Comparison Methods in pH and Nitrate Level Concentrations from Urban and Rural Bodies of Water

 

31 October 2002

 

Sarah Keuer, Sahar Ahmad and Melissa Battle

The water chemistry of an aquatic environment is essential to the survival and function of various species and vegetation. The experiment was conducted to compare differing pH methods using a wide-range chemical pH kit and pH color indicator strips. Nitrate level concentrations were determined using a nitrate color indicator kit. A standard color scale specific to each method was used in data collection. Results confirmed that there was not a significant difference in pH methods, and a similarity among nitrate concentrations in both urban and rural bodies of water.

 

Keywords: Nitrate, pH, color indicator   

 

Nitrate concentrations and pH levels in aquatic environments can have a substantial affect on plant and animal life. Nitrogen is present in the air as a gas N2, which is not useful to plant life. During nitrogen fixation, plants are able to convert nitrogen to ammonia (NH3). After fixation, the soil and plant life can then use the ammonia. Nitrogen that eventually ends in the soil can become embedded in sediment and is released back into the air as a gas through activities such as volcanic eruption, or enter into bodies of water through leaching. Leaching of nitrate (NO3-) into water can increase nitrate concentration. Factors that increase leaching of NO3- into water are commonly attributed to anthropogenic activities (Holloway 1998). The acidity and alkalinity of water is expressed as the pH. A pH ranging from 0 to 6 is considered acidic and a pH range between 8 and 14 is considered basic. A neutral pH is expressed as 7.

A study conducted in 1995 by Suberkropp and Chauvet indicated that the nutrients in water (nitrate and phosphate) were an important determinant for the breakdown of leaves in streams due to the direct affect on decomposers. In 1998, low nitrate levels were linked to surface water eutrophication, methaemoglobinaemia or “blue baby syndrome and several cancers (Holloway 1998). Similarly, pH changes in pond water resulted in the mortality of zooplankton (O’Brien and deNoyelles 1972). The pH of water also affects the biotic interactions of aquatic species (Warner 1993).

Methods

            In order to test our hypothesis, we gathered two water samples from each of the nine bodies of water. The method of extraction was to immerse the bottle under the water until the bottle filled up with water and immediately cork. The nine sites included Jackson Park pond, Lake Michigan, Lake Tichigan, Wisconsin River, Fox River, Lake Buttes des Morts, Tomahawk River, Lake Kawaguesaga and bog water. The samples were then brought back to the lab where a pH test called the LaMotte Colorimetric Octet Comparator was then performed. The procedure for the Octet Comparator was as follows: First, the test tube was rinsed out with the sample water and filled to the 5 mL line with sample water. Next, we added the indicator solution while holding the pipette vertically. The ample was then capped and inverted several times to mix the solution well. Finally, we inserted the test tube into the Octet Comparator and matched the sample color to a color standard given and recorded this as the pH. This procedure was repeated for each of the eighteen samples (two samples from each of the nine bodies of water) and the results were recorded.

            The next test was also performed to test the pH of the samples. However, for this experiment, pH paper was used. First, we measured 10 mL of the sample and poured it into a sterile glass container. We then dipped one strip of the pH paper into the 10 mL water sample for two seconds. That strip was then compared to the given chart of color standards within 30 seconds. Where the color of the pH paper matched the color on the chart, it was recorded as the pH. This procedure was then performed for all of the samples and the results were recorded.

            The final test performed in this experiment was that of the nitrate levels in the water samples. In order to test the nitrate levels of each of the samples, we used Luster Leaf Rapitest pond kit. We began by rinsing out the given container with the sample water. Then, 5 mL of sample water was extracted from the sample with a dropper and put into the container. We then broke open the capsule containing the powdered indicator substance and poured it into the container of sample water. The container was then capped an inverted several times to mix. Once the powder had dissolved, the color of the sample was compared to that of the given standard. The matching sample color was then recorded as the amount of nitrate in mg/L. This procedure was repeated for each of the samples.

Results

            The results that we found in our experiment were not the results we had expected to find. A key to the water samples is included in the report (see attached key). The pH levels of our water samples were very similar within the same method. For example, the results of the pH testing for method one (pH test kit) was similar with all water samples. The results of pH testing for method two (pH test strips) was similar with all the water samples (see Fig. 1). A Statistical test showed that the two pH-testing methods were not significantly different. Our t-test result was 3.64. The results of the nitrate testing also produced different results than we had expected. We thought that the levels of nitrates would be higher in the lakes and rivers located in the rural parts of Wisconsin than the lakes and rivers located in the urban parts of Wisconsin. Agricultural fertilizers add to the nitrate concentration levels in the soil. During rainfall, nitrates are leached further into the soil and eventually end up in stream waters that lead to other bodies of water. The results showed that the water samples from the bog, Jackson Park, and Wisconsin River had the highest pH results. The water samples from Fox River, Lake Buttes des Morts, Lake Tichigan, Lake Michigan, Tomahawk River and Lake Kawaguesaga had the lowest levels of nitrates (see Fig. 2).

 

Fig. 1 pH levels for sample locations using Chemical and Color Strip methods.

Fig. 2 Nitrate levels in mg/L for sample locations.

 

 

1

Cedarburg Bog in Cedarburg, WI (rural)

2

Fox River in Appleton, WI (urban)

3

Lake Buttes des Morts in Menasha, WI (urban)

4

Lake Tichigan in Tichigan, WI (urban)

5

Jackson Park Pond in Milwaukee, WI (urban)

6

Lake Michigan in Milwaukee, WI (urban)

7

Tomahawk River in Minocqua, WI (rural)

8

Wisconsin River in Rhinelander, WI (rural)

9

Lake Kawaguesaga in Minocqua, WI (rural)

Key:  Water Sample Locations

 

Discussion

            The experiment supported a difference in pH testing methods. The chemical method, or method one, resulted in several alkaline and neutral pH’s. There was not a sizeable difference in the pH levels of the various bodies of water, and the distinction between rural and urban bodies of water was insignificant. However, method two, or the color indicator strip test, resulted in a variety of pH levels for individual bodies of water. Nevertheless, the pH levels among rural and urban bodies of water were not substantially different. It can be concluded that the pH results were an indication of the differences among pH testing methods.

            The nitrate levels among urban and rural bodies of water ranged from 0.5 mg/L to 2.5 mg/L. The urban bodies of water contained higher nitrate levels when compared to rural bodies of water. It can be presumed that urban activities such as domestic industrial discharges and atmospheric emissions contributed to nitrate levels (Holloway 1998). Two rural bodies of water, the Bog water and Wisconsin River water, both contained higher nitrate levels when compared to other rural bodies of water. The area near the Wisconsin River may have resulted in a higher nitrate concentration due to livestock feeding and agricultural runoff (Holloway 1998). The bog water’s concentration is presumed higher due to the vast amount of vegetation and the contribution of plant litter to nitrate concentrations (Bohlen 2001).

            The experiment should be repeated using electronic methods for collecting data such as an ISE meter. This will allow for a more direct accuracy in pH levels and nitrate concentrations. Using a color indicator to determine levels and concentrations relies on the human eye, which may not always produce exact results. It is also important to determine the time of year to carry out the experiment. Agricultural runoffs will be greater during planting and harvesting seasons as opposed to dormitory seasons. This may mean that during May the nitrate levels in rural communities are higher. Yet in December, concentration levels are lower.

            Nitrate concentration and pH levels are important in aquatic communities and should be observed to prevent a decline or over abundance in species. It is also important to monitor the nitrate concentrations in urban and rural communities to prevent excessive nitrate ingestion, which can be harmful to humans (Mueller 2001).

 

References

 

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Interactions In a Northern Hardwood Forest. Ecology: 82(4), pp. 965–978.

Holloway, J and R. Dahlgren, B. Hansen, W. Casey. 1998. Contribution of Bedrock

Nitrogen to High Nitrate Concentrations in Stream Water. Nature: 395, pp. 785-788.

Mueller, B. 2001. Residential Water Source and the Risk of Childhood Brain Tumor.

Environmental Health Perspectives: 109(6) p551, p6.

O’Brien, J. and F. deNoyelles. 1972. Photosynthetically Elevated pH as a Factor of

Zooplankton Mortality in Nutrient Enriched Ponds. Ecology: 53 (4) pp. 605-614.

Suberkropp, K. and E. Chauvet. 1995. Regulation of Leaf Breakdown by Fungi in

Streams: Influences of Water Chemistry. Ecology: 76 (5) pp. 1443-1445.

Warner, S. and J. Travis, and W. Dunson. 1993. Effect of pH Variation of Interspecific

Competition Between Two Species of Hylid Tadpoles. Ecology: 74 (1) pp. 183-194.