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IGCSE Environmental Management Paper 2 — Topic 3 Water — Challenge

Environmental Management in Context — Topic 3 Challenge — source led
50 minutes
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0680
This paper covers the whole of Topic 3. The questions are not in syllabus order and they are not one question per sub-topic. Material from 3.1 to 3.6 is mixed across every question, exactly as Cambridge mixes it, so do not expect Question 1 to be about 3.1.

Instructions

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Question 1 — Source A, water availability
Total: 10 marks
SOURCE A — Access to a safely managed drinking water supply, five regions, one year
0 20 40 60 80 100 96 62 Region P 88 41 Region Q 99 93 Region R 74 28 Region S 91 55 Region T Population with access / % Region urban rural
Each bar shows the percentage of that region’s urban or rural population that has access to a safely managed drinking water supply. The regions are labelled P to T.
(a)(i)[1]
Using Source A, identify the region with the lowest rural access, and state the figure for that region.
Model Answer — 1(a)(i)
region S, 28%
both the letter and the figure with its unit are needed for the mark
⚠ If you missed marks here: an identify question from a source wants the figure as well as the label, and the unit as well as the number. Region S alone, or 28 alone, is half an answer. Also read the key: it is the rural bar that is asked for, and region S does not have the lowest urban bar.
(a)(ii)[2]
Calculate the difference, in percentage points, between urban and rural access in region Q. Show your working.
Model Answer — 1(a)(ii)
88 − 41   M1 for the correct subtraction from the chart
= 47 percentage points   A1
the working mark is available even if the arithmetic slips, so always write the subtraction down
⚠ If you missed marks here: two different numbers can be read off region Q and it is easy to grab the wrong pair. Check the key before you subtract. Note also that the answer is in percentage points, not per cent. A gap from 88% to 41% is 47 percentage points; calling it "47 per cent" means something different and a careful marker will notice.
(b)[3]
Describe the pattern shown in Source A. Use figures from the chart in your answer.
Model Answer — 1(b)
urban access is higher than rural access in every region shown, so the pattern holds across the whole chart rather than in one place
the rural values are far more spread out than the urban values: rural runs from 28% in region S to 93% in region R, while urban only runs from 74% to 99%
region R has both the highest values and the smallest gap, 99% urban against 93% rural, a gap of only 6 percentage points
accept instead of the third point: the region with the largest gap, Q at 47 percentage points, is not the region with the lowest rural access, which is S
1 mark per point, maximum 3. A point with no figure attached is capped at 1 mark for the whole answer
⚠ If you missed marks here: a describe question on a source is marked for figures. Writing "urban is higher than rural" describes the chart correctly and earns one mark at most, because it could have been written without looking. Quote the numbers, and quote a pair rather than a single value so the marker can see the comparison you are making.
(c)[1]
State one thing that Source A does not tell you.
Model Answer — 1(c)
it says nothing about sanitation or sewage treatment, which is a separate part of the same syllabus objective
it gives no population sizes, so a region with a high percentage may still contain more people without access than a region with a low one
it covers one year only, so it shows no trend over time
it does not say what "safely managed" was taken to mean, or how the figures were collected
any one of these scores
⚠ If you missed marks here: this is an AO3 mark and it is free if you practise it. The trick is to ask what a decision maker would still need to know. Percentages hide population size, one year hides a trend, and one variable hides everything else. Do not answer with something the chart does show.
(d)[3]
Region S and region Q both have poor rural access. Using Source A, suggest which of the two should be given priority for investment, and justify your choice.
Model Answer — 1(d)
1 mark for a clear choice supported by a figure quoted from the chart
1 mark for a second figure used in support, for example the size of the gap or the urban value in the same region
1 mark for a justification that goes beyond the numbers, for example naming what the chart cannot tell you and saying how that affects the decision
either choice can gain full marks. A typical strong answer for S: rural access is the lowest on the chart at 28%, so nearly three quarters of the rural population is without a safely managed supply, and the urban figure of 74% is also the lowest urban figure, so this is the weakest region overall rather than a region with one weak group
a typical strong answer for Q: the gap of 47 percentage points is the largest on the chart, and the urban figure of 88% shows the region already has the capacity to supply water, so extending an existing system to rural areas may reach more people per unit spent
the honest limitation, worth the third mark either way: the chart gives percentages and not population sizes, so we cannot tell which region contains more people without access
⚠ If you missed marks here: a suggest question has no single right answer and the marks are for the reasoning, not the choice. Two things separate a full answer from a half one. First, use figures from the source rather than general statements. Second, say what you cannot tell from the source and how it would change your decision. That last sentence is pure AO3 and most students never write it.
Question 2 — Source B, nutrients in a river
Total: 10 marks
SOURCE B — Nitrate concentration in a river through one year
0 5 10 15 20 25 30 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec fertiliser applied Nitrate concentration / mg per dm3 Month
The river runs beside arable fields. The shaded band marks the two months in which nitrate fertiliser was applied to those fields.
(a)[1]
Using Source B, identify the month with the highest nitrate concentration and state that concentration.
Model Answer — 2(a)
May, 28 mg per dm3
the unit is on the axis label, so it is available and it is expected
⚠ If you missed marks here: read the axis, not the shape. The peak of the line is easy to see, but the mark also needs the value read across to the vertical axis and the unit copied from the axis label. A month with no figure, or a figure with no unit, is not a complete identify answer.
(b)[2]
Calculate the percentage increase in nitrate concentration between February and May. Show your working.
Model Answer — 2(b)
(28 − 5) ÷ 5 × 100   M1 for change divided by the starting value
= 460%   A1
accept a correctly rounded equivalent
⚠ If you missed marks here: percentage change is divided by the starting value, never by the finishing one and never by the change. Dividing by 28 instead of 5 here gives about 82% and loses the accuracy mark, though the method mark survives if the working is written down. Write the division out even when you can do it in your head.
(c)[4]
Explain how the nitrate reaching this river leads to eutrophication.
Model Answer — 2(c)
nitrate is leached out of the soil by rain, or carried in by surface run off, so the river water becomes enriched with nutrients
the extra nutrients allow rapid growth of algae at the water surface
the algal layer blocks the light, so the plants beneath cannot photosynthesise and they die
decomposers break the dead material down, and their respiration uses up the dissolved oxygen, so organisms that need oxygen die
1 mark per linked step, in sequence
⚠ If you missed marks here: the last step is where the marks go missing. The algae do not poison anything; the damage is done by the bacteria that decompose the dead plants, because their respiration strips the oxygen out of the water. An answer that stops at "the algae block the light" has written three quarters of the chain. Also, leaching is the named process by which the ions get from the soil into the water, so use the word.
(d)[2]
Suggest two reasons why the nitrate concentration falls between May and December.
Model Answer — 2(d)
any 2 from:
no more fertiliser is applied after April, so the input of nitrate to the soil has stopped
the growing crops take the nitrate up from the soil, so less is left to be leached into the river
nitrate already in the river is carried downstream and diluted, so the concentration at this point falls
plants and algae in the river take the nitrate up as they grow through the summer
the answer must be tied to the source: the shaded band ends in April and the fall begins after the peak
⚠ If you missed marks here: the command word is suggest, so there is no remembered answer to recall. Look at what the source actually gives you: the shaded band tells you when the input stopped, and the line tells you when the fall began. A suggestion that ignores both is a guess, and a guess that happens to be right still reads as one.
(e)[1]
State one limitation of using Source B as evidence that fertiliser use causes eutrophication.
Model Answer — 2(e)
it is one river in one year, so it cannot show whether the pattern repeats or whether other rivers behave in the same way
the graph shows nitrate concentration only. It does not show oxygen levels, algal growth or any organism dying, so it does not show that eutrophication actually happened
the two events happen close together in time, but the source cannot on its own show that one caused the other. Something else that changes in spring could be responsible
any one of these scores
⚠ If you missed marks here: the strongest version of this answer is the second one: the graph measures the suspected cause and never measures the effect. Getting into the habit of asking "which variable is actually plotted here" will earn you this mark on almost any source.
Question 3 — Source C, a toxic substance in a food chain
Total: 10 marks
SOURCE C — A persistent toxic substance in a marine food chain
water 0.002 micrograms per kg microscopic plant material 0.05 micrograms per kg filter feeding invertebrates 0.5 micrograms per kg small fish 3.5 micrograms per kg large fish 21 micrograms per kg seabirds 105 micrograms per kg Direction of feeding: each arrow points from what is eaten to what eats it Mean concentration of the substance in the tissues at each level
Table 1
Level in the food chainMean concentration of the substance / micrograms per kg
water0.002
microscopic plant material0.05
filter feeding invertebrates0.5
small fish3.5
large fish21
seabirds105
Table 2 — large fish of three different ages, taken from the same population
Age of large fish / yearsConcentration in its tissues / micrograms per kg
28
521
1044
The substance is not broken down in the body and is not excreted. Table 1 gives the mean concentration at each level of the food chain. Table 2 gives the concentration in large fish of three different ages from that same population.
(a)[1]
Using Table 1, identify the concentration of the substance in seabirds.
Model Answer — 3(a)
105 micrograms per kg
the unit is given in the table heading and is expected in the answer
⚠ If you missed marks here: copy the unit across from the column heading. On a source question the unit is always available, so leaving it off is giving a mark away for nothing.
(b)[2]
Calculate how many times greater the concentration in seabirds is than the concentration in the water. Show your working.
Model Answer — 3(b)
105 ÷ 0.002   M1 for the correct division
= 52,500 times   A1
the answer is a ratio, so it has no unit. "52,500 times greater" is the expected form
⚠ If you missed marks here: the difficulty here is the decimal, not the division. Dividing by 0.002 means the answer is far larger than the numbers look, and a slip of one decimal place turns 52,500 into 525,000 or 5,250. If you are unsure, write 0.002 as a fraction of one and count the places.
(c)[4]
Using both tables, explain the difference between bioaccumulation and biomagnification.
Model Answer — 3(c)
bioaccumulation is the build up of a toxic substance in a single organism over time, because the substance is taken in faster than it can be broken down or excreted
evidence from Table 2: in large fish from one population the concentration rises from 8 at 2 years to 44 at 10 years, which is a build up within one kind of organism as it ages, at one level of the chain
biomagnification is the increase in concentration as the substance is passed up a food chain, because each consumer eats many organisms from the level below and keeps the substance from all of them
evidence from Table 1: the concentration rises from 3.5 in small fish to 21 in large fish to 105 in seabirds, which is an increase between different levels rather than within one
1 mark for each definition and 1 mark for each correct piece of supporting evidence
⚠ If you missed marks here: this is the pair the examiner is actually testing, and the way to keep them apart is to ask what is on the horizontal axis. Bioaccumulation is measured against time in one organism. Biomagnification is measured against position in a food chain. Table 2 has ages in it; Table 1 has levels. Match the table to the word and the answer writes itself. An answer that defines both correctly but cites the wrong table for each scores 2 out of 4.
(d)[2]
Explain why this substance is a greater risk to the seabirds than to the small fish.
Model Answer — 3(d)
the seabirds are at the top of the chain, and each one eats many organisms from the level below over its life, so the substance from all of them is concentrated into one body
the concentration in the seabirds, 105, is 30 times the concentration in the small fish, 3.5, so the dose reaching their tissues is far higher
1 mark for the mechanism, 1 mark for using the figures from Table 1
⚠ If you missed marks here: an explain question wants the mechanism, and the mechanism here is the number of meals. A consumer near the top eats a great many organisms from the level below, keeps the substance from every one of them, and cannot break it down or excrete it. Quote the two concentrations as well: on a source question the figures are the second mark.
(e)[1]
State one thing that Source C does not show.
Model Answer — 3(e)
it does not show any harm: a concentration is not the same as an effect, and nothing in the source says the organisms were damaged
it gives no sample sizes, and Table 1 gives means with no indication of how much variation lies behind them
it does not show where the substance came from or how it entered the water
Table 2 compares fish of different ages at one moment, so it does not follow the same fish through its life
any one of these scores
⚠ If you missed marks here: the fourth point is the sharpest and the least often spotted. Table 2 is not the same fish measured three times; it is three different fish that happen to be different ages. That is still good evidence, but it is a weaker kind of evidence than the table appears to offer, and noticing that is exactly the AO3 skill Paper 2 rewards.
Question 4 — Source D, responding to an oil spill
Total: 10 marks
SOURCE D — An oil slick off a coastline, with clean up costs
LAND SEA oil slick wind direction A B C D 10 km Key: A sandy beach used for recreation · B mangrove and mudflat, a feeding ground for seabirds · C rocky shore covered with seaweeds · D small fishing harbour
Table 1 — cost of clean up methods
MethodCost / thousand dollars per km of coast protected
booms and sorbents18
skimmers12
detergent spray7
controlled burning5
An oil tanker has released oil about ten kilometres offshore. The wind has been steady in the direction shown for two days. 24 km of coast is expected to be affected. The scale bar shows 10 km.
(a)[2]
Using Source D, identify which of the four sites is at greatest risk from the slick, and give evidence from the map for your choice.
Model Answer — 4(a)
site C
evidence, either of: it is the closest site to the slick, about 12 km measured against the scale bar; or it lies directly downwind, because the wind arrow on the map points along the line from the slick to C
1 mark for the correct site, 1 mark for evidence read from the map
site D also lies roughly downwind, but it is about 23 km away, nearly twice as far as C, so the oil reaches C first
site B is nearer than A or D, at about 14 km, but the wind is not blowing towards it, so distance alone does not put it at greatest risk
⚠ If you missed marks here: two separate pieces of information on this map point the same way, and a full answer uses at least one of them explicitly. Naming a site with no reason is one mark out of two. The wind arrow is the piece most people ignore: a slick does not spread as a circle, it is driven, so the nearest site is not automatically the one at greatest risk and the site straight downwind is. Here both tests agree on C, which is why it is the answer; check both before committing.
(b)[2]
Describe two impacts the oil could have on the coastal ecosystem at the site you chose.
Model Answer — 4(b)
any 2 from:
the oil coats the seaweeds on the rocky shore and blocks the light, so they cannot photosynthesise and they die
organisms that shelter or feed among the seaweeds lose their habitat and their food supply, so their numbers on that shore fall
oil coats the feathers of seabirds, so the feathers no longer trap air, and the birds lose both insulation and buoyancy
oil coats the gills of fish and of crustaceans, so they cannot take up oxygen from the water
toxic components of the oil are taken in by organisms and accumulate in their tissues
1 mark each. Naming an impact scores; the mechanism strengthens the answer but is not required at 1 mark each
⚠ If you missed marks here: the syllabus lists the groups affected, so answer in those terms: seabirds, marine mammals, fish, crustaceans, seaweeds, coral reefs and beaches. You are not required to name any particular species and no credit is given for doing so. Note the site you chose is a rocky shore covered with seaweeds, so an impact that fits that site reads better than a generic one.
(c)[2]
Using Table 1, calculate the total cost of protecting the whole affected coastline with booms and sorbents. Show your working.
Model Answer — 4(c)
18 × 24   M1 for cost per km multiplied by the length of coast
= 432 thousand dollars   A1
accept 432,000 dollars
⚠ If you missed marks here: the length of coast is not in the table. It is in the text above the map, and a question will often split the two numbers it wants you to multiply between two parts of the source. Before calculating, check you have taken each number from the right place and that the units match: thousand dollars per km multiplied by km gives thousand dollars.
(d)[4]
Evaluate the use of detergent spray rather than booms and sorbents on this coastline.
Model Answer — 4(d)
up to 3 marks for points on both sides, at least one each way, then 1 mark for a supported judgement.
In favour of detergent: it is much cheaper. At 7 against 18 thousand dollars per km, the whole 24 km costs 168 rather than 432 thousand dollars, a saving of 264
In favour of detergent: it can be sprayed from the air over a slick that is still offshore, so it can act before the oil arrives, and the wind is pushing the slick towards the shore now
Against detergent: the detergent is itself toxic to marine organisms, so it adds a second pollutant to the water
Against detergent: it breaks the oil into small droplets that mix down into the water rather than removing it, so the oil is dispersed into the ecosystem instead of being taken out of it
Against detergent: booms and sorbents actually remove the oil, which matters for a rocky shore covered with seaweeds where dispersed droplets would settle among the organisms
Judgement, 1 mark: a conclusion that names what the decision turns on and is consistent with the points made, for example: detergent buys speed and saves 264 thousand dollars, but it moves the oil into the water column rather than removing it, so on a shore whose value is its living seaweed community the cheaper method transfers the cost from the clean up budget to the ecosystem
a judgement with no reasoning behind it, or one that contradicts the points made above it, scores 0 of the last mark
⚠ If you missed marks here: an evaluate question is not a list with a sentence stuck on the end. Three things lift it. Use the figures you were given, because the cost difference is on the page and quoting it is free. Say who bears each cost: the saving goes to whoever pays for the clean up, the dispersed oil goes to the ecosystem. And make the judgement follow from what you wrote, rather than announcing a preference you never argued for.

Self-Assessment

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IGCSE Environmental Management 0680 — Paper 2 — Topic 3 Water — Challenge
For examination preparation only. Not an official Cambridge Assessment paper.