Analysis of the Ion Concentration Fluctuations in Olentangy River Water
Research Contributors: Amy Casaday, Lian Chen, Samantha King & Alyssa Sherry
Introduction
The question investigated was whether or not construction and heavy traffic flow affect the ion concentrations in the river, relative to an area with less traffic and consisting mostly of parks. Ions with appreciable concentrations were measured and compared between the two areas. Additionally, ion concentrations were compared between upstream and downstream both in 2009 and in 2011, and changes within each area were analyzed over the course of time. Although the EPA currently monitors the quality of water in rivers and streams nationally to determine whether they are considered healthy, it does not currently publish specific levels of inorganic ion criteria for non-drinking water.7 The Olentangy River hosts many recreational activities as well as provides habitation for an abundance of wildlife, therefore an excess in ion content could have an impact on the overall health of the area. Although the EPA is not currently monitoring all ion concentrations measured by this experiment, if concentration shows an increasing trend, the EPA may want to consider this in the future. Some important ions to be analyzed include: nitrates, which in high concentrations can affect infant health; chlorides, as high concentrations can lead to chloride poisoning; and, fluoride, which can have an impact in extreme concentrations. Low fluoride concentrations can lead to bone diseases, whereas high concentrations can lead to poisoning.
Research sites
In order to study the effect of construction on the content of Olentangy River water, several sites north of Lane Avenue were compared to sites from Lane to downtown Columbus. Because the northern areas are near parks (LINK to reference 1)1, there is no construction and little road traffic. The upstream area was determined to be North Dodridge to the Northmoor, Whetstone area. In contrast, much of Ohio State’s campus is currently under construction2, and sites from Lane to downtown are near that construction and heavier road traffic. The downstream area is defined as the area from Lane Avenue to Confluence Street in the downtown area. All river samples came directly from the Olentangy River, not tributaries.
Sample collection took place between Lane and Fifth Avenues along the Olentangy Trail. To ensure continuity in collection interval, samples were taken every two to three blocks. Collection sites were chosen based upon gaps in foliage and amount of pollution in the area. Because of the aesthetic nature of the Olentangy path, the nearest break in bushes occurred under or around overpasses. Great care was taken to avoid areas where litter was prevalent, as this could have tainted the samples. Each of the provided plastic bottles was rinsed at least three times and the washings were dumped cautiously downstream before the samples were collected.
The average concentration and its standard deviation were determined for each ion in each area for both years that it was analyzed. For each comparison, an F-test was performed and based on whether the standard deviations were significantly different or not an appropriate student’s t-test was performed. This test result was then compared to a table value at the 95% confidence level. If the value was larger than the table value, then the concentrations between the two areas or times were determined to be statistically different. The comparisons were:
- Upstream versus downstream in 2009
- Upstream versus downstream in 2011
- Upstream 2009 versus upstream 2011
- Downstream 2009 versus downstream 2011
Instrument Calibration and Method Validation
Each group was assigned several ions and prepared standards covering a given concentration range. This was done by preparing concentrated standards and diluting them to various concentrations in the range. The IC data for the standards was collected and used to create a calibration curve for each of the twelve ions being studied. Some ions had poor best-fit lines for the calibration curves, causing greater error in the calculated concentration of ions in the unknowns. Calibration plots from 2009 were referenced in these cases to get an idea of the approximate relationship between concentration and the IC data. As the signal of the IC can change over time, these previous plots were used strictly for reference and not for calculating unknown concentrations.
Data and Results
After constructing calibration curves for the various ions and using the best-fit line to determine the concentration of each ion in each of the water samples, the average concentrations along with their corresponding EPA standards for drinking water (not freshwater as that data is currently unavailable) were compiled into Table 1.
After constructing calibration curves for the various ions and using the best-fit line to determine the concentration of each ion in each of the water samples, the average concentrations along with their corresponding EPA standards for drinking water (not freshwater as that data is currently unavailable) were compiled into Table 1.
|
Ion |
Downstream (2011) | Upstream (2011) | Downstream (2009) | Upstream (2009) | |
|
Cl– |
38 |
46.44 |
48.73 |
62.05 |
250 |
|
F– |
0.22 |
0.22 |
0.43 |
0.39 |
4 |
|
SO42- |
55.95 |
67.96 |
72.00 |
88.79 |
250 |
|
PO43- |
1.14 |
1.17 |
0.68 |
0.64 |
|
|
NO3– |
16.32 |
13.96 |
6.23 |
8.02 |
10 |
|
NO2– |
n/a |
n/a |
Not measured |
Not measured |
1 |
|
Ac– |
n/a |
n/a |
Not measured |
Not measured |
Not regulated |
|
Na+ |
19.95 |
23.84 |
30.08 |
35.34 |
Not regulated |
|
K+ |
2.48 |
3.75 |
5.16 |
5.12 |
Not regulated |
|
NH4+ |
n/a |
n/a |
n/a |
n/a |
Determined by NO3– and NO2– |
|
Mg2+ |
0.10 |
0.11 |
17.84 |
21.42 |
Not regulated |
|
Ca2+ |
84.49 |
92.28 |
175.92 |
232.56 |
Not regulated |
| Table 1. The average concentrations (ppm) for each ion tested at each location site. n/a indicates that no appreciable concentration was detected by | |||||
For each of the four conditions that were compared, a student’s t-test was performed for each ion in order to determine if the differences in concentration between 2009 and 2011 were statistically significant. Table 2 shows that in each case, the discrepancy in ion concentration is significant for most of the ions.
|
Ion |
Upstream 2009 versus Downstream 2009 |
Upstream 2011 versus Downstream 2011 |
Upstream 2009 versus Upstream 2011 |
Downstream 2009 versus Downstream 2011 |
|
Cl– |
Yes |
Yes |
Yes |
Yes |
|
F– |
Yes |
Yes |
Yes |
Yes |
|
SO42- |
Yes |
Yes |
Yes |
Yes |
|
PO43- |
No |
No |
Yes |
Yes |
|
NO3– |
No |
Yes |
Yes |
Yes |
|
Na+ |
Yes |
Yes |
Yes |
Yes |
|
K+ |
No |
Yes |
Yes |
Yes |
|
Mg2+ |
Yes |
Yes |
Yes |
Yes |
|
Ca2+ |
Yes |
Yes |
Yes |
Yes |
| Table 2. A tabulation of the statistical differences for each ion as determined by appropriate student’s t-tests at the 95% confidence level (only ions measured in appreciable concentrations were compared). | ||||
Discussion and Conclusion
Nitrates and nitrites are primarily used in fertilizers, and as such are major components of runoff. Elevated nitrate levels in the bloodstream can cause a condition called methemoglobinemia, in which hemoglobin binds with nitrites instead of oxygen, effectively starving bodily tissues of oxygen. Infants are especially susceptible to this condition5. Phosphates are also used in fertilizers to enable higher plant absorption of nitrogen. However, important side effects to phosphate usage exist. People who have high-phosphate, low-calcium diets are generally at a higher risk for developing osteoporosis. Increased phosphate concentrations in surface waters promote algae and other organism growth that have high oxygen demands. In a process known as eutrophication, the algae consume large amounts of oxygen and prevent the sunlight from entering the water, thus making the system unlivable for other organisms6.
Various ion concentrations were tested for statistical differences in the aforementioned categories. Statistically significant differences were mostly observed over the course of two years as opposed to between locations. However, more ion concentrations vary now in 2011 than they did in 2009. Because the EPA does not closely monitor many of these ions (for example, the cations), it is difficult to determine whether the statistical differences in their concentrations are relevant as they may not pose a potential health risk at current concentrations. However, the ions’ increase in concentrations should continue to be monitored to evaluate potential risk in the future. The ions whose concentrations did differ and are monitored in drinking water are the nitrates, phosphates, and sulfates, as they can pose a significant health hazard when present at elevated levels in drinking water and possibly river water. Of those that showed a difference, both nitrate and phosphate concentrations were higher than the EPA’s recommended standards for drinking water. Elevated nitrate and phosphate levels can both be explained by an increase in fertilizer use at the parks rather than from construction sites further downtown. However, the fluctuation of ion concentrations over time and in between areas may indicate the need for increased monitoring of these ions in order to avoid future health risks. The only noticeable effect of the construction was a decrease in the concentration of most ions, again, with the exception of nitrate.
References
(1) Columbus Recreation and Parks Department. Whetstone Park. http://parks.columbus.gov/Facility.aspx?id=25948 (accessed Nov 19, 2011).
(2) The Ohio State University. Campus Construction Map. http://www.osu.edu/map/construction.php (accessed Nov 19, 2011).
(3) United States Environmental Protection Agency. Drinking Water Contaminants: National Primary Drinking Water Regulations. http://water.epa.gov/drink/contaminants/index.cfm (accessed Nov 17, 2011).
(4) North Carolina State University Water Quality Group. Water Resource Characterization DSS: Phosphorus. http://www.water.ncsu.edu/watershedss/info/phos.html (accessed Nov 22, 2011).
(5) Argonne National Library, EVS. Human health fact sheet: Nitrate and nitrite. http://www.ead.anl.gov/pub/doc/nitrate-ite.pdf (accessed November 22, 2011).
(6) Lenntech Water Treatment Solutions. Phosphorous. http://www.lenntech.com/periodic/elements/p.htm (accessed November 22, 2011).
(7) United States Environmental Protection Agency. National Recommended Water Quality Criteria. http://water.epa.gov/scitech/swguidance/standards/current/upload/nrwqc-2009.pdf (accessed Nov 29, 2011).