Pollution, Carbon & Climate Evidence — Chapter review · Physics & Environmental Science, Grade 12

Connect pollutant transport, carbon chemistry, radiation balance, and long-term evidence.

Review the key ideas

Pollution

Pollutant effects depend on exposure and chemistry; distinguish buildup within organisms, uptake from water, and concentration changes across feeding levels.

Climate Change

Greenhouse gases affect infrared energy balance; use dated climate observations, mechanisms, and alternatives to evaluate change. Supplied CO₂ values are practice comparisons.

Ocean Chemistry, Carbon & Acidification

Added dissolved CO₂ can lower pH and alter carbonate chemistry even while seawater remains basic.

Climate Data, Trends & Attribution

Interpret climate claims using baselines, timescales, mechanisms, and dated evidence.

Problem 1

Classify each source as point-source or nonpoint-source pollution: (a) a discharge pipe from one chemical plant, (b) pesticide runoff from thousands of farm fields, (c) a single smokestack, (d) oil and salt washing off a city's roads.
Answer and explanation

(a) point-source, (b) nonpoint-source, (c) point-source, (d) nonpoint-source.

Point-source pollution enters from one identifiable location you can point to and sample: the chemical plant's pipe (a) and the single smokestack (c). Nonpoint-source pollution comes from many scattered sources at once: runoff from thousands of fields (b) and oil washing off a whole city's roads (d). The nonpoint sources are harder to regulate because there is no single outlet to control.

Problem 2

Name one technology that reduces air pollution from vehicles, and briefly state what it does.
Answer and explanation

A catalytic converter, which chemically converts harmful exhaust gases into less harmful ones before they leave the tailpipe.

A catalytic converter sits in a car's exhaust system and uses catalysts to convert pollutants such as carbon monoxide and nitrogen oxides into less harmful carbon dioxide, nitrogen, and water. (Other acceptable answers include cleaner-burning or electric engines and particulate filters.) This is an example of a technological solution that reduces the impact of human activity on natural systems.

Problem 3

A persistent contaminant is .005 mg/kg in algae tissue. Each feeding transfer multiplies tissue concentration by 10 in a supplied model. Algae→insects→small fish→large fish→herons has four transfers. Find heron concentration.
Answer and explanation

50 mg/kg

.005×10⁴=50mg/kg; water-to-organism bioconcentration is a different comparison.

Problem 4

Explain why nonpoint-source pollution, such as farm and lawn runoff, is often harder to reduce than pollution from a single factory pipe.
Answer and explanation

Because it comes from many diffuse, scattered sources across the landscape rather than one identifiable outlet, so there is no single place to monitor, treat, or regulate.

A factory pipe is a point source: you can measure exactly what comes out of it and require the factory to treat it or shut it off. Nonpoint pollution enters from countless separate places at once — millions of acres of farms, lawns, and roads — whenever it rains. There is no single outlet to sample or plug, and controlling it means changing the behavior of huge numbers of people and land uses, which is why it is now a leading and stubborn cause of water pollution.

Problem 5

Explain the natural greenhouse effect without claiming Earth would necessarily be a uniformly frozen ball without it.
Answer and explanation

Greenhouse gases absorb and emit infrared radiation, making the surface substantially warmer than a simplified no-greenhouse radiative estimate. Regional ice and climate depend on more than one mean-temperature estimate.

Distinguish a mean energy-balance model from detailed geographic climate and avoid overinterpreting the simplified estimate.

Problem 6

A supplied CO₂ comparison uses 280ppm and 420ppm. Calculate the relative increase and state one item needed to interpret real observations.
Answer and explanation

50%; specify date/averaging and monitoring location or network.

140/280×100=50%. A real concentration claim requires dated, defined observations.

Problem 7

Give two reasons scientists are confident that recent global warming is caused by human activity rather than natural changes in the Sun.
Answer and explanation

The extra CO2 carries a chemical (isotopic) fingerprint identifying it as fossil-fuel carbon, and natural drivers like the Sun are either too weak or trending the wrong way; also, the upper atmosphere is cooling while the surface warms, the signature of trapped heat rather than a hotter Sun.

First, the added carbon dioxide has a distinctive mix of carbon isotopes that matches ancient fossil fuels, not volcanoes or the oceans, so we can trace the extra CO2 to human burning. Second, the natural drivers that changed past climates — the Sun's output, volcanic activity, and orbital wobbles — are all either too slow or currently pointing toward cooling, so they cannot explain the rapid recent warming. A clinching detail is that the upper atmosphere is cooling even as the surface warms; a brighter Sun would warm both, but heat being trapped near the surface by greenhouse gases cools the layers above — exactly what is observed.

Problem 8

Algae.01mg/kg to grazers.1 to fish 1: describe the pattern.
Answer and explanation

Each feeding transfer increases tissue concentration tenfold in the supplied model. It is not a rule for all substances.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 9

Chapter review: An outlet flows200 L/min at3 mg/L. Find pollutant mass emitted in1 h. Treatment captures80% into sludge with no chemical destruction; find waterborne and captured mass.
Answer and explanation

Initial mass=200×60×3=36000 mg=36 g. Waterborne residual=7.2 g; captured mass=28.8 g. The captured material remains in the full system account.

Initial mass=200×60×3=36000 mg=36 g.

Waterborne residual=7.2 g; captured mass=28.8 g.

The captured material remains in the full system account.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical or environmental mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 10

Why does more atmospheric CO₂ affect energy balance?
Answer and explanation

It changes infrared absorption/emission and radiative escape, causing system temperatures to adjust; evaluate multiple observations and forcing mechanisms.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 11

Chapter review: A model Earth absorbs242 W/m² and emits240 W/m² for10 s. Find stored-energy increase per area and explain why this alone does not give a surface-temperature change.
Answer and explanation

Increase=(242−240)×10=20 J/m². Temperature change also needs heat capacity, depth/distribution of storage and coupled responses; this is a supplied short model interval, not an actual climate measurement.

Increase=(242−240)×10=20 J/m².

Temperature change also needs heat capacity, depth/distribution of storage and coupled responses; this is a supplied short model interval, not an actual climate measurement.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical or environmental mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 12

A modeled pH fall of.30 gives factor 10^.30. Find factor.
Hints

Write the relationship first; substitute with consistent units.

Answer and explanation

2 times

10^.30≈1.995.

Problem 13

Why not equate acidification with warming?
Answer and explanation

They are distinct processes: acidification changes chemistry; warming changes temperature, though they can interact.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 14

Chapter review: A seawater sample changes frompH8.1 topH7.9. Estimate the[H⁺] ratio and explain whether that proves a58% carbonate decrease.
Answer and explanation

[H⁺] increases by10^0.2≈1.585, about58.5%. It does not prove the same carbonate decrease; alkalinity, dissolved carbon and coupled-equilibrium conditions are also required.

[H⁺] increases by10^0.2≈1.585, about58.5%.

It does not prove the same carbonate decrease; alkalinity, dissolved carbon and coupled-equilibrium conditions are also required.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical or environmental mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.

Problem 15

Name two pieces of information needed with a CO₂ concentration claim.
Answer and explanation

Location/network, date/interval, averaging method, units, and measurement method are examples.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 16

Why separate projections from observations?
Answer and explanation

Projections depend on future scenarios and models; observations describe measured past/current conditions.

Response criteria

  • State a scientifically accurate conclusion.
  • Show the calculation or mechanism that supports it.
  • Include units, conditions, or limits where relevant.

Problem 17

Chapter review: Two absolute global temperature estimates are14.6°C and15.0°C. Their baseline is14.0°C, then changed to14.2°C. Find both anomaly pairs and show whether their difference changes.
Answer and explanation

Original anomalies are0.6 and1.0°C; new anomalies0.4 and0.8°C. The difference remains0.4°C, so a uniform baseline shift changes offset rather than physical change.

Original anomalies are0.6 and1.0°C; new anomalies0.4 and0.8°C.

The difference remains0.4°C, so a uniform baseline shift changes offset rather than physical change.

Response criteria

  • Use the stated measurements or conditions, with correct units.
  • Connect the result to the physical or environmental mechanism or evidence relationship.
  • Identify the assumption, model limit or further evidence requested.
Take the chapter quiz

Browse all courses