IB ESS HL 6.4 Stratospheric Ozone Question Bank

22-24 km;
Note to examiners: Do not credit if units are omitted.

With reference to Figure, describe the importance of higher ozone concentration between 20 and 30 kilometers for living organisms.
a. Ozone in the stratosphere absorbs ultraviolet radiation from the sun / less ozone means more ultraviolet radiation reaching the earth's surface;
b. Ultraviolet radiation is harmful for living tissues / increasing the incidence of cataracts / mutation during cell division / skin cancer/melanoma / immune deficiency;
c. Increased ultraviolet radiation may reduce biological productivity / damage photosynthesising organisms including phytoplankton...;
d. ...disrupting food chains/ecological equilibria / e.g. reduction of krill population around Antarctica;

Note to examiners: Do not credit simplistic statements, like "protects life on Earth", "absorbs sun's rays".

a. Increased release of primary pollutants / VOCs \& NOx..;
b. ...due to increased population...;
c. ...due to increased living standards...;
d. ...leading to increased vehicular traffic/industrial production/fossil fuel burning/air-conditioning use;
e. Global warming increasing air-conditioning/energy use / perhaps leading to a localized increase in rate of photochemical reactions / increased urban heat island effect;
f. Increase in high rise buildings traps pollutants.

Note to examiners: No credit for "defects in data collection", "release of GHGs/CFCs".

ozone initially declined;
b. ozone stabilized / began to increase slightly;

Note: do not credit descriptions of the projected values.

Allow 1 mark for overall decline
Precise dates are not necessary for credit (i.e. accept change occurring around 2000).

halons/CFCs/HCFCsHBFCs/ $\mathrm{N}_{2} \mathrm{O}$ /methyl bromide/methyl chloroform/carbon tetrachloride/ chlorine/bromine:

Note: do not credit HFCs/ODSs

a. cell damage/premature aging of skin / skin cancer;
b. cataracts / eye damage;
c. immune system suppression;

Accept any year in range 2041-2043;

a. Montreal Protocol resulted in unprecedented international cooperation to address loss of ozone (and its influence still continues);
b. banned use of CFCs/ phasing out of CFCs/ ozone depleting substances /refrigerants/aerosols/recycling of refrigerants;
c. alternatives to CFCs (HFCs/HCFCs) were developed reducing harm to ozone;
d. education/awareness campaigns led to changes in consumer preferences;
e. ozone reforms due to natural reversible chemical reactions/processes / ODSs eventually begin to break down/dissipate;