IB ESS Topic 8

Which of the following pollutants contributes to eutrophication?

• pesticides

• chemical fertilizers

• heavy metals

• oil

Answer explanation

Only chemical fertilizer contain nitrogen and phosphorous that drive eutrophication.

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NGSS.MS-LS2-5

NGSS.MS-ESS3-4

An example of an organic pollutant is

• Radioactive waste from a nuclear power plant

• Chemical fertilizer applied to fields

• Animal manure from a feedlot

• An oil spill in the ocean

Answer explanation

The only example of organic pollution is animal manure. The others are inorganic.

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NGSS.MS-LS2-4

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Nitrogen in groundwater is more likely when

• located near/under forested areas

• located near/under agricultural fields

• located near/under industrial areas

• soils are exposed to acid deposition

Answer explanation

Nitrogen is not typically a natural component of groundwater and usually indicates fertilizer contamination from agriculture and/or failed septic systems. The other options are not sources for nitrogen in groundwater.

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NGSS.MS-LS2-4

NGSS.MS-ESS3-4

Nutrient rich runoff from fertilized fields causes

• adaptation

• eutrophication

• biomagnification

• denitrification

Answer explanation

The addition of nutrients into water bodies from fertilized fields will most likely lead to eutrophication and not biomagnification as nutrients are biodegradable. Eutrophication is the increase of nitrates in water, while denitrification reduces nitrates concentrations.

Tags

NGSS.MS-LS2-4

Eutrophication is:

• the decrease in oxygen content of water due to an explosion of decomposers

• an important energy flow in the nitrogen cycle

• a process used to purify water

• the gradual improvement of water quality in lakes and rivers

Answer explanation

Eutrophication starts with the increased input of nutrients which results in an increase in surface algae that block out sunlight to deeper parts of the water body. The increase in algae results in a temporary increase of smaller consumers but as they can't keep up with algal growth, much of the algae remains uneaten and when it dies falls to the bottom where decomposers increase using up oxygen. Larger consumers begin to die resulting in more decomposers until the complete food web collapses.

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NGSS.MS-LS2-4

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Which of the following does NOT occur at the end stage of eutrophication?

• Average dissolved oxygen content of water decreases

• Water nutrient content increases

• Producers increase

• Diversity increases

Answer explanation

As eutrophication progresses and dissolved water content decreases, the food web collapses, reducing diversity.

Tags

NGSS.MS-LS2-4

NGSS.MS-LS2-5

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Biochemical oxygen demand is measured in

• percent (%)

• parts per billion (ppb)

• milligrams per liter (mg/L)

• grams per liter (g/L)

Answer explanation

The correct units of measurement are milligrams per Liter or parts per million (ppm).

The cheapest strategy for reducing pollution is

• Clean up and restoration of polluted sites once development is complete

• Altering human activity that produces the pollution

• Regulating and reducing the pollutants at the point of emission

• Develop and instal technology to reduce pollution at acceptable levels

Answer explanation

Preventing pollution of the environment is always going to be much cheaper and effective in the long run than cleaning up once the ecosystem is already polluted. Even if all of the pollution can be removed, restoring the ecosystem to what it was before is almost impossible. While pollution reducing technology can minimize ecosystem impact, the cost of its development is often more expensive than changing the human behavior.

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NGSS.HS-ESS3-4

NGSS.HS-ETS1-3

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An example of 'Altering human activity that produces the pollution' to prevent eutrophication of water bodies is

• Banning the use of phosphate based detergents

• Replace chemical fertilizer with organic matter (i.e. compost)

• Treat runoff to remove nutrients before it enters the water body

• Pump air through the water body to increase dissolved oxygen levels.

Answer explanation

Although banning the use of phosphate based detergents is a regulation, more importantly it changes the human activity causing the pollution. The other examples do not change the human activity causing the pollution leading to eutrophication as in each a certain amount of nutrient is still being produced before it is either treated, diverted or removed after it was created.

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Two different factories release effluent into different initially clean rivers.:Factory A adds 3000 L per day with a BOD of 10 mg per LFactory B adds 1200 L per day with a BOD of 20 mg per LWhich statement correctly explains which factory is adding the most pollution resulting in the biochemical oxygen demand (BOD)?

• Factory A because it adds more pollution per day

• Neither, because the river takes it away, so preventing the pollution from increasing.

• Factory A because it adds more volume

• Factory B because the effluent has a higher BOD

Answer explanation

Since BOD is a concentration, the total amount of pollution causing the biochemical demand is determined by multiplying the concentration by the volume of effluent added.

Tags

NGSS.MS-LS2-4