Water+Quality+and+Rainfall

=//**Effects of Rainfall on Water Quality**//=

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**Introduction**
Acid rain is one of the ways in which humans are adversely affecting our environment. Acid rain, rain that has reacted with acids in the air causing it to become more acidic, affects mostly aquatic ecosystems, but also terrestrial environments, in an adverse manner. It greatly affects bodies of water in watersheds, such as in Flat Rock Brook Nature Center, because the soil has a limited ability to neutralize the acids in the rain. When the stream and the soil surrounding the water lose their ability to neutralize the acids, the stream becomes acidic, causing changes in the ecosystem. Acid rain also causes the soil in the surrounding environment to release aluminum and other metals into the stream, hurting the life in the water. Since harming only one part of an ecosystem can create an enormous change in the environment, acid rain is a problem that needs to be curtailed quickly in order to prevent further damage. Rainfall can also affect the quality of water through the rain that lands on the street and flows into the brook. This rain could pick up substances such as oil and put them into the stream.

Rain is naturally a weak acid, having a pH around 5.7. The natural acidity is caused by carbonic acid, which is formed when water and carbon dioxide in the air react. The acidity in the rain caused by humans is in the form of nitric acid, sulfurous acid, and sulfuric acid. The first step in the creation of nitric acid is the making of nitrogen oxide, which is formed when nitrogen gas and oxygen gas react at extremely high temperatures, such as those in the engines of automobiles and in electrical power stations. Nitrogen oxide can then react with oxygen in the air to form nitrogen dioxide (NO2). Nitrogen dioxide can be carried by the wind and come into contact with water in the air, forming nitric acid. sulfurous acid is formed when sulfur dioxide (SO2) released from the burning of fossil fuels reacts with water in the air. However, before the sulfur dioxide reacts with the water, it can form sulfur trioxide, which can react with water to create the stronger sulfuric acid. A harmful effect of the sulfuric acid other than the acidity is that it can bond with calcium ions in soil. The calcium sulfate that is formed is unsoluable, making the calcium unable to circulate through soil and unable to be picked up by plants. If this calcium is not replaced, plant life suffers and sometimes dies.

Our experiment was designed to test whether this area contains a substantial amount of acid rain and how much the acid rain affected the pH of Flat Rock Brook. The general procedure for the experiment consists of collecting samples of water from Flat Rock Brook before it rains and testing those samples for pH, and collecting samples of water from the same spots after it rains and testing those samples for pH. If there was acid rain in this area, it would be signified by a drop in pH from the before rain samples to the after rain samples.

**Methods and Materials**
When conducting this experiment, a GPS and water bottles were needed beforehand. The first time Flat Rock Brook Nature Center was attended, different locations were picked to study the different effects that the rainfall of those locations.

Locations: The locations picked were as follows: Location A: 40°52.675 N, 73°57.741 W Location B: 40°52.701 N, 73°57.757 W Location C: 40°52.721 N, 73°57.820 W

Location D: 40°52.734 N, 73°57.869 W

When attending Flat Rock Brook Nature Center for the first time, yellow tape was added to nearby trees so that the locations could be found when later attending, and observations were taken of the locations. Once each spot was attended to following the first trip, one of the four water bottles was used to take a sample from the water and the water bottles were labeled based on their corresponding location. When all four water bottles were filled from each of the four locations, the pH meter was used to measure the pH for all four of the samples obtained, and a pen or pencil was used to record the pH on a notepad.

Graphs of Dates
The first set of graphs includes four graphs, each representing one of the four dates we went to Flat Rock Brook Nature Center. The x axis represents the location and the y axis represents the pH.

Graphs of Locations
The second set of graphs includes four graphs, each representing one of the four location we went to Flat Rock Brook Nature Center. The x axis represents the date attended that location and the y axis represents the pH.

Overall Graph
This third set made up of one graph combines all of the data from all of the dates and locations.

Observations
Location A Location B Location C Location D
 * Highest elevation of all four locations
 * Rocks partially blocking the flow of water
 * About 5 feet across
 * Water moving at a slow to medium speed
 * Lower elevation than Location A
 * No obstruction
 * Shallow water
 * Wide area of water movement
 * Water moving at a slow speed
 * Lower elevation than Location B
 * Lots of foliage
 * Area was the heart of McFadden Pond
 * Lowest elevation of all of the locations by a good amount
 * Lots of rocks
 * Waterfalls
 * Water moving at a fast speed

Calculations
Change in pH= pH of water for the day of rain or after rain - pH of water for the day when it hadn't rained recently (2/20) Average Change= (Sum of every change)/3

Location A
5/17- 7.91-7.45=0.46 5/28- 7.91-7.41=0.50 5/31- 7.91-7.25=0.65 (0.46+0.50+0.65)/3= 0.54

Location B
5/17- 7.93-7.42=0.51 5/28- 7.93-7.35=0.58 5/31- 7.93-7.59=0.34 (0.51+0.58+0.34)/3= 0.48

Location C
5/17- 7.95-7.64=0.31 5/28- 7.95-7.23=0.72 5/31- 7.95-7.43=0.52 (0.31+0.72+0.52)/3= 0.52

Location D
5/17- 8.80-7.55=1.25 5/28- 8.80-7.65=1.15 5/31- 8.80-7.78=1.02 (1.25+1.15+1.02)/3= 1.14

**Conclusion**
The results of this experiment showed that there was about an average of a 0.50 drop in pH from the water before it rained to the water after the rain in Locations A-C, and a 1.14 drop in pH in Location D. Location D, however, seems to be an outlier due to the pH measurement done before the rain, 8.80, which is almost a full point higher than the other locations' readings. Although the numbers in Location D taken after the rain do tend to be a little higher than those of the other three locations, they are not as extreme as the 1.0 difference before the rain. From this data, we can conclude that Flat Rock Brook is more acidic and has a lower pH after rain than before it. Although we can not conclude whether this drop is due to acidity in the rain caused by humans rather than the natural acidity, we think that the manmade acidity accounted for at least some of the drop in pH. Also, Location D, which has the lowest elevation and a fast current, had the highest recorded pH of the four locations, while Location A, which has the highest elevation and a medium-paced current, had the lowest. The date with the lowest pHs recorded, and therefore the highest change was May 28. This was probably because of the amount of rainfall the day before, which was noticeably higher than the rainfall the day before May 17 and the rainfall on May 31. Even though we recorded the pH of the water only hours after it rained on May 31, the low amount of rainfall caused that pH to be higher than on the other dates.

For experimental error, the first error that we had occurred during the different manners of measuring the pH of the water. The first time we went to Flat Rock Brook Nature Center we took the pH meter with us and measured the pH directly in the water as opposed to through water bottles. When measuring the pH, we did not know that we were supposed to move the pH meter around in the water. Although at some points there was current and the water was moving when the pH meter was not, at Location C there is no flow of the water, so although that measurement appears to fit in with the rest of the data, that could be an experimental error since neither the water nor the pH meter was moving. The direction of this error is unknown because the water around the spot we kept the pH meter in could have had a higher or lower concentration of H3O+, thereby being able to make the pH higher or lower than it should be.

Another possible error is the calibration of the pH meter. The pH meter could have been calibrated differently each time the pH meter was used, so the pH values could have been higher or lower than they should have been. Therefore, the direction of this error is unknown because the calibration can affect the data in any way.

A third possible source of error occurred when taking the measurement of the pH on February 20 from Location D. February 20 was the only day when we measured the pH directly in the water, as opposed to measuring it from a sample collected in a water bottle. The one noticeable difference with Location D compared to the rest of the locations is that the speed of the flow of water at Location D is much faster than that of the other locations since Location D is below the waterfall. Because the water is moving so fast, it is possible that the rapid movement of the water had an effect on the pH meter’s ability to react with the H3O+ molecules in the water. Because of this rapid movement, it is possible that less H3O+ molecules reacted with the pH meter because the molecules were moving too fast to react with the pH meter to get a good reading. If that was the case, the reading would be higher than it should have been because the pH would be higher since the formula for pH is –log([H3O+]), meaning that if the concentration of H3O+ is lower, the pH will be higher. So if less of the H3O+ molecules can react with the pH meter, then the measured concentration will be lower and the pH will be higher than it should be. The direction of this error is in our direction of error because the pH for Location D on February 20 was higher than it should be, and this error would give us a higher pH reading.

Another resulting error could have occurred by dirt in the water. When we went to Flat Rock Brook Nature Center on May 31, the water was much dirtier than it was the other days. So when we were collecting samples, there was some dirt inside of those samples especially from the sample at Location A, possibly affecting the reading of the pH meter either way.

There are also factors that could have controlled the pH during the time period of our experiment that could have caused a change in the pH of the water that are not related to acid rain, one of them being pollution. During our experiment, there may have been pollution occurring in the water that may have caused the pH to fluctuate during our experiment. For example, the cumulative pollution between February and May may have made a change of pH of the water at the locations we examined. So if we were to measure directly before the rain of a day before or of measurements, the reading may be different from the original reading in February. The direction of this error could go either way since the pollution could have made it more acidic or basic, or possibly not have any effect at all.

Our results show that there is a significant drop in pH when it rains, and humans can help lessen that drop by reducing our dependence on fossil fuels and combustion engines, the sources of acid rain. If a viable alternative energy source to fossil fuels was found, such as wind or solar power, the rain would be less acidic as there would be fewer sulfur dioxide emissions, leading to less acid rain. The drop in acid rain would help stop the disruption of the aquatic ecosystems, creating a better environment. If there was another viable way to power cars other than combustion, such as hydrogen fuel cells, we could further reduce the amount of acid in the rain.

There are many research topics that we could pursue after doing this experiment, one of them being how the quantity of the rainfall would affect the pH of the stream. We could see what relationship the quantity of rain has with the drop in acidity of the stream. Another possible experiment would be to calculate the drop in pH at other bodies of water in order to see which areas have the highest amounts of acid rain and which areas’ soil and water have the best capacity to neutralize the acid rain. We could also do a similar experiment with other types of precipitation, such as sleet, snow, and hail, to see if they would have a similar effect on the pH of the brook. Another experiment related to this one that we could do is to test if rain affects any other measures of water quality, such as dissolved oxygen or conductivity. Finally, we could also test the water in the stream for metals to see if there was acid rain, as we know from our research that the soil gives off metal when its acidity is too high.