iblabexample1[1]

7/31/2019 iblabexample1[1]

1/4

6-10-08

Chase Lake Formal Lab Soil pH

Question: Does the distance from the lake effect the pH of the soil?

Hypothesis: Since Chase Lake is very polluted, I think the lake and the soil closest to the

lake will be more acidic than soil farther inland. If the lake is very acidic it will most likely

leak some of its acidity into the nearest soil, lowering the pH of soil close to the lake incomparison with soil farther away. Also, Chase Lake has probably accumulated a lot of

acidic rain over the years, which should again make the soil closer to the lake have a lower

pH and soil farther away have a higher pH.

Independent Variable: the distance from the lake the soil sample is taken from

Dependent Variable: the pH of the soil sample

Controlled Variables: amount of soil taken, amount of distilled water added to soil, ground

level the soil is taken from, and type of distilled water used to add to the soil and clean theinstruments

Materials:

Small shovel

Plastic 100ml tube with a top cover

Field study tape measure

4 bottles of the same distilled water

pH probe with GLX attachment

access to a lake

Procedure:

1. Use the field tape measure to make a transect extending 2 meters from the edge ofthe lake inland.

2. Fill the tube with 30ml of lake water taken from the area of water adjacent to the

transect.3. Use the pH probe to find the pH of the water and record this data.


2/4

4. Clean off the pH probe with some of the distilled water so its pH returns to normal.

5. Clean out the tube that held the lake water with some distilled water.

6. Measure 40cm away from the waters edge along the transect and use the shovel totake a sample of soil from the grounds surface.

7. Use the soil from the sample and fill the tube with 10ml of soil making sure to pack

the soil down well and evenly with your fingers.8. Fill the tube with an additional 20ml of distilled water so that the overall waterline

in the tube is at 30ml.

9. Close the tube tightly with the cap.10. Shake the tube up so that all the soil is evenly mixed with the water and there are no

major clumps of soil.

11. Open the tube and measure the pH of the soil solution with the pH probe. Record

this measurement.12. Clean out the tube and wash the pH probe with the distilled water.

13. Repeat steps 6-12 except measure 80-cm, then 120cm, then 160cm and finally

200cm from the waters edge so that there is a total of 4 measurements recorded

(including the waters pH).14. Repeat steps 1-13 four more times except make four new, different transects from

as many different regions of the lake as possible.

Data Collection & Processing

Data Table of Soil pH at Chase Lake at Different Transects

Transect Distance from Water (cm) 0.5cm pH of soil 0.1pH

#1 0 (the actual water)

40

80

120160

200

7.05

6.6

6.6

5.45.6

6.1


40

80120

160

200

7.1

6.1

6.15.9

5.9

5.7


40

80120

160200

6.0

5.3

5.66.7

6.55.4


4080

120

6.0

5.35.5

6.1


3/4

160

200

6.3

6.3

Data Table of Average Soil pH out of the 4 Transects

Distance from Water (cm) 0.5cm Average pH of Soil 0.1pH

0 (the actual water itself) 6.540 5.8

80 6.0

120 6.0

160 6.1

200 5.9

Conclusion & Evaluation

According to the average data of soil pH vs. the distance away from the lake taken

from 4 different transects the hypothesis that soil pH will be lower closer to the lake and


4/4

higher farther away from the lake was found to be incorrect. In fact, it seems like

according to the data there is no relationship between soil pH and the distance of the soil

away from the water. From 40cm away to 160cm away the pH seemed to be increasingslightly because the pH values went from 5.8 to 6.1, which isnt too much of a difference

(only 0.3pH), but from 160cm to 200cm the trend ended and the pH decreased from 6.1 to

5.9.In the individual transects there seemed to be no trend in the data either. Distance fromthe water had no bearing on soil pH. For example, in transect #4 the pH increased over

40cm to 200cm from 5.3 to 6.3, but in transect #2 the pH decreased over 40cm to 200cm

from 6.1 to 5.7. Also, the data of the average soil pHs (not including the pH of the wateritself) only fluctuated by about 0.3 pH over the 2 meters, which is not a very significant

difference.

The fact that there was no relationship found between the distance from the waters

edge and soil pH couldve been due to the many sources of error during this experiment.One of the largest sources of error that I saw was the effectiveness of the pH probes.

Despite the fact that we tried to keep the starting pH of the probe constant by always

cleaning it off with water in between measurement sometimes the PH probe would

randomly stay at a low pH of like 6 or a high ph of 8 after having been cleaned and juststanding in the open air. I think that sometimes the pH probes readings were randomly

off. Another source of error was the small sample size of the experiment. We only tookfour transects when we should have tried to do more like ten. If we had done more

transects this wouldve reduced the error caused by problems like when the pH probes

decided not to work right. Another source of error is that there was no way to regulate thematerials incorporated into the soil when the soil sample was taken. For instance, some of

the soil samples taken farther inland had to be dug up from mossy grass whereas the soil

samples taken closer to the water were taken from bare dirt. The soil taken from the grass

might have included plants that were not apart of the soil like moss or grass that could haveeffected the soil pH somehow.

One possible way to improve this lab would be to make the transects longer like 10

meters long, and to still take soil samples every 40cm. By only using 2 meter transects wemight have not noticed trends that continued and took shape later on, farther away from the

lake. Another possible way to improve this lab would be to have taken soil samples right at

the edge of the lake soil samples from the actual lake bed by taking soil from the lake andletting it dry out in a strainer over night and then measuring its pH as we did with the rest

of the soil samples. These extra samples would give us more valuable information like if

there was a difference of soil pH in soil that had been in direct contact with the lake versus

soil samples taken inland. The last way to improve this lab would be to make sure that atransect was taken in every different soil environment from around the lake. For instance,

if there was a part of the lake bordered by trees we shouldve taken a transect there, and if

there was a part bordered by rushes and cattails we should have taken one there andetcetera, etcetera until every different type of land bordering the lake had a transect taken

by it. This would account for any differences in soil pH caused by the vegetation

surrounding the soil, and hopefully minimize the effects of these differences by havingthem all equally represented.

iblabexample1[1]

Documents