River pH Upstream and Downstream
Taking 12 samples from each location, I tested whether water pH of the Milwaukee rivers were more acidic upstream or downstream. The pH of the river downstream was only slightly different than upstream with an average pH of 6.33 downstream and 7.0 upstream. Data was not significant with a P > 0.05. My hypothesis was rejected.
The deposit of sediments cannot be an adequate indicator for pH levels in water (Schuhmacher 1993). Even though the deposit of different sediments can affect the pH of water, one also has to take into consideration stream currents and other run offs in the water.
This experiment was designed to see if water downstream has a more acidic pH than water upstream. If the pH of water both upstream and downstream fluctuate greatly then the hypothesis that water downstream will have a lower pH were falsified. If the pH of water downstream is significantly lower than the pH of water upstream, then the hypothesis that the water downstream will be more acidic were supported. If the hypothesis that downstream water will be more acidic one could predict that all minerals and sediment from runoff is pushed downriver by the current
(Li-Ming He, Zhen-Li He 2008).
Materials and Methods
On October 29th, 2009, at approximately 6:45 pm, twelve sites downstream on the Milwaukee River were selected on east Erie St. in Milwaukee, WI (Map 1), haphazardly. Using unknown brand of pH strips, I collected the pH of each of the twelve sites. After collecting data I then selected twelve sites haphazardly from the Kinnickinnic River at Pulaski Park on 16th and Cleveland (Map 2), Milwaukee, WI. These sites were the upstream sites. I again used the pH strips to collect the pH of each of the twelve sites. The data were analyzed using Microsoft® Excel® 2004 for Mac, and a 1 tail t-test was done.
There was no significant difference between the pH levels of water upstream and water downstream (Fig. 1, P= 0.097). The upstream sites had an average pH of 7 (Fig. 1, St. Dev. +/-1.35). The downstream sites had an average pH of 6.33 (Fig. 1, St. Dev. +/-1.07). The t-test suggests there was no significant difference between pH upstream and downstream with a P value of 0.097.
Figure 1. Average pH level of water upstream and downstream with standard deviation error bars. P= 0.097
There was no significant difference between the two sites tested. One possible explanation could be that downstream is bigger and more diluted than upstream, so acids would be diluted with more water, causing pH to be less acidic. A variable to consider is the time of day samples are taken must be consistent. Another thing that could have affected my results was if there was a rainfall recently. The oxygen concentration within the river water can also play a big role in the differing pH levels (Simonsen, Harremoes 1978).
My findings are not consistent with my hypothesis that water pH downstream would be more acidic; therefore my hypothesis is not supported. If I had to do this experiment again, I would take more samples, and take samples from each location at the same time of day.
Li-Ming He, Zhen-Li He (2008). Water quality prediction of marine recreational beaches receiving watershed baseflow and storm water runoff in southern California, USA. Water Research, 42(10), 2563-2573. Retrieved from ScienceDirect database.
Simonsen, J, Harremoes, P (1978). Oxygen and pH fluctuations in rivers. Water Research, 12(7), 477-489 Retrieved from ScienceDirect database.
Schuhmacher, M (1993). Evaluation of the effects of temperature, pH, and bioproduction on Hg concentration in sediments, water, mollusks and algae of the delta of the ebro river. Science of the Total Environment, 134(1),117-125 Retrieved from ScienceDirect database.