Pollution — Drills · Grade 12 Science

Chapter: Pollution, Carbon & Climate Evidence

What these drills covers

By the end of Pollution you should be able to:

6 questions, multiple choice, numeric and written answer, each with a worked explanation.

Vocabulary used: pollutant, point-source pollution, nonpoint-source pollution, eutrophication, biomagnification.

Problem 1

Which of the following is an example of point-source pollution?
  1. Runoff from many farm fields after a rainstorm
  2. A single pipe carrying waste from one factory into a river
  3. Exhaust from all the cars across a city
  4. Pesticides drifting off thousands of separate lawns
Answer and explanation

A single pipe carrying waste from one factory into a river

Point-source pollution comes from one identifiable outlet you can point to and regulate — like a single factory's discharge pipe. The others are diffuse, nonpoint sources.

Problem 2

Which air pollutant, released by burning coal and oil, is a major cause of acid rain?
  1. Nitrogen gas (N2)
  2. Water vapor
  3. Sulfur dioxide
  4. Oxygen
Answer and explanation

Sulfur dioxide

Sulfur dioxide (along with nitrogen oxides) dissolves in cloud water to form acids that fall as acid rain; oxygen, nitrogen gas, and water vapor are harmless components of clean air.

Problem 3

A toxin measures 0.03 ppm in algae tissue and biomagnifies about 10 times at each of two steps up the food chain (algae → zooplankton → fish). About what is its concentration, in ppm, in the fish?
Answer and explanation

3 ppm

Two tenfold steps: 0.03 × 10 × 10 = 0.03 × 100 = 3 ppm. This supplied teaching factor applies between feeding levels; water-to-organism uptake is bioconcentration.

Problem 4

Explain the difference between bioaccumulation and biomagnification.
Answer and explanation

Bioaccumulation is the buildup of a persistent pollutant within a single organism over its lifetime, because it stores the toxin faster than it can get rid of it. Biomagnification is the increase in that pollutant's concentration from one trophic level to the next up a food chain, because each predator eats many contaminated prey. Bioaccumulation happens within an individual; biomagnification happens across a food chain.

Problem 5

Why are plastics an especially persistent pollutant of land and water?
  1. They are only ever found inside sealed landfills
  2. They quickly biodegrade into harmless nutrients
  3. They dissolve completely in water within a few days
  4. Many common plastics fragment into persistent smaller particles instead of rapidly biodegrading under ordinary environmental conditions
Answer and explanation

Many common plastics fragment into persistent smaller particles instead of rapidly biodegrading under ordinary environmental conditions

Degradation depends on polymer and conditions; fragmentation alone does not establish complete biodegradation.

Problem 6

A factory discharges warm, contaminated water from a single pipe into a river. Propose one technological solution that would reduce this pollution's impact, and explain how it helps.
Answer and explanation

The factory could install a wastewater treatment system that removes contaminants (and cools the water) before it is released, so the water returned to the river is clean and closer to the river's natural temperature. Because this is a single point source, treating it at the outlet is practical and directly reduces the harm to the river's ecosystem — an example of a technological solution that lessens human impact on a natural system.

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