6.3 & 6.4:

Question 1

primary pollutants:

Answer 1

• emitted directly from a process (which can either be natural eg. volcanic eruptions or human made eg. industry, motor vehicle exhausts)
• examples: carbon monoxide (from incomplete combustion of fossil fuels), carbon dioxide, oxides of sulphur & nitrogen

Question 2

secondary pollutants:

Answer 2

• formed when primary pollutants undergo a variety of reactions with other chemicals already present in the atmosphere (can be a photochemical reaction in the presence of sunlight)
• eg. tropospheric ozone, particulates from gaseous primary pollutants

Question 3

formation of tropospheric ozone =

Answer 3

nitric oxide + oxygen -> nitrogen dioxide. when nitrogen dioxide absorbs sunlight, it is broken apart into nitric oxide and oxygen atoms. oxygen atom + oxygen molecule = ozone
* ^ under normal conditions, most ozone molecules oxidise nitric oxide back into nitrogen dioxide.

Question 4

effects of ozone:

Answer 4

damage to plants (degrades chlorophyll so photosynthesis & productivity is reduced)

in humans; causes breathing difficulties, increases susceptibility to infections, eye irritation

also damages materials by bleaching fabrics.

Question 5

dangers of particulates:

Answer 5

• respiratory filters cannot filter them out so they enter our body and stay there causing asthma & other lung problems
• many of them r cancer causing
• in industrial areas crops become covered w particulate which reduces productivity since less sunlight reaches plants.

Question 6

photochemical smog:

Answer 6

it is formed when ozone, nitrogen oxides and gaseous hydrocarbons from vehicle exhausts interact with strong sunlight. complex reactions create many chemicals in photochemical smog including VOCs (volatile organic compounds), PANs, ozone, aldehydes, carbon monoxide and nitrous oxides.

highly reactive VOCs oxidize nitrogen oxide into nitrogen dioxide without breaking down any ozone molecules in the process. this leads to a build- up of ozone near ground level and smog formation.

because nitrogen dioxide is an important component of smog, smog can be seen as a brown hue above the city.

all these chemicals are strongly oxidizing and affect materials and living things. at higher concentrations, smog can cause coughs and decreased ability to concentrate.

factors for occurrence -
* local topography (low lying cities, valleys - more susceptible to smug)
* climate (no wind, warm days)
* population density (more population = more pollutants = more smog)
* fossil fuel use

Question 7

thermal inversion:

Answer 7

on warm days, the normal air over cities which is warm and has a tendency to rise is trapped by an even warmer layer on top - trapping pollution at ground level. occurs most often in warm dry climates.

Question 8

pollution management: smog

Answer 8

• consume less, burn less fossil fuel
• purchase energy efficient technologies
• use public transit
• re-greening of cities (absorbs CO2)
• government regulation