Analyze and interpret quantitative data

Nutrient pollution along a river

Units 2, 5 and 8
10 points
About 23 minutes

You can use a calculator on this question, just like on exam day.

You read values and trends from a data table or described graph, explain what the data show about an environmental problem, and propose and justify a solution. On the exam: Question 2 of 3 in the 70-minute free-response section (Section II is 40% of the exam score).

The question and its sources

A river flows past a hog concentrated animal feeding operation (CAFO) and, 3 km farther downstream, the outfall pipe of a town's sewage treatment plant. A water-quality team sampled four sites on the same summer afternoon. The water temperature was 20 °C at every site.

Table 1: Water-quality data

Site	Location	Nitrate (mg/L)	Phosphate (mg/L)	Dissolved oxygen (mg/L)	Number of fish species found
1	5 km upstream of the CAFO	0.8	0.02	9.1	12
2	Just downstream of the CAFO	6.5	0.35	6.0	7
3	Just downstream of the sewage plant outfall	8.9	0.60	3.2	3
4	15 km downstream of the outfall	3.1	0.15	7.4	9

Source: Hypothetical data

Suggested time: 23 minutes

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Part (a)

1 point

Identify the site with the lowest dissolved oxygen concentration.

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Part (b)

1 point

Describe the relationship between nitrate concentration and dissolved oxygen across the four sites.

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Part (c)

1 point

Explain how high nutrient levels can lead to low dissolved oxygen at Site 3.

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Part (d)

1 point

Explain why fewer fish species were found at Site 3 than at Site 1.

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Part (e)

1 point

A student claims the data show that the CAFO is the cause of the high nitrate level at Site 3. Explain why the data do not fully support this claim.

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Part (f)

1 point

Describe one reason that water quality at Site 4 is better than at Site 3.

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Part (g)

1 point

Describe one threat to human health, other than nutrient pollution, posed by waste from CAFOs.

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Part (h)

1 point

Describe how a sewage treatment plant can reduce the amount of phosphate it releases into the river.

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Part (i)

1 point

Propose one realistic solution to reduce nutrient runoff from the CAFO.

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Part (j)

1 point

Explain how the solution you proposed in part (i) would improve water quality in the river.

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