Quiz 3 (Post-Midterm)

Question 1

How is acid rock drainage formed?

Answer 1

Pyrite reacting with water and oxygen

Question 2

What are tailings? Give two ways tailings are commonly managed at mine sites.

Answer 2

Tailings are finely ground rock and mineral processing operations, including processing chemicals

1. Water-based slurry into tailing ponds (sedimentation lagoons enclosed by dams built to capture and store the tailings
2. Dry stack tailings

Question 3

Explain why it is important to determine heavy metal bioavailability on a remediation site.

Answer 3

• Because they don’t decay and they can enter the food web.
• To see if the metals are essential or non-essential, as they act differently. Essential metals are only toxic at significant levels, while non-essential metals are much more toxic.

Question 4

Which plant species might be useful for the revegetation of tailings and why? (5)

Answer 4

Marsh horsetail
- initial rapid decrease in compaction of the tailings
- initial rapid increase in inorganic nitrogen
- decreases conductivity of the tailings
- provides soil aeration through rhizomes
rapid decomposition and mineralization of litter

Willows:
- Tolerates poor soil conditions from mine tailings
- Increases soil stability

Balsam poplar
- Builds soil organic matter
- Provides shade to other species

Tamarack
- invades the site at 1.5m per year
- tolerates poor drainage sites

Black Spruce
- Invades at 1.5m per year
- creates a stable, mature environment

Question 5

Under aerobic hydrocarbon degradation hydrocarbon degrading microbes can synthesize _____ for growth and release ___ and ___?

Question 6

F3/F4 hydrocarbons are more or less as volatile as F1/F2 hydrocarbons.

Answer 6

F3/F4 are less volatile because they have stronger bonds and a more resilient chemical structure, which makes them less volatile and harder to break apart.

Question 7

What is biostimulation?

Answer 7

Stimulating activity in indigenous soil microbes through nutrient addition and optimizing environmental conditions (O2, pH, temperature)

Question 8

Explain the difference between in-situ and ex-situ hydrocarbon remediation.

Answer 8

Ex-situ: excavation of polluted soil and placement into chemcially secure landfarm
In-situ: treatment of contaminated soil in its natural place (situation)