Sara Reszczynski

Claire Quiner

Erica Steen

Research Project

BI 341

 

pH and Nitrate Levels in Rural and Urban Lakes

 

Abstract:

We tested the levels of pH and nitrate in water samples collected from rural and urban locations in the areas of Southeast and Central Wisconsin.  The pH value was significantly higher for the rural water samples when compared with urban.  The nitrate values varied between the two water samples, however not enough to be considered significant.

Keywords:  Nitrate, pH, rural water, urban water

Introduction:

Contaminants in water systems pose a great health risk to humans and other living things that consume them.  Several factors affect the amount of pollutants in a water system.  For the purposes of this study we will focus on fertilizers, waste run-off, city sewage, and industrial waste.  We will focus on these things since industrial manufacturing and farming (both livestock and crops) are two prominent sources of revenue in the state of Wisconsin (Roe, 2002). 

High nitrate in water can cause oxygen flow problems when fed to infants causing methemoglobinemia.   This disease causes a baby’s skin to become blue due to lack of oxygen flow (DNR, 2003).  Breast feeding mothers drinking water high in nitrate content can also cause this affect in their children.  Water high in nitrates has shown to be correlated with certain types of cancer and can cause birth defects when given to a pregnant mother (DNR, 2003).  When high nitrate content water is consumed over a longer period of time other health effects can be caused such as diuresis, increased starchy deposits and hemorrhaging of the spleen (EPA, 2006).

Health effects due to low pH are directly a problem for fish and other aquatic animals (Barreca, 2003) but have indirect effects for their consumers.  At a pH level of 5.0 and lower, reproduction is hindered in most fish species and a pH level of 3.0 and lower is toxic to all fish species (DNR, 2006).  The lower the pH the higher the rate of metal solubility in the water which poses health risks to consumers of fish, especially, humans, eagles, loons, and osprey.  Water with a pH of 4.0, contains 4.8 mg/l of aluminum while water with a pH level of 8.0, contains 4.8 x 10 -12 mg/l of aluminum (DNR, 2006).

As mentioned before many factors affect the levels of nitrate and pH in water.  High rates of pollution from sewage, leaky septic tanks, storm water run-off and dairy waste provide nutrients for algae growth in water.  As algae die they decompose. Decomposition and photosynthesis produce CO2.   As CO2 dissolves into water, it becomes carbonic acid which lowers the pH.  The more algae present, the more decomposition and photosynthesis will take place.  Thus the more algae present in a body of water the lower the pH levels will be (Lake Access, 2003).  Phosphorus is another nutrient that increases algae growth since it is a limiting factor in many bodies of water (Barreca, 2003), however it was not tested for in our study. 

Nitrate contaminates water through similar modes that pH does: fertilizers, animal wastes, septic tanks, municipal sewage treatment systems, and decaying plant debris (DNR, 2003). The maximum nitrate level for drinking water, as set by state and federal governments is 10 milligrams per liter (DNR, 2003). 

Since industrial waste is so high in Milwaukee we predicted that pH would be lower in our urban samples and that nitrate levels would be higher when compared with our rural water samples.

Methods

On 10/15/06 we collected rural samples between 11am and 2pm from Necedah, WI. and Arkdale, WI.  The first sample was taken from Buckhorn Lake directly from the water surrounding the boating dock.  The second sample was taken from a pond, separate from Buckhorn Lake, about 200 meters northwest from the boating dock.  Buckhorn Lake is located about 12.9 kilometers south of Necedah on County Highway G.  The third sample was taken from the Petenwell Lake directly from the water surrounding the boating dock.  Petenwell Lake boating dock is located directly across the bridge between Juneau and Adams Counties on State Highway 21 (traveling east from the town of Necedah).  The fourth sample was taken from the Yellow River about 100 meters south of the Yellow River Dam.  The fifth sample was taken in The Necedah Wildlife Refuge from Suk Cerny water reserve.  The Refuge is located about 6.5 kilometers west of Necedah on Hwy 21.  On 10/17/06 the urban water samples were taken from various locations in Milwaukee County.  The samples were taken from Jackson Park pond located at 35th and Forest Home, Kosciuszko Park pond located at 7th and Lincoln, Wilson Park pond located at 16th and Howard at, Scout Lake Park pond on S. Loomis Ave, and Sheridan Park from Lake Michigan off of Packard and Layton Ave.  Approximately 500 mL water was taken from each location.  The water samples were tested using the LaMotte limnology test kit model AM-02 code 5902-01 which contained the test kit for nitrogen, the LaMotte nitrate-N phosphate test kit model NPL code 3119, and for pH the LaMotte Wide Range pH test kit model P-3100 code 2117.  The procedure followed for testing nitrate and pH can be found in these kits.

Results

 

            After testing urban and rural water samples, we found that Milwaukee’s (urban) water samples have significantly higher pH levels than Necedah’s (rural) water.  This inference was supported by our p-value which was 0.036616904.  The water samples were also tested for nitrate levels.  The p-value of 0.104 showed that the difference between the two is not significant.  The average of pH values was 6.4 for rural and 5.1 for urban, see figure 1.  The average level of nitrate in rural water was 0 and the average level in urban water was .52, see Figure 2.  The standard deviation for the rural water pH tests is 0.65 and for urban water pH tests is 0.74, see Table 1.  The standard deviation for the nitrate levels in the urban water samples is .79 and for rural samples it is 0, see Table 2.  We found the lowest pH level, 4, in an urban site.  All of our rural water samples tested to have no nitrates in them. 

Table 1: Data and statistics for the pH of water samples in rural and urban areas.

 

Rural Water

Urban Water

 

 

 

pH

5.5

5

 

6

6

 

6.5

5.5

 

7

5

 

7

4

 

 

 

Average pH

6.4

5.1

St. Dev.

0.651920241

0.74162

 

 

 

p-value pH

0.036616904

 

 

 

Figure 1: Average pH in rural and urban water samples.

 

Table 2.  Data and statistics for nitrate content of urban and rural water samples.

 

Rural Water

Urban Water

Nitrate

0

0

 

0

0.88

 

0

0

 

0

0

 

0

1.76

 

 

 

Average Nirate

0

0.528

St. Dev.

0

0.787096

p-value N

0.104

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Figure 2: Average nitrate levels in rural and urban water samples.

 

Discussion:

 

Our hypothesis that contamination would be greatest in water samples found in urban areas was supported.  Water pH was highest in rural areas and the nitrate level of water was lowest there.  There is sound reasoning to explain why we got the results that we did.  In rural Wisconsin there is a lot of farming which results in waste run off and the pH increases (Barreca, 2003).  When it rains, run-off from livestock can raise the nutrient levels in near-by bodies of water, causing algae growth, raising the pH content. 

Another factor that may have affected our results was that we collected our urban samples after a heavy rain. The pH of southeastern Wisconsin rain has been found to be 4.4 which can be considered acidic (DNR, 2006).  This may have lowered the pH level of the urban water samples due to the acid content in the rain (DNR, 2006). 

If we were to do this study again we would not collect our water samples after heavy rains.  We would also do additional water testing such as phosphorus and metals such as aluminum and mercury.  We could also test fish metal contents to determine the quality of lake water.

 

 

 

 

 

 

 

 

 

 

 

 

Bibliography:

 

Barreca, J.  (2003).  “Focus on White River pH Water Clean Up Plan”.  Retrieved October 6, 2006 from http://www.ecy.wa.gov/water.html.

 

Lake Access (2003).  pH: Measuring the Acidity and Alkalinity of Lakes.  Retrieved 10.31.06 from http://lakeaccess.org/lakedata/lakedata.html.

 

 

Roe, Richard, (2002).  Introducing Wisconsin.  Wisconsin Legislative Reference Bureau.  Retrieved on 10.31.06 from http://www.legis.state.wi.us/lrb/pubs/special/introwis.pdf

 

Wisconsin Department of Natural Resources (2003).  Nitrate.  Retrieved on 10.31.06 from http://www.dnr.state.wi.us/org/water/dwg/nitrate.htm#what%20is.

 

Wisconsin Department of Natural Resources (2006).  pH Acidity, Understanding Lake Data.  Retrieved on 10.31.06 from http://www.dnr.state.wi.us/org/water/fhp/lakes/under/index.htm#carb.

 

U.S. Environmental Protection Agency (2006).  Ground and Drinking Water.  Retrieved on 10.31.06 from www.epa.gov