Environmental Management 0680 | Paper 2 Mock 01 | Environmental Management in Context

(a) Main gas produced during anaerobic digestion: [1]

Methane (CH\(_4\)) [1]. Methane is the combustible component of biogas that provides the energy for cooking and lighting when burned.

(b)(i) Fuel type with the highest CO\(_2\) equivalent emissions (from Table 1): [1]

Firewood (45 kg CO\(_2\) equivalent per month) [1].

(b)(ii) One advantage of biogas over kerosene: [1]

Biogas costs only $3 per month (a maintenance fee) compared to $12 per month for kerosene, making it significantly cheaper and more affordable for low-income households [1].

(Other valid advantages: biogas produces far lower CO\(_2\) emissions (8 vs. 38 kg/month); produces very low indoor air pollution vs. medium for kerosene; is produced locally from farm waste rather than requiring a 25 km trip to purchase.)

(c) How switching from firewood to biogas could reduce deforestation: [2]

1. If households switch from firewood to biogas for cooking, they will no longer need to cut down trees and collect branches from surrounding woodland for fuel. The 85% of households previously relying on firewood represents enormous daily timber extraction [1].
2. This reduced demand for firewood would allow the woodland to regenerate naturally, reducing the soil erosion and water quality problems in the River Ondo that deforestation has caused [1].

(d) How the biogas digester produces gas from organic waste (from diagram and text): [3]

1. Cattle dung and crop waste are mixed with water in the mixing pit and loaded into the sealed underground digester tank through the input channel [1].
2. Inside the sealed tank, bacteria break down the organic matter under anaerobic conditions (without oxygen). This biological decomposition process is called anaerobic digestion [1].
3. The decomposition releases biogas (mainly methane), which rises and collects in the dome above the tank. From there, it is piped through a gas line directly to household cooking stoves for use as fuel [1].

(e) How the digestate could benefit local farmers: [2]

1. The digestate is rich in plant-available nutrients (nitrogen, phosphorus, potassium) that crops need to grow, making it an effective organic fertiliser [1].
2. Farmers can spread the digestate on their fields to improve crop yields while reducing or eliminating the need to purchase expensive chemical fertilisers. The digestion process also kills many weed seeds and pathogens present in raw dung, making it a safer and more effective soil amendment [1].

(f)(i) Why some farmers are reluctant to supply cattle dung: [1]

Farmers currently spread cattle dung directly on their fields as fertiliser and are concerned that diverting it to the biogas digester will reduce the fertility of their soil, leading to lower crop yields [1].

(f)(ii) One way to address this concern: [2]

The project organisers could explain and demonstrate to farmers that the digestate returned from the biogas plant is actually a more effective fertiliser than raw, unprocessed dung [1]. During anaerobic digestion, the nutrients in the dung are converted into chemical forms that are more readily absorbed by plant roots, while harmful pathogens and weed seeds are destroyed. Farmers would receive the digestate back as a superior fertiliser, so their soil fertility would improve rather than decline [1].

(g) Difference in CO\(_2\) equivalent emissions between firewood and biogas: [1]

\[ 45 - 8 = 37 \text{ kg CO}_2 \text{ equivalent per month} \] [1]

A household switching from firewood to biogas would reduce its monthly greenhouse gas emissions by 37 kg CO\(_2\) equivalent - a reduction of over 82%.

(h) Two social benefits of the biogas plant for Village M: [4]

1. Women and children previously spent an average of 3 hours per day collecting firewood from surrounding woodland [1]. Switching to biogas, which is piped directly to homes, eliminates this daily burden entirely. The time saved can be used for education (attending school or studying), income-generating activities, childcare, or rest - dramatically improving quality of life, especially for women and girls [1].
2. Indoor air pollution from burning firewood is rated as "High" in Table 1, causing respiratory diseases that are a leading cause of illness and death in rural communities worldwide [1]. Biogas produces "Very low" indoor air pollution, so switching significantly improves the respiratory health of household members, particularly women and children who were exposed to firewood smoke for hours every day while cooking [1].

(a) Two uses of sand and gravel in the construction industry [1 each, max 2]:

1. Concrete production: Sand is mixed with cement and water to make concrete, which is used for building foundations, walls and floors.
2. Road surfaces: Gravel is used as aggregate for road surfaces and in the production of asphalt.

Other valid answers include: glass manufacture, land reclamation, drainage fill, or mortar.

(b) Using Fig. 4 to describe the locations of extraction sites:

1. The five extraction sites are spread along a 25 km stretch of the Padma River in the Faridpur District [1].
2. Sites A and B are in the upstream section near Goalundo, while sites D and E are in the downstream section near Daulatdia and Nagarbari [1].
3. Site C is positioned in the middle section near Rajbari. Eroded bank sections (shown with wavy lines on the map) are visible near sites B, D and E, suggesting that extraction has destabilised the river banks in those areas [1].

(c) Changes in sand extraction and river depth (Table 4):

1. Sand extraction increased steadily from 2.4 million m³ in 2010 to 9.8 million m³ in 2025, more than quadrupling [1].
2. Average river depth decreased from 12.5 m to 7.2 m, a decline of 5.3 m or approximately 42% [1]:

\[\text{Percentage decrease} = \frac{12.5 - 7.2}{12.5} \times 100 = 42.4\%\]

3. The increase in extraction corresponds closely with the decrease in depth, confirming that sand removal is directly lowering the riverbed [1].
4. The trend is consistent across the entire period with no sign of recovery in any year, indicating ongoing and unsustainable pressure on the river system [1].

(d) Effects of sand removal on the river ecosystem:

1. Benthic habitat destruction: Removing sand destroys the riverbed habitat where invertebrates and fish depend on stable substrate for shelter, feeding and breeding [1].
2. Increased turbidity: Dredging operations stir up fine sediment, reducing light penetration in the water. This affects aquatic plants that need sunlight for photosynthesis [1].
3. Altered flow conditions: Changes in river channel depth and flow speed alter the distribution of species adapted to particular conditions, reducing biodiversity [1].
4. Fish spawning disruption: Fish such as hilsa that require sandy substrates for spawning cannot breed in areas where the sand has been removed. Table 4 shows fish catch declining from 1,850 to 510 tonnes per year [1].
5. Noise disturbance: Vibration and noise from suction dredging equipment disturbs aquatic organisms, causing them to avoid areas near extraction sites [1].

(e) How sand mining increases flood and erosion risk:

1. Bank collapse: Mining lowers the riverbed, which undercuts the river banks and causes them to collapse. The bank erosion rate increased from 3.2 to 12.5 m per year (Table 4), destroying farmland and buildings along the shore [1].
2. Increased flow velocity: A deepened channel can increase water velocity during floods, meaning floodwater moves faster and with more erosive force against downstream settlements [1].
3. Weakened natural levees: Natural levees along the banks are weakened by extraction, making them more likely to breach during monsoon floods and allowing water to inundate low-lying areas [1].
4. Quantitative evidence: The number of flood events along this stretch increased from 2 in 2010 to 7 in 2025, directly corresponding with the increase in extraction [1].

(f) Three ways the government could manage sand extraction [max 4 marks]:

1. Licensing and quotas: Introduce a system that limits the total volume extracted per year to a level the river can naturally replenish through sedimentation. Crack down on the estimated 15 unlicensed operations [1+1].
2. Seasonal bans: Enforce a ban on extraction during the monsoon period (June to September) when banks are most vulnerable to erosion and flood risk is highest [1].
3. Alternative materials: Promote the use of manufactured sand from crushed rock and recycled building materials as substitutes for river sand in the construction industry [1].

Other valid suggestions include: buffer zones near villages, environmental monitoring, fines for illegal extraction, or relocation of sites away from vulnerable areas.

(g) Why demand for sand has increased rapidly in Bangladesh:

1. Population growth: Bangladesh has over 170 million people and a growing population, creating demand for housing, schools, hospitals and other buildings [1].
2. Urbanisation: Dhaka (population over 22 million) and other cities are expanding rapidly with rural-to-urban migration, requiring large-scale residential and commercial construction [1].
3. Infrastructure projects: Government investment in major infrastructure - roads, bridges, flood defences and the Padma Bridge - has increased demand for concrete and aggregate [1].

(a)(i) Using Fig. 1, the approximate rates in 1950:

• Birth rate: approximately 47 per 1000 [1].
• Death rate: approximately 44 per 1000 [1].

These values are read from the y-axis where each line begins on the left side of the graph in 1950.

(a)(ii) The natural increase (the gap between the birth rate and death rate lines) has changed significantly:

1. In 1950, the natural increase was very small, approximately 3 per 1000, because the birth rate and death rate were almost equal [1].
2. By 2010, the gap had widened considerably because the death rate fell much more rapidly than the birth rate. The natural increase in 2010 was approximately 14 per 1000 (birth rate ~20, death rate ~6) [1].

(b) Two reasons why the death rate in Country R has fallen [2 marks each: 1 for reason, 1 for explanation]:

1. Improved healthcare: Better access to healthcare services, including vaccinations and treatment of infectious diseases, has reduced deaths from preventable illnesses such as measles, malaria and tuberculosis [1+1].
2. Better nutrition and water: Improved nutrition from increased food supply, and access to clean water and sanitation, have reduced deaths from malnutrition and waterborne diseases such as cholera and dysentery [1+1].

(c) Natural increase is the difference between the birth rate and the death rate, usually expressed as a percentage of the population [1]. Country Z has a negative natural increase (-0.1%) because its death rate (11 per 1000) exceeds its birth rate (10 per 1000) [1], meaning more people are dying each year than are being born. The population would shrink without immigration [1].

(d) Two differences between Country X (Stage 2) and Country Z (Stage 4) [2 marks each: 1 for each side of the comparison]:

1. Birth rate: Country X has a much higher birth rate (42 per 1000) compared to Country Z (10 per 1000) [1+1].
2. Life expectancy: Country X has a much lower life expectancy (58 years) compared to Country Z (82 years), reflecting differences in healthcare, nutrition and living conditions [1+1].

Other valid comparisons include: infant mortality rate (65 vs 4), or total fertility rate (5.6 vs 1.5).

(e)(i) The total fertility rate in Country S fell significantly from 5.8 in 1970 to 1.3 in 2020 [1]. The steepest decline occurred between 1970 and 1980 (5.8 to 2.7), coinciding with the introduction of the population control policy. The rate of decrease slowed after 1990 [1].

(e)(ii) The population continued to grow despite sub-replacement fertility because of population momentum:

1. The large number of women of childbearing age, born during the earlier high-fertility period, continued to have children. Even with fewer children per woman, the total number of births remained high because there were so many mothers [1].
2. Each woman had fewer children, but the total births still exceeded the number of deaths because the population structure had a large proportion of young adults who were reproducing [1].
3. The population also benefited from declining mortality - people were living longer, so fewer were dying relative to the total, contributing to net growth [1].

(f) Two problems from a very low fertility rate over a long period [1 each]:

1. Ageing population with labour shortages: A shrinking workforce leads to labour shortages and slower economic growth, with fewer workers to drive productivity.
2. Increased dependency costs: Growing costs for elderly care, pensions and healthcare as the proportion of elderly dependents rises, while fewer working-age taxpayers fund these services.

(g) Two reasons why Village Q has more children per family than Village P [2 marks each: 1 for the factor, 1 for explanation]:

1. Limited healthcare access: Only 35% of people in Village Q have access to healthcare (compared to 95% in Village P), meaning contraception and family planning services are less available. Fewer women can choose to limit their family size [1+1].
2. Lower education and literacy: The literacy rate in Village Q is only 58% (versus 92% in Village P). Lower education levels, particularly for women, mean less awareness of family planning methods and fewer career opportunities that might encourage smaller families [1+1].

(h) Improving education for women in Village Q could reduce the birth rate because:

1. Family planning knowledge: Educated women are more likely to understand and use family planning methods, leading to fewer unplanned pregnancies [1].
2. Career opportunities: Education provides women with career pathways, so they may delay having children to pursue employment and choose to have fewer overall [1].
3. Quality over quantity: Educated mothers tend to prioritise quality of life and resources for each child, investing in fewer children's education and health rather than having a large number [1].

(i) Calculating the percentage increase in the city's population:

Increase = 7,200,000 - 2,400,000 = 4,800,000 [1]

\[\text{Percentage increase} = \frac{4\,800\,000}{2\,400\,000} \times 100 = 200\%\] [1]

(j) Three strategies to manage challenges from rapid urban growth [2 marks each, max 6]:

1. Water and sanitation infrastructure: Invest in expanding the water supply network and sanitation systems to provide clean water and safe waste disposal for the growing urban population, reducing waterborne diseases [1+1].
2. Affordable housing: Build affordable housing and upgrade informal settlements to reduce overcrowding, improve living conditions and reduce the health risks associated with inadequate shelter [1+1].
3. Public transport: Develop efficient public transport networks (buses, rail) to reduce traffic congestion and air pollution from private vehicles, while connecting people to employment and services [1+1].

Other valid strategies include: expanding healthcare and education services, developing satellite towns, or implementing waste management systems.

(k) The birth rate in Country R has declined more slowly than the death rate because:

1. Birth rates are influenced by social and cultural factors that change slowly, such as traditional values favouring large families, religious beliefs about contraception, and the economic value placed on children as farm labourers and old-age support [1].
2. These attitudes take longer to shift than the medical and technological advances (vaccines, clean water, antibiotics) that reduced death rates rapidly [1].

(l) One reason why Country S relaxed its population control policy [1]:

• Concern about the rapidly ageing population and a future shortage of working-age people to support economic growth and fund pensions for the elderly.

Other valid answers include: growing gender imbalance, or the policy being seen as restricting personal freedom.

(a)(i) Definition of food miles: [1]

Food miles is the distance that food is transported from where it is produced to where it is consumed or sold [1]. A higher number of food miles generally means more fuel is burned during transport, contributing more carbon dioxide emissions to the atmosphere.

(a)(ii) Transport distances (from Table 1): [1]

The vertical farm produces food just 5 km from the consumer, while imported food travels 8,500 km [1]. This represents a 1,700-fold difference in transport distance.

(b)(i) Two advantages of vertical farming over importing (from Table 1): [2]

1. The vertical farm produces 45 kg per m\(^2\) per year compared to just 3.5 kg for conventional farming - nearly 13 times more food from the same footprint. This is because vertical stacking multiplies the effective growing area within a single building [1].
2. The vertical farm uses only 12 litres of water per kg of food compared to 85 litres for conventional farming - an 86% reduction. The closed water recycling system captures and reuses drainage, whereas open-field farming loses water to evaporation and runoff [1].

(b)(ii) Percentage reduction in CO\(_2\) emissions when food is produced locally: [2]

\[ \text{Reduction} = 890 - 120 = 770 \text{ g per kg} \] [1]

\[ \text{Percentage reduction} = \frac{770}{890} \times 100 = 86.5\% \] [1]

Producing food in the vertical farm reduces CO\(_2\) emissions per kilogram by 86.5% compared to importing it.

(c)(i) How reducing food miles lowers carbon dioxide emissions: [2]

1. Shorter transport distances mean fewer vehicle journeys and less fuel is burned for road and air freight. Trucks, ships, and cargo aircraft all combust fossil fuels during transport, releasing CO\(_2\). A 5 km delivery produces negligible transport emissions compared to an 8,500 km international journey [1].
2. Locally produced food does not require energy-intensive refrigerated containers for long-distance transport. Cold chain logistics consume significant electricity (often from fossil fuels) to keep perishable goods fresh over thousands of kilometres and several days of travel [1].

(c)(ii) How the water recycling system uses water more efficiently: [2]

1. The water recycling system collects water that drains through the growing trays after passing over plant roots, then filters, sterilises, and recirculates it back to the plants in a closed loop [1].
2. Very little water is lost because the entire system is enclosed, preventing evaporation from soil surfaces and drainage into the ground. On conventional farms, a large proportion of irrigation water evaporates from exposed soil surfaces or drains away unused through the subsoil [1].

(d)(i) Two reasons why some residents may oppose vertical farms: [2]

1. The production cost is 4.80 EUR per kg, four times the 1.20 EUR for imported food. Consumers, especially those on lower incomes, would pay significantly higher prices for locally grown produce at a time when food affordability is already a concern [1].
2. The LED lighting system consumes large amounts of electricity. If this electricity comes from fossil fuel sources, the farm may still contribute substantially to carbon emissions despite eliminating transport emissions. Currently, solar panels supply only 15% of the farm's electricity needs [1].

(d)(ii) One social benefit of community rooftop gardens: [1]

Community rooftop gardens provide shared green spaces where residents can socialise, build community connections, and work together while growing food, helping to reduce social isolation in dense urban areas [1].

(e) How urban farming can improve food security for City M: [2]

1. Growing food within the city reduces dependence on imported food, making the population less vulnerable to disruptions in international supply chains caused by extreme weather events, political conflicts, pandemics, or transport failures [1].
2. Year-round production in vertical farms (365 days vs. 180 for conventional farms) ensures a continuous supply of fresh vegetables even during the long northern European winter, when outdoor growing is impossible and imports become more expensive [1].

(f) Three ways the city government could encourage more local food growing: [3]

1. Provide grants or subsidies to help residents purchase seeds, compost, and growing equipment for home or community gardens, reducing the financial barrier to starting [1].
2. Offer free training workshops on urban growing techniques such as container gardening, composting, and vertical growing methods, giving residents the knowledge and confidence to grow food successfully [1].
3. Reduce business taxes for restaurants, shops, and supermarkets that source a minimum percentage of their produce from local urban farms, creating market demand that makes urban farming economically viable [1].

(a) Hypothesis, independent variable, and dependent variables: [4]

Hypothesis: As distance downstream through farmland increases, the nitrate and phosphate concentrations in the river water will increase and the dissolved oxygen concentration will decrease [1].

Independent variable: Distance downstream from the control site / sampling site location along the river [1].

Dependent variables (any two): Nitrate concentration (mg/l), phosphate concentration (mg/l), dissolved oxygen (mg/l), algal cover (%), number of invertebrate species [1].

Control variable: Time of sampling, method of measurement, volume of water sampled, position in the river channel (centre), or season of measurement [1].

(b) Method for collecting reliable water quality data: [6]

1. At each sampling site, collect water samples from the centre of the river channel (to avoid edge effects where water is shallower and may not be representative) using clean, sterilised sampling bottles [1].
2. Measure dissolved oxygen concentration using a portable digital dissolved oxygen probe held just below the water surface, and record the reading in mg/l [1].
3. Measure nitrate and phosphate concentrations in the water samples using colorimetric field test kits. Add the reagent tablet to a measured volume of sample water and compare the resulting colour to a calibrated chart to read the concentration [1].
4. Estimate algal cover by lowering a 0.5 m x 0.5 m quadrat to the riverbed at three random positions. Calculate the mean percentage of the quadrat area covered by algae [1].
5. Collect invertebrate samples using the kick-sampling technique: hold a net downstream while disturbing the riverbed substrate by kicking for a standardised 30 seconds. Transfer all caught organisms to a white sorting tray, identify each species using a field guide, and count the number of different species [1].
6. Take at least three replicate measurements at each site and calculate the mean value to improve reliability and reduce the effect of random variation [1].

(c) Pattern shown by the results from Site P to Site T (from Table 1): [7]

1. Nitrate concentration increased progressively from 2.1 mg/l at the upstream control site (P) to a maximum of 18.3 mg/l at Site S (the furthest downstream farm site), then decreased to 12.6 mg/l at Site T [1].
2. Phosphate concentration followed the same pattern, increasing from 0.08 mg/l at Site P to 0.81 mg/l at Site S, then decreasing to 0.54 mg/l at Site T [1].
3. Dissolved oxygen showed the opposite trend, decreasing from 9.4 mg/l at Site P to only 3.1 mg/l at Site S, then partially recovering to 5.6 mg/l at Site T [1].
4. Algal cover increased from 5% at Site P to 75% at Site S, then decreased to 40% at Site T, following the same pattern as the nutrient levels [1].
5. The number of invertebrate species decreased from 18 at Site P to just 4 at Site S, then partially recovered to 9 at Site T [1].
6. Overall, water quality was highest at Site P (upstream of all farms) and lowest at Site S (downstream of all three farms), with some recovery at Site T which is 3 km beyond the last farm [1].
7. Nutrient levels and algal cover are inversely correlated with dissolved oxygen and species diversity: as nutrients and algae increase, oxygen and biodiversity decrease [1].

(d) Explanation of the pattern with reference to eutrophication: [8]

1. Nitrogen-based and phosphate-based fertilizers are applied to the arable farmland (maize, beans, sugarcane). During rainfall, surface runoff washes dissolved fertilizer from the red laterite soil into the river, because no vegetation buffer strips exist between fields and the river bank [1].
2. Nutrient concentrations accumulate as the river passes through successive farm sites (Q, R, S), each adding more fertilizer runoff. This explains the progressive increase from 2.1 mg/l nitrate at P to 18.3 mg/l at S [1].
3. The elevated nutrient levels cause eutrophication - the excessive enrichment of the water with nutrients. This stimulates rapid growth of algae (an algal bloom), as shown by algal cover increasing from 5% at P to 75% at S [1].
4. The dense algal bloom covers the water surface, blocking light from reaching submerged aquatic plants beneath. Without light, these plants cannot photosynthesise and they die [1].
5. When the algae eventually die (their lifecycle is short) and the dead underwater plants decompose, aerobic decomposer bacteria consume large amounts of dissolved oxygen during their respiration [1].
6. This biological oxygen demand reduces dissolved oxygen from 9.4 mg/l at Site P to only 3.1 mg/l at Site S - a level too low for many aquatic organisms to survive [1].
7. The low oxygen levels cause fish and oxygen-sensitive invertebrate species (such as mayfly and stonefly larvae) to die or migrate, reducing biodiversity from 18 species to only 4. The surviving species are typically pollution-tolerant organisms like bloodworms [1].
8. At Site T, 3 km downstream of the last farm, partial recovery occurs because no additional nutrient input enters the river, the water re-oxygenates through turbulent flow and mixing with air, and dilution gradually reduces nutrient concentrations [1].

(e) Evaluation of reliability and suggested improvements: [8]

Reliability concerns:

1. Only five sampling sites were used along 10 km, which may not provide a sufficiently detailed picture of how water quality changes. There could be other pollution sources between the measured points [1].
2. Measurements were taken on a single occasion, so results could be affected by unusual conditions on that particular day. The 15 mm of rainfall the previous week may have caused an atypical flush of fertilizer into the river [1].
3. Algal cover estimation using quadrats is subjective and depends on the observer's judgement. Different students may estimate different percentages for the same quadrat, reducing consistency [1].
4. There is no information about whether replicate measurements were taken at each site. Without replication, there is no way to assess the variability of the data or calculate confidence intervals [1].

Improvements:

1. Increase the number of sampling sites, particularly between the farms and downstream, to more precisely identify where pollution enters the river and how concentration changes with distance [1].
2. Repeat measurements on several different dates across seasons (wet and dry) to account for variation due to weather, farming calendar, and seasonal changes in river flow [1].
3. Use standardised digital instruments rather than visual estimation where possible (e.g. a turbidity meter instead of visual assessment of water clarity) to reduce subjective error [1].
4. Include a second upstream control site to confirm that Site P is genuinely unaffected by other potential pollution sources [1].

(f) How the investigation could be extended: [7]

1. Monitor water quality over a full year to identify seasonal patterns, particularly comparing wet and dry seasons when surface runoff volumes and fertilizer application schedules differ [1].
2. Measure additional water quality indicators such as biological oxygen demand (BOD), turbidity (cloudiness), pH, and water temperature to build a more complete picture of river health [1].
3. Investigate which specific invertebrate species are present at each site. Use indicator species such as mayfly nymphs (clean water indicators) and rat-tailed maggots (pollution indicators) to create a biotic index score that quantifies water quality biologically [1].
4. Survey fish populations at each site to assess whether larger organisms higher in the food chain are also affected by the deteriorating water quality [1].
5. Measure the types and quantities of fertilizer applied on each farm to correlate input volumes with measured river nutrient levels and identify which farming practices cause the most pollution [1].
6. Investigate whether planting buffer strips of vegetation (grasses, shrubs, trees) between the farms and the river bank could intercept and filter runoff before it reaches the water [1].
7. Test soil samples from farmland near the river to determine how much applied fertilizer remains in the soil versus how much is being washed into the river, informing recommendations for more efficient fertilizer use [1].