is a shallower lake with the mean depth at 4 meters. However, there were not as many residential homes located on the lake. At the site we tested, the homes seemed to be newer or recently remolded. They may have better septic systems established in these homes. This could contribute to the low nitrate readings as well as a smaller population of people living on the lake.

            With the knowledge that we gained through our research, we could speculate that the shallower the lake or pond the higher the level of nitrates in the water. However, this is untrue at the time we tested. The ponds which are usually shallow had nitrate reading that were low and high. The same was true for the lakes. If we were to test perform this test again, we would like to look at the nitrate differences between different seasons between the lakes and ponds that we tested, and would like to test during an algae bloom and when there isn’t one occurring in a particular lake to compare the different nitrate levels. We would like to see if an agricultural area versus a non agricultural area influenced the nitrate levels in lakes and ponds, and we would also like to test nitrates in lakes and ponds with similar depths to see if there is a correlation between depth of water and nitrate levels. The last test in which we would perform would be to test whether there would be a nitrate level difference at different depths in the lake or pond.

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References:

Department of Natural Resources (1999). Lake Maps. Wisconsin Lakes Book PUB-FM800. Retrieved on October 27, 2006 from http://www.dnr.state.wi.us/

Environmental Literacy Council (2002). Unbalancing the nitrogen Cycle. Retrieved on October 23, 2006 from http://www.enviroliteracy.org/article.php/682.php

Kevern, N., et all.(1996). Lake Classification Systems Part 1. The Michigan Riparian, Michigan Lake and Streams Associations. Retrieved on October 27, 2006 from http://www.mlswa.org/lkclassif1.htm

National Oceanic and Atmospheric Administration (2006). About our Great Lakes: Lake by Lake Profiles. Retrieved on October 18, 2006 from http://www.glerl.noaa.gov/pr/ourlakes/lakes.html

University of Washington (2000). Water Quality Parameters. Retrieved on October 25 2006 from http://depts.washington.edu/natmap/water/1fldh2o.html

University Corporation for Atmospheric Research (2003). Nitrate Protocol-Introduction. The Globe Program. Retrieved on October 28, 2006 from http://www.globe.gov/tctg/sectionpdf.jsp?sectionID=156

Water Watch (2006). Nitrate-Nitrite-Nitrogen. Retrieved on October 25, 2006 from http://www.state.ky.gov/homepage_repository/nitrogen.htm

Moffat, A. (1998). Global Nitrogen overload problem grows critical. Retrieved on October 16, 2006 from Expanded Academic.

Rice University (2000). Water Quality: The Importance of Nitrates. Retrieved on October 25, 2006 from http://www.ruf.rice.edu/cbensa/Nitrate/index.html