Water Quality Lab
By: Elise Butterworth
Partners: Amanda, Skye
Pre Lab Questions:
1. Why is rain water normally slightly acidic?
Rain water is normally slightly acidic because of carbon dioxide in the
atmosphere. Carbon dioxide dissolves and turns into carbonic acid. This mixture makes the
pure water slightly acidic with a pH of 5.6 (Measuring Acid Rain, 2012).
2. Why are oxygen-demanding wastes pollutants?
Oxygen demanding wastes are pollutants because they reduce the amount of
dissolved oxygen in a body of water. This also creates an oxygen sag curve, which lessens or
eliminates organisms that require high levels of oxygen. When the body of water is cleansed the
populations can return to normal (Miller 2001).
3. How does B.O.D. relate to D.O.?
Biological Oxygen Demand is the amount of oxygen needed by aerobic
organisms to decompose organic material. If the amount of waste is high, then a lot of
microorganisms will be present in order to break down the waste. The B.O.D level will rise
because of the high demand for D.O. The D.O. levels will begin to drop because of the
organisms using the oxygen (Biological Oxygen Demand, 2015).
4. What are ways in which sedimentation occurs in waterways?
Sediments occur in waterways by transportation such as wind, surface runoff, or
gravity to water sites that are downhill or downwind (Miller 2001).
5. What is the impact of sedimentation on aquatic species?
Sedimentation disrupts the process of photosynthesis by causing an increase in
water turbidity that blocks sunlight. A reduction in sunlight can reduce plant growth.
Sedimentation can also affect aquatic species visibility, making it harder for the fish to find and
catch their prey. Also, sediments can clog the gills of fish such as trout, and this interrupts their
breathing (Soil in Our Streams, 2015).
6. What is the impact of warmer aquatic temperatures on aquatic species?
Elevated temperatures reduce the amount of dissolved oxygen and increase
respiration, oxygen demand, and metabolism in aquatic species. This low supply and high
demand of oxygen leads to the death of many species. There is also a maximum temperature that
organisms can tolerate, and higher temperatures most often correlate with death among most
aquatic organisms (Water Temperature Affects on Fish and Aquatic Life, 2015).
Data Table:
WEIGHING
FACTOR:
.10
TOTAL:
0 mg/L
Q-VALUE
/QUALITY:
98
Phosphates (PO4 )
1 mg/L
40
.10
4
D.O.
3 mg/L
D.O.
25 % Saturation
13
.17
2.21
5
30
.11
3.3
0 oC
150 mg/L
93
80
.10
.07
9.3
5.6
40 NTU
23
.08
1.84
72
.11
7.92
positive
.16
TEST
TEST RESULTS:
Nitrates (NO3-)
3-
pH
Iron
.02 ppm
Copper
0 ppm
Hardness
0 ppm
Alkalinity
20 ppm
Temperature #1
10 oC
Temperature #2
10 oC
ΔoC
TDS
TSS (Turbidity)
B.O.D.
B.O.D.
Macroinvertebrates
Macroinvertebrates
Macroinvertebrates
Fecal Coliform
9.8
.4 mg/L Dark D.O.
2.6 Δ mg/L D.O.
1 # Intolerant (Group 1)
1 # Moderate (Group 2)
2 # Tolerant (Group 3)
colonies/100 mL
Water Quality Index (WQI) = 43.97 x 1.19 = 52.32 or Average Water Quality
Cumulative Index Value = 7 , Poor Pond Quality
1x3=3
1x2=2
2x1=2
POST-LAB QUESTIONS:
1. Based on the WQI value for our Eco-Studies Pond, what would be its Water Quality
Rating? Explain your overall pond assessment as it relates to WQI.
The ponds water quality rating would be average. This is because the pH level
was adequate. Although, the dissolved oxygen levels were fairly low so this would
decrease the quality of the water because of a loss of species. In addition, turbidity
levels were moderate, and concentrations of phosphates and nitrates were not too high.
2. Of all of the tests performed, which should have the greatest impact on the Water Quality
Rating? Explain why.
Dissolved oxygen would have the greatest impact on the WQR because
without oxygen in the pond, aerobic species would not be able to survive.
3. If our Eco-Studies Pond showed high NO3ˉ levels, what might be the source?
High levels of nitrates could come from fertilizer runoff that is coming from grass
surrounding the pond. Also, nitrates may enter the pond by animal waste.
4. What might be the cause of high turbidity? Explain your answer.
High turbidity could be caused by soil erosion that creates a buildup of sediment
in the water. Some examples of sediments are soil and silt. Another cause of high
turbidity could be excess growth of algae from nitrates and phosphates that enter the
water. Lastly, organic and inorganic material could cause cloudiness in the water.
5. What might be two causes of a higher temperature in the different sides of the pond?
Both sides of the pond had a temperature of 10 degrees Celsius. Although,
difference in water quality could come from shading on one side of the pond. For
example, mod one could potentially block sunlight from side of the pond closest to it.
Also, sediment eroding from the slight hill on the side of the pond farthest away from the
mods, could cause turbidity. This would block sunlight and lower water temperatures on
that side.
6. What problem might result from a higher pond temperature?
A higher pond temperature decreases levels of dissolved oxygen, which causes an
increase in biological oxygen demand. This deficit of supply can instigate the death of
many organisms.
7. We did not test for fecal coliform bacteria. Why might this test not be necessary for our
Eco-Studies Pond?
Fecal Coliform bacteria may not be necessary to test because it is known that
the many organisms living in the pond produce fecal matter. So in effect, fecal
coliform bacteria should be present in moderate amounts.
8. Discuss the importance of the “other chemical” tests and what information can be learned
from each.
Hardness in water measures the concentrations of divalent salts and alkalinity
measures base concentrations. Alkalinity testing is important because in ponds with low
alkalinity levels, certain nutrients are unavailable to aquatic plant life. Information such
as how stable the environment is can be learned by alkalinity levels because these bases
neutralize acids, buffering pH levels. Hardness testing is also important because hard
water has a higher concentration of alkaline earths. Again, information about pH can
be learned through hardness tests. Also, testing copper levels is important because copper
can be toxic to aquatic organisms. From the test, dissolved oxygen levels can be
estimated because high levels of copper can kill algae, which depletes dissolved oxygen `
levels. Testing for iron is also important because it plays a factor in organism health. Low
levels of iron decrease metabolism rates in some aquatic species (Water Temperature
Effects on Fish and Aquatic Life, 2015).
9. Explain how indicator species are used to assess water quality and explain why they are a
good measure for determining water quality. (Hint: Compare your cumulative index
value with your water quality index.)
The presence or absence of indicator species can aid in determining water quality.
For example, the presence of trout can indicate high levels of dissolved oxygen and clean
water. Also, bottom dwelling species can be used to assess water quality because the
water is filtered through their bodies. If the water is polluted than the organisms will
show signs of this. Lastly, indicator species such as cattails, can be removed from their
environment and analyzed to determine the exact pollutants contained in a body of
water. Indicator species are a good measure for water quality because they provide early
warning signs of damage to an ecosystem. The cumulative index value and water quality
index value were somewhat similar, so indicator species can provide around the same
results as water quality tests (Miller, 2001).
Citations:
Measuring Acid Rain. (n.d.). Retrieved December 4, 2015, from
http://www3.epa.gov/acidrain/measure/index.html
Miller, T. (2001). Living in the environment: Concepts, problems, and alternatives. Belmont,
Calif.: Wadsworth Pub
Biological Oxygen Demand. (n.d.). Retrieved December 4, 2015, from
http://www.polyseed.com/misc/BODforwebsite.pdf
(n.d.). Retrieved December 4, 2015, from
http://www.bae.ncsu.edu/programs/extension/wqg/sri/sediment5.pdf
Water Temperature Effects on Fish and Aquatic Life. (n.d.). Retrieved December 5, 2015, from
http://sciencefairwater.com/physical-water-quality-parameters/water-temperature/watertemperature-effects-on-fish-and-aquatic-life/
Water Quality Concerns for Ponds (Water Quality). (n.d.). Retrieved December 11, 2015, from
http://extension.psu.edu/natural-resources/water/ponds/pond-management/pondconstruction/water-quality-concerns-for-ponds