3. Hypothesis
The pH level of the rivers near residential areas will be lower than 8 and higher than 6.
3.1 Reasoning: Industries, factories and motor vehicles emit poisonous gases like nitrogen oxide and sulphur dioxide into the surroundings. When these gases mix with the water vapour, they form acids and cause the pH level around that area to change.
Water bodies near these industrial or commercial sites with factories and vehicles everywhere will most likely have a higher pH level compared to the water bodies near the residential sites. Residential areas are mostly inhabited with people to live in, so there will not be a lot of bustling activities compared to industrial or commercial sites. This is because industrial and commercial sites often dump unwanted waste into the rivers, not just emit poisonous gases.
As residential areas do not have any of these substances or gases being dumped into rivers except for an occasional litter every now and then, the pH level of the rivers near residential areas will be near neutral.
4. Methodology
1) Prepare an empty plastic bottle, at least 5 metre of raffia sting, plastic bags, gloves and universal litmus paper for the field trip.
2) Choose a river/canal, preferably where the water is moving and is not stagnant.
3) Put a clean stone into the empty bottle so that the plastic bottle will be able to sink into the water instead of floating on the water surface.
4) Tie the raffia string around the neck of the bottle and let the bottle down into the water.
5) Try to obtain the water sample beneath the water surface and nearer to the centre of water body.
6) Wearing gloves, pull the bottle of water up and dry it with a paper towel or wet tissue.
7) Dip half the universal indicator into the bottle of water and record down the pH level of the water sample.
8) Take pictures of the whole process, and also pictures of the surroundings/location.
9) If there are people there, interview them about the usage of water and the water body.
5. Results and Analysis
5.1 Table of Results
Results of 25 different water samples in different locations shown in the table below.
5.2 Graph of Results
5.3 Analysis
From the results obtain from above, it is found that almost all of the rivers near residential areas has a pH level equal to or lower than 8. However, there are a few water bodies near residential rivers that exceed the pH level of 8, i.e. water sample No.3. Water sample 3 is also near a commercial site, with pipes situated above the river. This would mean that occasionally, there will probably be a few leaks from the pipes every now and then. However, water sample 9, taken near a residential and commercial site, has only a pH value of 7.5. Referring back to the table, it can be seen that there are no pipes nearby, and it is overall a clean and debris-free river. The commercial areas (high rise buildings) are not very near, and trees/plants can be seen along the sides. In water sample 11, it must be taken into consideration that it is most likely to be a manmade river/lake, as a fountain can be spotted in the middle of the water body. The pH level for that water sample is about 6, probably due to the fact that the people maintaining the river adds in chemicals which help keep it clean i.e. no algae, odour etc. In majority of these rivers, fishes and plants are present, as most of the species can survive pH levels from 5.5 to 8.5. However, only water sample 10 showed no signs of life, even though the pH level is 7. This is probably due to the fact that the residency along that area is not as developed as the others, so people living there throw rubbish directly into the river. As seen from the picture, there are also pipes situated above the water body, and drains leading into the river.
Except for water sample 7 (pH level of 8.73), the others has a pH level of 8.5 or lower, making it suitable enough for fishes to survive. Theoretically, the pH of the rivers near the industrial and commercial areas are supposed to have a pH lower than 7, as the poisonous gases released around that area causes acid rain. However, the rivers in these industrial areas are alkaline. This is most probably due to the other chemicals released by the factories, as those chemicals may be very alkaline. In addition, the temperature at which all these pH levels were tested at is very low (during winter), so the pH levels may have changed because of this reason. Also, the pH strips have been exposed to the surroundings, which mean it would have been exposed to the water vapour around it. The water vapour may have caused the pH to change as well. Moreover, if we look at the different sites, there are some rivers which are used for more than one purpose i.e. water sample 3.
Looking at the graph, we can see that all rivers near residential areas have a pH ranging from 6 to 8. We can also spot an outlier, water sample 7, which is taken near an industrial site. As previously mentioned, factories and rubbish dumps along the river can affect the pH level greatly. All commercial and industrial rivers has a pH level equal to or higher than 8, and all water bodies near residential areas have a pH ranging from 6 to 8. In the pie chart, it can be seen that majority of the water bodies in Shanghai has a pH value ranging from 7 to 8. Majority of these rivers are near residential areas, which shows that the land uses around these areas do not affect the rivers as badly as the others. However, it must also be taken into consideration that there are also other factors which determines the seriousness of water pollution.
6. Conclusion
The results from the field study showed that the pH levels of the water bodies near residential areas are 6-8. In a few cases where the pH value is not in that range, it was due to the other types of land use it was used for, or the area was not as developed as the others. This proves that residential areas do not affect the pH value of the river as much as industrial or commercial areas, because not much chemicals are disposed of into rivers compared to the other areas. Therefore, my hypothesis is correct.
7. Evaluation
7.1 Reliability
The field study could be improved as the results could have been repeated twice each for the average result to be taken. However, there were no problems when achieving the results and the apparatus used were all reliable and in good condition, with the exception of the universal pH indicator. The pH indicator was a little polluted with other substances, so when the testing was done it could have affected the results. The method was precise, taking note of the details. For example, the stone which was placed in the bottle was cleaned so that there would be no foreign substances. If it could be improved, I would use a data logger instead, as the pH value would be more accurate.
7.2 Validity
As the apparatus used measured everything needed, i.e. universal indicator to measure the pH value of the river, I could say that the field study was valid. The method carried out obtained the results needed and supported my hypothesis. However, as the universal indicator was slightly contaminated, I could have used a different pH strip.
8. Bibliography
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Krantz, D., Kifferstein, B. (N/D). Water Pollution and Society, Umich. Retrieved 13th Dec, 2010, from: