1. Perchloroethylene is an industrial solvent that can be used for metal
degreasing. If 2480 L of perchloroethylene were accidentally leaked
into the environment and entered the groundwater, how many tonnes
of iron would be needed to purify the groundwater using an
underground permeable wall? (perchloroethylene density =
1.623 g mL") (5 marks)
2. Consider a lake containing 39 ppb of parathion, which has a log Kow =
3.8. (5 marks)
a. If a sample of lake water was mixed with octanol, what is the
expected concentration of parathion in the octanol?
b. Assuming the body weight of a fish is 4% fat, what is the
equilibrium concentration of parathion in the fish swimming in
3. After applying 2,4-D to turf, an experiment was conducted measuring
the concentration of 2,4-D that was present over time. The 2,4-D
concentration was 8o ppm on day zero, 45 ppm on day 14, and 6 ppm
on day 56. (5 marks)
a. Do a first-order kinetic plot to determine the rate constant for
the disappearance of 2,4-D.
b. What is the half-life for disappearance of 2,4-D in this
4. A toxic heavy metal has a whole body half-life of about 16 years.
a. The ADI (RfD) of this metal for food is 2.3 x 10-3 mg
What is the acceptable daily intake for a 75 kg person?
b. What is the whole body level of this metal if ingestion were
maintained at ADI? [Hint: Atmospheric residence time
analysis calculations are very similar.]
5. A water treatment plant has a holding tank that has a base of 10.0 m
by 12.0 m. The tank is filled to 7.0 m with water. (5 marks)
a. What pressure of C12 gas must be maintained above the surface
of the water to obtain 3.0 ppm of dissolved Cl2 gas? (Assume
KH(Cl2) = 2.4 X mol these conditions.)
b. What is the mass of the C12 gas dissolved into the water of this
1. Dioxins have a log Kow of 6.8. Based on this, explain why granulated
activated charcoal is considered to be the best available treatment
technology for dioxins in water. (5 marks)
2. For dioxins in fathead minnows the BCF = 29,200 and the half-life for
elimination of dioxins from is 14.5 days.  (5 marks)
a. For an aquatic habitat where the dioxin concentration of
0.015 ppt, what is the concentration of dioxin in fathead
b. If a minnow is taken from the contaminated habitat and placed
in a clean laboratory water tank, how many days will it take for
the dioxin concentration in the minnow to drop to 0.10 ppb?
3. Perfluorooctane sulfonate (PFOS) is considered to be a persistent
environmental pollutant, with a half-life in natural water being
approximately 41 years. It is resistant to hydrolysis, photolysis, and
aerobic and anaerobic biodegradation. Explain why PFOS is so
resistant to these processes. (5 marks)
4. Chemical dechlorination is a method for destroying PCB waste. How
many kilograms of potassium ethoxide (KOEt, or KOC2H5) is needed
to react with 450 kg of 2,3',4',5'-tetrachlorobiphenyl? (5 marks)
5. Indian mustard (brassica juncea) can be used for phytoremediation
of lead in soil because it has the ability to hyperaccumulate lead by a
factor of 17. The average crop yield is about 4.0 kg per square metre.
a. Calculate the expected plant concentration of lead if the soil
contains 28o ppm lead.
b. What mass of lead would potentially be recovered from a crop
planted on one square kilometre of soil with 28o ppm lead?
c. Another plant has a lead hyperaccumulation factor of 34, but
the crop yield is 2.8 kg per square metre. Is this plant a better
alternative to Indian mustard for phytoremediation of lead?
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