Figure 1: Concentration of atmospheric pollutants associated
with photochemical smog
Identify one primary pollutant from the pollutants shown in Figure 1.
//hydrocarbons
Outline why the pollutant named in Part 1 is referred to as a primary pollutant.
impacts environment directly on emission / undergoes no chemical change before impacting environment / is active on emission
Note: Even if response to 3(a)(i) is wrong full credit (ECF) can be given for appropriate definition of primary pollutant.
Outline one reason why there is an increase in nitrogen oxides and hydrocarbons early in the day.
increase in fossil fuel combustion/increased traffic/transport/industry/power plants
Explain the changes in ozone concentration over the period shown in Figure 1.
Award
- ozone is (a secondary pollutant) produced from nitrogen oxides/NOx reacting with oxygen;
- it increases as more accumulates in atmosphere due to human activity/fossil fuel use;
- sunlight/heat catalyses this reaction so it increases towards midday;
- later, ozone decreases due to dispersal by wind/less fossil fuel use/light becoming less intense;
Note: Do not credit any further detail of chemical process of ozone formation.
State one environmental impact of the accumulation of ozone shown in Figure 1.
Award
- damages plants (crops and forests) / reduces photosynthesis/plant growth;
- increase susceptibility to diseases/other pollutants;
habitat deterioration; - change in water and nutrient cycles;
- loss of biodiversity;
- impacts human health e.g. eye irritation/respiratory illness;
- damages fabrics and rubber materials;
- contributes to global warming/climate change / adverse weather;
Note: Do not credit responses that address ozone depletion.
Outline two local conditions that may increase the severity of photochemical smog.
Award
- low-lying topography/valley/mountains/high-rise buildings;
- low windspeed/air movement;
- thermal inversion / hot humid days;
- high population density/heavy use of fossil fuels;
- cities closer to equator get more intense sunlight;
