Identify four factors that make the use of the insecticide DDT controversial.

Explain how human activities continue to affect stratospheric ozone.

To what extent is the use of solid domestic waste (SDW) as an energy source beneficial to a society?

DDT…

1. is a very effective/affordable insecticide;
2. can help in the management of insect borne diseases/malaria/zika;
3. can help in the control of agricultural pests, improving harvests;
4. is a persistent (organic) pollutant / causes soil degradation/aquatic pollution;
5. has negative effects on human health;
6. bioaccumulates in the bodies of organisms;
7. biomagnifies in food chains;
8. causes impact on non-target species/death of birds of prey/top carnivores;
9. reduces biodiversity;

Introductory explanations:

1. ozone depleting substances (ODSs)/CFCs disrupt (the dynamic equilibrium of) ozone formation;
2. ODSs are halogenated organic gases such as chlorofluorocarbons (CFCs) / halons;
3. ....used as cooling agents (old refrigerators, air-conditioning units) / aerosol propellants (spray cans) / blowing agents (insulating foams) / fire-extinguishers / cleaning solvents (electronic equipment) / pesticides;
   
   Activities that lead to increase/restoration of ozone:
4. pollution management may be achieved by reducing the manufacture and release of ozone-depleting substances;
5. methods for this reduction include recycling refrigerants/developing alternatives to gas-blown plastics/ halogenated pesticides/propellants and aerosols/developing non-propellant alternatives;
6. the Montreal Protocol (on Substances that Deplete the Ozone Layer (1987)) (and subsequent updates) is an international agreement for the reduction of use of ODSs;
7. this is considered to be a very successful international agreement;
8. national governments complying with the agreement made national laws and regulations to decrease the consumption/production of ODSs;
   
   Mechanisms that lead to reduction/destruction of ozone:
9. UV light breaks apart the ODSs/CFCs and releases a halogen atom;
10. halogen atom breaks an ozone molecule apart and combines with an oxygen atom;
11. oxygen atoms combine with the oxygen from the halogen and release the halogen to start the process again;
12. .… the halogen is considered a catalyst / why the reaction is cyclical;
    
    Explanations of “continuing” effect on ozone:
13. ODSs/CFCs have a very long lifetime in the atmosphere / there is a time lag from removal of ODSs to the end of ozone destruction;
14. halogen atoms are removed very slowly from stratosphere; (Cl by a chemical reaction with methane forming hydrochloric acid)
15. an illegal market for ozone-depleting substances persists and requires consistent monitoring;
16. some countries are still not complying with international agreements on bans;
17. HCFCs may have lower ozone depleting potential, but still destroy ozone (not phased out before 2020);
18. increasing GCC/GHGs affect polar weather conditions (increasing temperature difference between troposphere and cooler stratosphere), thus affecting the distribution of ozone (positively in 2019, negatively in 2020); (Note that this should be the only link with GCC accepted)

Notes: Award [5 max] if there are no explanations of “continuing” effect on ozone.
Accept CFCs as alternative to ODSs.

Refer to paper 2 markbands, available under “your tests”  tab > supplemental materials

The following guide for using the markbands suggests certain features that may be offered in responses. The five headings coincide with the criteria given in each of the markbands (although “ESS terminology” has been conflated with “Understanding concepts”). This guide simply provides some possible inclusions and should not be seen as requisite or comprehensive. It outlines the kind of elements to look for when deciding on the appropriate markband and the specific mark within that band.

Answers may include:

• understanding concepts and terminology types and sources of SDW; increasing trend (overpopulation); consumerism; methods of SDW disposal (landfill, incineration, recycling, composting); strategies for managing SDW including zero-waste programmes; energy production, e.g. trash to energy systems; environmental indicators; sustainability; pollution – air, atmosphere, water;
• breadth in addressing and linking disposal of SDW to climate change and pollution; impact on resource use and exploitation; perspectives from EVSs; range of perspectives from a societal and cultural angle; differences due to development level; energy security;
• examples could include different countries’ strategies; examples of sustainability plans for cities; examples of impact of incineration or landfills; examples of climate change goals and integration;
• balanced analysis could include a range of societies challenges; a variety of perspectives from an EVS angle; contradiction of energy production needs and reduction of resource use; contrast of MEDCs to LEDCs;
• a conclusion that is consistent with, and supported by, analysis and examples given e.g. the use of SDW as an energy source can be very beneficial for a city in reducing its waste disposal needs and greenhouse gas emissions however it can lead to a reduction in impetus to reduce waste production and therefore resource use as the society becomes dependent on the waste as an energy source;

Majority were able to identify one or two controversial aspects of DDT although few gained full credit.

Majority were able to link stratospheric ozone and ozone depleting substances like CFC but frequently answers were confused with aspects of greenhouse gases and global warming.

Majority of answers were completely valid but rarely did they explore the question with sufficient breadth.